BIOLOGY - 12Advanced

• Introduction :Organic compounds store potential energy.With the help of enzymes a cell systematically breaks-down

complex organic molecules ( E ↑ ) to simpler substances ( E↓ )Some of energy released can be used to do work. The rest ( most ) lost as heat.

Complex org. molec. ( E ↑ )

simple substances ( E↓ )

Systematic breaking-down energy

Cellular activities

Heat

UNIT–1 : Biological energetics

Mitochondria

• Respiration : breaking-down of food molecules to produce energy.

• There are two types of respiration :

Aerobic respiration Anaerobic respirationBreaking-down of food molecules Breaking-down of food molecules In the presence of oxygen in the absence of oxygen to produce energy to produce energy

Respiration

Glucose lactic acid + energyC6H12O6 2 C3H5O3 + energy

Glucose alcohol + CO2 + energyC6H12O6 2 C2H5OH + 2 CO2 + energy

Glucose + oxygen carbon dioxide + water + energy

C6H12O6 + O2 6CO2 + 6 H2O + 38 ATP

Respiration

Type of respiration Aerobic Anaerobic

Oxygen With Without

Oxidation of glucose Complete Incomplete

Energy yield High Low

Products CO2 and H2O Lactic acid or alcohol + CO2

Compare between aerobic and anaerobic respiration.

• Energy produced in respiration can be used in :1. Muscle working.

2. Active transport.

3. Nerve impulses.

4. Biosynthesis.

5. Keeping body temperature constant.• BUT

remember that : not all energy is used up a lot is lost as heat.

Respiration

• Compare respiration with combustion :

Respiration

Respiration Combustion

Inside the cell Outside the cell

Enzyme regulated No enzymes

Energy produced step-by-step

Energy produced at once

Slow Fast

• Occur in the absence of O2.

• Occur totally in cytoplasm.

• The cell is incompletely oxidize glucose.

• Produce little amount of energy ( 2 ATP ) so most of the energy remains in the organic molecule.

• It is a 2 stages process :1. Glycolysis.

2. Regeneration of NAD+.

• Two types :1. Lactic acid fermentation ( in animals ).

2. Alcoholic fermentation ( in plants ).

Anaerobic respiration• Occur in the absence of O2.

• Occur totally in cytoplasm.

• The cell is incompletely oxidize glucose.

• Produce little amount of energy ( 2 ATP ) so most of the energy remains in the organic molecule.

• It is a 2 stages process :1. Glycolysis.

2. Regeneration of NAD+.

• Two types :1. Lactic acid fermentation ( in animals ).

2. Alcoholic fermentation ( in plants ).

Regeneration of NADGLYCOLYSIS

• Note : only the first stage of anaerobic resp. produces ATP, so what is the importance of the second stage?[ If the supply of NAD stops anaerobic respiration stops ]

• The second step Regenerate NAD from NADH by reduction of pyruvate.so production of ATP continue.

Anaerobic resp.

NAD

NADH

Glucose

Pyruvic acid

Lactic acid

ATP

• Why does the athlete breathe heavily for several minutes after the race?

During the rapid exercise the body can`t supply enough oxygen to the muscle.

( developing oxygen dept )So, the muscle begin to produce ATP by lactic acid fermentation.Building of lactic acid cause a painful sensation.

• What is the fate of lactic acid?Oxidised by liver.

Lactic acid fermentation

ATP ( Adenosine triphosphate )- A nucleotide.- Acts as an energy currency of the cell.

( intermediary molecule between energy producing and energy consuming reactions )

- Structure :1. Adenine base.2. Ribose sugar.3. Three phosphate groups.

- How does ATP synthasize in respiration?1. Substrate level phosphorylation ( in glycolysis & krebs cycle )2. Oxidative level phosphorylation ( in electron transport chain )

ATP structure and function

Aerobic respiration

• Occur in the cytoplasm of all living organisms.

• No need for oxygen.

• Glucose is broken down into two pyruvates.

• This process consists of three stages:

1. Glycolysis

C C C C C C GlucoseATP

ADP

C C C C C C P

C C C C C C PP

Glucose phosphate

C C C PC C CP PGAl

PyruvateC C C

ATP

ADP

ATP

ADP

ATP

ADPNAD

NADH

NAD

NADH

Glycolysis

Fructose-1,6-diphosphate

C C C

Activation stage

Splitting stage

Oxidation anf rearrangement

C C C C C C P Fructose phosphate

1. Glucose molecule activated by 2 ATP to form hexose diphosphate.

2. The hexose diphosphate split into 2 triose phosphate.

3. The trioses oxidised in energy yielding phase to produce 2 pyruvate.

4. 4 ATP and 2 NADH2 produced

2 Pyruvate

Glucose 2 ATP ( 4 - 2 )

2 NADH2

Glycolysis

In the presence of oxygen pyruvic acid enters the matrix of mitochonderia and three things happen :1. Decarboxylation : CO2 molecule removed from the pyruvic acid.2. Dehydrogenation : hydrogen removed and transferred to NAD+ to form

NADH.H+.3. The resulting acetate ( 2C ) combines with coenzyme A ( CoA ) forming :

acetyle CoA which enters the krebs cycle.

