MCAT_ Biochemistry exam with correct answers 2024.

MCAT: Biochemistry exam with correct
answers 2024




amino acid - ANSWER-molecules that contain:
1. an amino group (-NH2)
2. carboxyl group (-COOH)
3. R group/side chain - determines the chemical properties
4. Hydrogen atom (-H)

main focus is on alpha aa's
- not every amino acid is an alpha aa (GABA)
- not every amino acid is coded for a codon
- some aa's are converted to non codon coded aa for specific reasons

- in eukaryotes they are all L configuration

alpha amino acid - ANSWER-aa that the amino group and the carboxyl group are
attached to the same carbon (alpha carbon of the carboxylic acid)

alpha carbon is chiral (beisdes glycine)
- optically active
- in eukaryotes they are all L configuration

R group - ANSWER-side group of the amino acid
every amino acid has a different one
determines the properties of the amino acids and thus their functions

GABA - ANSWER-gamma aminobutyric acid
amino group and carboxyl group are not on the same carbon

,amino group is on the gamma carbon from the carbonyl

proteinogenic amino acids - ANSWER-20 alpha amino acids
amino acids that are encoded by the human genetic code through codons

since they are all chiral at the alpha carbon (besides glycine)
- L CONFIGURATION

have at least two group that can be protonated/deprotonated
- two (maybe three) pka's

chiral amino acids - ANSWER-the alpha carbon in alpha aa's
optically active
has four different groups attached to it

exception - glycine (has two H's)

L configuration - goes to the S absolute configuration

G - ANSWER-Glycine
*GLY*
R group - H
ACHIRAL (not L or D)
smallest amino acid
*nonpolar, non-aromatic R group*

hydrophobic - interior of proteins

Cahn Ingold Prelog System - ANSWER-L amino acids are S configuration

AMINO GROUP IS TO THE LEFT in a fisher projection

C - ANSWER-Cysteine
*CYS*
R group = -CH2SH
*polar side chain*
has a *thiol* group
-since sulfur is larger and less electronegative than oxygen SH bond is weaker than an
OH bon
-makes SH prone to OXIDATION reaction
L amino acid

,*R absolute configuration *

A - ANSWER-Alanine
*ALA*
R Group = -CH3
*nonpolar, non-aromatic R group*
alkyl side chain with one carbon makes it nonpolar
L amino acid
S absolute Configuration

hydrophobic - interior of proteins

R - ANSWER-Arginine
*ARG*
R group = -CH2CH2CH2-NH-C(=NH)NH2
*positive/basic Side Chain*
-three nitrogens in its side chain
*positive charge is delocalized over all three nitrogen atoms*
L amino acid
S absolute Configuration

hydrophilic - surface of proteins

N - ANSWER-Asparagine
*ASN*
R group = -CH2C(O)NH2
*polar side chain*
*amide side chain*
L amino acid
S absolute Configuration

hydrophilic - surface of proteins

D - ANSWER-Aspartic Acid/ ASPARTATE
*ASP*
R group = -CH2C(O)OH
*Negative/Acidic Side Chain*
L amino acid
S absolute Configuration

hydrophilic - surface of proteins

, E - ANSWER-Glutamic Acid/ GLUTAMATE
*GLU*
R group = -CH2CH2C(O)OH
*Negative/Acidic Side Chain*
L amino acid
S absolute Configuration

hydrophilic - surface of proteins

Q - ANSWER-Glutamine
*GLN*
R group = -CH2CH2C(O)NH2
*polar side chain*
*amide side chain*
L amino acid
S absolute Configuration

hydrophilic - surface of proteins

H - ANSWER-Histidine
*HIS*
R group = imidazole
*positive/basic Side Chain*
-aromatic ring with two nitrogens
L amino acid
S absolute Configuration

hydrophilic - surface of proteins

I - ANSWER-Isoleucine
*ILE*
R group = -CH(CH3)CH2CH3
*nonpolar, non-aromatic R group*
terminal primary amino group
L amino acid
alkyl side chain with four carbons makes it nonpolar
S absolute Configuration

hydrophobic - interior of proteins