Biochemistry

Question 1

Define glycogenesis

Answer 1

The synthesis of glycogen from glucose

Question 2

For glucose to do anything it must first be phosphorylated to ____1_______
In conversion to glycogen there is also a second phosphorylation to _____2_____ which is a good way to determine that glycogen is being made
This is then converted to ____3_____

Answer 2

1) Glucose-6-phosphate
2) Glucose-1-phosphate
3) UDP glucose

Question 3

What is the rate limiting enzyme of glycogenesis and what does it do? Why is it rate limiting?

Answer 3

Glycogen synthase which synthesises glycogen from UDP glucose. It can only add one glucose molecule to glycogen at a time and cannot add branches.

Question 4

Define glycogenolysis

Answer 4

This is the breakdown of glycogen to form glucose

Question 5

Glycogenolysis is catalysed by ______1______
In the liver G6P can be ________2_________
In skeletal muscle G6P cannot be dephosphorylated but instead _________3__________

Answer 5

1) glycogen phosphorylase
2) dephosphorylated and resulting glucose released into the blood stream
3) used to provide energy by glycolysis and TCA

Question 6

Define gluconeogenesis

Answer 6

This is the synthesis of glucose from metabolic precursors

Question 7

Gluconeogenesis involves highly unfavourable reactions and requires energy as ______1_______
It requires four rate limiting enzymes which are ______2________

Answer 7

1) the three irreversible reactions of glycolysis must be bypassed
2) Pyruvate kinase and PEP carboxykinase which are in the mitochondria. Fructose-1,6-bisphosphatase and Glucose-6-phosphatase which are in the cytosol.

Question 8

What is the cori cycle?

Answer 8

A process in which lactate can be converted to glucose during exercise.

Question 9

Describe basic idea of the cori cycle

Answer 9

Blood transports lactate to the liver
Liver concerts lactate back to glucose
Glucose is released into the blood stream
This buys time and shifts metabolic burden from muscle to other organs.

Question 10

What is the main energy store in adipose tissue?

Answer 10

Triglycerides

Question 11

What is lipolysis?

Answer 11

The breakdown of triglycerides to fatty acids and glycerol

Question 12

Before fatty acids can be oxidised they have to be converted to____1_____ this occurs in the _____2____

Answer 12

1) coA derivatives

2) cytoplasm

Question 13

Acyl-coA is transported into the ___1_____ by the ___2_______

Answer 13

1) mitochondrial matrix

2) carnitine shuttle

Question 14

The four products of each beta oxidation cycle are

Answer 14

acetyl-coA
FADH2
NADH + H+
A fatty acyl-coA shortened by two carbons

Question 15

Ketone bodies are formed in ______1______ from the __________2___________
They diffuse into the ____3_____ and ______4_______
They are important molecules of energy metabolism for the _____5______ and _____6______

Answer 15

1) Liver mitochondria
2) acetyl-coA of beta oxidation
3) bloodstream
4) peripheral tissues
5) heart muscle
6) renal cortex

Question 16

The most common ketone body is

Answer 16

acetylacetate

Question 17

In lipid anabolism citrate from the TCA is metabolised in the ___1_____ to form ____2____ which is then used to generate ___3______

Answer 17

1 cytoplasm
2 acetyl-coA
3 malonyl-coA

Question 18

What reaction is the rate limiting step in lipid anabolism?

Answer 18

generation of malonyl-coA from acetyl-coA by acetyl-coA carboxylase

Question 19

Synthesis of fatty acids occurs in cytoplasm of _____________ this happens when ______

Answer 19

liver cells

citrate concentrations are high and excess is transported out of the mitochondrial matrix

Question 20

Why must excess amino acids be metabolised as nitrogen waste products?

Answer 20

There is no storage form and ammonia and ammonium ions are highly toxic

Question 21

What is the major site of amino acid degradation?

Answer 21

The liver

Question 22

4 major nitrogen contains excretion products?

Answer 22

urea, uric acid, creatine kinase and ammonium ions. Most is secreted as urea in ureine

Question 23

3 steps involved in urea synthesis?

Answer 23

Transamination
Deamination
Ornithine urea cycle

Question 24

After removal of urea group what happens to the the remaining carbon skeletons?

Answer 24

converted into major metabolic intermediates

Question 25

What are ketogenic amino acids degraded to>

Answer 25

Acetyl-coA or acetoacetyl-coA and can give rise to ketone bodies or fatty acids

Question 26

What are glucogenic amino acids degraded to?

Answer 26

Pyruvate or TCA cycle intermediates and can be converted into phosphoenolpyruvate and then glucose