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