14--RESPIRATION IN PLANTS

CHAPTER NO.14 RESPIRATION IN PLANTS

A141

INTRODUCTION:All Living Organisms need energy for carrying out daily life activities be it absorption transport movements even breathing. The energy comes from food. Respiration is a process in which the respiratory substrates sucrose, starch, glucose or other sugars,fats, organic acids, proteins etc. are broken down through oxidation accompanying with the release of energy and its storage or conservation in the form of ATP with CO,

release as a consequence.CeH120¢+6Or -.----- 6CO2 +60 +2870KJ

All the energy required for the life process is obtained by oxidation of some

macromolecules that we call ‘food’.

Only green plants and cyanobacteria can prepare their own food by the process

of photosynthesis they trap light energy and convert it into chemical energy that is

stored in the bonds of carbohydrate like glucose, sucrose and starch.In green plants too, not all cells, tissue, and organs photosynthesis, only cells containing chloroplasts that are most often located in the superficial layers, carry out photosynthesis. Hence, ever in green plants all other organs, tissue and cells

that are non-green need food for oxidation.

Hence, food has to be trans located to all non-green parts. Animals are heterotrophic i.e. they obtain food from plants directly (herbivores) or indirectly (carnivores). Saprophytes like fungi are dependent on dead and decaying matter.So ultimately all the food that is respired for life process comes from photosynthesis.

Photosynthesis of course takes place within the chloroplasts whereas the breakdown of complex molecules to yield energy takes place in cytoplasm and mitochondria. The breaking of C-C bonds of complex compounds cells to stay active or they also require O»for and give out CO, have system in place through oxidation within the cells, leading to release of considerable amount of energy is called respiration.

Respiratory Substrates:Like animals, the plants also require energy for growth, development metabolism and other life activities.The energy mainly comes from respiratory breakdown of various substrates.The substrates are called organic nutrients and synthesized inside the plants by anabolic processes.These organic substances which are present in large amounts in plant cells and

respired completely to CO2 and H2O are called respiratory substrates under

natura! conditions only carbohydrate is oxidized. This respiratory is called floating respiration.If the carbohydrates are used up and its storage becomes acute, other protoplasmic substrates may also be catabolised. This is termed as protoplasmic

respiration.During oxidation within a cell all the energy contained in respiratory substrate is not released free into the cell, the energy or in a single step. It is released in a serious of slow step wise reactions controlled enzymes and it is trapped as chemical energy in the form of ATP.Hence it is important to understand that the energy released by oxidation in

respiration is not used directly but it is used to synthesis ATP. which is broken

down whenever and wherever energy needs to be utilized. Hence, ATP acts as cell energy currency of the cell.

‘Do Plants breathe????????'All plants respire to provide energy for their cell to stay active or alive. They also require

QO» for respiration and give out CO, plants have system in place that ensure the

availability of O2 But plants unlike animals have no specialized organs for gaseous exchange but they have stomata and lenticels for their purpose. There are several reasons why plants can get along without respiratory organs.

a) Unlike animals the plants do not have a great demand for gaseous exchange.It is because the rate of respiration in plant organs (such as roots, stem and leaves) is far lower than that of animals.

b) Plant organs are designed in such a way that their living cells are located

close to surface where atmospheric gases can diffuse easily. The leaves and

other tender parts have stomata and bark has lenticels.

c) Moreover, loose packing of parenchyma cells in leaves, stem and root.

d) When cells photosynthesis, availability of O2 is not a problem in their cells

since Oo is released within cells provides a system of intercellular spaces that

facilitates free movement of gases inside the organs.

e) Every part of plant takes care of its own gas exchange needs, so there is very

little transport of gases from one part to another. Plants stem and leaves so of

plants exchange gases for respiration separately.

Respiration in Roots:Roots the underground part of the plants absorbs air from air spaces present between soil particles. Thus, the oxygen absorbed through roots is used to release energy which is later used for the transportation of minerals and salts from the soil.

Respiration in Stems:In case of stem, the air gets diffused in the stomata and passes through various parts of the cell for respiration. The CO, Produced during this stage also diffuses through the stomata. In higher plants or woody plants the gaseous exchange is carried out by lenticels.

Respiration is leaves:Leaves comprise tiny pores referred to as stomata. The exchange of gases takes place via stomata through the process of diffusion. Each stoma is controlled by guard cells.The opening and closing of stoma help in exchange of gases between atmosphere and interior of leaves.

LET US KNOW WHAT WE HAVE LEARNT!

A. MCQs:

1. Where does the energy required to carry life processes come from?

(a) Food

(b) House

(d) Galaxy

2. What are lenticels?

(a) Openings on the surface of the bark

(b) Openings on the surface of roots

(d) Pores on stem

3. Which of the following gases do plants require for respiration?

(a) Oz

(b) CO,

(d) HO

4. Why plants can get along without the need for specialised respiratory organs?

(a) It would be an extra expense

(b) They don't like it

(d) Oxygen is easily available for all the parts of the plants

5. The breaking of which of the following bonds leads to release of energy?

(a) P-P bonds

(b) C-C bonds

(d) S-S bonds

B. TRUE/FALSE:

(a) During oxidation within a cell, all the energy is released into a single step.

(b) Photosynthesis and respiration take place all the time in plants.

C. FILL UPS:

(a)__——S——SSsoare the openings found on older stems.

(b)_—=—s——S_sis main respiratory substrate.

green plants.

ANSWER KEY: PART -A

A. MCQ's:

Ans. 1 (a) Explanation All the energy required for life processes is obtained by the oxidation of some macromolecules that we call as food. All living organisms need energy to carry out daily life activities.

Ans. 2 (a) Explanation in stems, the living cells are organised in thin layers inside and beneath the bark. They also have openings called lenticels. The cells in the interior are dead and only provide mechanical support.

Ans. 3 (a) Explanation Plants do not require CO2, N2 or water vapor for respiration.Like human beings, plants also require oxygen for respiration so that they can release CO2. It is through photosynthesis, that they require carbon dioxide and release oxygen in a very large amount.

Ans. 4 (c) Explanation Each plant part takes care of its own gas-exchange needs,

Plants do not present great demands for gas exchange.

Ans. 5 (b) Explanation The breaking of the C-C bonds of complex compounds through

oxidation within the cells, leads to the release of a considerable amount of energy. This process is known as respiration.

B. True/False:

Ans. 1 False Explanation: During oxidation within a cell, all the energy contained in the respiratory substrate is not released in a single step because then all the energy would be lost in a single step and the cell would not be able to store the synthesised energy for its future use.

Ans. 2 False Explanation: Although respiration in plants occurs all the time,

photosynthesis only occurs in the presence of sunlight.

Ans. 3 True Explanation: Lenticels facilitate gaseous exchange but these gases are transported to the intracellular spaces by the process of diffusion.

