Respiration

Question 1

Stages of
aerobic
respiration

Answer 1

1) Glycolysis
2) Link reaction
3) Krebs cycle
4) Oxidative phosphorylation

Question 2

Location of
glycolysis

Answer 2

Cytoplasm

Question 3

Glycolysis

Answer 3

• Substrate level phosphorylation
  phosphorylation of glucose to
  glucose phosphate, using 2 ATP
• glucose phosphate splits into two
  triose phosphate (3C) molecules
• both triose phosphate molecules
  are oxidised (reducing NAD) to form
  2 pyruvate molecules (3C)
• releases 4 ATP molecules
• Net gain of 2 ATP and reduced NAD

Question 4

Coenzymes

Answer 4

• A molecule which aids / assists
  an enzyme
• NAD and FAD in respiration both
  gain hydrogen to form reduced
  NAD (NADH) and reduced FAD
  (FADH)
• NADP in photosynthesis gains
  hydrogen to form reduced NADP
  (NADPH)

Question 5

Products of
glycolysis

Answer 5

• Net gain of 2 ATP
• 2 reduced NAD
• 2 pyruvate molecules

Question 6

How many ATP
molecules does
glycolysis produce

Answer 6

• 2 ATP molecules used to
  phosphorylate glycose to
  glucose phosphate
• 4 molecules generated in
  oxidation of triose phosphate to
  pyruvate
• net gain 2 ATP molecules

Question 7

Location of the
link reaction

Answer 7

Mitochondrial matrix

Question 8

Link reaction

Answer 8

• Reduced NAD and pyruvate
  are actively transported to
  matrix
• pyruvate is oxidised to
  acetate (forming reduced
  NAD)
• carbon removed and CO2
  forms
• acetate combines with
  coenzyme A to form
  acetylcoenzyme A (2C)

Question 9

Products of the
link reaction per
glucose molecule

Answer 9

• 2 acetylcoenzyme A molecules
• 2 carbon dioxide molecules
  released
• 2 reduced NAD molecules

Question 10

Location of
the Krebs
cycle

Answer 10

Mitochondrial matrix

Question 11

Krebs cycle

Answer 11

• acetyl coenzyme A releases a two-carbon molecule, which reacts with a four-carbon molecule to produce a six-carbon molecule

4C molecule = oxaloacetate

6C molecule = citrate

• Coenzyme A is freed up to return to the link reaction, where it can combine with more acetate
• a series of oxidation-reduction reactions occur, during with the 6C molecule is converted back into a 4C molecule; during these reactions:

coenzymes NAD and FAD are reduced

ATP is produced by substrate-level phosphorylation

carbon dioxide is lost

Question 12

Products of the
Krebs cycle per
glucose

Answer 12

• per glucose = 2 turns of the
  cycle
• 8 reduced coenzymes
  6 reduced NAD
  2 reduced FAD
• 2 ATP
• 4 carbon dioxide

Question 13

Location of
oxidative
phosphorylation

Answer 13

Cristae of mitochondria

Question 14

Mitochondria
structure

Answer 14

• Double membrane with inner
  membrane folded into cristae
• enzymes in matrix

Question 15

Role of reduced
coenzymes in
oxidative
phosphorylation

Answer 15

• Accumulate in mitochondrial
  matrix, where they release their
  protons (H+) and electrons (e-)
• regenerate NAD and FAD to be
  used in glycolysis/ link reaction
  / Krebs cycle

Question 16

Role of electrons
in oxidative
phosphorylation

Answer 16

• Electrons pass down series of
  electron carrier proteins, losing
  energy as they move
• energy released pumps H+ from
  the mitochondrial matrix to the
  intermembrane space
• electrochemical gradient
  generated

Question 17

How is ATP made
in oxidative
phosphorylation

Answer 17

• Protons move down
  electrochemical gradient back
  into matrix via ATP synthase
• ATP created
• movement of H+ is
  chemiosmosis

Question 18

Role of oxygen
in oxidative
phosphorylation

Answer 18

• Oxygen is the final electron
  acceptor in electron transfer
  chain
• oxygen combines with protons
  and electrons to form water
• enables the electron transfer
  chain to continue

Question 19

How would lack
of oxygen affect
respiration

Answer 19

• Electrons can’t be passed along the
  electron transfer chain
• Oxygen is the final electron acceptor in
  the electron transport chain
• → Without it, oxidative phosphorylation
  stops, and no ATP is produced by the
  mitochondria
• the Krebs cycle and link reaction stop
  because NAD and FAD (converted from
  reduced NAD/FAD as they release their H
  atoms for the ETC), cannot be produced

Question 20

Oxidation

Answer 20

• Loss of electrons
• when a molecule loses hydrogen

Question 21

Reduction

Answer 21

• Gain of electrons
• a reaction where a molecule
  gains hydrogen

Question 22

Location of
anaerobic
respiration

Answer 22

• Cytoplasm
  glycolysis only source of ATP

Question 23

Anaerobic
respiration in
plants & microbes

Answer 23

• Pyruvate produced in glycolysis
  is reduced to form ethanol and
  CO2
• pyruvate gains hydrogen from
  reduced NAD
• reduced NAD oxidised to NAD so
  can be reused in glycolysis
• 2 ATP produced

Question 24

Anaerobic
respiration
animals

Answer 24

• Pyruvate produced in glycolysis
  is reduced to form lactate
• pyruvate gains hydrogen from
  reduced NAD
• reduced NAD oxidised to NAD so
  can be reused in glycolysis
• 2 ATP produced

Question 25

Lipids as respiratory substances

Answer 25

- Glycerol from lipid hydrolysis converted to acetylcoenzyme A - can enter the Krebs cycle

Question 26

Other respiratory substances

Answer 26

- Fatty acids and amino acids can enter the Krebs cycle for continued ATP synthesis - Fatty acids are broken into 2-carbon units that form acetyl-CoA. Amino acids are deaminated and enter the Krebs cycle as various intermediates.

Question 27

Proteins as respiratory substances

Answer 27

Amino acids from protein hydrolysis can be converted to intermediates within Krebs cycle