CBI7/8 - Key Metabolic Pathways and Regulation of Metabolism

Question 1

Give overall chemical equation for aerobic respiration .

Answer 1

C6H12O6 + 6O2 —> 6CO2 + 6H2O

Question 2

What are the four stages of aerobic respiration

Answer 2

Glycolysis
Oxidative decarboxylation
Krebs cycle
Oxidative phosphorylation

Question 3

Discuss investment and payback phase during glycolysis.

Answer 3

Investment phase is the input of energy, as some stages in glycolysis use ATP.
Payback phase is the production of energy, where ATP is produced.

Question 4

Give overall chemical equation for glycolysis.

Answer 4

Glucose + 2NAD+ + 2ADP + 2Pi —> 2pyruvate + 2NADH + 2H+ + 2 ATP + 2H2O

Question 5

Give names of chemical structures in correct order during glycolysis

Answer 5

Glucose
Glucose 6 phosphate 
Fructose 6 phosphate 
Fructose 1,6 bisphosphate
Dihydroxyacetone phosphate + glyceraldehyde 3 phosphate 
Glyceraldehyde 3 phosphate x2
1,3 bisphosphoglycerate x2 
3 phosphoglycerate 
2 phosphoglycerate 
Phosphoenolpyruvate
Pyruvate

Question 6

How many steps are involved in glycolysis

Answer 6

10

Question 7

Which steps are irreversible during glycolysis

Answer 7

Steps 1, 3, 10

Question 8

Give names of enzymes involved in glycolysis in order

Answer 8

Hexokinase
Phosphoglycose isomerase
Phosphofructokinase
Fructose bisphosphate aldolase 
Triose phosphate isomerase 
Glyceraldehyde phosphate dehydrogenase 
Phosphoglycerate kinase
Phosphoglycerate mutate 
Enolase
Pyruvate kinase

Question 9

What electron carriers are produced in glycolysis

Answer 9

2 NADH molecules

Question 10

Which molecule in glycolysis feeds into oxidative decarboxylation

Answer 10

Pyruvate

Question 11

Give general overview of oxidative decarboxylation

Answer 11

Pyruvate gets decarboxylated to form acetate and co enzyme A is added to it

Question 12

Give overall during oxidative decarboxylation

Answer 12

Pyruvate + NAD+ + CoA —> acetyl-CoA + NADH + CO2 + H+

Question 13

Where does glycolysis occur in the cell

Answer 13

Cytosol

Question 14

Where does oxidative decarboxylation occur in the cell

Answer 14

Mitochondrial matrix

Question 15

Which two stages does oxidative decarboxylation link in aerobic respiration

Answer 15

End of glycolysis and start of Krebs cycle

Question 16

Which enzyme is used during oxidative decarboxylation

Answer 16

Pyruvate dehydrogenase

Question 17

Where does Krebs cycle occur

Answer 17

Mitochondrial matrix

Question 18

Discuss general overview of Krebs cycle

Answer 18

Two carbon acetyl-coA reacts with 4 carbon oxaloacetate to produce 6 carbon citrate which is oxidised and cycle repeated to produce electron carriers.

Question 19

What happens to electron carriers NAD+ and FAD

Answer 19

Become reduced to form NADH and FADH2

Question 20

How many and of what type of electron carriers are produced in one cycle of Krebs cycle

Answer 20

3 NADH and 1 FADH2

Question 21

Which nucleotide is made in Krebs cycle

Answer 21

GTP

Question 22

List enzymes used in Krebs cycle in order

Answer 22

Citrate synthase
Aconitase 
Isocitrate dehydrogenase 
Alpha-ketoglutarate dehydrogenase 
Succinyl-coA synthetase
Succinct dehydrogenase 
Fumarase
Malate dehydrogenase

Question 23

List chemical species in Krebs cycle

Answer 23

Acetyl coA + oxaloacetate gives citrate 
Isocitrate 
Alpha-ketoglutarate 
Succinyl-coA
Succinate 
Fumarate 
Malate

Question 24

What is the role of oxygen in oxidative phosphorylation

Answer 24

Terminal electron acceptor producing water

Question 25

What is the general process of oxidative phosphorylation

Answer 25

Electron carriers become oxidised giving energy to pump H+ across inner membrane which creates chemiosmotic gradient to produce ATP

Question 26

How many ATP molecules are produced per electron carrier

Answer 26

NADH - 2.5 ATP | FADH2 - 1.5 ATP

Question 27

Discuss electron movement in oxidative phosphorylation

Answer 27

Electrons from NADH passed to complex I and through coenzyme Q to complex III. Electrons from FADH2 passed to complex II to complex III. Electrons pass through cytochrome C and through complex IV, being accepted by oxygen as final electron acceptor to form water. h+ move into inter membrane space whilst electrons move. Protons then pass through ATP synthase through inner membrane, producing aTP.

