Lecture 7 Cellular Metabolism part 2

Question 1

Glycogenesis

How is it stimulated?

Answer 1

Glycogen synthesis
formation of glycogen from glucose (glucose -> glycogen)
the hormone insulin stimulates glycogen synthesis when blood [glucose] is high

Question 2

Where is glycogen stored?

Answer 2

mostly in the liver

some in skeletal muscle

Question 3

Glycogenolysis
role in homeostasis of glucose?
How is it stimulated?
What happens in skeletal muscle?

Answer 3

Glycogen breakdown
glycogen -> glucose
In the liver glycogen in converted to glucose and released into the blood to maintain glucose homeostasis
(helps between meals)
The hormones glucagon stimulates glycogenolysis in the liver when blood glucose is low .
In skeletal muscle glycogen -> glucose, metabolized in active muscle cells

Question 4

Protein Metabolism

Answer 4

Proteolysis
 -protein catabolism 
 -deamination 
Protein synthesis
Tissue Utilization of proteins

Question 5

Proteolysis

• protein Catabolism
• Deamination

Answer 5

Protein Catabolism: hydrolysis of polypeptides to amino acids
Deamination- removal of the amino group
- Keto acids enter the Citric Acid Cycle and release Co2+H2O+energy
NH3 is converted into urea and excreted by the kidneys

Question 6

Example of Keto Acids

Answer 6

oxaloacetate and pyruvate

Question 7

Keto bodies

Answer 7

Acidic

excess creates issues

Question 8

Transamination in proteolysis

Answer 8

-NH2 group is transferred to another amino acid

Question 9

Tissue Utilization of Proteins

Answer 9

Normal protein turnover in cells

protein metabolism increases during starvation, injury, heavy exercise, high protein diet

Question 10

What does excess fat catabolism produce?

why may this happen?

Answer 10

produces ketone bodies which are acidic
this happens with low carb diet that has an increase in eating fats and proteins
starvation
diabetes

Question 11

Lipolysis (fat metabolism)
what is it?
steps?

Answer 11

Lipolysis is catabolism of fats and other lipids
a. Hydrolysis of triglycerides; broken into fatty acids and glycerol
b. Beta oxidation- stepwise oxidation of fatty acids
- fatty acids are broken into 2C units -> acetyl CoA -> Krebs cycle -> CO2 +H2O
- high energy yield >100 ATP per fatty acid
2X more energy yield per gram than carbohydrates

Question 12

Lipid Synthesis

fat metabolism

Answer 12

fatty acids are synthesized from 2C units of acetyl CoA

fatty acids are combined with glycerol to form triglycerides and phospholipids

Question 13

tissue utilization of fatty acids

• what uses fatty acids?
• stored?
• broken down by?

Answer 13

triglycerides are stored mostly in adipose tissue
lipids are transported in the blood by lipoproteins (HDL & LDL)
liver, heart, and resting skeletal muscle use mostly fatty acids for energy
fatty acids are broken down only by aerobic metabolism
excess fat catabolism -> formation of ketone bodies (metabolic acidosis)

Question 14

Gluconeogenesis

Answer 14

making new glucose
formation of glucose from non-carbohydrate sources: amino acids, glycerol, lactate
-occurs mostly in the liver
-important when glycogen stores are depleted or during fasting
-stimulated by hormones cortisol and glucagon
-keeps glucose supply to brain going

Question 15

Introconversion of substrate (3)

Answer 15

glucose -> acetyl CoA -> fatty acids (lipid synthesis)
Amino acids -> Keto acids -> glucose (gluconeogenesis)
glucose -> keto acids -> amino acids (transamination)