Amino Acid Metabolism

Question 1

Essential Amino Acids

Answer 1

• Must be obtained from the diet
• Can’t be synthesized by the body
• 9 total
• Methionine
• Threonine
• Valine
• Histidine
• Isoleucine
• Phenyl-alanine
• Tryptophane
• Leucine
• Lysine

Question 2

Nonessential Amino Acids

Answer 2

• Can be synthesized in suffieicnt amounts from the intermediates of metabolism or from essential AA
• 11 total
  *

Question 3

Synthesis of Nonessential AA

(from where)

Answer 3

• All nonessential AA (except tyrosine) are sunthesized from common intermediates that are part of the TCA cycle
• Pyruvate
• Oxaloacetate
• a-Ketoglutarate

Question 4

Synthesis of L-Tyrosine

Answer 4

• Formed from an essential AA
• L- Phenylalaine

Question 5

Transamination

Answer 5

• Transfers an amino group to a ketoacid to form new amino acids
• Catalyzed by aminotransferases

Question 6

Deamination

Answer 6

• Removal of an amine group from an amino acid
• Catalyzed by deaminases

Question 7

AA used for the brain

Answer 7

• Glutamate
• Brain produces glutamine
• Nervous systems makes about 40 NT’s with nitrogen derived AA’s
  *

Question 8

Products of AA’s

Answer 8

Tyrosine –> Thyroid hormones, Melanin

Tryptophan –> Serotonin, Melatonin, Niacin

Arginine –> Nitric Oxide

Glutamate –> GABA

Histidine –> Histamine

Question 10

Degradation of AA’s

(Catabolism)

Answer 10

• Glucogenic
• Ketogenic

Question 11

Glucogenic AA’s

Answer 11

• Catabolism of AA produces pyruvate or one of the intermediates of the TCA cycle

Question 12

Ketogenic AA’s

Answer 12

• Catabolism yields acetoacetate
• Acetyl CoA
• Acetylacetyl CoA

Question 14

Pyruvate is converted to glucose via _______

Answer 14

Gluconeogenesis

Question 15

The TCA cycle is integral in linking these 3 important pathways

Answer 15

• Carbohydrate Metabolism
• Amino Acid Metabolism
• Fatty Acid Metabolism

Final common pathway

Central role in gluconeogenesis & lipogenesis

Question 17

The catabolism of ketogenic amino acids gives rise to _____ and _____.

Answer 17

Acetoacetate and acetyl CoA

Question 18

The catabolism of glucogenic amino acids yields ______ or ______.

Answer 18

Pyruvate or one of the other intermmediates of the TCA cycle

Question 19

The final breakdown product of all amino acids, releases the following toxic compound into cells:

Answer 19

Ammonia

Question 20

In the skeletal muscle, what is the primary final produce of glycolysis?

Answer 20

Lactate

Question 21

During the fed state, blood glucose levels _____, insulin ____ and glucagon goes ____.

Answer 21

• Blood glucose increases
• Insulin increases
• Glucagon decreases

Question 22

Discuss the tissue inter-relationships in the fasting state.

Answer 22

• High glucagon levels
• Glycogenolysis occurs in the liver and brain
• RBC’s use the glucose released
• Adipocytes release free fatty acids and glycerol from stored triglycerides
  
  • Will be used by the muscles for energy
• Liver converts the FFA to ketone bodies that are used by the brain and muscle as a source of energy
• Protein in the muscle is broken down
  
  • travels to the liver for gluconeogenesis
  • Ammonia generated enters the urea cycle for excretion
  • Lactate made by RBC’s and glycerol from the adipose are also used for gluconeogenesis

Question 23

Discuss the tissue inter-relationships in the fed state.

Answer 23

Plasma:

• Increased insulin and bile acid

Liver:

• Transcriptional regulation = decreased bile acid synthesis and gluconeogenesis

Blood glucose increases, insulin released, and glucagon levels decrease

• Fats and proteins are absorbed in the intestine
• Stimulates liver to store glucose as glycogen
  
  • Can also break into Acetyl Co-A to make triglycerides
• Glucose is used up by the brain and by RBC’s to release energy
  
  • Brain uses glucose and breaks into acetyl CoA to form TG
  • RBC’s use pyruvate to break down lactate
• Glucose and VLDL’s are stored as TG in adipose tissue
  
  • Will store as glycogen in the muscle if the TCA cycle can’t use it
• Insulin stimulates the uptake of AA’s and protein synthesis