AQA A Level Biology - Respiration

What is the purpose of respiration ?

To release energy from glucose

To produce ATP

What is the general equation for aerobic respiration ?

6O2 + C6H1206 --> 6H2O + 6CO2 + energy

What do plants need energy for ? (name 5)

1. Photosynthesis

2. Active transport of minerals via roots

3. DNA replication,

4. Cell division,

5. Protein synthesis

What do animals need energy for ? (name 6)

1. Muscle contraction

2. Maintaining a constant body temperature

3. Active transport

4. DNA replication

5. Cell division

6. Protein synthesis

What is the chemical name for ATP?

Adenosine triphosphate

What are the 3 components of ATP?

1 molecule of adenine

1 molecule of ribose

3 molecules of phosphate ions

How is ATP formed?

Condensation reaction between adenosine diphosphate (ADP) and inorganic phosphate (Pi)

Catalysed by ATP synthase

Which enzyme catalyses the condensation reaction between ADP and Pi ?

ATP synthase

What is phosphorylation ?

Adding phosphate to a molecule

How does ATP move through the cell ?

Diffusion

Which enzyme catalyses the hydrolysis of ATP ?

ATP hydrolase

What are the 6 properties of ATP ?

1. Stores and releases small amount of energy so none wasted as heat

2. Small, soluble molecule so easily transported

3. Easily hydrolysed so energy releases instantly

4. Quickly resynthesised

5. Make other molecules more reactive (phosphorylation)

6. Can't pass out of cell so immediate energy supply

What is the compensation point ?

The level of light intensity (in plants) where the rate of respiration and photosynthesis are the same

How could you find a plant's compensation point ?

Plot a graph of light intensity against net oxygen production

Find the light intensity when net oxygen production =0

What are 3 differences between aerobic and anaerobic respiration ?

1. Aerobic uses oxygen, anaerobic doesn't

2. Aerobic has 4 stages, anaerobic just has glycolysis

3. Aerobic produces CO2 and H2O, anaerobic produced lactic acid (animals) and ethanol (yeast)

Where does glycolysis occur ?

Cell cytoplasm

Which 3 coenzymes are used in (aerobic) respiration ?

NAD, FAD, coenzyme A

Which stage of respiration is an anaerobic process and why ?

Glycolysis

Uses no O2

What are the 2 stages of glycolysis ?

1. Phosphorylation of glucose

2. Oxidation of triose phosphate

What is the purpose of glycolysis ?

To produce pyruvate from glucose

Describe what happens when glucose is phosphorylated (3 stages)

1. ATP donates Pi to glucose to form glucose phosphate (and ADP)

2. ATP donates Pi to glucose phosphate to form hexose bisphosphate (and ADP)

3. Hexose bisphosphate split to form 2 molecules of triose phosphate

Describe what happens when 2 molecules of triose phosphate is oxidised

2 molecules of triose phosphate are oxidised to 2 molecules of pyruvate

2 molecules of NAD are reduced to reduced NAD

4 molecules of ATP are produced from 4 molecules of ADP/Pi

What is the net production of ATP in glycolysis ?

2 ATP

2 used and 4 produced

What is the reduced NAD produced in glycolysis used for ?

Oxidative phosphorylation

What is the pyruvate produced in glycolysis used for ?

Actively transported into the mitochondrial matrix

Link reaction

Why does glycolysis take place in the cytoplasm ?

Glucose can't cross the mitochondrial membrane

It's too big

Describe the process after glycolysis in yeast/plants (2 stages)

1. Pyruvate loses CO2 to form ethanal

2. Ethanal reduced to ethanol and reduced NAD oxidised to NAD

What is the purpose of anaerobic respiration ?

To produce ATP by glycolysis

Oxidises reduced NAD from glycolysis to NAD to allow glycolysis to continue

Describe the process of lactate fermentation

Pyruvate reduced to lactate (lactic acid)

Reduced NAD oxidised to form NAD

Where does the link reaction occur ?

Matrix of the mitochondria

What is the purpose of the link reaction ?

To convert pyruvate to acetyl coenzyme A

Describe what happens during the link reaction

1. Pyruvate is decarboxylated to form acetate

2a. Pyruvate is oxidised to acetate

2b. NAD is reduced to reduced NAD

3. Coenzyme A combines with acetate to form acetyl coenzyme A

Where is the acetyl coenzyme A used ?

Krebs Cycle

Where is the reduced NAD used ?

Oxidative phosphorylation

What happens to the CO2 produced in the link reaction ?

Lost as a waste product

What happens in the Krebs Cycle ?

ATP and reduced coenzymes are produced in a series of redox reactions

CO2 is lost as a waste product

Where does the Krebs Cycle take place ?

Matrix of the mitochondria

Describe what happens in the Krebs Cycle

1. Aceyl CoA reacts with a 4 carbon compound to form a 6 carbon compound and coenzyme A

2. The 6 carbon compound forms a 5 carbon compound

3. The 5 carbon compound reforms the 4 carbon compound

What is substrate level phosphorylation ?

When a phosphate group is directly transferred from one molecule to another

e.g. the production of ATP in the Krebs Cycle

What is the CoA produced in the Krebs Cycle used for ?

The Link Reaction

What are the reduced enzymes produced in the Krebs Cycle used for ?

Oxidative phosphorylation

What is oxidative phosphorylation ?

The process where energy from electrons from reduced coenzymes is used to synthesise ATP

Describe the stages of oxidative phosphorylation

1. NAD/FAD release H atoms (split to H+ and e-)

2. Electrons move down electron transport chain and lose energy at each electron carreir

3. Energy used to actively transport protons into intermembrane space from mitochondrial matrix (forms electrochemical gradient)

4. Protons move down electrochemical gradient into matrix via ATP synthase

5. The protons and electrons combine with oxygen to form water

What is the importance of oxygen in aerobic respiration?

FINAL ELECTRON ACCEPTOR

in oxidative phosphorylation

If there is no glucose, what substances can enter the Krebs Cycle ?

Breakdown products of lipids

Amino acids

REQUIRED PRACTICAL