Metabolic Stores COPY COPY Flashcards
Where is glycogen stored?
Mainly in liver and skeletal muscle
Glycogen can cover energy needs for how long?
3-5 hours
When glycogen is broken down what does it produce?
Glucose-6-Phosphate (cannot be transported across membranes)
What major form of stored fuel is used by the body and why are these the major form?
Lipids
-Used as major form as the triglycerides/triacylglycerols can produce six times the amount of energy as glycogen
What is the general structure of triglycerides
Esters of glycerol and fatty acids
What is most of the fat in the body stored as?
Triglycerides
What is the breakdown of fats called?
Lipolysis
Describe the breakdown of triglycerides
Lipases digest triglycerides into glycerol and 3 fatty acids.
How are fatty acids broken down and what do they form?
Broken down via beta oxidation forming a two carbon acyl unit that combines with Coenzyme A to form Acetyl-Coenzyme A. Although no ATP is formed by this directly, the hydrogen ions and electrons removed by oxidation are passed to the electron transport chain
Fatty acids and glycerol released by adipose tissue are metabolised where?
In the liver
The break down of fatty acids occur when?
When other fuel sources are not available
The breakdown of fatty acids eventually leads to the formation of what? and name some examples
Ketone bodies. Examples include; acetoacetate, 3-hyrdoxybutyrate and acetone
Why do ketone bodies form?
Because the acetyl-CoA formed from the breakdown of fatty acids cannot enter the citric acid cycle since oxaloacetate becomes depleted as the liver converts it to pyruvate to form glucose
What happens to unused amino acids
They are used as metabolic fuel because the cannot be stored
What happens when amino acids are deaminated?
It produces NH4 and a keto acid which are intermediates of the glycolytic pathway or krebs cycle
When amino acids cannot release their amino groups as NH4+, what do they do?
They pass their amino group to a keto acid in a process called transamination. This keto acid can then be fed into glycolysis/krebs cycle while the remaining amino acid can be deaminated and used similarly
What is the feature of NH4+ that means it is disposed of quickly and how is this done?
The group is very toxic so the body very quickly turns it into urea
What us Gluconeogenesis
The formation of glucose from non-carbohydrate sources
What molecules are fed into gluconeogenesis
Glycerol from the triglycerates and the carbon back bone from amino acids
Where does gluconeogenesis occur?
Mostly in the liver
What is the most effective fuel?
Carbohydrates
What fuel sources does the brain use?
Normally just glucose but in times of starvation it can use ketone bodies formed in other tissues
Why cannot the brain use fatty acids as a fuel source?
Because they cannot pass the blood brain barrier
Why does the brain require a constant supply of glucose/glycogen?
Because it cannot store glucose or glycogen
What fuel can the skeletal muscle use?
Glucose, fatty acids and ketone bodies
How much of the glycogen reserves are found in skeletal muscle/
3/4s so a very large amount
When muscle protein is broken down what happens to the amino acids?
They pass their amino groups (transamination) to pyruvate to form alanine.
