A5. Aerobic and Anaerobic Respiration

Question 1

Aerobic vs anaerobic respiration
Respiration can be done aerobically (with oxygen) or anaerobically (without oxygen). Both types of respiration produce ___, but anaerobic respiration produces less. Both also start with the process of _____________. The stages after ____________differ.

Answer 1

Aerobic vs anaerobic respiration
Respiration can be done aerobically (with oxygen) or anaerobically (without oxygen). Both types of respiration produce ATP, but anaerobic respiration produces less. Both also start with the process of glycolysis. The stages after glycolysis differ.

Question 2

Mitochondria
The reactions in aerobic respiration take place in the mitochondria. The folds (______) in the ________membrane of the mitochondrion provide a ________ __________ _______to maximise ______________.

Answer 2

Mitochondria
The reactions in aerobic respiration take place in the mitochondria. The folds (cristae) in the inner membrane of the mitochondrion provide a large surface area to maximise respiration.

Question 3

Coenzymes
As you saw in photosynthesis, a coenzyme is a molecule that ____ ____ ____________of an ____________by _____________a __________ _______from one ____________to another. Coenzymes used in respiration include ____, coenzyme _and ____. NAD and FAD transfer ____________from one molecule to another. This means they can _________(give hydrogen to) or __________(take hydrogen from) a molecule. Coenzyme A transfers __________between molecules

Answer 3

Coenzymes
As you saw in photosynthesis, a coenzyme is a molecule that aids the function of an enzyme by transferring a chemical group from one molecule to another. Coenzymes used in respiration include NAD, coenzyme A and FAD. NAD and FAD transfer hydrogen from one molecule to another. This means they can reduce (give hydrogen to) or oxidise (take hydrogen from) a molecule. Coenzyme A transfers acetate between molecules

Question 4

Aerobic respiration
There are four stages in aerobic respiration:

Answer 4

1. Glycolysis.
2. The link reaction.
3. The Krebs cycle.
4. Oxidative phosphorylation.

Question 5

Glycolysis
Glycolysis makes __________ from ___________. Glycolysis involves splitting one molecule of __________(with 6 carbons-6C) into ____smaller molecules of _________(3C). The process happens in the _____________of cells. Glycolysis is the first stage of both aerobic and anaerobic respiration and doesn’t need oxygen to take place—so it’s an anaerobic process.

Answer 5

Glycolysis
Glycolysis makes pyruvate from glucose. Glycolysis involves splitting one molecule of glucose (with 6 carbons-6C) into two smaller molecules of pyruvate (3C). The process happens in the cytoplasm of cells. Glycolysis is the first stage of both aerobic and anaerobic respiration and doesn’t need oxygen to take place—so it’s an anaerobic process.

Question 6

Stages in glycolysis
There are two stages in glycolysis-_________________and ____________. First, ____is used to _____________ ___________to _______ ____________. _________________is the process of adding phosphate to a molecule. Then _________ _____________is __________, releasing ___. Overall there’s a net gain of _ ____and _ _____________ ____.

Answer 6

Stages in glycolysis
There are two stages in glycolysis - phosphorylation and oxidation. First, ATP is used to phosphorylate glucose to triose phosphate. Phosphorylation is the process of adding phosphate to a molecule. Then triose phosphate is oxidised, releasing ATP. Overall there’s a net gain of 2 ATP and 2 reduced NAD.

Question 7

Stages in glycolysis - 2 Steps

Answer 7

1. Phosphorylation - Glucose is phosphorylated using a phosphate from a molecule of ATP. This creates 1 molecule of glucose phosphate and 1 molecule of ADP. ATP is then used to add another phosphate, forming hexose bisphosphate. Hexose bisphosphate is then split into 2 molecules of triose phosphate.
2. Oxidation - Triose phosphate is oxidised (loses hydrogen), forming 2 molecules of pyruvate. NAD collects the hydrogen ions, forming 2 reduced NAD. 4 ATP are produced, but 2 were used up in stage one, so there’s a net gain of 2 ATP.

Question 8

Exam Tip
The important thing to remember here for your exams is that 1 molecule of glucose gets phosphorylated using 1 molecule of ____to produce 1 molecule of ____________ ____________.

Answer 8

Exam Tip
The important thing to remember here for your exams is that 1 molecule of glucose gets phosphorylated using 1 molecule of ATP to produce 1 molecule of glucose phosphate.

Question 9

Tip: Remember the first part of OILRIG - oxidation is loss, so when triose phosphate is oxidised it _______ ___________.

Answer 9

Tip: Remember the first part of OILRIG - oxidation is loss, so when triose phosphate is oxidised it loses hydrogen.

Question 10

The products of glycolysis - aerobic respiration
Here’s what happens to all the products of glycolysis in aerobic respiration.

Answer 10

Question 11

Tip: Glycolysis takes place in the cytoplasm of cells because glucose can’t cross the _______ _______________ _____________. Pyruvate can cross this membrane, so the rest of the reactions in aerobic respiration occur within the _______________.

Answer 11

Tip: Glycolysis takes place in the cytoplasm of cells because glucose can’t cross the outer mitochondrial membrane. Pyruvate can cross this membrane, so the rest of the reactions in aerobic respiration occur within the mitochondria.

Question 12

The products of glycolysis - anaerobic respiration
In anaerobic respiration, the pyruvate produced in glycolysis is converted into ___________(alcoholic fermentation) or ___________(lactate fermentation) using ___________ ____.

The production of lactate or ethanol ____________oxidised ____. This means ___________can continue even when there isn’t much ________around, so a small amount of ____can still be produced to keep some ____________ _________going… clever.

Answer 12

The products of glycolysis - anaerobic respiration
In anaerobic respiration, the pyruvate produced in glycolysis is converted into ethanol (alcoholic fermentation) or lactate (lactate fermentation) using reduced NAD.

The production of lactate or ethanol regenerates oxidised NAD. This means glycolysis can continue even when there isn’t much oxygen around, so a small amount of ATP can still be produced to keep some biological process going… clever.

Question 13

Alcoholic fermentation - This occurs in plants and yeast.

Answer 13

Question 14

Lactate fermentation - This occurs in animal cells and some bacteria.

Answer 14

Pyruvate ——- lactate
via reduced NAD to NAD