18.5 Anaerobic Respiration

Question 1

What is the comparison of aerobic and anaerobic respiration

Answer 1

-aerobic is more efficient
-aerobic produced around 38 molecules of ATP per glucose
-anaerobic produces 2 molecules of ATP per glucose

Question 2

When does anaerobic respiration occur

Answer 2

-in absence of oxygen
-when oxygen cannot be supplied fast enough to respiring cells

Question 3

What are the three categories that organism fall into which is determined by their dependence on oxygen or not

Answer 3

-Obligate anaerobes
-Fucultative anaerobes
-Obligate aerobes

Question 4

What are obligate anaerobes

Answer 4

-cannot survive in presence of oxygen
-almost all are prokaryotes, some fungi

Question 5

What are facultative anaerobes

Answer 5

-synthesise ATP by aerobic respiration if oxygen is present
-can switch to aerobic respiration in absence of oxygen
eg. yeast

Question 6

What are obligate aerobes

Answer 6

-can only synthesise ATP in the presence of oxygen
-can supplement ATP through anaerobic respiration when O2 concentration is low but only for short periods of time, compounds produced have to be broken down when oxygen becomes available again
eg. mammals

Question 7

What is fermentation

Answer 7

the process by which complex organic compounds are broken down into simple inorganic compounds without the use of oxygen or the involvement of an electron transport chain

Question 8

What organisms does lactate fermentation take place in

Answer 8

mammals

Question 9

What organisms does alcoholic fermentation take place in

Answer 9

yeast and plants

Question 10

What are the two types of anaerobic respiration

Answer 10

lactate fermentation
alcoholic fermentation

Question 11

What are the steps of lactate fermentation

Answer 11

1. pyruvate acts as a hydrogen acceptor taking the hydrogen from NADH, to form NAD. And is catalysed by lactate dehydrogenase. The pyruvate is converted into lactate and NAD is regenerated
2. lactate is converted back into glucose in the liver with the use of oxygen so oxygen debt occurs

Question 12

Is lactate fermentation reversible

Answer 12

yes, can be converted back into pyruvate for aerobic respiration when O2 is present

Question 13

Why can lactate fermentation not occur indefinitely

Answer 13

-not enough ATP is generated to maintain vital processes for a long time
-accumulation of lactic acid lowers pH leading to protein denaturing effecting respiratory enzymes and muscle filaments

Question 14

Why can lactate fermentation not occur indefinitely

Answer 14

-not enough ATP is generated to maintain vital processes for a long time
-accumulation of lactic acid lowers pH leading to protein denaturing effecting respiratory enzymes and muscle filaments

Question 15

Is alcoholic fermentation reversible

Answer 15

no

Question 16

What is the process of alcoholic fermentation

Answer 16

1. Pyruvate undergoes decarboxylation by the removal of a CO2 molecule and catalysed by pyruvate decarboxylase to form ethanal.
2. Ethanal acts as a hydrogen accepted and accepts a hydrogen from NADH which forms NAD, forming ethanol
3. The regenerated NAD can continue to act as a coenzyme so glycolysis can occur

Question 17

Why can alcoholic fermentation not occur indefinitely

Answer 17

-not enough ATP is generated to maintain vital processes for a long time
-ethanol is a toxic waste product to yeast cells, they are unable to survive if ethanol accumulates to above 15%

Question 18

Why is alcoholic fermentation beneficial to humans

Answer 18

-make food
eg. bread, beer, wine