Uth Biochemistry Block Iii Lecture 1

Front 1

List the nonessential amino acids. These can all be derived from glucose pathways.

Back 1

Serine, Glycine, Glutamate, Glutamine, Alanine, Aspartate, Asparagine, Proline, Cysteine*, and Arginine**

Hint 1

Note: "C-G-A-S and Proline"

Front 2

What is cysteine derived from?

Back 2

Carbons are derived from glucose via serine, however the sulfur group is derived from methionine.

Front 3

What is unique about arginine biosynthesis?

Back 3

Arginine IS an essential amino acid in times of growth and tissue injury (think clinical correlate: burn victims) because of its biosynthetic localization in the urea cycle in liver.

Front 4

What amino acid is neither nonessential or essential?

Back 4

Tyrosine is derived from an essential amino acid, phenylalanine.

Front 5

How are amino acids absorbed from the intestinal lumen?

Back 5

Primarily Na+ dependent symporter manner due to a LOWER concentration of Na+ inside the cell. This concentration is kept by Na+, K+-ATPase.

Front 6

How are amino acids transported out of the cell into the blood stream?

Back 6

Facilitated transporter.

Front 7

What are transamination reactions?

Back 7

Transfer of amino groups between amino acids and alpha-ketoacids (ex: alpha-ketoglutarate, OAA, pyruvate).

Front 8

What do they utilize?

Back 8

PLP (pyridoxal phosphate) as a cofacter, derived from Vit. B6.

Front 9

What amino acids utilize the alpha-ketoglutarate pathway?

Back 9

Glutamate, Glutamine, Proline, Arginine.

Front 10

GDH catalyzes what rxn? What provides reducing power?

Back 10

a-ketoglutarate + NH4 to Glutamate (reversible). Reducing power from NADH or NADPH.

Front 11

Transaminase (with PLP) produces what when a-ketoglutarate and an amino acid are involved?

Back 11

Glutamate. Alpha keto acid is released. Reversible.

Front 12

Glutamine carries how many nitrogen groups? And why is this important?

Back 12

2; most abundant amino acid in the serum due to its efficiency in carrying nitrogenous groups. Can be used for carbon energy (make glucose or transfered back to alpah-ketoglutarate).

Front 13

Glutamate to Glutamine?

Back 13

Glutamine Synthetase. Utilizes one ATP and a free ammonia.

Front 14

What catalyzes the reverse reaction? Glutamine to Glutamate.

Back 14

Glutaminase. Releases free ammonia.

Front 15

Proline Synthesis.

Back 15

Step 1: Glutamate + ATP + NADPH goes to Glutamate semialdehyde. In the mitochondria.
Step 2: Spontaneous cyclization (nonenzymatic). Reduce again with NADPH = proline. Occurs in cystol. Know that the nitrogen comes from glutamate.

Front 16

Arginine biosynthesis, and where is it localized?

Back 16

Glutamate goes to glutamate semialdehhyde which then undergoes transamination to form ornithine (component of urea cycle). Ornithine goes to Arginine. Urea cycle only found in the liver.

Front 17

What does arginase do?

Back 17

Converts arginine back to ornithine releasing urea.

Front 18

What is derived from OAA?

Back 18

Aspartate and Asparagine.

Front 19

OAA goes to ____ via ____ which can then form ____ with ____ enzyme.

Back 19

OAA goes to Aspartate cia transamination (PLP) which can then form Asparagine with asparagine synthetase (glutamine and ATP both needed for rxn).

Front 20

Asparagine to Aspartate... what enzyme?

Back 20

Asparaginase. Releases free ammonia.

Front 21

What amino acids are derived from intermediates of glycolysis?

Back 21

Alanine, serine, glycine, and cysteine.

Front 22

When you transaminate pyruvate you make ____ which can be used to ____. The nitrogens come from ____.

Back 22

Alanine. Can be used for transport of nitrogen to the liver. Nitrogen from glutamate.

Front 23

Serine is produced from ____.

Back 23

Glycolytic intermediate 3-phosphoglycerate.

Front 24

Regulation of serine production.

Back 24

Serine can repress 3-phosphoglycerate dehydrogenase (negative feedback). This is the rate limiting step and represses transcription of this enzyme. A second allosteric negative feedback is phosphoserine phosphatase.

Front 25

Glycine is formed from ____ where ____ donates one of its carbons to ____ forming ____.

Back 25

Glycine is formed from serine where serine donates one of its carbons to FH4 forming N5,N10-CH2-FH4 (methylenetetrahydrofolate).

Front 26

Cysteine is synthesized from the carbons and nitrogen of ____ and the sulfur of ____ which is derived from ____.

Back 26

Serine
Homocysteine
Methionine (an essential amino acid)

Front 27

Name the enzyme that metabolically regulates cysteine biosynthesis.

Back 27

Cystationine Synthase (PLP). Negative allosteric regulation... feedback loop.

Front 28

Serine + Homocysteine go to ____ via ____.

Back 28

Cystathionine via Cystationine synthase.

Front 29

Cystathionine goes to ____ via cystathionase.

Back 29

Cysteine.

Front 30

Homocystinuria

Back 30

Increased homocysteine and homocystine (disulfide version) due to abnormal homo. metabolism. Associated with neural tube defects and vascular disease.

Front 31

Cystinuria

Back 31

Defect in transport cell that permits the resorption of cystine in renal tubular cells. Aggregates and develop cystine stones (cystine is disulfide form).

Front 32

Cystinosis

Back 32

Cannot remove cystine from lysosomes. Accumulate and form crystals.

Front 33

BH4 is synthesized from ____.

Back 33

GTP

Front 34

Phenylalanine hydroxylase (PAH) catalyzes what reaction?

Back 34

Phenylalanine to Tyrosine. Mixed function oxidase with cofactor BH4. Requires molecular oxygen. BH4 is oxidized to BH2 and must therefore be reduced back to BH4 for next round with NADH.

Front 35

PKU

Back 35

Phenylketonuria is a deficiency in:
Classic- PAH
Nonclassic- dihydropteridine reductase

Common. Screened at birth. Accumulate phenylalanine and phenylketones (due to transamination) which are cytotoxic. Can cause serious neurological disorders.