C. Fill Ups:

Ans. 1 Lenticels Explanation: Lenticels are raised pores in the stem of woody plant that allow exchange between atmosphere and internal tissue.

Ans. 2 Glucose Explanation: Glucose is the main respiratory substrate that is oxidised

course of respiration.

Ans. 3 Photosynthesis, Respiration Explanation: During Day light, Photosynthesis the dominant process as a result amount of O2 Released during day times is 10 times greater than amount of O2 Utilised in day time, because Respiration is more dominant in night than day time.

PART: B SHORT ANSWER TYPE QUESTIONS:

(a) How is the energy released and stored during oxidation of compounds in

respiration?

(b) What are the respiratory substrates? Name the most common respiratory

substrate.

PART: C LONG ANSWER TYPE QUESTIONS:

(a) Plants lack a specialized respiratory system. How do they carry out respiratory

process? Explain.

A142

INTRODUCTION

GLYCOLYSIS:It is the first step of cellular respiration that brings about break down of

GLUCOSE into TWO molecules of PYRUVIC ACID, through enzyme mediated reactions.The term glycolysis has originated from Greek words, Glycos for sugar, and lysis for splitting.

It is also called EMP pathway because its details were given by Embden, Meyerhof and Parnas in 1930s.

DEFINITION:-Glycolysis is a process by which one molecule of glucose (6C)

breaks into two molecules of pyruvic acid (3C).

PROPERTIES:-

1. It occurs in cytoplasm outside the mitochondria.

2. It is anaerobic phase.

3. It is present in all cells.

4. One molecule of glucose is reduced to two molecules of pyruvate.

5. No CO: is produced as there is no decarboxylation in glycolysis.

STEPS OF GLYCOLYSIS :-Glycolysis is completed in the following steps:-

1. Phosphorylation

2. lsomerisation

3. Phosphorylation

4. Cleavage

5. Phosphorylation & Dehydrogenation

6. Dephosphorylation

7. Rearrangement

8. Dehydration

9. Dephosphorylation

In plants, the glucose is derived from sucrose, which is the end product

of photosynthesis, or from storage carbohydrates. Sucrose is converted into glucose and fructose by the enzyme,

invertase, and these two monosaccharides readily enter the glycolytic pathway. Glucose and fructose are phosphorylated to give rise to glucose-6- phosphate by the activity of the enzyme hexokinase This phosphorylated form of glucose then isomerizes to produce fructose-6-phosphate.

ATPIS UTILISED AT TWO STEPS:

1. Conversion of glucose into glucose-6-phosphate.

2. Conversion of fructose-6-phosphate into fructose1, 6-bisphosphate.The fructose1, 6-bisphosphate is split into Di Hydroxy Acetone Phosphate (DiHAP) and 3- Phospho Glycer Aldehyde (PGAL).There is one step where NADH*H* is formed from NAD+ ;

this is when 3-phosphoglyceraldehyde(PGAL) is converted to 1, 3- Bi Phospho Glycer Ate (BPGA). PGAL is oxidised and with inorganic phosphate to get converted into BPGA.The conversion of BPGA to 3- Phosphor Glyceric Acid (PGA), is also an energy yielding process; this energy is trapped by the formation of ATP.Another ATP is synthesised during the conversion of PEP (Phospho

Enol Pyruvate) to Pyruvic Acid.Pyruvic Acid is then the key product of glycolysis.

LET US KNOW WHAT WE HAVE LEARNT!

A) VERY SHORT ANSWER TYPE QUESTIONS

a. MULTIPLE CHOICE QUESTIONS:

1. Glycolysis is present in:

(a) All cells

(b) RBCs

(d) Platelets

2. Glycolysis is also called

(a) EMP pathway

(b) Cleavage

(c)Anaerobic

(d) Dehydration

3. The term glycolysis has originated from

(a) Greek words

(b) Latin words

(c)Germanwords

(d) None of these

4. In glycolysis, one molecule of glucose breaks into two molecules of

(a) glucose

(b) Pyruvic acid

(d) Kinase

5. Gycolysis is a

(a) Anaerobic phase

(b)Aerobicphase

(d) None

b. FILL IN THE BLANKS:

1. The key product of glycolysis is :

2. In plants,the glucose is derived from .

3. It occurs in outside the mitochondria.

c. TRUE/FALSE:

1. It is a aerobic phase.

2. Coz is produced as there is no decarboxylation in glycolysis.

3. Glycolysis is present in all cells.

ANSWER KEY: PART-A

A.MULTIPLE CHOICE QUESTIONS:

1. (a)AIl cells.Glycolysis is present in all cells.

2. (a)JEMP Pathway. Glycolysis is also called EMP pathway because its

details were given by Embden, Meyerhof and Parnas in 1930s.

3. (a)Greek words. The term glycolysis has originated from Greek words.

4. (b)Pyruvic acid. Glycolysis is a process by which one molecule of glucose (6C) breaks into two molecules of pyruvic acid (3C).

5. (a)Anaerobic phase.Glycolysis is anaerobic phase.

B. FILL INTHE BLANKS:

1. The key product of glycolysis is Pyruvic acid.

2. In plants, the glucose is derived from sucrose.

3. It occurs in cytoplasm outside the mitochondria.

C.TRUE/FALSE:

1. False. Glycolysis is anaerobic phase.

2. False. No COz is produced as there is no decarboxylation in glycolysis.

3. True. Glycolysis is present in all cells.

(A) SHORT ANSWER TYPE QUESTIONS:

1. What is glycolysis?

2. What are the properties of glycolysis?

3. What are the steps of glycolysis?

(C) LONG ANSWER TYPE QUESTIONS:

1. Give the schematic representation of glycolysis.

A143

INTRODUCTION:The mechanism of breakdown of food materials within the cell to release

energy, and the trapping of this energy for synthesis of ATP is called cellular respiration.The breaking of the C-C bonds of complex compounds through oxidation

within the cells, leading to release of considerable amount of energy is

called respiration.The compounds that are oxidised during this process are known as

respiratory substrates.The energy released by oxidation in respiration is not used directly but is used to synthesise ATP, which is broken down whenever energy needs to be utilised; hence, ATP acts as the energy currency of the cell.During the process of respiration, the complete combustion of glucose takes place, which produces CO2 and H20 as end products, yields energy most of which is given out as heat.Fermentation is the incomplete oxidation of glucose under anaerobic

conditions by sets of reactions.

1. ALCOHOL FERMENTATION:In a plant cell, glycolysis leads to the formation of pyruvic acid. Further, itis broken down based on the availability of oxygen. In the absence of oxygen, the cell undergoes fermentation.The term ‘fermentation’ is derived from the Latin word ‘fever,’ which means‘to boil’. In it, complex substances like carbohydrates undergo incomplete

oxidation. Based on the end product, the process can classified as either

alcohol fermentation or lactic acid fermentation.The fermentation of alcohol takes place in yeast, which are facultative

anaerobes. In them, pyruvic acid is reduced to carbon dioxide and ethanol with the help of enzymes. In this process, first the pyruvate is decarboxylated by pyruvate decarboxylase to acetaldehyde.The enzyme, alcoho! dehydrogenase, uses NADH to reduce the acetaldehyde molecule to ethanol. The NAD+ so formed is re-used in the

glycolysis process. Yeast is widely used in the production of alcohol beverages like wine and beer and to bake of bread.

