Week 5 - Metabolism 1

Question 1

Describe metabolism

Answer 1

The complete set of catabolic and anabolic reactions that occur within living cells

Question 2

Define anabolic and catabolic reactions

Answer 2

Anabolic = synthesises large molecules from small ones
Catabolic = breakdown f big molecules into small ones

Question 3

What is the first step of sugar oxidation

Answer 3

Glycolysis

Question 4

Describe glycolysis

Answer 4

10 reactions, where ATP is used in reactions 1-3. NAD is then reduced later on and in steps 7-10 ATP is generated. Net yield of 2 ATP

Question 5

What do you start with and end with in glycolysis

Answer 5

Glucose at the start and 2 x pyruvate at the end

Question 6

What is the regulatory enzyme of glycolysis and what’s is it inhibited and stimulated by

Answer 6

PFK
Stimulated by AMP and fructose-2,6-bisphosphate
Inhibited by ATP, low pH an citrate

Question 7

Where does lactate come from

Answer 7

When no O2 present pyruvate accepts electrons to form lactate

Question 8

Where does pyruvate go and what happens to it

Answer 8

Into the mitochondria where it’s decarboxylated into acetyl CoA

Question 9

How do fats become Acetyl CoA

Answer 9

Beta oxidation

Question 10

Describe how fatty acids prepare for beta oxidation

Answer 10

Fatty acids become fatty acyl CoA and move into mitochondria

Question 11

Describe beta oxidation

Answer 11

Beta oxidation 4 reactions which reduces amount of carbons on fatty acyl CoA until the fatty acid is completely degraded. Forms acetyl CoA, NADH and FADH2 per cycle.

Question 12

Describe the TCA cycle

Answer 12

Complete oxidation of C on acetyl CoA to yield 3NADH 1FADH and 1GTP
(Acetyl CoA + Oxaloacetate -> citrate -> isocitrate -> a-ketoglutarate -> succinyl CoA -> succinate -> fumarate -> malate -> oxaloacetate)

Question 13

Which 2 enzymes control the TCA cycle

Answer 13

Isocitrate dehydrogenase and a-ketoglutarate dehydrogenase

Question 14

What stimulates and inhibits isocitrate dehydrogenase

Answer 14

Stimulated by
ADP, NAD, Isocitrate
Inhibited by
ATP, NADH

Question 15

What stimulates and inhibits a-ketoglutarate dehydrogenase

Answer 15

Stimulated by
ADP
Inhibited by
Succinyl CoA, ATP, NADH

Question 16

Where is the major site of amino acid degradation

Answer 16

Liver (sometimes muscles)

Question 17

Name the steps in amino acid metabolism

Answer 17

Amino acids -> transamination* -> deamination

• amino acids can also go back into tissue protein

Question 18

Describe transamination

Answer 18

Amino group on a protein is transferred to a keto acid. The amino group is accepted by the first keto carbon on the keto acid

Question 19

What enzyme catalyses transamination

Answer 19

Aminotransferases

Question 20

Name the two keto acids which accept amino groups

Answer 20

a-ketoglutarate (forms glutamate) and oxaloacetate (forms aspartate)

Question 21

What is the important reactant needed for deamination

Answer 21

Glutamate

Question 22

Describe deamination and what is it catalysed by

Answer 22

Glutamate has amino group, which is removed as ammonia.
Catalysed by glutamate dehydrogenase

Question 23

What is important for the urea cycle

Answer 23

Aspartate

Question 24

Describe the urea cycle

Answer 24

Arginine* -> ornithine -> citrulline -> argininosuccinate* -> arginine
*aspartate added to form argininosuccinate and fumarate removed to form arginine
*H2O comes in to remove urea and form ornithine

Question 25

How many intermediates can the remaining C skeletons form

Answer 25

7

Question 26

Describe the glucose alanine cycle

Answer 26

Muscles use BCAAs during prolongues exercise, glutamate build up forms alanine, which is released and taken by liver to be transaminated

Question 27

Describe gluconeogenesis

Answer 27

The formation of glucose from non carbohydrate precursors

Question 28

Where does gluconeogenesis occur

Answer 28

Liver

Question 29

Describe gluconeogenesis

Answer 29

The reversal of glycolysis except for three steps in order to make it energetically favourable