The link reaction

Pyruvate ( 3C )

CO2 NAD+ NADH.H+

CoA

Acetyle CoA ( 2C )

Remember : - 2 pyruvate molecules are formed from each glucose molecule. - So, the reaction happen twice and 2 Acetyle CoA resulted with 2 NADH.H+

It takes place in the matrix of mitochondria and includes the following reactions :

1. Acetyle CoA combine oxaloacetate ( 4C ) to form 6C compound ( citrate ).

• A series of reactions takes place where the citrate both decarboxylated and dehydrogenated.

– CO2 is released as waste product.

– Hydrogen is picked up by 2 electron acceptors ( NAD & FAD )

• As a result the oxaloacetate is regenerated to combine with more acetyl CoA.

Krebs cycle

Krebs cycle

For each 1 turn of Krebs cycle : For each 2 turns of Krebs cycle :

- 3 NADH.H+ produced. - 6 NADH.H+ produced.

- 1 FADH2 produced. - 2 FADH2 produced.

- 1 ATP molecule produced. - 2 ATP molecule produced.

- 2 CO2 molecules released. - 4 CO2 molecules released.

Krebs cycle

Electron transport chain

Where does the energy that was in the glucose molecule has gone?

- Most is still in the reduced coenzymes ( NADH, FADH )

- Only 4 ATP molecules produced directly ( by substrate level phosphorylation )

from 1 glucose molecule ( 2 from glycolysis + 2 from krebs cycle )

What is the final stage of aerobic respiration? What is its importance?

electron transport chain ( e.t.c. )

importance : - couples the transport of electrons with the production of ATP

- most of ATP is produced during this stage

by oxidative phosphorylation

Electron transport chain

Where in the cell does e.t.c. occur?

in the cristae of the inner membrane of mitochondria.

Components of the e.t.c. :

- group of carrier proteins

( cytochromes )

- ATP synthase protein.

Cytochrome complexes

Electron transport chain

How does the mitochondria couple the transport of electrons with ATP synthesis?

( CHEMIOSMOSIS )

- High energy electrons from NADH and FADH2 are passed to e.t.c.

- These electrons are passed from carrier protein to the next .

- At the end of the chain there is an enzyme that combine these electrons with H+

and oxygen to form water.

- As the electrons passes along the chain, they lose most of their energy.

- This energy is used to pump hydrogen ions across the inner membrane

( from the matrix to the intermembrane space ).

- H+ gradient is created across the inner membrane.

- H+ diffuses down the proton gradient through the ATP synthase protein.

- The diffusion of H+ drives the phosphorylation of ADP to ATP

Chemiosmosis

Electron transport chain

How many ATP molecules produced for each :

- 1 NADH 3 ATP

- 1 FADH2 2 ATP

What is the function of oxygen in respiration?

oxygen serves as the final electron acceptor in the electron transport

chain.

so oxygen is essential for getting rid of low-energy electrons and hydrogen

ions, the wastes of cellular respiration.

What is the importance of e.t.c.?

1. release energy from NADH and FADH2 to be stored ( temporary ) in ATP.

1. Regenerate NAD and FAD so that the process of respiration proceeds

from glycolysis to link-reaction and krebs cycle.

Why does the an aerobic respiration stops after glycolysis ? ? ! !

TOTALS

Glycolysis

Link reaction

Krebs cycle

2 ATP 2 NADH

2 ATP 2 NADH

2 ATP 6 NADH 2 FADH2

2 ATP

e.t.c.

4ATP 18ATP 6ATP 6ATP

4 ATP directly produced 34 ATP indirectly produced

38 ATP is produced / 1 glucose

- Food gives us energy.

- Carbohydrates and fats are high energy foods.

- Energy of food is measured in kJ ( 1 kJ = 1000J ).

- To measure the amount of energy in food :

1. Burn the food to give-out energy.

2. Use energy to heat-up water.

3. The hottest water the more

energy content.

RESULTS

mass of peanut ( g ) Temp. of water ( start ) Temp. of water ( end )Temp. riseOf water

3.5 28.5 65.0 ??

3.5 g

65

28.5

20 ml

Calculations :

Temperature rise ( ΔT ) = end temp. – start temp.

= 65 - 28.5

= 36.5 C

Energy ( J ) = temperature rise X 20 X 4.2

= 36.5 X 20 X 4.2

= 3066 J

Energy content ( J/g ) = energy give ( J ) / weight of peanut ( g )

= 3066 / 3.5

= 876 J/g

= 0.876 kJ/g