2. LACTIC ACID FERMENTATION:The ermentation of lactic acid is carried out by bacteria like Lactobacillus.In them, pyruvic acid is reduced to lactic acid. The NADH formed in the glycolysis process is re-oxidised to NAD+ by alcohol dehydrogenase to be

re-used in the glycolysis process.During physical exercise, muscle cells undergo anaerobic respiration. The enzyme, lactate dehydrogenase, uses NADH to reduce the pyruvate molecule to lactate.In this process, NADH is re-oxidised to NAD and used in the glycolysis pathway. The accumulation of lactate is the reason for the stiffness in the muscles. Both alcohol and lactic acid fermentation yield less energy.Not even 7% of the energy present in the glucose is released, and of that,

only some amount of energy is trapped in the form of ATP. Thus, anaerobic

respiration yields a net gain of 2 ATPs after deducting the ATPs required for

the preparatory phase of glycolysis.

In anaerobic respiration, the NADH formed is re-oxidised. Thus, the synthesis of ATP from NADH molecules similar to aerobic respiration is also not possible. Also, the products formed are either alcohol or lactic acid,which is hazardous in nature. In fact, yeast is poisoned to death when the concentration of alcohol reaches fourteen percent. Fermentation releases

less energy than the process followed in the presence of oxygen.

LETS US KNOW WHAT WE HAVE LEARNT!

PART: (A) VERY SHORT ANSWER TYPE QUESTIONS:

a) MULTIPLE CHOICE QUESTIONS:

Q1. The fermentation which is carried by yeast is called:

a. Pyruvic fermentation

b. Acrylic fermentation

c. lactic acid fermentation

d. Alcoholic fermentation

Q2. Where fermentation takes place?

a. Mitochondria

b. Ribosomes

c. Cytoplasm

d. Vacuole

Q3. The applications of fermentation include:

A. Cereal products

B. Dairy products

C. Beverage products

D. All of above

Q4. Which is formed when NADH reduces the Pyruvate?

A. Three carbon sugar

B. Four carbon sugar

C. Lactic acid

D. Acetic acid

Q5. Fermentation reaction occurred in the earliest primitive environment of

earth that did not contain:

A. Hydrogen

B. Free oxygen

C. Carbon

D. Nitrogen

b) FILL IN THE BLANKS:

1. The fermentation is process.

2. In alcoholic fermentation, NADH reduces the pyruvate into .

3. Anaerobic respiration yields net gain of ATP.

c) TRUE/FALSE:

1. Lactic acid fermentation reaction is older than aerobic respiration.

2. The glucose is not completely degraded during fermentation.

3. Obligative anaerobic organisms survive only in the presence of molecular

oxygen.

ANSWER KEY: PART-A

a. MULTIPLE CHOICE QUESTIONS

1. D; The NADH, reduces the pyruvate into alcohol. It takes place in some fungi

(yeast) and bacteria.

2.C

3.D

4.C

5.C

b. FILL IN THE BLANKS:

1. Anaerobic

2. Alcohol

3. 2ATPs

c. TRUE/FALSE:

1. TRUE: Fermentation has evolved very early in the history of life. At that time

the earth's atmosphere contained no oxygen.

2. TRUE: A large amount of unusable energy still remains in the products. As

glucose do degrade completely. Only two molecules of ATP are formed during

glycolysis and no more ATP is produced.

3. FALSE: Obligate anaerobic organisms include certain types of bacteria. These

organisms survive only in the complete absence of molecular oxygen. Its

example is clostridium sp.

PART: (B) SHORT ANSWER TYPE QUESTIONS:

1. What do you mean by the term fermentation?

2. Where does the fermentation takes place?

3. Explain lactic acid fermentation?

PART: (C) LONG ANSWER TYPE QUESTION:

1. Explain the process of fermentation and its types?

144

INTRODUCTION:RESPIRATION is a biochemical process which is common in all living

organisms.

Cellular respiration can be of two types:

AEROBIC and ANAEROBIC. Aerobic means “with air”. Therefore, aerobic respiration is the process of cellular respiration that uses oxygen to produce energy from food. This type of respiration is common in most of the plants and animals, including humans,

birds and other mammals.While breathing, we inhale air that contains oxygen and we exhale air rich in carbon dioxide. As we breathe in, the oxygen-rich air is transported to all the parts of our body and ultimately to each cell. Inside the cell, the food, which contains glucose, is broken down into carbon dioxide and water with the help of oxygen. The process of breaking down the food particles releases energy, which is then utilized by our body. The energy released via aerobic respiration

helps plants and animals, including us, grow.

THERE ARE TWO TYPES OF RESPIRATION:

AEROBIC RESPIRATION - Takes place in the presence of oxygen.

ANAEROBIC RESPIRATION - Takes place in the absence of oxygen.

AEROBIC RESPIRATION:For aerobic respiration to take place within the mitochondria, the final product of glycolysis, pyruvate is transported from the cytoplasm into

the mitochondria.The crucial events in aerobic respiration are:The complete oxidation of pyruvate by the stepwise removal of all the hydrogen atoms, leaving three molecules of CO.,( The first process takes place in the matrix of the mitochondria )The passing on of the electrons removed as part of the hydrogen

atoms to molecular O, with simultaneous synthesis of ATP.(The second process is located on the inner membrane of the mitochondria.)Pyruvate, which is formed by the glycolytic catabolism ofcarbohydrates in the cytosol, after it enters mitochondrial matrixundergoes oxidative

decarboxylation by a complex set of reactionscatalysed by pyruvic

dehydrogenase. The reactions catalysed by pyruvicdehydrogenase require the

participation of several coenzymes, including NAD and Coenzyme A.

During this process, two molecules of NADH are produced from the metabolism of two molecules of pyruvic acid (produced from one glucose molecule during glycolysis).

The acetyl CoA then enters a cyclic pathway, tricarboxylic acid cycle,

more commonly called as Krebs' cycle.

The process can be simply explained with the help of the following equation:

Glucose + Oxygen — Carbon dioxide + Water + Energy What is the overall equation of aerobic cellular respiration?

The equation for aerobic cellular respiration is:CsHi1206 + 602 ———_——> 6CO2 + 6H20 + 38ATP

Aerobic respiration is a continuous process and it happens all the time inside

the cells of animals and plants.

