anaerobic respiration

Question 1

give examples of microorganisms that carry out anaerobic respiration

Answer 1

• yeast
• some prokaryotes

Question 2

give examples of animal tissues that might carry out anaerobic respiration

Answer 2

muscle tissue

Question 3

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

Answer 3

oxygen acts as the final electron acceptor

Question 4

how many ATP molecules are produced by anaerobic respiration and how?

Answer 4

2
- from substrate level phosphorylation

Question 5

what does anaerobic respiration include?

Answer 5

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

Question 6

why can the link reaction and krebs cycle not occur?

Answer 6

• reduced NAD cannot be oxidised
• oxidative phosphorylation wont take place and so the yield of ATP decreases

Question 7

summarise anaerobic respiration in animal cells, and yeast and higher plants

Answer 7

animal cells : pyruvate becomes reduced and accepts the hydrogen from reduced NAD forming lactate

yeast and higher plants : ethanal becomes reduced and accepts the hydrogen from reduced NAD to form ethanol

Question 8

what is meant by the term respiratory substrate?

Answer 8

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

Question 9

list some of the roles of lipids in living organisms

Answer 9

• protection of vital organs
• thermal insulation
• metabolic water
• buoyancy

Question 10

list some of the roles of proteins in living organisms

Answer 10

• enzymes
• hormones
• antibodies

Question 11

describe lipids as a respiratory substance

Answer 11

• used as an energy source when carbohydrate levels are low
• contain twice as much energy per unit gram as carbohydrates

Question 12

what is the name of the bond broken when lipids are hydrolysed?

Answer 12

ester

Question 13

what happens to the products of lipid digestion?

Answer 13

• 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 co-enzyme A

Question 14

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

Answer 14

length of hydrocarbon chain determines how many acetyl coenzyme A molecules are made, and therefore how many Krebs cycles occur

Question 15

why are very large numbers of ATP produced as a result of using lipids as a respiratory substance?

Answer 15

each fatty acid produces many 2C fragments which means the Krebs cycle can go many time producing large numbers of reduced NAD and reduced FAD to fuel the ETC

Question 16

when is protein used as a respiratory substance?

Answer 16

only used after reserves of carbohydrates and lipids have been used up (e.g a person suffering from starvation)

Question 17

how are proteins used as respiratory substances?

Answer 17

• firstly, they are hydrolysed into amino acids (peptide bonds broken)
• in the liver, the amine group is removed (deamination)
• removed amine group is converted to ammonia and then combined with CO2 to produce urea which is excreted as urine

rest of amino acid forms a KETO ACID:
- some keto acids are fed into glycolysis
- some keto acids are converted into Krebs cycle intermediate (4C,5C,6C)