Quiz 1 (Protein/AA Metabolism)

Question 1

Defective transport of nonpolar/neutral amino acids, especially ____, can lead to ____ Disease.

Answer 1

Tryptophan / Hartnup

*key characteristic = photosensitivity

Question 2

Defective transport of dimer is cystine and dibasic amino acids can lead to ___.

(What are theses amino acids?)

Answer 2

Cystinuria

*key characteristic = cystine crystals in the kidneys causing abdominal pain

(“COLA” - Cystine / Ornithine / Lysine / Arginine)

Question 3

Essential Amino Acids

Answer 3

“TIM HRKL VolsWagon Ferrari”

Or

“My Tall Handsome Vegan Friend Is Reliably Watering Kale Leaves”

Methionine (M) / Threonine (T) / Histidine (H) / Valine (V)/ Phenolalanine (F) / Isoleucine (I) / Arginine (R) / Tryptophan (W) / Lysine (K) / Leucine (L)

Question 4

Alpha-ketoglutarate can act as a precursor for the synthesis of which amino acid(s)?

Answer 4

Glutamate

*Glutamate —> Glutamine / Histidine / Proline / Arginine

Question 5

Pyruvate can act as a precursor for the synthesis of which amino acid(s)?

Answer 5

Valine / Alanine* / Leucine

*directly

Question 6

OAA can act as a precursor for the synthesis of which amino acid(s)?

Answer 6

Aspartate* / Asparagine / Lysine / Methionine / Threonine / Isoleucine

*directly

Question 7

3-Phosphoglycerate can act as a precursor for the synthesis of which amino acid(s)?

Answer 7

Serine* / Cysteine / Glycine

*directly

Question 8

Exopeptidases attack the ____ of a protein.

Endopeptidases attack the ____ of a protein.

Answer 8

Exo- = C- and N- terminus ends

Endo- = digestive (specific) sites within the protein

Question 9

Lysosomes sequester Intracellular proteolytic enzymes that are active when ___.

Answer 9

pH = 5

*because the lysosome creates a low pH environment, these enzymes are active within the lysosomes, but not outside them (where pH =7)

Question 10

The catalytic core of a proteosome is termed as the ___ subunit.

Answer 10

20S

Question 11

Ubiquitin receptors in the ___ regulatory unit of a proteosome target multi-Ubiquitin chains.

Answer 11

19S

Question 12

Cleaving of peptide bonds in a proteosome is made possible by ____ which acts as a nucleophile.

Answer 12

-OH of Threonine

Question 13

Trypsinogen, an inactive zymogen, is activated by an ___ that is embedded in the intestinal mucosa.

Answer 13

Enterokinase

Question 14

What role do enteropeptidases play in protein digestion?

Answer 14

They convert the zymogen trypsinogen to active trypsin

Question 15

Ketogenic / Glucogenic Amino Acids

Answer 15

Ketogenic (only) = Lysine / Leucine
*form precursor for ketone bodies or fatty acids (Acetyl-CoA or Acetoacetate)

Both = Phenolalanine / Tryptophan / Tyrosine / Isoleucine / Threonine
*”FWY IT”

Glucogenic = all others
*form precursors for glucose metabolism

Question 16

What are the 3 main steps in amino acid metabolism?

Answer 16

1. Aminotransferase / Transaminase = shuffling of amine groups
2. Glutamate Dehydrogenase
3. Urea Cycle = repackaging and excretion of amine group as ammonium

Question 17

___ is the ketoacid of aspartate.

Answer 17

OAA (Oxaloacetate)

Question 18

Transaminase reaction require the use of the coenzyme ___ which is a derivative of ___.

Answer 18

PLP (pyridoxyl-5’-phosphate)

Vitamin B6

Question 19

Transamination reaction transfer amino groups to ___.

Answer 19

Alpha-keto acids.

Question 20

Glutamine Synthetase converters Glutamate to Glutamine in order to trap ___.