ANAEROBIC RESPIRATION:Anaerobic means “without air”. Therefore, this type of cellular respiration does not use oxygen to produce energy.Sometimes there is not enough oxygen around for some organisms to

respire, but they still need the energy to survive. Due to lack of oxygen, they

carry out respiration in the absence of oxygen to produce the energy they

require, which is referred to as anaerobic respiration.Anaerobic respiration usually occurs in lower plants and microorganisms.

In the absence of oxygen, the glucose derived from food is broken down into

alcohol and carbon dioxide along with the production of energy.

There are two main types of anaerobic respiration:

ALCOHOLIC FERMENTATION

LACTIC ACID FERMENTATION

ALCOHOLIC FERMENTATION:In fermentation, say by yeast, the incomplete oxidation of glucose is achieved under anaerobic conditions by sets of reactions where pyruvic acid is converted to CQz2, and ethanol.The enzymes, pyruvic acid decarboxylase and alcohol dehydrogenase

catalyse these reactions.

Fermentation: Anaerobic Respiration

Glucose — Alcohol + Carbon dioxide + Energy

LACTIC ACID FERMENTATION:Other organisms like some bacteria produce lactic acid from pyruvic acid. In animal cells also, like muscles during exercise, when oxygen is inadequate for cellular respiration pyruvic acid is reduced to lactic acid by lactate

dehydrogenase. The reducing agent is NADH+H which is reoxidised to NAD+ in both the processes.Cramps occur when muscle cells respire anaerobically. Partial breakdown of

glucose, due to lack of oxygen, produces lactic acid and the accumulation of

lactic acid causes muscle cramps. That is why a hot shower after heavy sports relieves the cramps as it improves blood circulation in the body, which in turn enhances the supply of oxygen to the cells.Glucose — Lactic acid + Energy

Anaerobic respiration is also used by multi-cellular organisms, like us, as a

temporary response to oxygen-less conditions. During heavy or intensive

exercise such as running, sprinting, cycling or weight lifting, our body

demands high energy. As the supply of oxygen is limited, the muscle cells

inside our body resort to anaerobic respiration to fulfil the energy demand.

Anaerobic respiration produces a relatively lesser amount of energy as compared to aerobic respiration, as glucose is not completely broken down in the absence of oxygen.Where does the aerobic and anaerobic respiration occur in the cell?In the cell, Aerobic respiration occurs within the mitochondria of a cell, and the anaerobic respiration occurs within the cytoplasm of a cell. The primary difference between aerobic and anaerobic respiration is the presence or absence of oxygen during the processes.

CONCLUSION:The fundamental difference between aerobic and anaerobic respiration is the usage of oxygen in the process of cellular respiration. Aerobic respiration, asthe name suggests, is the process of producing the energy required by cells

using oxygen. The by-product of this process produces carbon dioxide along

with ATP — the energy currency of the cells. Anaerobic respiration is similar to

aerobic respiration, except, the process happens without the presence of

oxygen. Consequently, the by-products of this process are lactic acid and

ATP.Contrary to popular belief, multicellular organisms, including humans, use anaerobic respiration to produce energy, though this only happens when the

muscles do not get adequate oxygen due to extremely vigorous activity.

LET US KNOW WHAT WE HAVE LEARNT!

PART: A VERY SHORT ANSWER TYPE QUESTIONS.

A) MULTIPLE TYPE QUESTIONS:

1) Which is the correct equation for aerobic respiration in humans?

a) glucose + oxygen — carbon dioxide + water

b) glucose + oxygen — lactic acid

c) glucose — lactic acid

d)both a and b

2) Which is the correct equation for anaerobic respiration in humans?

a)glucose — lactic acid + water

b)glucose + water — lactic acid

c)glucose — lactic acid

d)all the above

3) Which of these is a difference between aerobic and anaerobic respiration in

humans?

a) Aerobic respiration releases less energy than anaerobic respiration does

b) Glucose is completely broken down in aerobic respiration but not in anaerobic

respiration

c) Aerobic respiration produces ethanol but anaerobic respiration does not

d) Same amount of energy released in both type of respiration

4) Where in the cell do most aerobic respiration reactions happen?

a) In the nucleus

b) In the cell membrane

c) In the mitochondria

d) In the chloroplast

5) Which of these is a correctly balanced equation for respiration?

a) CeHi206 + 302 — CO2 + 3H20

b) CeHi206 + 602 — 6CO.+ 6H20

c) CeHi120¢ + 602 — 6CO> + 3H,0

d)C6H1206+302 =3CO2 +3H20

6) During hard exercise, what causes an ‘oxygen debt'?

a) build- up of lactic acid

b) build- up of carbon dioxide

c) build- up of oxygen

d) build- up of water

7) What products are made during anaerobic respiration in yeast?

a) Carbon dioxide and water

b) Ethanol and water

c) Ethanol and carbon dioxide

d) Ethanol and lactic acid

B) FILL UPS:

1) respiration can take place in the absence of oxygen.

2) More energy is released during respiration.

3) The end product of aerobic respiration are and carbon dioxide.

C) TRUE OR FALSE:

1) Respiration is an anabolic process.

2) Glucose is completely oxidised during aerobic respiration.

ANSWER KEY: PART -A

1)d

2)a

3) b

4)c

5) b

6)a

7)c

B: FILL UPS:

1) anaerobic

2) aerobic

3) water

C: TRUE OR FALSE:

1) False (It is a catabolic process as break down of glucose takes _ place to

release energy.)

2) True

PART B: VERY SHORT TYPE QUESTIONS:

Q1 What is aerobic respiration?

Q2 Write the reaction of alcoholic fermentation?

Q3 Where does aerobic respiration occur in cell?

PART C: LONG TYPE QUESTIONS:

Q1 Differentiate between aerobic and anaerobic respiration?

A145

INTRODUCTION:In this section we will discuss the third stage of cellular respiration — the transfer of electrons from NADH and FADH2 to oxygen and the

accompanying conversion of redox energy to ATP. The transfer of electrons

from NADH and FADH:z to oxygen involves a sequence of electron carriers arranged in Electron Transport System or Electron Transport Chain and results in the formation of H2O. This chain is present in the inner mitochondrial membrane.

ELECTRON TRANSPORT SYSTEM:-An electron transport system or chain is a series of COENZYMES and CYTOCHROMES that take part in the passage of electrons from a chemical to its ultimate acceptor.

Inner mitochondria membrane possesses five complexes.Complex V is connected with ATP synthesis (Fo-F; particles).Complexes | to IV are involved in electron transport.

Complex | (NADH-Ubiquinone Oxidoreductase Complex):-It has a large L-shaped enzyme with one arm in matrix and other in the

membrane. There is a FMN containing flavoprotein and six iron sulphur

centres.The complex performs two processes.

