Protein and Amino Acid Met

Question 1

Identify biological roles for amino acids

Question 2

Can we use amino acids for energy (via oxidation)? Under what conditions might this happen?

Question 3

What are reasons that excess amino acids can be challenging for mammalian metabolism?

Question 4

briefly describe the digestive enzyme for proteins: proteases

Question 5

briefly describe the digestive enzyme for proteins: peptidases

Question 6

what is a zymogen?

Question 7

Removal of the amino group is the first step: how are -ketoglutarate and glutamine involved?

Question 8

Distinguish between oxidative deamination and transamination

Question 9

Why can’t ammomiun (NH4+) travel in the bloodstream? How are NH4+ equivalents carried (provide different examples)?

Question 10

what are the reactions of the glucose-alanine cycle?

Question 11

where are the reactions in the glucose-alanine cycle primarily located?

Question 12

what is the physiological function of the glucose-alanine cycle?

Question 13

What are some different forms of nitrogen excreted by different organisms?

Question 14

What are transaminase enzymes? What is the reaction catalyzed by alanine transaminase?

Question 15

What are the steps of the urea cycle (know the reactions and the enzymes)?

Question 16

How does –NH3 enter the mitochondria and become ammonia (there is more than one mechanism)?

Question 17

How is free ammonia captured in the mitochondrial matrix by carbamoyl phosphate synthase I?

Question 18

How does the nitrogen in the urea cycle leave the mitochondria (two ways)?

Question 19

How does nitrogen enter the urea cycle (two ways)?

Question 20

How does urea leave the cycle, and what happens to the final product(s)?

Question 21

Why do the urea cycle and the citric acid cycle make up the “Krebs Bicycle” (how are they connected)?

Question 22

Describe how the urea cycle may be regulated.

Question 23

Describe ketogenic vs. glucogenic amino acids.

Answer 23

-ketogenic: metabolizes products into ketone bodies; leucine and lysine
-glucogenic: AA broken down into products for gluconeogenesis

Question 24

What are some possible fates of carbon skeletons resulting from amino acid degradation (can they intersect with pathways we have already studied)?

Question 25

What happens to amino acids that can yield carbon skeletons containing 2 carbons?

Answer 25

-make ketone bodies
-can be turned into acetyl Co-A

Question 26

What happens to amino acids that can yield carbon skeletons containing 3 carbons?

Answer 26

-can be turned into pyruvate to be used in gluconeogenesis
-ex. threonine can be cleaved into glycine and acetaldehyde

Question 27

What happens to amino acids that can yield carbon skeletons containing 4 carbons?

Answer 27

-can be turned into oxaloacetate to be used for gluconeogenesis via TCA

Question 28

What happens to amino acids that can yield carbon skeletons containing 5 carbons?

Answer 28

-become a-ketoglutarate
-ex. histidine, ornithine, glutamate

Question 29

How is glycine degraded? Follow it through the pathways of central metabolism

Answer 29

-glycine comes from the cleavage of threonine
-glycine can become other AA to become pyruvate
**

Question 30

What can happen if genetic defects affect amino acid catabolism—find one example.

Question 31

brief overview of the processing of xenobiotic compounds

Answer 31

-xenobiotics: molecules the body sees as foreign
-not naturally produced, must be eliminated
-cleaved into smaller fragments
-made more hydrophilic for elimination

Question 32

What happens in Phase I?

Answer 32

-foreign molecule oxidized and cleaved
-become more hydrophilic
-sometimes metabolites are active
-add a handle for attack
-enzymes: esterases, oxidases, dehydrogenases

Question 33

What happens in Phase II?

Answer 33

-conjugation to larger molecules (ex. glutathione) to increase solubility
-attacks handle on molecule
-molecule further inactivated
-enzymes: transferases

Question 34

What are cytochrome P450 enzymes?

Answer 34

-responsible for catalyzing many of the Phase 1 reactions
-oxidatively modify substrate molecules using NADPH and O2
-found in inner mito mem and ER

Question 35

What are amine monooxygenases?

Answer 35

-monoamine oxidases
-enzyme has FAD fixed in it for redox
-deactivate neurotransmitters
-convert amine to aldehyde
-two isoforms: MAO-A, MAO-B

Question 36

Which AA’s can become Succinyl CoA?

Answer 36

-Met
-Val
-Ile

Question 37

Which AA can become acetyl CoA, fumarate and acetoacetate?

Answer 37

-Leu
-Lys
-Tyr
-Phe
-Trp

Question 38

How does monoamine oxidase link to central metabolism?

Answer 38

-it produces ammonium which can be used in the urea cycle

Question 39

Differentiate between glucuronic acid and glutathione

Answer 39

-glucuronic acid: ox form of glucose (has carb acid); uses UDP-glucuronic acid
-glutathione: tripeptide of glycine, cysteine and glutamate
-uses glutathione-S-transferase