Question 28

Discuss malate-aspartame shuttle.

Answer 28

Couples cytosolic NADH oxidation to mitochondrial NAD+ reduction, forming NADH in the mitochondrial matrix.

Question 29

Discuss glycerol-phosphate shuttle.

Answer 29

Couples cytosolic NADH oxidation to mitochondrial FAD reduction, forming FADH2 in mitochondrail matrix.

Question 30

What are the two shuttle systems in aerobic respiration and why are they required.

Answer 30

Malate aspartame shuttle. Glycerol phosphate shuttle. | Inner mitochondrial membrane is impermeable to NAD+ and NADH.

Question 31

What are the three alternative sources of energy, in terms of metabolic substrate.

Answer 31

Carbohydrates. Proteins and lipids.

Question 32

Discuss use of carbohydrates a metabolic substrate, and subsequent uses.

Answer 32

Enters cycle as glucose or phosphorylated glucose. Converts to glycogen for storage. Made into acetyl co A, then can produce ketone bodies, fatty acids or cholesterol.

Question 33

Discuss use of proteins as a metabolic substrate and further uses.

Answer 33

Proteins broken down into amino acids which can enter cycle as pyruvate or acetyl coA. Can be used to produced ATP or fatty acids and ketone bodies. Removed from body as urea in urine.

Question 34

Discuss use of lipids as a metabolic substrate and subsequent uses.

Answer 34

Lipids can be broken down into fatty acids and glycerol high can enter cycle as pyruvate or acetyl coA. Can. Be made into ketone bodies by beta-oxidation.

Question 35

Define hypoglycaemia.

Answer 35

Low blood glucose concentration.

Question 36

Define hyperglycaemia .

Answer 36

Increased blood glucose levels,

Question 37

Define the postprandial state or period.

Answer 37

Period after eating meal where blood plasma glucose levels increase.

Question 38

Define normoglycaemia.

Answer 38

Normal glucose concentration within blood,

Question 39

What is the location of gluconeogenesis.

Answer 39

Liver and adrenal cortex.

Question 40

Gluconeogenesis is the reverse of what process.

Answer 40

Glycolysis.

Question 41

Which steps in glycolysis are different to gluconeogenesis.

Answer 41

Steps 1,3 and 10. In reverse order also.

Question 42

Step 1 of glycolysis - give reverse for gluconeogenesis, including appropriate enzymes.

Answer 42

Glycolysis - glucose —> glucose-6-phosphate by hexokinase. Reverse happens for gluconeogenesis with glucose-6-phosphatase. Glycolysis - fructose-6-phosphate —> fructose-1,6-bisphosphate by phosphofructokinase. Reverse happens for gluconeogenesis with fructose-1,6-bisphosphatase Glycolysis - phosphoenolpyruvtae —> pyruvate by pyruvate kinase. Reverse happens for gluconeogenesis by pyruvate carboxylase (PC) and phosphoenolpyruvate carboxykinase (PEP-CK)

Question 43

What factors emulate gluconeogenesis rate.

Answer 43

AMP/ATP. Insulin/glucagon. Gene expression

Question 44

Drug to inhibit complex I in oxidative phosphorylation. How does it work.

Answer 44

Rotenone. Prevents transfer of electrons to coenzyme Q. Blocks use of NADH as electron carrier.

Question 45

Drug to inhibit complex II in oxidative phosphorylation. How does it work.

Answer 45

Malonate. Prevents transfer of electrons from electron carrier FADH2.

Question 46

Drug to inhibit complex III in oxidative phosphorylation. How does it work.

Answer 46

Antimycin. Blocks use of electron carriers

Question 47

Drug to inhibit complex IV and how does it work.

Answer 47

Cyanide. Blocks respiration in the electron transport chain preventing production of ATP.

Question 48

What drug inhibits ATP synthase in oxidative phosphorylation and how.

Answer 48

Oligomycin. Binds to ATP synthase prevents phosphorylation of ADP.

Question 49

Define ionophores.

Answer 49

Chemicals that reversible bind ions.

Question 50

Give examples of ionophores that act as metabolic regulators.

Answer 50

FCCP and DNP.