(a) Exergonic transfer of proton from NADH + H* to ubiquinone NADH + H* + Q — NAD* + QH:

(b) Endergonic transfer of four protons to outer chamber or intermembrane

space 4H* (matrix) — 4H* (outer chamber)

Complex Il (Succinate-Ubiquinone Reductase

Complex):- The complex passes electrons from succinate to FAD, FeS centres and Ubiquinone. It does not pump protons.

Complex Ill (Ubiquinone Cytochrome C Oxidoreductase or Cytochrome B C

Complex):- It has a Fes Centre; Two B Cytochromes and Membrane bound c; and c cytochromes.The complex transfers 04 protons to intermembrane space or outer chamber,02 from QHz and 02 from matrix.

Complex IV (Cytochrome Oxidase):-This complex carries electrons from Cytochrome C to molecular oxygen.It has two Heme groups, a and as and two copper ions, CuA and CuB.

The complex provides electrons to oxygen, protons for formation of metabolic water besides pushing two protons from matrix side to outer chamber.2H* + O27 — H20

During the passage of electrons from NADH to oxygen, some ten protons

(H*) collect in the outer chamber or intermembrane space. As a result a high

Electrochemical Potential Gradient develops across the inner mitochondrial

membrane. It is called Proton Motive Force.

OXIDATIVE PHOSPHORYLATION :-Oxidative phosphorylation is the synthesis of energy rich ATP molecules from ADP and Inorganic Phosphate with the help of Energy liberated during oxidation of reduced coenzymes (NADH, FADHz2) produced in respiration.The complex that takes part in ATP synthesis is called ATP synthase.It is also called Fifth Complex.

ATPase functions as tiny motor which is moved by H* or protons when there is Proton Gradient.The method of ATP synthesis through Proton Gradient was proposed by Peter Mitchell in his Chemi Osmotic Hypothesis.

LET US KNOW WHAT WE HAVE LEARNT!

PART: A VERY SHORT ANSWER TYPE QUESTIONS:

(A) MCQs:

1. Electron transport system is present in which part of mitochondria:

(a) Inner membrane

(b) Outer membrane

(d) Stroma

2. Oxidative phosphorylation results in the formation of:

(a) Oxygen

(b) ADP

(d) NADH

3. Which of the following is the complex Il of ETS?

(a) NADH dehydrogenase

(b) Succinate dehydrogenase

(d) ATP synthase

4. ATP synthesis by ATP synthase is driven by the movement of:

(a) protons

(b) NADH

(d) All of the above

5. Which of the following complexes of ETS does not account for the pumping out of protons from mitochondrial matrix?

(a) Complex |

(b) Complex III

(d) Complex IV

(B) TRUE/ FALSE:

1. The carrier molecules of the electron transport system are located in the cytosol.

2. At the end of electron transport chain, hydrogen combines with carbon dioxide to form water.

(C) FILL IN THE BLANKS:

1. pairs are moved into outer chamber when electrons pass from NADH to oxygen.

2. Complex V is connected with synthesis

3. Complex IV carries electrons from cytochrome c to .

ANSWER KEY: _PART-A

(A) MCQs:

1. (a) Inner membrane (Electron transport system is located in the inner mitochondrial membrane).

2. (c) ATP + H2O(Oxidative phosphorylation results in the formation of ATP and water).

3. (b) Succinate dehydrogenase (Complex Il of electron transport system is Succinate dehydrogenase).

4. (a) Protons (ATP synthase enzyme produce ATP with the help of proton motive force).

5. (c) Complex Il (Complex Il of electron transport system does not account for pumping of protons from mitochondrial matrix).

(B) TRUE/FALSE:

1. False (The carrier molecules of the electron transport system are located in the inner mitochondrial membrane).

2. False (At the end of electron transport chain, hydrogen combines with the oxygen to form water). At the end of electron transport chain, hydrogen combines with carbon dioxide to form water).

(C) FILLIN THE BLANKS:

1. Ten protons (10 electron pairs moves out into outer chamber when electrons pass from NADH to oxygen)

2. ATP(ATP synthase is the fifth complex which is connected with ATP synthesis)

3. Molecular oxygen (Complex IV cytochrome oxidase carries electrons from cytochrome c to oxygen).

PART B: SHORT ANSWER TYPE QUESTIONS:

1. Which portion of aerobic respiration results in greatest amount of

ATP production?

2. What is oxidative phosphorylation?

PART C: LONG ANSWER TYPE QUESTIONS:

1. What is electron transport system? Explain it in detail.

A146

INTRODUCTION:Respiratory pathway involves three steps-Glycolysis, Kreb’s cycle and

Electron transport chain. Glycolysis or EMP occurs in cell cytoplasm. Kreb’s

cycle or citric acid cycle or carboxylic acid cycle in eukaryotes operates in

mitochondrial matrix and ETC is located in inner mitochondrial membrane.

One FADH: in ETC produces 2ATP and one NADH: in ETC produces 3ATP.

RESPIRATORY BALANCE SHEET Respiratory Balance sheet is the sheet representing the theoretical value about the net gain of ATP for each molecule of glucose oxidised in plants.

ASSUMPTIONS ON WHICH CALCULATIONS OF ATP GAIN ARE MADE:-

1. There is sequential, orderly pathway functioning, with one substrate

forming the next and with glycolysis, TCA cycle and ETS pathway following

one after the other.

2. The NADH synthesised in glycolysis is transferred into the mitochondria and undergoes oxidative phosphorylation.

3. None of the intermediates in the pathway are utilised to synthesise any

other compound.

4. Only glucose is being respired-no other substrates are entering the pathway at any of the intermediary stages.But this kind of assumptions are not valid in a living system ; all pathways work simultaneously and do not take place one after the another;substrates enter the pathways and are withdrawn from it as and when necessary;ATP is utilised as and when needed .Yet, it is useful to do this exercise to find the efficiency of the living system. Hence, there can be a net gain of 38 ATP molecules during aerobic respiration of one molecule of glucose.

1. Glycolysis:

a) It consumes two ATP molecules and form four ATP molecules through substrate level phosphorylation. So, there is net gain of

b) Glycolysis produces 2 NADH (+H*). It forms [J through oxidative phosphorylation

2.Gateway Step:2 molecules of pyruvate yield 2 NADH (+H*) during oxidative decarboxylation. In oxidative phosphoylation they yield

Kreb’s cycle: Two cycles from 2 acetyl CoA yield the following:

a) Substrate level phosphorylation

b)6 NADH(+H*) are formed in three steps of oxidation. They yield

through oxidative phosphorylation.

c)2 FADH: are formed. Their oxidative phosphorylation yield J

LET US KNOW WHAT WE HAVE LEARNT!!

