1. To know the importance of chemical energy in biological processes 2. To understand the role of ATP 3. To draw the structure of ATP 4. 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

Respiration Energy is released in respiration A 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 Anaerobic respiration – takes place in absence of oxygen

The role of ATP (adenosine triphosphate) The short term energy store of the cell Often 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 energy The 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 + P i + 30 KJ mol -1 (H 2 O) (ATPase) ATP ADP + P i + 30 KJ mol -1 (H 2 O) Draw the hydrolysis of ATP on page 286

The 2 nd 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 + P i + 30 KJ mol -1 (H 2 O) (ATPase) ADP AMP + P i + 30 KJ mol -1 (H 2 O) 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 ATP Instant 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 wate r NADH FADH 2 CO 2

Draw glycolysis reaction on page Glucose (6C) phosphorylated to Glucose phoshate (6C) The phosphate comes from ATP Glycolysis -the splitting of glucose 3. Glucose phosphate (6C) phosphorylated to fructose biphosphate (6C) 4. Fructose biphosphate (6C) is split into two molecules of glycerate 3 phosphate 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) 7. 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 + CO 2 1. Pyruvate decarboxylated - CO 2 removed 1. Pyruvate decarboxylated - CO 2 removed 2. Pyruvate dehydrogenated – hydrogen removed 2. Pyruvate dehydrogenated – hydrogen removed 3. Acetate (2C) combines with coenzyme A 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 cycle in matrix of mitochondria Draw Krebs cycle on page 288