Integration of whole body metabolism Flashcards

1
Q

How much energy does the brain use and what is it used for

A
  • Uses 100-120g of glucose daily
  • Over half of the energy used is for Na+ K+ transport to maintain membrane potential and the synthesis of neurotransmitters
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How is glucose transported in the brain

A

GLUT3, which has a low Km therefore is saturated at low glucose concentrations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Why aren’t fatty acids used for energy

A

Since they are used membrane biosynthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How does cardiac muscle get its energy

A

It is exclusively aerobic with little or no glycogen stores

Fatty acids are the main source of energy but lactate and ketone bodies can be used

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What does cardiac muscle require

A

Requires the TCA cycle and oxidative phosphorylation

Lactate converted to pyruvate which is made into acetyl CoA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is adipose tissue

A

Reservoir of metabolic energy in the form of triglycerides

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How are adipose tissue filled

A

Lipids are not actually synthesised in the tissue apart from post starvation recovery
However fatty acids are made in the liver and come from our diet
Chylomicrons bring them to the tissue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How is fat mobilisation influenced

A

Glucagon and insulin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Kidney role

A

Main role is to produce urine

During starvation the kidney may contribute half of the blood glucose through gluconeogenesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What does the liver do

A

Provides fuel for the brain, muscles and other peripheral organs
Takes its energy from alpha-keto-ketoacids
Very little of the glucose is used as an energy source, most of its used for synthesis of fats or used as a temporary store in the form of glycogen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Hexokinase vs Glucokinase

A

In non-hepatic tissue, most cells have hexokinase which phosphorylates glucose trapping it in the cell
Hexokinase is saturated at much lower levels of glucose, so its activity plateaus at much lower concentration of glucose
However glucokinase is minimally activate at low concentrations of glucose but maximally active at high concentrations of glucose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How is glucose transported into hepatocytes =

A

GLUT-2, since its not insulin sensitive.

Its instantly phosphorylated by glucokinase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How is glucose transported out of hepatocytes

A

Glucose-6-phosphate is converted to glucose by the action of glucose-6-phosphatase
It is then transported out of the cell and into the blood by GLUT-2 which is concentration dependant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How is glucose taken up by muscle cells and what happens to it

A

Glucose is taken up into muscle by GLUT-4 which is insulin dependant
Its converted into G6P by hexokinase so there is a low free glucose concentration in the cell
Glycolysis of the G6P is a rapid source of ATP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How is a sprint powered

A

ATP stores
Glycolysis
Glycogen
Creatine phosphate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What reaction does creatine kinase facilitate

A

Creatine phosphate + ADP = ATP + creatine kinase

17
Q

What type of respiration is most effective for sprinting but what are the downfalls

A

Anaerobic respiration but produces of lactate and a fall in pH

18
Q

What is the liver Cori cycle

A

Lactate from pyruvate and amino acids from muscle protein breakdown will be converted into alanine
Alanine and lactate will be transported to the liver where it combines to form pyruvate
This pyruvate is converted into glucose through gluconeogenesis and is then transported back to the muscle

19
Q

What is the flow of molecules during the fed state

A

Initially the flow of molecules is to the liver

Then the excess glucose and fatty acids are stored

20
Q

Where is glucose stored and what is it used for

A

Stored as glycogen in the liver and used as a glucose source for the brain. It can store roughly 100g of glucose

21
Q

Where is excess glucose stored and how

A

Initially excess glucose is stored in muscle as glycogen. The muscle can store around 500g of glucose
Any extra glucose is converted to fatty acids and stored in adipocytes

22
Q

What is glucose in the liver used for and why

A

Some of it is used to make NADPH in the pentose phosphate pathway
NADPH is a substrate in fatty acid synthesis
The liver will also be making acetyl CoA for triglyceride formation

23
Q

How are fats delivered to the muscle

A

Through VLDLS, resting muscle will use fatty acids as a source of energy

24
Q

What are amino acids used for

A

Used for protein synthesis and the excess is converted to keto-acids and ultimately urea

25
What processes are active in the fed state
Glycolysis, glycogen synthase and fatty acid synthesis are active
26
What processes are inactive in the fed state
Glycogenolysis, gluconeogenesis and fatty acid degradation are inactive
27
What molecules are produced in the fed state
Glycogen and fatty acids
28
What molecules are not produced in the fed state
Glucose and ketone bodies
29
Where does the body gets its energy source in the famine state
Glycogen and fatty acid energy stores will be used first | Lastly protein will be used as an energy source
30
What happen in the post absorptive stage
Blood glucose will drop after several hours after the last meal The major energy source will be glycogen
31
What enzymes and hormones will be active and why
There will be an increase in phosphorylase a activity so glycogen breakdown will increase Glucagon will mainly be active so normal blood glucose levels can be maintained so brain function continues
32
What processes are active during the post absorptive stage
Glycogenolysis, gluconeogenesis and fatty acid degradation are active
33
What processes are inactive during the post absorptive stage
Glycolysis, glycogen synthesis and fatty acid synthesis are inactive
34
What molecules are produced during the post absorptive stage
Glucose and ketone bodies
35
What molecules are not produced during the post absorptive stage
Glycogen and fatty acids
36
What happens in early starvation
Glucose is released from the liver due to gluconeogenesis and glycogenolysis Fatty acids are mobilised from adipose tissue Glucose use falls as muscle switches to fatty acid oxidation Insulin drops causing GLUT4 expression by muscle to fall reducing glucose uptake
37
What happens in intermediate starvation
Glycogen stores are depleted Increased lipolysis and ketogenesis Increased gluconeogenesis to maintain blood glucose Increased beta hydroxybuterate production Further starvation sees the kidney take over gluconeogenesis from the liver
38
What happens in prolonged starvation
Beta hydroxybuterate plateaus at 20 days Brain starts to use ketone bodies as an energy source as well so the need for glucose drops Lactate and glycerol are required are used as gluconeogenic precursors Lactate is recycled back by the Cori cycle to produce pyruvate Glycerol and amino acids are oxidised Proteins are broken down forming amino acid precursors
39
What happens to molecules produced by the skeletal muscle
Alanine formed from the transamination of pyruvate is released into the blood, taken up by the liver and converted into glucose The muscle cannot form urea so the liver removes nitrogen and releases pyruvate