PART: A- VERY SHORT ANSWER TYPE QUESTION:

(A) MULTIPLE CHOICE QUESTIONS:

1. Kreb’s cycle produces how many ATP molecules at substrate level

phosphorylation: -

(a) 2 ATP molecules

(b) 4 ATP molecules

(d) 8 ATP molecules

2. The NADH molecules produced during Kreb’s cycle starting from acety CoA are:-

(a) 4

(b) 6

(d) 2

3. Amount of FADH2 molecules produced during Kreb’s cycle are:-

(a)2

(b)3

(d)6

4. The oxidation of two molecules of FADH2 yields how many molecules

of ATP :-

(a)2 ATP molecules

(b)4 ATP molecules

(d)8 ATP molecules

5. Which process produced ATP, during aerobic respiration :-

(a)Glycolysis

(b)Kreb’s cycle

(c)Electron Transport Chain

(d)Both b and c

B) TRUE/ FALSE:

1. Glycolysis can produce ATP in aerobic respiration.

2. 12 NADH molecules are produced during Kreb’s cycle starting from

acetyl CoA.

3.4 ATP molecules are produced by substrate level phosporylation in

glycolysis.

C) FILL-UPS:

1. 2 FADH molecules in Kreb’s cycle produces .

2. Two molecules of pyruvic acid produce ATP upon complete oxidation in mitochondrial respiration.

ANSWER KEY: PART -A

A) MULTIPLE CHOICE QUESTIONS

1. (A) 2 ATP Molecules are produced by substrate level phosphorylation

2. (B) 6 NADH molecules are produced from 2 molecules of cety! CoA

3. (A) 2 FADH2 molecules are produced in kreb’s cycle.

4. (B) 4 ATP molecules are produced from two FADH2

5. (d) Both b and c

TRUE /FALSE

1. False (Glycolysis is an anaerobic pathway)

2. False (6 NADH are produced in Kreb’s cycle)

3. True

C)FILL UPS

1.4 ATP

2.30 ATP

PART- B: SHORT ANSWER TYPE QUESTIONS:

Q1. Write a note on ATP production in glycolysis.

Q2. Give ATP production in link reaction.

Q3. Give ATP production in Kreb’s cycle starting from Acetyl CoA.

PART-C: LONG ANSWER TYPE QUESTION:

1. Explain respiratory balance sheet during oxidation of one molecule of glucose.

A147

The breaking of C-C bonds of complex compounds through oxidation with in the cells, leading to release of energy is called respiration.Respiratory substrates used in respiratory pathway are carbohydrates,fats and proteins. Proteins are degraded by Proteases, fats by lipases

and carbohydrates by amylases.EE Glycerol changes to glyceldehyde-3-phosphate and

converted to Dihydroxy Acetone Phosphate. Then it enters the pathway as acetyl Co-A.

But breakdown of respiratory substrates provides carbon skeleton for synthesis of large number of essential plant products such as polysaccharides, proteins, fats, nucleic acids, pigments, cytochromes etc.

Thus the same respiratory process which

act as catabolic pathway for respiratory substrates also act as anabolic pathway for synthesis of various metabolic products. The respiratory pathway, therefore act as catabolic as well as anabolic pathway. So it is better to call it amphibolic pathway.

LET US KNOW WHAT WE HAVE LEARNT!

PART: A _VERY SHORT ANSWER TYPE QUESTION:

A)Multiple Choice Type Questions:

Q1. For the fats to be respired, what are they broken into?

(a) Glycerol and Fatty acid

(b) Glycerol and ethanol

(d)Glycerol only

Q2. Which of the following are responsible for degradation of proteins?

(a) Lipases

(b) DNAase

(d) Proteases

Q3. What would happen if organisms need to synthesise fatty acids which had already broken down into acetyl CoA ?

(a) Acetyl CoA would be withdrawn from the pathway.

(b) Acetyl CoA would be further broken down.

(d)Glycerol would be produced

Q4. What is an amphibolic pathway?

(a) Breaking down processes.

(b) Another name for catabolic processes.

(d) Another name for anabolic processes.

Q5. What is common in respiration mediated breakdown of fats, carbohydrates and

proteins.

a) Pyruvic acid

b) Acetyl CoA

c) Glyceraldehyde -3-phosphate

d) Fatty acid and Glycerol

B) TRUE/FALSE:

1. Glycerol would enter the pathway after being converted to malic acid.

2. The respiratory pathway comes into picture in both the breakdown and

synthesis of fatty acids.

3. In respiratory pathway fats are first broken down into glycerol and ethanol.

C) FILL- UPS:

1. is common in respiratory mediated breakdown of fats, carbohydrates

and proteins.

2. Respiratory pathway is pathway.

ANSWER KEY: PART-A

(A)MULTIPLE CHOICE QUESTIONS:

1. (A) Glycerol and fatty acid

2. (D) Proteases

3. (A) Acetyl CoA would be withdrawn from the pathway.

4. (C) Amphibolic pathway means both anabolic as well as catabolic processes.

5. (B) Acetyl CoA

TRUE/FALSE:

1. False (Glycerol is first converted to glyceraldehydes -3 -phosphate)

2. True

3. False (Fats are first broken down to fatty acids and glycerol)

FILL-UPS:

1. Aceyl CoA

2. Amphibolic pathway

PART: B - SHORT ANSWER TYPE QUESTION:

1. What do you mean by catabolism?

2. Why respiratory pathway is known as Amphibolic pathway.

3. What is common in_ respiratory mediated breakdown of fats,carbohydrates and proteins?

PART: C - LONG ANSWER TYPE QUESTIONS:

1. Explain respiratory pathway as an amphibolic pathway with diagram.

A148

INTRODUCTION:Hello students, as we have completed chapter no. 4 respiration in plants.Now we will discuss about differences or comparison type questions.

Some of the important differences in the chapter Respiration in Plants are

described as given below:

Respiration and Combustion

Aerobic and Anaerobic Respiration

Aerobic respiration and Fermentation

Alcoholic fermentation and Lactic acid Fermentation.

Glycolysis and Fermentation.

Glycolysis and Kreb's cycle

A149

IN THIS CHAPTER OF “RESPIRATION IN PLANTS” WE HAVE LEARNT Plants perform photosynthesis to create sugars (such as glucose), this, along with oxygen is used to produce energy which is used in the plant's growth. The process of

releasing energy is called respiration. Respiration is essentially the process

of photosynthesis but in reverse.

C6H120, + 602 —__”_ 6CO2 + 6H20 +32 ATP ( Energy)

RESPIRATION: Respiration is an essential process for all the living being on the planet. The mere fact that taking in oxygen and releasing out carbon dioxide in fractions of seconds gives energy to living organisms, is wonderful.4 The act of breathing in oxygen to metabolise food for the production of energy is called respiration. The process remains the same for all living organisms-plants as well as animals.The process of respiration occurs in the mitochondria and the cytoplasm.

