Respiration: aerobic (C1)

Question 1

What is respiration; process type, substrates, energy?

Answer 1

Respiration is a CATABOLIC process involving a series of ENZYME-CATALYSED reactions in cells, where energy-rich RESPIRATORY substrates, e.g. glucose and fatty acids, are broken down to release energy: some is trapped as CHEMICAL energy in ATP and some is released as HEAT energy

Question 2

During respiration what bonds are broken, formed and released?

Answer 2

high energy C-C, C-H and C-OH bonds
are broken, LOWER energy bonds are formed and the
DIFFERENCE is released and used to attach iP to ADP to make ATP

Question 3

Aerobic respiration definition

Answer 3

release of LARGE quantities of ATP energy from glucose or anther organic respiratory substrate in the PRESENCE of OXYGEN
*co2 is produced

Question 4

Anaerobic respiration definition

Answer 4

takes place in the ABSENCE of OXYGEN and produces LACTATE in animal cells and co2 and ETHANOL in yeast cells, with a SMALL yield of ATP energy

Question 5

Aerobic resp. equation

Answer 5

GLUCOSE + OXYGEN —–> CARBON DIOXIDE + WATER + ATP

Question 6

The breakdown of a glucose molecule to carbon dioxide and water in aerobic respiration involves what reactions?
+ where do they take place?

Answer 6

• glycolysis (cytoplasm/cytosol)
• the link reaction (mitochondrial matrix)
• the Krebs cycle (mitochondrial matrix)
• electron transport chain
  (inner mitochondrial matrix/cristae)

Question 7

Energy budget of the breakdown of glucose

under aerobic conditions (overall ATP produced)

Answer 7

38 ATPs per glucose molecule formed as follows:
• net 2 ATPs in glycolysis (substrate-level phosphorylation)
• 0 in the links reaction
• 2 ATPs in the Krebs cycle (substrate-level
phosphorylation)
• 34 ATPs from oxidative phosphorylation (using
chemiosmosis) from 10 reduced NAD (2 from
glycolysis, 2 from the link reaction, six from the
Krebs cycle) and 2 reduced FAD (Krebs cycle).

Question 8

In energy budgets, why is maximum yield never quite reached? estimates?

Answer 8

38 ATPs of maximum yield is never quite reached due to…

• losses (leaky membranes)
• cost of moving pyruvate and ADP into the mitochondrial matrix

*current estimates range at around 30 to 32 ATP per glucose

Question 9

How many reduced NADs and FADs per glucose molecule?

Answer 9

10 reduced NADs (2 glycolysis, 2 links, 6 krebs)

2 reduced FADS (2 krebs)

Question 10

Alternative substrates: how lipids are used in respiration?

Answer 10

lipids ——–> glycerol + fatty acids

• glycerol is converted to a 3-carbon sugar (triose phosphate), an intermediate of glycolysis and so can enter glycolysis
• long chain fatty acid chains molecules are split into
2C acetate fragments and are fed into the Krebs
cycle as acetyl co-enzyme A;

Question 11

Alternative substrates: how amino acids are used in respiration?

Answer 11

proteins ——-> amino acids

• proteins are hydrolysed into their constituent amino
acids, which are deaminated (removal of amine group) in the liver, forming a keto acid and ammonia
• some keto acids are fed into glycolysis (e.g.
pyruvic acid aka pyruvate) and some others are fed into the Krebs cycle.