Biology A2 9700 (12-17)

Explain why the respiration of glucose in anaerobic conditions produces less ATP than in aerobic conditions. [5]

1 only glycolysis / conversion of glucose into pyruvate, occurs; 2 (only) produces 2 molecules of ATP (net); 3 (only) substrate-linked phosphorylation (occurs); 4 pyruvate converted to lactate or ethanol depending on the organism; 5 lactate or ethanol is energy-rich, but not as much as ATP from aerobic processes; 6 oxygen is not available as final electron acceptor, limiting processes that generate ATP; 7 electron transport chain / chemiosmosis / oxidative phosphorylation does not occur, which is where most ATP is produced in aerobic conditions; 8 no additional substrate-linked phosphorylation from Krebs cycle occurs; 9 the efficiency of ATP production is significantly lower in anaerobic respiration compared to aerobic respiration.

2 (only) produces 2 molecules of ATP (net) ;

3 (only) substrate-linked phosphorylation (occurs) ;

4 pyruvate converted to lactate ;

5 lactate is energy-rich /AW ;

6 oxygen not available as final electron acceptor ;

7 electron transport chain / chemiosmosis / oxidative phosphorylation, does not occur ;

8 most ATP is produced (in aerobic conditions) in, electron transport chain / chemiosmosis / oxidative phosphorylation ;

9 no additional substrate-linked phosphorylation from Krebs cycle

Name the type of reaction that occurs when larger more complex biological molecules are made from smaller molecules. [1]

Anabolic

Explain why ATP is needed in the first part of glycolysis. [2]

1. To phosphorylate glucose

2 stops glucose from leaving the cell

3 activates glucose

4 to make fructose 1,6-bisphosphate

State the precise locations of substrate-linked phosphorylation reactions in aerobic respiration. [1]

Cytoplasm and mitochondrial matrix

Explain what happens to pyruvate in the link reaction in aerobic respiration [2]

1 decarboxylated

2 dehydrogenated

3 acetyl group joins coenzyme A to make acetyl coenzyme A

Describe the differences between the process of chemiosmosis in mitochondria and the process of chemiosmosis in chloroplasts. [3]

MITOCHONDRIA

• oxidative phosphorylation

• occurs in inner mitochondrial membrane

• reduced NAD gives protons

• oxygen final proton acceptor

• makes water

CHLOROPLASTS

• photophosphorylation

• occurs in thylakoid membrane

• photolysis gives protons

• NADP final proton acceptor

• makes NADPH

Outline the role of NAD in respiration in aerobic conditions. [4]

1 acts as coenzyme

2 to dehydrogenase

3 carries hydrogen atoms

4 to ETC for oxidative phosphorylation

5 NAD is reduced then oxidised in ETC

State the total number of molecules of carbon dioxide removed in the link reaction and Krebs cycle for each molecule of glucose respired. [1]

6

Suggest why carbon dioxide is transported in the blood mainly as hydrogen carbonate ions and not as carbonic acid. [1]

Hydrogen carbonate ions prevents decrease in blood pH

Explain why less ATP is produced when yeast respired in anaerobic conditions compared to when yeast respires in aerobic conditions. [5]

In yeast

1 only glycolysis occurs

2 2 ATP produced

3 no oxygen as final electron acceptor

4 so pyruvate does not enter mitochondria

5 Oxidative phosphorylation cycle does not occur

6 Oxidative phosphorylation produce most ATP

7 pyruvate converted to ethanol

8 ethanol still energy-rich

Explain how rice is adapted to grow with its roots submerged in water. [5]

1 low conc. of oxygen in water

2 rice cells have aerenchyma

3 gases diffuse through aerenchyma down to root cells

4 allows aerobic respiration

5 some leaves trap air underwater due to ridges on leaves

6 ethanol produced from respiration under anaerobic conditions

7 root cells can tolerate ethanol

8 root cells produce ethanol due to anaerobic conditions

9 some varieties of rice have high rate of respiration under anaerobic conditions to generate more ATP

State the precise location of glycolysis in the cell. [1]

Cytoplasm

State how the glucose and oxygen requirements of these cancer cells differ from normal cells. [2]

Cancer cells

1 need more glucose

2 need less oxygen

3 produce small amount of ATP per glucose

Define the term respiratory quotient [2]

Volume of carbon dioxide produced divided by volume of oxygen consumed per unit time

Outline the role of carriers in the inner mitochondrial membrane. [2]

1 splits hydrogen into electrons and hydrogen ions

2 electrons move alone ETC, carriers provide energy

3 energy used to pump hydrogen ions into inter membrane space

Explain why it is an advantage to the cell for the inner membrane of the mitochondrion to be folded. [2]

1 increase surface area

2 more carriers for ETC

3 more ATP produced from respiration

Describe the role of inner mitochondrial membrane in chemiosmosis [4]

1 site of ETC

2 pumps hydrogen ions to inter-membrane space

3 causes electrochemical proton gradient

4 protons diffuse to matrix

5 through ATP synthase

6 ADP + Pi —> ATP

7 site of oxidative phosphorylation produce most

Explain how the structure of the inner mitochondrial membrane is linked to its functions [5]

1 it is folded

2 forms large surface area

3 for electron carriers

4 for ATP synthesis

5 it is impermeable to protons

6 so causes high concentration of protons in intermembrane space

7 for proton pumps

Outline two examples of movement in cells that use ATP [2]

1 movement of vesicles through cytoplasm

2 flagella beating

3 exocytosis of digestive enzymes

Compare the pathways by which pyruvate is converted to ethanol or to lactate. [5]

Similarities

1 reduced NAD used in both

2 NAD regenerated in both

Differences

In yeast

• yeast is decarboxylated

• reaction is irreversible

• occurs in two steps

• ethanal accepts Hydrogen

• ethanol dehydrogenase allows ethanal accepts H

In lactate

• lactate not decarboxylated