Respiration is defined as the process by which the complex carbon bonds between

compounds are broken down by the process of oxidation within the cells to release

energy.The compounds that get oxidised during this process are called respiratory

substrates. The first set of compounds that are usually utilised as substrates are

carbohydrates, followed by fats and proteins. Energy is released in the form of

ATP.This chapter is thus the gateway to cellular respiration, which deals with the

mechanism of food disintegration inside the cells to discharge energy. ATP, which

are the energy boosters for a cell, is synthesized through the released energy,

which for this purpose is trapped. Respiration is the stepwise oxidation of

complex organic molecules and release of energy as ATP for various cellular

metabolic activities. Various enzymes (biocatalysts) catalyze this process.

LET’S KNOW WHAT WE HAVE LEARNT!!!

NCERT EXERCISE QUESTIONS WITH SOLUTIONS —

QUESTION2: WHAT ARE RESPIRATORY SUBSTRATES?NAME THE MOST COMMON RESPIRATORY SUBSTRATE.

Ans:Respiratory substrates are organic substances. They are oxidized during

respiration to release energy within living cells. Carbohydrates, proteins, fats,

and organic acids are common respiratory substrates. The most common respiratory substrates are glucose (carbohydrates). It is a type of hexose monosaccharide.

QUESTION 3:GIVE THE SCHEMATIC REPRESENTATION OF GLYCOLYSIS.

Ans: Glycolysis is the partial oxidation of glucose or similar hexose sugar into

two molecules of pyruvic acid through a series of enzyme mediated reaction

releasing some ATP and NADR2. It occurs in cytoplasm

QUESTION 4: WHAT ARE THE MAIN STEPS IN AEROBIC RESPIRATION?WHERE DOES IT TAKE PLACE?

Ans: The main steps of aerobic respiration are as follows: Glycolysis, Link

reaction, Krebs cycle and Terminal oxidation.

1. Glycolysis (EMP Pathway): The process of breakdown of glucose into

pyruvic acid is known as glycolysis. Glucose is partially oxidized to form two

molecules of pyruvate, two NADH, and two ATP. This is a common pathway

for both aerobic and anaerobic modes of respiration. It takes place in the

cytoplasm.

2. Link Reaction (Gateway Reaction): Pyruvic acid undergoes oxidative

decarboxylation to form acetyl CoA and NADH. This reaction occurs within

the matrix of mitochondria.

3. Krebs' Cycle (TCA Cycle): The Krebs’ Cycle occurs within the matrix of

mitochondria. The net gain of energy is equal to 24 ATP molecules along

with other products.

4. Terminal Oxidation: Electron Transport System or oxidative phosphorylation takes place in the inner mitochondrial membrane.

QUESTION 5: EXPLAIN ETS. |

Ans: The electron transport system (ETS) is also called Oxidative Phosphorylation. It is present in the inner mitochondrial membrane. It's a metabolic pathway that allows electrons to go from one carrier to the next. The passes of electrons from NADH and FADH2 to oxygen (O2) is facilitated by five multiprotein complexes in the ETS. The complexes are:

Complex | (NADH dehydrogenase),

Complex II (Succinate dehydrogenase),

Complex Ill (Cytochrome bc1 Complex),

Compiex IV (Cytochrome c oxidase) and

Cytochrome V (ATP Synthase).

The steps involved in ETS are as follows:

I. Electrons from NADH produced in the inner mitochondrial matrix during

the citric acid cycle are oxidized by NADH dehydrogenase (Complex 1).

Il. this, electrons are transferred to Ubiquinone which receives reducing

equivalents via FADH2 (Complex Il).

Il. Ubiquinol (reduced ubiquinone) is then oxidized with the transfer of electrons to Cytochrome c via Cytochrome bc1 Complex (Complex III).

IV. Cytochrome c oxidase Complex (Complex IV) contains cytochromes a, a3 and two Cu centers. When electrons travel from one carrier to another in

V. the electron transport chain via complex | to IV, they are connected to ATP Synthase (complex V).

VI. Complex V consists of components like F1 (peripheral membrane protein

complex) and F2 (integral membrane protein complex). At F1 ATP is synthesized from ADP and Pi. Protons passing through channels formed by FO are coupled to the catalytic site of F1.

Vil. One molecule of NADH (oxidized) provides 3 molecules of ATP. One

molecule of FADH2 produces 2 molecules of ATP.

QUESTION 8: WHAT ARE THE ASSUMPTIONS MADE DURING THE CALCULATION OF NET GAIN OF ATP?

Ans:Calculating the net gain of ATP for each glucose molecule oxidized is double, but it could only be a theoretical exercise in practice. These calculations can only be

made based on the following assumptions:

I. There is a sequential, orderly pathway is in function, with one substrate

forming the next and glycolysis, TCA cycle, and ETS pathway occurring

one after the other.

Il. | The NADH produced during glycolysis is transferred to the mitochondria

and undergoes oxidative phosphorylation. None of the intermediates in the pathway is used to make another compound.

Ill. Only glucose is respired. No other alternative substrates enter the

pathway at any of the intermediate stages.

These kinds of assumptions, however, are not valid in a living system. All

pathways occur simultaneously and do not occur one after the other. Substrates

enter the pathways and are withdrawn from them as needed. ATP is used as and

when it is required. Multiple factors influence enzymatic rates. As a result, aerobic respiration of one molecule of glucose can result in a net gain of 36 ATP molecules.

QUESTION 9: DISCUSS “THE RESPIRATORY PATHWAY IS AN AMPHIBOLIC

Ans: The amphibolic pathway is the one that is used for both breakdown

(catabolism) and build-up (anabolism) reactions. Respiratory pathways are

mainly a catabolic process that serves to run the living system by providing energy.

Several intermediates are produced by the respiratory pathway. Many of them

serve as raw materials for the formation of both primary and secondary metabolites.

Acetyl CoA is essential not only for the Krebs cycie but also for the synthesis of

fatty acids, aromatic compounds, steroids, terpenes and carotenoids. In amination,

a-ketoglutarate forms glutamate (an important amino acid). In amination, OAA

(Oxaloacetic acid) produces aspartate. Aspartate and glutamate are components

of proteins.When fatty acids are used as a substrate, they are broken down to acetyl CoA before entering the respiratory pathway. Acetyl CoA is withdrawn from the

respiratory pathway when the organism needs to synthesize fatty acids.As a result, the respiratory pathway is involved in both the breakdown and synthesis of fatty acids.

Similarly, respiratory intermediates serve as a link during the breakdown and

synthesis of proteins. Catabolism is the breaking down processes within a living

organism, while anabolism is the synthesis of new ones. Since the respiratory

system is engaged in both anabolism and catabolism in plants, it is better to think

of it as an amphibolic instead of a catabolic pathway.

QUESTION 10: DEFINE RQ. WHAT IS ITS VALUE FOR FATS?

Ans:Respiratory quotient (RQ) or respiratory ratio can be defined as the ratio of the volume of CO2 evolved to the volume of O2 consumed in respiration over a given period. The value of respiratory quotient depends on the type of respiratory

substrate. Its value can be equal to one, zero, more than one or less than one.

