Amino Acid Structure and Function Lecture 5 Ford Flashcards
What does an amino acid look like at physiological pH? Why?
It is in a zwitterion form (neutral form) because at physiological pH, the amino group is protonated because we are below its pKa value, but the carbonyl group is deprotonated because we are above its pKa value
What form of amino acids is the physiologically relevant form?
L form amino acids
What are the hydrophobic AA?
G, A, P, V, L, I, M, W, F
What are the polar AA?
S, T, Y, N, Q, C
What are the positively charged AA?
K, R, H
What are the negatively charged AA?
D, E
What makes cysteine an odd but extremely important AA?
It can form disulfide bridges with other cysteine residues to form cystine; these are important in protein folding and function
What are the tiny AA?
A, C, G, S
What are the small AA?
P, D, T, N
What are the medium AA?
V, E, H, Q
What are the large AA?
I, K, L, R, M
What are the very large AA?
Y, F, W
What are the essential AA?
F, V, W, T, I, M, H, R, K, L
Mnemonic: PVT TIM HALL
What are the non-essential AA?
A, N, D, C, Q, E, G, P, S
Which essential AA do we have to consume because they are difficult to produce enough of on our own?
R and M
Where do you find the 21st AA (selenocysteine) and the 22nd AA (pyrrolysine)?
21st in all 3 domains of life and are important for health; 22nd in only some prokaryotes (methanogens) and these are present in the intestinal microbiome
What can nonproteinogenic AA be used for?
Can be used in non-ribosomal protein synthesis (NRPS), in the production of antibiotics via NRPS, can be found in bacterial cell walls, neurotransmitters, toxins/antimicrobials, and are found in metabolism intermediates
Primary Structure
Chain of AA
Secondary Structure
Local folding of the polypeptide chain
Tertiary Structure
Folding of the secondary structure
Quaternary Structure
Interaction of multiple peptides
Where do you find the peptide bond in proteins?
Between the carbonyl carbon of one AA and the amino nitrogen of the next AA
What modifications can be made during primary structure of a protein?
Enzymatic cleavage of signal sequences, chemical modifications of side chains (phosphorylation, glycosylation, methylation)
What is the pka of the ionizing side chain of Arginine?
12.5
What is the pka of the ionizing side chain of Aspartic acid
4.1
What is the pka of the ionizing side chain of cysteine?
8.3
What is the pka of the ionizing side chain of histidine?
6.0
What is the pka of the ionizing side chain of lysine?
10.0
What is the pka of the ionizing side chain of tyrosine?
10.1
What are the health benefits of selenocysteine?
- reduce oxidative stress with vitamin E
- growth of cerebellar neurons
- moderate inflammatory responses
What results from a selenium deficiency?
Keshan (cardiomyopathy) Statin intolerance (rhabdo)
What results from too much selenium?
Hair and nail brittleness, garlic breath, GI neurons lesions, and other bad things
