Anaerobic Respiraton And Alternative Respiratory Substrates

Question 1

what are some microorganisms that carry out anaerobic respiration?

Answer 1

yeast (facultative anaerobe)

bacteria (obligate anaerobe and killed by normal concentrations of oxygen)

Question 2

what part of the body in animals does anaerobic respiration take place, when and why?

Answer 2

animal muscle tissue

during extreme exercise

since muscles cells temporarily deprived from O2

Question 3

in the absence of oxygen only glycolysis will occur. explain why?

Answer 3

absence of oxygen means there is no final electron acceptor in the ETC

chain cannot take on additional electrons, so cannot continue to oxidise reduced FAD and reduced NAD

Question 4

why can’t the link reaction and Krebs cycle not occur in the absence of oxygen?

Answer 4

because reduced NAD can’t be reoxidised

oxidative phosphorylation won’t take place so yield of ATP molecules produced by anaerobic respiration is greatly reduced

Question 5

how many molecules of ATP are produced from anaerobic respiration (it is less than aerobic)

Answer 5

gross production - 4 molecules of ATP

net gain - 2 molecules of ATP because 2 molecules of ATP are used up to phosphorylate glucose

Question 6

what must happen for glycolysis to continue in the absence of oxygen?

Answer 6

NAD must be regenerated

anaerobic respiration involves reoxidation of NAD where pyruvate acts as the hydrogen acceptor rather than oxygen

this then allows glycolysis to begin again

Question 7

what happens to pyruvate in animal cells?
(diagram on page 3)

Answer 7

pyruvate becomes reduced and accepts the hydrogen from reduced NAD forming lactate (lactic acid)

Question 8

what is used instead of pyruvate to be the hydrogen acceptor in yeast and higher plants and what happens to it?
(diagram on page 3)

Answer 8

ethanal becomes reduced and accepts the hydrogen from reduced NAD to form ethanol

Question 9

draw out the process of glycolysis in anaerobic respiration in animals during vigorous exercise and how many ATP produced?

Answer 9

diagram on page 4 IMPORTANT

net gain of ATP - 2

Question 10

draw the process of glycolysis during anaerobic respiration in yeast and higher plants (fermentation)

Answer 10

diagram on page 5 IMPORTANT

Question 11

which cells are most likely to use the lactate pathway?

Answer 11

skeletal muscle cells

Question 12

how is lactate transported around the body?

Answer 12

diffuses into blood where it dissolves in the plasma

Question 13

what symptoms may a person have due to lactic acid build up?

Answer 13

disorientated, nausea, can stop muscles contracting (muscle cramping)

Question 14

which cells require oxygen for the removal of lactate?

Answer 14

hepatocytes (liver cells)

Question 15

what is the oxygen debt?

Answer 15

extra oxygen, when you heavy breath after strenuous exercise, to your liver cells to enable them to metabolise lactate

Question 16

what does acetyl CoA link making it an important molecule?

Answer 16

links glucose, fatty acid and amino acid metabolism

Question 17

under certain circumstances, what other molecules other than glucose can be used as respiratory substrates?

Answer 17

lipids (fats)
proteins (amino acids)

Question 18

define respiratory substrate

Answer 18

means a molecule that can be oxidised through respiration to fuel the synthesis of ATP

Question 19

describe lipids as a respiratory substrate

Answer 19

used as an energy source when carbohydrate levels are too low

contain twice as much energy per unit gram as carbohydrates

Question 20

what must happen first to lipids before it is used, give the equation and what bond is broken?

Answer 20

must be hydrolysed
involves addition of water in a hydrolysis reaction

lipid -> glycerol + fatty acids

ester bond

Question 21

what happens to the products of lipid digestion?

Answer 21

glycerol is phosphorylated by ATP, dehydrogenated and converted into triose phosphate (3C)
this is an intermediate of glycolysis so can then enter glycolysis

fatty acid chains, these long hydrocarbon chains are split into 2C acetate fragments
each of these fragments can enter the Krebs cycle as acetyl coenzyme A

Question 22

why are very large numbers of ATP produced as a result of the fragmentation of fatty acid chains?

Answer 22

each fatty acid produces many 2C fragments

this means the Krebs cycle can happen many times producing large numbers of reduced NAD and reduced FAD to fuel the ETC

Question 23

why does the precise number of ATP molecules produced depend upon the length of the hydrocarbon chain of the fatty acid?

Answer 23

the longer the hydrocarbon chain, the more CH2 repeats and therefore ‘acetates’

Question 24

when are proteins used as a respiratory substrate?

Answer 24

rarely used, usually only used after reserves of carbohydrates and lipids have been used up e.g. when individual is suffering from starvation

Question 25

describe how proteins are used as a respiratory substrate (diagram on page 9)

Answer 25

firstly, they're hydrolysed into their constituent amino acids then, in the liver the amine group is removed from amino acids - deamination the removed amine group is converted to ammonia and then combines with CO2 to produce urea which travels in the blood stream to the kidneys to be excreted in the urine the rest of the amino acid (residue) forms a keto acid: some keto acids e.g. pyruvate are fed into glycolysis some keto acids are converted into Krebs cycle intermediates so fed into the Krebs cycle

Question 26

draw out the entire process of anaerobic respiration and include respiratory substrates

Answer 26

diagram on page 10 IMPORTANT