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Text of Respiration

BIOLOGY - 12Advanced

UNIT1 : Biological energetics 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. Complex org. molec. ( E ) The rest ( most ) lost as heat.Systematic breaking-down energy Cellular activities Heat

simple substances ( E )


Respiration Respiration : breaking-down of food molecules to produce energy. There are two types of respiration :Aerobic respirationBreaking-down of food molecules In the presence of oxygen to produce energy

Anaerobic respirationBreaking-down of food molecules in the absence of oxygen to produce energy

Glucose lactic acid + ose + oxygen carbon dioxide + water + energyenergy C6H12O6 2 C3H5O3 + C6H12O6 + O2 6CO2 + 6 H2O + 38 ATP Glucose alcohol + CO2 + energy energy C6H12O6 2 C2H5OH + 2 CO2 + energy

RespirationCompare between aerobic and anaerobic respiration. Anaerobic Without Incomplete Low Lactic acid or alcohol + CO2 Type of respiration Oxygen Oxidation of glucose Aerobic With Complete High CO2 and H2O

Energy yield Products

Respiration Energy produced in respiration can be used in : Muscle working. Active transport. Nerve impulses. Biosynthesis. Keeping body temperature constant.

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

Respiration Compare respiration with combustion :

RespirationInside the cell Enzyme regulated Energy produced step-by-step Slow

CombustionOutside the cell No enzymes Energy produced at once Fast

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 : Glycolysis. Regeneration of NAD+.

Two types :1. Lactic acid fermentation ( in animals ). 2. Alcoholic fermentation ( in plants ).

Anaerobic resp. 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. GLYCOLYSIS Glucose Regeneration of NAD Lactic acid


ATP Pyruvic acid

Lactic acid fermentation 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

ATP structure and functionATP ( 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?Substrate level phosphorylation ( in glycolysis & krebs cycle ) Oxidative level phosphorylation ( in electron transport chain )

Aerobic respiration

1. Glycolysis 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:

GlycolysisActivation stageC C C C C C


ATP ADPC C C C C C Glucose P



P Fructose phosphate

ATP ADPP C C C C C C Fructose-1,6-diphosphate P

Splitting stageP C C C NAD NADH C C C






Oxidation anf rearrangement

Glycolysis Glucose molecule activated by 2 ATP to form hexose diphosphate. The hexose diphosphate split into 2 triose phosphate. The trioses oxidised in energy yielding phase to produce 2 pyruvate. 4 ATP and 2 NADH2 produced 2 Pyruvate Glucose 2 ATP ( 4 - 2 ) 2 NADH2

In the presence of oxygen pyruvic acid enters the matrix of mitochonderia and three things happen : Decarboxylation : CO2 molecule removed from the pyruvic acid. Dehydrogenation : hydrogen removed and transferred to NAD+ to form NADH.H+. The resulting acetate ( 2C ) combines with coenzyme A ( CoA ) forming : acetyle CoA which enters the krebs cycle.CO2 NAD + NADH. +H Co A

The link reaction

Pyruvate ( ( 3C

Acetyle CoA ( ( 2C

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

Krebs cycleIt 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 : - 3 NADH.H+ produced. - 1 FADH2 produced. - 1 ATP molecule produced. - 2 CO2 molecules released.

For each 2 turns of Krebs cycle : - 6 NADH.H+ produced. - 2 FADH2 produced. - 2 ATP molecule produced. - 4 CO2 molecules released.

Electron transport chain

s the energy that was in the glucose molecule has gone?

still in the reduced coenzymes ( NADH, FADH )

ATP molecules produced directly ( by substrate level phosp

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

e final stage of aerobic respiration? What is its importance transport chain ( e.t.c. )

nce : - couples the transport of electrons with the producti - most of ATP is produced during this stage by oxidative phosphorylation

Electron transport chainWhere 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 chainHow 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.


Electron transport chainHow many ATP molecules produced for each : - 1 NADH - 1 FADH2 3 ATP 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.


GlycolysisLink reaction Krebs cycle









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.g 3.5 ml 20 28.5 65

RESULTSmass of peanut ( g ) 3.5Temp. of water ( start ) Temp. of water ( end ) Temp. rise Of water




Calculations :Temperature rise ( T ) = 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