Ch 12 Respiration

Question 1

What is the GCSE equation for respiration?

Answer 1

C6H12O6 + 6O2 → 6CO2 + 6H2O + energy transferred

Question 2

What is the main function of respiration?

Answer 2

Formation of ATP

Question 3

Why is ATP a better intermediate source for energy than glucose

Answer 3

ATP hydrolysis is a single reaction that releases small amounts of energy with little heat lost to the environment

Question 4

What are the features of mitochondria?

Answer 4

Question 5

What are the two types of phosphorylation of ADP to produce ATP?

Answer 5

1. Substrate-level phosphorylation
2. Oxidative phosphorylation - formation of ATP via the

Question 6

What is substrate-level phosphorylation?

Answer 6

Direct transfer of a phosphate group from a reactive intermediate substrate to ADP

Question 7

What is oxidative phosphorylation?

Answer 7

Formation of ATP via the ETC of aerobic respiration, where oxygen is the final electron acceptor

Question 8

What are coenzymes?

Answer 8

Molecules required by enzymes to function
e.g NAD, FAD, NADP, Co-enzyme A

Question 9

What are the 4 stages of respiration and what happens in each one

Answer 9

Question 10

Where does glycolysis occur?

Answer 10

Cytoplasm
occurs in both aerobic and anaerobic respiration

Question 11

Diagram for glycolysis

Answer 11

Question 12

What happens at each stage of glycolysis

Answer 12

Question 13

What is produced during glycolysis?

Answer 13

2 x reduced NAD, 2 x pyruvate (3C), 4 x ATP

Question 14

What is the link reaction and where does it occur

Answer 14

• Takes place in the matrix of the mitochondria
• Pyruvate moves into the mitochondria by active transport and is oxidised to acetate to combine with acetyl co-enzyme A
• Happens twice for one molecule of glucose
• Involves decarboxylation (removal of CO2)
• Only occurs in aerobic respiration

Question 15

Diagram of the link reaction

Answer 15

Question 16

Overall equation for the link reaction

Answer 16

Pyruvate + NAD + CoA –>acetyl CoA + NADH2 + CO2

Question 17

Diagram of the Kreb’s cycle

Answer 17

Question 18

What are the stages of the Kreb’s cycle

Answer 18

• Acetyl coenzyme A (2C) combines with 4C molecule to produce a 6C molecule, releasing coenzyme A
• The 6C molecule loses 2 x carbon dioxide to give a 4C molecule (decarboxylation)
• 6C molecule is oxidised, and reduced NAD and reduced FAD are produced (redox reactions)
• ATP is produced through substrate level phosphorylation

Question 19

Where does the Kreb’s cycle take place

Answer 19

In the matrix of the mitochondria

Question 20

What are the reactants and products for the link reaction and the Kreb’s cycle

Answer 20

Question 21

Where does oxidative phosphorylation take place?

Answer 21

On the inner mitochondrial membrane

Question 22

Diagram of oxidative phosphorylation

Answer 22

Question 23

What is the final electron acceptor in oxidative phosphorylation?

Answer 23

Oxygen

Question 24

What are the stages of oxidative phosphorylation (similar to photosynthesis)

Answer 24

• rNAD and rFAD are oxidised and the H splits into protons and electrons
• Electrons move to electron transfer chain and electrons are transferred along the ETC by series of redox reactions, releasing energy with each reaction
• Protons (from rNAD and rFAD) are pumped across the inner mitochondrial membrane into the intermembrane space, using energy from redox reactions, establishing proton gradient across the membrane
• Protons move back into the mitochondrial matrix by facilitated diffusion through the channel protein, activating ATP synthase (chemiosmosis)
• Phosphorylation of ADP + Pi to ATP using energy from electrons’ redox reactions and ATP synthase
• Protons combine with electrons from ETC and oxygen to form water
• Oxygen is the final electron acceptor

Question 25

What affects respiratory efficiency

Answer 25

* Total number of ATP produced from a single glucose molecule depends on efficiency of the cell * Heat energy lost to the environment reduces efficiency of energy transfer from glucose to ATP * By releasing energy from glucose in a multi-stage reaction, reduces the amount of energy lost to the environment

Question 26

How are other respiratory substrates used in respiration

Answer 26

Lipids: * Lipids are hydrolysed to glycerol and fatty acids * Glycerol is phosphorylated to form triose phosphate (enters glycolysis) * Fatty acids are broken down to 2C molecules to form acetyl CoA (enter Krebs Cycle) Proteins: * Amino acids deaminated (amino group removed) * If 3C remain – enter as pyruvate * If 4 or 5C remain – enter as Krebs Cycle intermediates

Question 27

Equation for anaerobic respiration in plants

Answer 27

GCSE equation : Glucose --> ethanol + carbon dioxide + energy transferred At the end of glycolysis *pyruvate loses a carbon dioxide molecule * pyruvate is converted to ethanol using H2 from the oxidising of reduced NAD

Question 28

Diagram of anaerobic respiration in plants

Answer 28

Question 29

Equation for anaerobic respiration in animals

Answer 29

GCSE equation: Glucose lactic acid + energy transferred At the end of glycolysis, * pyruvate is converted to lactate using H2 from the oxidising of reduced NAD

Question 30

What is the effect of lactate build-up in muscles?

Answer 30

* Lactate in solution is lactic acid * lactic acid decreases the pH of cytoplasm/tissue fluid * This causes enzymes to denature * This causes muscle fatigue if this occurs in muscles

Question 31

What happens to the lactate produce during anaerobic respiration

Answer 31

* Oxidises to pyruvate in anaerobic conditions * converted to glycogen and stored in the liver

Question 32

What is a respirometer used for?

Answer 32

To measure the rate of respiration (Must be airtight as they rely on pressure changes to work) * An increase in volume leads to an increase in pressure * Movement will always be from an area of higher pressure to an area of lower pressure

Question 33

How is the syringe used to reset the apparatus in a respirometer

Answer 33

Open the three way tap and push air back into the apparatus to reset the manometer fluid

Question 34

What happens in a respirometer in aerobic respiration experiments

Answer 34

* Organisms absorb oxygen and release carbon dioxide by diffusion * Carbon dioxide is absorbed by potassium hydroxide (soda lime) * Absorbed oxygen reduces gas volume and therefore gas pressure * Manometer fluid moves towards the organisms as pressure is now lower in experiment tube compared to the control tube

Question 35

What happens in a respirometer in anaerobic respiration experiments

Answer 35

* Uses yeast as the respiring organism * Layer of oil on top of yeast/glucose solution to make conditions anaerobic * Yeast releases CO2 by diffusion CO2 released increases gas volume and therefore gas pressure * Manometer fluid moves away from yeast as pressure in the experiment control tube is now higher than in the control tube

Question 36

How do you calculate rate of aerobic respiration using a respirometer and what are the units

Answer 36

* Weigh the mass of the woodlice before the experiment * Record the distance moved by the manometer fluid in the set time * Use the radius of the tube and calculate volume as ∏r2 x distance * Divide volume by time, and then divide this by mass of woodlice * Therefore the units are mm^3 s^-1 g^1 (mm cubed per second per gram)