chapter 14: cellular respiration

Question 1

what is aerobic respiration?

Answer 1

• it occurs in presence of oxygen and results in the complete breakdown of respiratory substrates

Question 2

what is anaerobic respiration?

Answer 2

it occurs in absence of oxygen and results in partial breakdown of respiratory substrates

Question 3

what is the purpose of respiration?

Answer 3

the chemical energy released during respiration is used by cells to synthesise ATP from ADP and inorganic phosphate
- subsequently during hydrolysis of ATP to ADP and inorganic phosphate releases energy which is used in cellular work

Question 4

ATP:
what is the role of ATP

Answer 4

• it is a short term carrier of energy which provides a ready source of chemical energy
• it transfer energy from energy yielding reactions to energy requiring reactions
• hence, ATP is a small and water-soluble molecule which can move easily between cytosol and organelles by diffusion
• the rapid conversion of ATP to ADP and back to ATP again ensures that ATP is continuously recycled in cells

Question 5

ATP:
what is the structure of ATP?

Answer 5

• a ribose sugar
• an adenine base
• a chain of three phosphates
• the two end phosphate groups of each ATP are attached by phosphoanhydride bonds which are high energy bonds

Question 6

ATP:
what happens during the hydrolysis of ATP?

Answer 6

• phosphoanhydride bonds can be hydrolysed to release a large amount of free energy to do cellular work
• most energy exchanges in cells involve cleavage of only the endmost phosphate group
• the hydrolysis of ATP to ADP and an inorganic phosphate ion involves the breaking of the phosphoanhydride bond, by the addition of water which releases a large amount of energy for cellular work

Question 6

SYNTHESIS OF ATP:
- the addition of an inorganic ____ group to ADP to from ATP is a ___ reaction which requires the input of ___
- the enzymes which catalyses this reaction includes ___ and a class of enzymes known as kinases

the three types of phosphorylation reactions that can occur to synthesize ATP from ADP and inorganic phosphate group:
1. photophosphorylation
2. substrate-level phosphorylation
3. oxidative phosphorylation

Question 6

when does NAD and FAD get reduced and how many ATP molecules do they generate?

Answer 6

NAD > NADH: during glycolysis and Krebs cycle
FAD > FADH2: during Krebs cycle

NADH generates 3 ATP molecules
FADH2 generates 2 ATP molecules

Question 6

aerobic respiration:
- carry out aerobic respiration only in the presence of ___ in order to produce ___
- it involves the complete ___ of glucose into ____ and ____
- the ____ released from the oxidation of glucose is used to synthesise ATP
- the equation for aerobic respiration is:

Answer 6

aerobic respiration:
- carry out aerobic respiration only in the presence of oxygen in order to produce ATP
- it involves the complete oxidation of glucose into carbon dioxide and water
- the chemical energy released from the oxidation of glucose is used to synthesise ATP
- the equation for aerobic respiration is:
C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy

Question 7

what are the different stages of aerobic respiration and where do they occur?

Answer 7

stage 1: glycolysis, cytosol
stage 2: link reaction, mitochondrial matrix
stage 3: krebs cycle, mitochondrial matrix
stage 4: oxidative phosphorylation, inner membrane of mitochondria

Question 8

stage 1 of aerobic respiration: glycolysis

where does glycolysis occur and what happens during glycolysis?

Answer 8

• it occurs in the glycolysis of all cells
• glycolysis is a metabolic pathway during which one glucose molecule is split and oxidised into two pyruvate molecules
• it does not require oxygen; it can occur in both AEROBIC and ANAEROBIC conditions

Question 8

stage 1 of aerobic respiration: glycolysis
what is the process of glycolysis? what are the two phases in glycolysis?

Answer 8

energy investment phase:
- phosphorylation of glucose (6C) by ATP to give glucose-6-phosphate (6C)
- glucose-6-phosphate (6C) is isomerised into its isomer, fructose-6-phosphate (6C)
- fructose-6-phosphate is phosphorylated by ATP to form fructose-1,6-phosphate (6C)

lysis:
- fructose-1,6-phosphate (6C) is then split into two glyceraldehyde-3-phosphate (G3P-3C)

energy payoff stage:
for each G3P molecule,
- during dehydrogenation, hydrogen atoms are removed and transferred to NAD to form NADH
- enough energy is released at this stage to form 2 molecules of ATP via substrate level phosphorylation
- 1 molecule of pyruvate is formed in the process

Question 9

what are the products formed at the end of glycolysis?

Answer 9

• 2 pyruvate
• 2 ATP
• 2 NADH
• 0 CO2
• 0 FADH2