Answer 20

Nitrogen

*for later excretion in the Urea Cycle

Question 21

Met, Thr, Ile, and Val can be metabolized to form ___ which can be converted to ___ (an intermediate of the TCA cycle).

Answer 21

Propionyl CoA

Succinyl CoA

Question 22

Mutations in ___ are the most common cause of homocystinuria.

Answer 22

CBS (cystathione beta-synthase)

*enzyme used in the metabolism of Methionine

Question 23

Deficiencies in pathways for metabolizing branched chain amino acids results in ___.

What are these amino acids?

Answer 23

Maple Syrup Urine Disease
*usually caused by deficient activity of BCKD complex

Val / Ile / Leu

Question 24

Phenylalanine metabolizes into ___ by the enzyme ___.

Answer 24

Tyrosine

Phenylalanine Hydroxylase
*if defective, leads to Phenylketonuria (neurological problems / musty urine)

Question 25

Hypothyroidism vs. Hyperthyroidism

Answer 25

Hypo- = low T4 / high TSH Hyper- = high T4 and T3 / low TSH *T3 and T4 (thyroxine) are made by Thyroglobulin which consists of Tyrosine resides

Question 26

Key amino acid derivative: Tyrosine —> ? Serine —> ? Glutamate —> ? Tryptophan —> ?

Answer 26

Tyrosine —> thyroid hormones (T3/T4); endocrine hormones (dopamine); melanin Serine —> Acetylcholine (involved in neurotransmission) Glutamate —> GABA Tryptophan —> Serotonin (which is converted to Melatonin); NAD+ and NADP+ (requires Vitamin B6)

Question 27

Grave’s Disease results from defective metabolism of ___.

Answer 27

Tyrosine

Question 28

Albinism is a result of the inability of ____ to be converted to melanin, resulting in a lack of pigmentation.

Answer 28

Tyrosine

Question 29

Ammonia is removed as ___ and ___ in the brain.

Answer 29

Glutamate / Glutamine *other tissues: Alanine / Glutamine

Question 30

What occurs when there is excess ammonium?

Answer 30

Glutamate Dehydrogenase will continue to generate glutamate from alpha-ketoglutarate to use up the NH4+ This lowers the pool of alpha-ketoglutarate, which lowers TCA cycle activity, learning to unconsciousness

Question 31

Pyruvate is the alpha-keto acid of ___.

Answer 31

Alanine

Question 32

The urea cycle primarily takes place in the ___.

Answer 32

Liver

Question 33

An Alanine Aminotransferase (ALT) is used in the removal of excess NH4+ from the ___.

Answer 33

Muscle

Question 34

Reactions of ALT and GLDH

Answer 34

ALT - transamination *transfer of NH3 onto Glutamine GLDH - oxidative deamination *generation of NH4+

Question 35

What is the rate limiting enzyme of the Urea Cycle?

Answer 35

Carbamoyl Phosphate Synthetase

Question 36

Urea production is ___ by a high protein diet and ___ by a high carb diet.

Answer 36

Increased / decreased *proteins tend to bring in amino acids with Nitrogen

Question 37

A defect in ___ can cause hyperammonemia since ammonium ions cannot enter the Urea Cycle.

Answer 37

CPS-1 (Carbamoyl Phosphate Synthetase)

Question 38

Ammonia (NH3) is a toxic agent while ammonium (NH4+) is not because...

Answer 38

As an uncharged molecule, ammonia can permeate/cross membranes and cause pH imbalances leading to swelling of cells

Question 39

Creatine is made from which 3 amino acids?

Answer 39

Arg / Gly / Met

Question 40

___ serves as a diagnostic for myocardial infarction.

Answer 40

CK-MB (creatine kinase)

Question 41

Basic essential amino acids:

Answer 41

His / Lys

Question 42

Branched chain amino acids are initially metabolized in the ___ because the enzyme ____ is in higher concentration there.

Answer 42

Muscles / branched-chain amino acid transferase

Question 43

Urea is synthesized in the liver from ___ and ___.

Answer 43

Aspartate / Carbamoyl Phosphate