Respiration

Question 1

Why do organisms need to respire ?

Answer 1

Respiration Produces ATP as an energy currency for:
- Active transport against concentration gradients e.g. to absorb nutrients from small intestine/soil
- Metabolic reactions e.g. to form peptide bonds in protein synthesis
- Muscle contraction
Release heat energy for thermoregulation

Question 2

Describe the structure of mitochondria

Answer 2

Surrounded by a double membrane
Folded inner membrane forming the Cristae: Site of electron transport chain
Fluid matrix: Contains mitochondrial DNA, Respiratory enzymes,lipids,proteins

Question 3

Name the 4 main stages in aerobic respiration and where they occur

Answer 3

• Glycolysis : Cytoplasm
• Link Reaction : Mitochondrial matrix
• Krebs Cycle : Mitochondrial matrix
• Oxidative Phosphorylation via electron transfer chain : membrane of cristae

Question 4

Outline the stages of glycolysis

Answer 4

1. Glucose is phosphorylated to hexose bisphosphate by 2x ATP
2. Hexose bisphosphate splits into 2x triose phosphate (TP)
3. 2x Triose Phosphate is oxidised to 2x pyruvate
   Net gain of 2x reduced NAD & 2x ATP per glucose

Question 5

Draw a flowchart to represent what happens during glycolysis

Answer 5

Refer to GoodNotes

Question 6

How does pyruvate from glycolysis enter the mitochondria ?

Answer 6

Via active transport

Question 7

What happens during the links reaction ?

Answer 7

1. Oxidation of pyruvate to acetate.
   Per pyruvate molecule : net gain of 1 x CO² (decarboxylation) & 2H atoms (Used to reduce 1xNAD)
2. Acetate combines with coenzyme A (CoA) to form Acetylcoenzyme A

Question 8

Give a summary equation for the link reaction

Answer 8

Pyruvate + NAD + CoA —> Acetyl CoA + Reduced NAD + Co²

Question 9

What happens in the Krebs cycle ?

Answer 9

series of redox reactions produces:
-ATP by substrate-level phosphorylation
-Reduced coenzymes
-Co² from decarboxylation
Begins when acetyl group from Acetyl CoA (2C) reacts with oxaloacetate (4C). Cycle regenerates oxaloacetate

Question 10

Outline the stages of the Krebs Cycle

Answer 10

Refer to GoodNotes

Question 11

What is the electron transfer chain (ETC) ?

Answer 11

• Series of Carrier proteins embedded in membrane of the cristae of mitochondria
• Produces ATP through oxidative phosphorylation via chemiosmosis during aerobic respiration

Question 12

What happens in the electron transfer chain (ETC)

Answer 12

• Electrons released from reduced NAD & FAD undergo successive redox reactions
• The energy released is coupled to maintaining a proton gradient or released as heat
• Oxygen acts as final electro acceptor

Question 13

How does chemiosmosis produce ATP during aerobic respiration ?

Answer 13

• Some energy released from the ETC is coupled to activate the transport of H+ ions (protons) from mitochondrial matrix into inter membrane space
• H+ ions move down concentration gradient into mitochondrial matrix via channel protein ATP synthase.
• ATP synthase catalyses ADP + Pi —> ATP

Question 14

State the role of oxygen in aerobic respiration

Answer 14

Final electron acceptor in electron transfer chain
(Produces water as a byproduct)

Question 15

Name the stages in respiration that produce ATP by substrate-level phosphorylation

Answer 15

• Glycoloysis (Anaerobic)
• Krebs Cycle (aerobic)

Question 16

What happens during anaerobic respiration in animals ?

Answer 16

Only glycolysis is able to continue
Reduced NAD + Pyruvate —> NAD + Lactate
Lactate will bind with oxygen in the liver forming Glucose, to be used in glycolysis

Question 17

What happens during anaerobic respiration in some microorganisms e.g. yeast and some plant cells ?

Answer 17

• Only glycolysis continues so much less ATP is produced compared to aerobic respiration
• Pyruvate is decarboxylation to from ethanal
• Ethanal is reduced to ethanol using reduced NAD to produce oxidised NAD for further glycolysis

Question 18

Draw a low chart to show how ethanol is produced during anaerobic respiration

Answer 18

Refer to GoodNotes

Question 19

What are the benefits of being able to respire Anaerobically ?

Answer 19

• ATP production for vital metabolic processes continue
• Production of ethanol/lactate converts reduced NAD back into NAD so glycolysis can continue = maximum yield of ATP in the conditions

Question 20

Suggest how a student could investigate the effect of a named variable on the rate of respiration of a single-called organism

Answer 20

1. Use respirometer (pressure changes in boiling tube cause a drop of coloured liquid to move)
2. Use a dye as a terminal electron acceptor for the ETC

Question 21

What is the purpose of sodium hydroxide solution in a respirometer set up to measure the rate of aerobic respiration?

Answer 21

Absorbs CO² so that there is a net decrease in pressure as O² is consumed

Question 22

How could a student calculate the rate of respiration using a respirometer?

Answer 22

Volume of O² Produced or CO² consumed/time x mass of sample

Volume = Distance moved by coloured drop x (0.5 x capillary tube diameter)² x π

Question 23

Name 2 types of molecules that can be used as alternative respiratory substrates

Answer 23

• Amino Acids from proteins
• Glycerol and fatty acids from lipids

Question 24

What is the respiratory quotient (RQ) ?

Answer 24

RQ = carbon dioxide produced / oxygen consumed

Can be used to determine :
- Respiratory substrate being used (carbohydrates: 1.0, lipids: 0.8, proteins 0.9)
- If organism is undergoing anaerobic respiration (anaerobic values are larger)

Question 25

Why do different respiratory substrates have different re;active energy values ?

Answer 25

Depends on the number of hydrogens in the structure which are oxidised to water e.g. the number of hydrogens is greater in fatty acids than carbohydrates