1. To know the importance of chemical energy in biological processes

2. To understand the role of ATP3. To draw the structure of ATP4. To understand the stages in aerobic

respiration: glycolysis, link reaction, Kreb’s cycle and the electron transport chain

1. Movement e.g. movement of cilia and flagella, muscle contraction

2. Maintaining a constant body temperature to provide optimum internal environment for enzymes to function

3. Active transport – to move molecules and ions across the cell surface membrane against a concentration gradient

6. Secretion – the packaging and transport of secretory products into vesicles in cells e.g. in the pancreas

5. Bioluminescence – converting chemical energy into light e.g. ‘glow worms’

4. Anabolic processes e.g. synthesis of polysaccharides from sugars and proteins from amino acids

RespirationEnergy is released in respirationA series of oxidation reactions taking place

inside living cells which releases energy to drive the metabolic activities that take place in cells

Aerobic respiration – takes place in the presence of oxygen

Aerobic respiration – takes place in the presence of oxygen

Anaerobic respiration – takes place in absence of oxygen

Anaerobic respiration – takes place in absence of oxygen

The role of ATP (adenosine triphosphate)The short term energy store of the cellOften called the ‘energy currency’ of the cell

because it picks up energy from food in respiration and passes it on to power cell processes.

Draw the structure of ATP on page 286

ATP made up of:Adenine (a base)Ribose (a pentose sugar)3 phosphate groups

How ATP releases energyThe 3 phosphate groups are

joined together by 2 high energy bonds

ATP can be hydrolysed to break a bond which releases a large amount of energy

Hydrolysis of ATP to ADP (adenosine diphosphate) is catalysed by the enzyme ATPase

(ATPase)

ATP ADP + Pi + 30 KJ mol-1

(H2O)

(ATPase)

ATP ADP + Pi + 30 KJ mol-1

(H2O)Draw the hydrolysis of ATP on page 286

The 2nd phosphate group can also be removed by breaking another high energy bond.

The hydrolysis of ADP to AMP (adenosine monophosphate) releases a similar amount of energy

(ATPase)

ADP AMP + Pi + 30 KJ mol-1

(H2O)

(ATPase)

ADP AMP + Pi + 30 KJ mol-1

(H2O)AMP and ADP can be converted back to ATP by

the addition of phosphate molecules

The production of ATP – by phosphorylation

- Adding phosphate molecules to ADP and AMP to produce ATP

Phosphorylation is an endergonic reaction – energy is used

Hydrolysis of ATP is exergonic - energy is released

Phosphorylation is an endergonic reaction – energy is used

Hydrolysis of ATP is exergonic - energy is released

Advantages of ATPInstant source of energy in the cell

Universal energy carrier and can be used in many different chemical reactions

It is mobile and transports chemical energy to where it is needed IN the cell

Releases energy in small amounts as needed

Answer sample past paper question on sheet

Aerobic respiration –– to release energy 4 main stages

glucose

pyruvate

Acetyl coenzyme A

Hydrogen atoms

Glycolysis

Link reaction

Krebs cycle

Electron transport chain

oxygen water

NADH FADH2

CO2

Draw glycolysis reaction on page 287

1. Glucose (6C) phosphorylated to Glucose phoshate (6C)

1. Glucose (6C) phosphorylated to Glucose phoshate (6C)

The phosphate comes from ATP

The phosphate comes from ATP

Glycolysis -the splitting of glucose

3. Glucose phosphate (6C) phosphorylated to fructose biphosphate (6C)

3. Glucose phosphate (6C) phosphorylated to fructose biphosphate (6C)

4. Fructose biphosphate (6C) is split into two molecules of glycerate 3 phosphate

4. Fructose biphosphate (6C) is split into two molecules of glycerate 3 phosphate

5. Each Glycerate 3 –phosphate (3C) is converted to pyruvate (3C)

5. Each Glycerate 3 –phosphate (3C) is converted to pyruvate (3C)

6. H+ is removed and transferred to the hydrogen acceptor NAD (nicotinamide adenine dinucleotide)

6. H+ is removed and transferred to the hydrogen acceptor NAD (nicotinamide adenine dinucleotide)7. 2 x 2 ATP produced7. 2 x 2 ATP produced

Glycolysis in detail

Takes place in cytoplasm of cells

Does not need oxygen – first stage of aerobic respiration and only stage of anaerobic respiration

Although glycolysis yields energy it does need an input of energy to get the reaction started

Glycolysis – overview

Glycolysis produces from 1 molecule of glucose:

2 molecules of ATP in total (4 ATP are produced but 2 are used at the start)

2 molecules of NADH2 (reduced NAD)2 molecules of pyruvate to enter the link

reaction

Glycolysis produces from 1 molecule of glucose:

2 molecules of ATP in total (4 ATP are produced but 2 are used at the start)

2 molecules of NADH2 (reduced NAD)2 molecules of pyruvate to enter the link

reaction

The link reaction in mitochondria in presence of oxygen

Pyruvate (3C)

Acetate (2C)

Coenzyme A

Acetyl coenzyme A

NAD+

NADH + H+CO2

1. Pyruvate decarboxylated - CO2 removed

2. Pyruvate dehydrogenated – hydrogen removed

3. Acetate (2C) combines with coenzyme A

Don’t forget this happens TWICE as 2 molecules of pyruvate are formed from each glucose molecule

Krebs cyclein matrix of mitochondria

Draw Krebs cycle on page 288