Anaerobic Respiration and Substrates

Question 1

What are microorganisms that carry out anaerobic respiration?

Answer 1

-Yeast - Saccharomyces cerevisiae
(facultative anaerobe)
-Bacteria - Clostridium perfringens
(obligate anaerobe)

Question 2

What tissue carries out anaerobic respiration?

Answer 2

Animal muscle tissue during extreme exercise.

Question 3

In the absence of oxygen, why will only glycolysis occur?

Answer 3

-No oxygen to act as the final electron acceptor in ETC .
-Pyruvate remains in the cytoplasm once formed

Question 4

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

Answer 4

-because the reduced NAD cannot be reoxidised- oxidative phosphorylation will not take place and so the yield of ATP molecules produced by anaerobic respiration is greatly reduced.

Question 5

How many ATP molecules are produced by anaerobic respiration? (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

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

Answer 6

-NAD must be regenerated.
-Anaerobic respiration involves the reoxidation of NAD, where pyruvate acts as the hydrogen acceptor rather than oxygen.
-This then allows glycolysis to begin again.

Question 7

How is NAD regenerated in animal cells?

Answer 7

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

Question 8

How is NAD regenerated in yeast and higher plants?

Answer 8

Ethanal becomes reduced and accepts the hydrogen from reduced NAD to form ethanol.

Question 9

What is the process of the regeneration of NAD in animal cells?

Answer 9

-TP is oxidised (loss of Hydrogen). This hydrogen is accepted by NAD+ to form NADH/H+. Pyruvate is released. Pay off stage also makes 2ATP (per TP) = vital to cell!
-Re-oxidised NAD+ must continually be regenerated: it is now used again in glycolysis (to keep the “pay-off” stage going)
-Reduced pyruvate (hydrogen from NADH/H+) is lactate

Question 10

What is the process of the regeneration of NAD in yeast and higher plants?

Answer 10

-TP is oxidised (loss of Hydrogen). This hydrogen is accepted by NAD+ to form NADH/H+. Pyruvate is released. Pay off stage also makes 2ATP (per TP) = vital to cell!
** Remember alcoholic fermentation occurs in the cytoplasm of yeast cells (all the enzymes for this step are located here)

Question 11

Where does lactate fermentation occur?

Answer 11

in the cytoplasm of muscle cells (all the enzymes for this step are located here)

Question 12

When does anaerobic respiration take place in animals and what happens?

Answer 12

-During vigorous exercise asthe human body cannot get sufficient oxygen to the muscle cells.
-Instead of respiring aerobically these cells can only produce ATP by glycolysis. -Pyruvate is converted into lactate

Question 13

What happens in anaerobic respiration in yeast and higher plants?

Answer 13

pyruvate in converted into entangled and carbon dioxide

Question 14

nn

Answer 14

bb

Question 15

What is Acetyl CoA and what does it do?

Answer 15

an important molecule, which links glucose, fatty acid and amino acid metabolism
-in addition to glucose, under certain circumstances, lipids (fats) and proteins (amino acids) can be used as respiratory substrates.

Question 16

What does the term respiratory substrate mean?

Answer 16

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

Question 17

What does the term respiratory substrate mean?

Answer 17

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

Question 18

What are some of the roles for lipids in living organisms?

Answer 18

Energy storage – e.g. in seeds.
Thermal insulation under skin.
Protection from damage – vital organs (heart/kidneys).

Question 19

What are some of the roles of proteins in living organisms?

Answer 19

-Globular proteins - enzymes (E.G. amylase), hormones (E.G. insulin), antibodies, haemoglobin, carrier proteins.
-Fibrous proteins - keratin, collagen.

Question 20

When are lipids used as a respiratory substrate?

Answer 20

Lipids are used as an energy source when carbohydrate levels are low.
Lipids contains twice as much energy per unit gram as carbohydrates.

Question 21

What must be firstly done to lipids for them to be used as an energy source?

Answer 21

They must be hydrolysed- the addition of water in a hydrolysis reaction

Question 22

What is the name of the bonds broken when lipids are hydrolysed?

Answer 22

ester bond

Question 23

What happens to the products of lipid digestion?

Answer 23

•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 24

Why are very large number of of ATP produced as a result of lipid digestion?

Answer 24

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

Question 25

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

Answer 25

-Each fatty acid chain will produce a different number 2C fragments.
-The longer the chain the more fragments and more ATP produced

Question 26

When is protein used as a respiratory substrate?

Answer 26

only used after reserves of carbohydrates and lipids have been used up, for example, when an individual is suffering from starvation.

Question 27

How are proteins used as respiratory substrates?

Answer 27

-Firstly, they are hydrolysed into their constituent amino acids.
-Then in the liver the amine group is removed from amino acids, this is called 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 kidnevs to be excreted in the urine.
-The rest of the amino acid (residue) forms a keto acid.

Question 28

What happens to the ketoic acids formed in protein hydrolysis?

Answer 28

-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.