Biochemistry

Question 0

What does each cycle of beta oxidation yield?

Answer 0

1 Acetyl-CoA
1 FADH2
1 NADH + H+
1 fatty acyl-CoA (shortened by 2 carbon atoms)

Question 1

Where does beta oxidation occur and what is it?

Answer 1

Mitochondrial matrix
Cycle of reactions
Four steps of each cycle

Question 2

How many oxidation cycles occur for an even numbered saturated fat?

Answer 2

The fat is C2n

n-1 cycles is required for complete catalysis

Question 3

What are the products of the breakdown of a C14 fatty acid?

Answer 3

7 acetyl-CoA
6 FADH2
6 NADH + 6H+

Question 4

When and where are ketone bodies formed?

Answer 4

Under fasting conditions (hypoglycaemia)

In liver mitochondria

Question 5

What are ketone bodies formed from?

Answer 5

Acetyl-CoA from beta oxidation

Question 6

Where do the ketone bodies go after formation?

Answer 6

Diffuse into blood and move to peripheral tissues

Question 7

Where are ketone bodies important for metabolism?

Answer 7

Brain
Heart muscle
Renal cortex

Question 8

What happens to ketone bodies once they reach peripheral tissues?

Answer 8

Converted back to acetyl-CoA which enters the TCA cycle

Question 9

What do ketone bodies do in the brain?

Answer 9

Used in energy production

Used in neurotransmitter synthesis

Question 10

What happens if ketone bodies are allowed to accumulate under extreme starvation?

Answer 10

Ketoacidosis

Question 11

Are ketone bodies toxic to peripheral tissues which prefer glucose?

Answer 11

No

Question 12

What process drives lipogenesis and where does it occur?

Answer 12

Fatty acid synthesis in the liver

Question 13

What is the role of acetyl-CoA carboxylase?

Answer 13

Converts acetyl-CoA to malonyl-CoA

Question 14

What is the role of malonyl-CoA?

Answer 14

A major fatty acid synthesis precursor

Question 15

What is acetyl-CoA carboxylase activity regulated by?

Answer 15

Nutrient and energy status

Question 16

Where in the cell does fatty acid synthesis occur?

Answer 16

Cytoplasm

Question 17

What cofactors are involved in fatty acid synthesis and degradation?

Answer 17

Synthesis - NADPH (reductant)

Degradation - NAD+, FAD (oxidant)

Question 18

Do fatty acid synthesis and degradation have length constraints?

Answer 18

Synthesis - Yes (stops at C16)

Degradation - No

Question 19

What effect does insulin have on acetyl-CoA carboxylase?

Answer 19

It signals the fed state

Stimulates storage of fuels and synthesis or proteins

Question 20

What do glucagon and adrenaline do?

Answer 20

Glucagon signals the starved state
Adrenaline signals requirement for energy
Glycogen stores are mobilised

Question 21

What does citrate do?

Answer 21

Stimulates acetyl-CoA carboxylase allosterically

It’s levels are high when acetyl-CoA and ATP are abundant

Question 22

What does palmitoyl-CoA do?

Answer 22

Antagonises acetyl-CoA carboxylase

It is abundant when fatty acids are in excess

Question 23

Is fatty acid synthesis induced during glucagon-mediated glucose release?

Answer 23

No

Question 24

What is the donor molecule of carbon atoms to a growing fatty acid?

Answer 24

Malonyl-CoA

Question 25

Does the phrase “citrate stimulates allosterically” mean that citrate helps insulin to stimulate the catalytic activity of acetyl-CoA carboxylase?

Answer 25

No

Question 26

What is the alternate name for the urea cycle?

Answer 26

Ornithine cycle

Question 27

Where do the nitrogens come from to synthesis urea?

Answer 27

One from free ammonium

One from aspartic acid

Question 28

Does the removal of the amino group only occur in liver cells?

Answer 28

No

Question 29

Is free ammonium toxic?

Answer 29

Yes

Question 30

Are amino groups from amino acids directly transferred to carbamoylphosphate?

Answer 30

No

Question 31

What does gluconeogenesis require?

Answer 31

Four liver enzymes

Question 32

How does gluconeogenesis proceed?

Answer 32

Via the synthesis of oxaloacetate in mitochondria

Oxaloacetate accepts acetyl groups in the TCA cycle

Question 33

Is gluconeogenesis energy consuming or energy producing?

Answer 33

Consuming

Question 34

What is glycogenin?

Answer 34

A protein at the centre of a glycogen polymer

Question 35

How many glucose molecules can covalently bind to glycogenin?

Answer 35

Four

Question 36

Why is the catalytic activity of glycogenin important?

Answer 36

It’s ability to bind four glucose molecules to itself is important because glycogen synthase can only add glucose molecules to an existing glycogen chain