RQ= Volume of CO2 evolved / Volume of O2 consumed Its value is one for carbohydrates. However, it is always less than one for fats as fats consume more oxygen for respiration than carbohydrates.

It can be illustrated through the example of tripalmitin fatty acid, which consumes

145 molecules of O» for respiration while 102 molecules of CO» are evolved. The

RQ value for tripalmitin is 0.7.

QUESTION 11: WHAT IS OXIDATIVE PHOSPHORYLATION?

Ans:The process by which ATP is formed as a result of the transfer of electrons from

NADH or FADH: (electron donors) to O: (electron acceptor) by a series of electron

carriers is known as oxidative phosphorylation. The oxidation-reduction reactions are involved in the formation of proton gradient. This process, which occurs in mitochondria, is the primary source of APT in aerobic organisms.For example, when glucose is completely oxidized to CO. and H.2O, oxidative phosphorylation generates 26 of the 30 molecules of ATP.

12: WHAT IS THE SIGNIFICANCE OF THE STEPWISE RELEASE OF ENERGY IN RESPIRATION?

Ans: The following are the benefits of stepwise release of energy in

respiration:

1) There is a gradual release of chemical bond energy, which is easily trapped in

the formation of ATP molecules.

2) The temperature of the cell is not allowed to rise.

3) Energy waste is reduced.

4) A variety of intermediates can be used in the production of a variety of

biochemicals.

5) Different substances can undergo respiratory catabolism via their metabolic

intermediates.

6) Each step of respiration is regulated by its enzyme. Specific compounds can

either increase or decrease the activity of various enzymes. This aids in controlling the rate of respiration as well as the amount of energy released.

A150

RECAPITULATION:Plants also breathe. During respiration plants take in oxygen and release carbon dioxide. The breaking of C-C bonds of complex compounds through oxidation within cells leading to release of energy is called respiration. It is an exergonic and catabolic-physico-chemical process. Respiration occurs in three phases:

1. External respiration

2. Internal respiration

3. Cell respiration.

According to dependence on oxygen, the cellular respiration can be classified in

two types:

AEROBIC RESPIRATION

ANAEROBIC RESPIRATION

AEROBIC RESPIRATION It occurs inside mitochondria and is divided in 4 phases:-

Glycolysis is also called EMP Pathway and pyruvic acid is the key product.

Oxidative decarboxylation is aerobic oxidation and decarboxylation of

pyruvic acid obtained from glycolysis.

The TCA cycle starts with condensation of acetyl group with oxaloacetic acid

(OAA) and water to yield citric acid.

Electron transport system is present inside inner mitochondrial membrane and it is the metabolic pathway through which electron passes from one carrier to another.

ANAEROBIC RESPIRATION Also called as Fermentation, here the incomplete oxidation glucose is achieved under anaerobic conditions where pyruvic acid is converted to ethanol and CO2.

LET US KNOW WHAT WE LEARN?

PCS

Ans. It is an exergonic and catabolic physio-chemical process which

Involves exchange of O2 and CO2 through liquid medium and oxidation of

Glucose..

Ans. The nutrients which provide energy by its oxidation inside the body Tissue is called respiratory fuel.

Ans. Glucose

Ans. 2ATP, 2GTP.

Ans. Glycolysis.

Ans. When proteins are used as respiratory fuel then it is called Protoplasmic respiration.

Ans. Amphibolic pathway is that pathway which is both anabolic and catabolic in nature. Respiratory pathway is mainly catabolic releasing energy in steps. The intermediate for this functions as raw materials for anabolic synthesis of a number of organic substancesfrom acetyl CoA.

Ans. Convertion of ADP or ATP by the electron transport system in aerobic

respiration is called oxidative phosphorylation. During this process the

pphosphorylation occurs in the inner mitochondrial membrane when hydrogen

protons pass through ATP synthetase complex. The energy required, for

phosphorylation comes from oxidation reduction process in respiration and

therefore, the process is called oxidation phosphorylation.

Ans. Anaerobic respiration produces very little energy i.e., about 5% as

compared the aerobic respiration. The reasons are :

1) There is incomplete breakdown of respiratory substrate

2) At least one of the products of anaerobic respiration is organic. It can be

further oxidised to release energy.

3) NADH is produced during glycolysis is often used up.

4) ATP formation does not occur during regeneration of NAD+.

5) Electron transport chain is absent.

6) Oxygen is not used for receiving electrons and protons.

Ans. Glycerol phosphate shuttle system and maltate asparate shuttle

system.

Ans. Glycolysis is stepped process by which one molecule of glucose breaks into 2 molecules of pyruvic acid.

Ans. When carbohydrates and fats are used as fuel, it is called floating respiration.

Ans. Peter Mitchell proposed chemiosmatic mechanism of ATP synthesis which states that ATP synthesis occur due to H+ flow through a membrane.

Ans. The difference in H+ concentration across inner mitochondrial

membrane is called proton gradient.

Ans. The proton gradient and membrane electric potential collectively

called proton motive force.

eC‘

Ans. Glycolysis is also known as Embden-Meyerhof pathway. It occurs in cytoplasm. The various steps involved in glycolysis are as follows:-

1. Phosphorylation of glucose: Glucose is converted into glucose-6- phosphatewith the help of ATP. The reaction is carried in the presence of enzyme hexokinase and Mg++.

2. lsomerisation : Glucose- 6- phospate is converted into its isomer fructose-6- phosphate. This reaction takes place in presence of enzyme phosphoglucoisomerase .

3. Phosphorylation : Fructose 6-phosphate is again phosphorylated by means of ATP in the presence of phosphofructokinase.

4.Splitting : fructose 1,6-diphosphate splits up into 3-carbon compounds.

These are glyceraldehydes 3-phosphate and dehydroxyacetone 3- phosphate. DHAP is changed into glyceraldehydes -3-phiosphate in the presence of enzyme phosphotrioseisomerase.

5. Dehydrogenation and Phosphorylation: Glyceraldehyde-3-phosphate losses hydrogen to NADto form NADH2 and use inorganic phosphate to form 1,3-diphosphoglycerate. The reaction is catalysed by enzyme glyceraldehyde phosphatedehydrogenase.

6. Formation of ATP: One phosphate bond of 1,3-diphosphoglycerate is linked by high energy bond and produces ATP in the presence of enzyme phosphoglycerate kinase.

7.lsomerisation: 3-phosphoglycerate is changed to isomer 2- phosphoglycerate in the presence of enzyme phosphoglyceromutase.

8. Dehydration: 2-phosphoglycerate is changed into phosphoenol pyruvate

in the presence of enzyme enolase and cofactor Mg++.

9. Formation of ATP_ and Pyruvate: phosphate bond of PEP carries higher

amount of energy. It is transferred toADP by enzyme pyruvate kinase,Mg++and K+. This produces ATP and Pyruvate.