Metabolic Stores COPY Flashcards
Where is glucose mainly stored as glycogen ?
In liver and muscle
How much moderate exercise does the glycogen supply in the liver and muscle allow for ?
3-5 hours
How is glycogen broken down and used as fuel ? Does any of the processed used to break it down use ATP ?
Most (90%) Wis converted directly to glucose-6-P without consuming ATP
This is only possible if the glucose-6-P is to be in the cell in which it is formed (NO ATP, phosphorylation process)
If glucose is required elsewhere in the body, glycogen converted to glucose (through hydrolysis), and then it is phosphorylated when it has been transported to its destination (x1 ATP used)
What are the major form in which fuel is stored ?
Lipids
How much more energy can lipids produce relative to glycogen, weight-for weight ?
Triglycerides* (= triacylglycerols*) can produce about six times as much energy as glycogen
Which reaction produces esters ?
Alcohol with an organic acid
What is the difference between a diacyl glycerol and a triacyl glyerol ?
One of the alcohol groups of glycerol is not esterified
Describe the process of lipolysis, and state where each step occurs. Which step(s) are responsible for ATP production ?
- Lipase digests triglycerides into glycerol and 3 FAs
CYTOSOL:
- FAs combined with CoA, becoming fatty acyl CoA
- Transporter takes fatty acyl coA into mitochondria
- Glycerol becomes a glycolysis substrate, forming pyruvate
MITOCHONDRIA
- Beta oxidation chops 2-carbon acyl units off the FAs
- Acyl units become acetyl coA and can be used in the citric acid cycle (along with the pyruvate formed from glycerol)
Electrons removed during fatty acid oxidation are passed along the respiratory chain, so indirectly producing ATP
Where are the fatty acids and glycerol released by adipose tissue mainly metabolized ?
In the liver
When do ketone bodies form ?
Under conditions when other fuels are not available, breakdown of fatty acids leads to the formation of ketone bodies (STARVATION)
What are the main ketone bodies ?
Acetoacetate, 3-hydroxybutyrate and acetone
Why are ketone bodies produced when other fuels are not available (starvation) ?
Because acetyl-CoA formed in the breakdown of fatty acids cannot enter the citric acid cycle since oxaloacetate becomes depleted because the liver converts it to pyruvate to produce glucose (gluconeogenesis).
As a result, Acetyl CoA is converted to ketone bodies
What is the distinctive smell of ketone bodies ? You could smell it in the breath of which type of person ?
Fruity
Someone fasting
What are the different ways in which proteins broken down and stored or used as fuel ?
- Dietary proteins broken down into AAs
- Either incorporated into new proteins, converted to carbohydrates (storage) or used as metabolic fuel (used)
- If used, then: some deaminated, yielding NH4 + a keto acid (intermediates of the glycolytic pathway or of the citric acid cycle)
- Others cannot be deaminated so pass their amino group to a keto acid (mainly α-ketoglutarate) = TRANSAMINATION. Resulting keto acid fed into glycolysis or citric acid cycle (as pyruvate, acetyl-CoA, α-ketoglutarate or oxaloacetate), while resulting AA deaminated and used similarly
- NH4+ formed (through direct deamination or transamination followed by deamination) v toxic so rapidly converted to urea (less toxic, passed through the blood to the kidney, then excreted in urine)
What is anabolism ?
Synthesis of more complex molecules (requires ATP)