BIO CHEMISTRY EXAM 2025 QUESTIONS AND
ANSWERS
Amino Acids
Have an amino group, carboxylic acid, hydrogen atom, and an R group attached to a central α-carbon
Amino Acid Structure
1. Chiral (L) except for glycine, and have the (S) configuration, except for cysteine.
2. Side Chains determine the chemistry and function of amino acids.
Nonpolar, nonaromatic
Glycine, Alanine, Valine, Leucine, Isoleucine, Methionine, and Proline
Aromatic
Tryptophan, Phenylalanine, and Tyrosine
Polar
,Serine, Theronine, Asparagine, Glutamine, and Cysteine
Negatively Charged (Acidic)
Aspartic Acid and Glutamic Acid
Positively Charged (Basic)
Lysine, Arginine, and Histidine
Amino Acid Chemistry
-Amphoteric
-Protonated at low pH
-Zwitterion at neutral pH
-Fully deprotonated at high pH
pL
Determine by averaging pKa values that refer to protonation and deprotonation of the zwitterion
Peptide Bonds
Formed through condensation (dehydration) reaction with a nucleophilic amino group attacking an
electrophilic carbonyl. Broken through hydrolysis.
,Protein Structure
Primary, Secondary, Tertiary, and Quaternary
Primary Structure
Linear sequence of amino acids
Secondary Structure
Local structure, stabilized by hydrogen bonding:
α-helices and β-pleated sheets
Tertiary Structure
Three-dimensional structure stabilized by hydrophobic interactions, acid-base interactions (salt bridges),
hydrogen bonding, and disulfide bonds
Quaternary Structure
Interactions between subunits, heat and solutes cause denaturation
Structural Proteins
Generally fibrous, include collagen, elastin, keratin, actin, and tubulin
, Motor Proteins
Capable of force generation through a conformational change. Include myosin, kinesin, and dyenin
Binding Proteins
Bind a specific substrate, either to sequester it in the body or hold its concentration at a steady state
Cell Adhesion Molecules (CAMs)
Bind cells to other cells or surfaces. Include cadherins, integrins, and selectins
Antibodies (immunoglobulins/Ig)
Target a specific antigen, which may be a protein on a surface of a pathogen (invading organism) or a
toxin
Ion Channels
Can be used for regulating ion flow into or out of a cell. There are three main types of ion channels:
ungated, voltage-gated, and ligand-gated channels
Enzyme-linked Receptors
Participate in cell signaling through extracellular ligand binding and initiation of second messenger
cascades
ANSWERS
Amino Acids
Have an amino group, carboxylic acid, hydrogen atom, and an R group attached to a central α-carbon
Amino Acid Structure
1. Chiral (L) except for glycine, and have the (S) configuration, except for cysteine.
2. Side Chains determine the chemistry and function of amino acids.
Nonpolar, nonaromatic
Glycine, Alanine, Valine, Leucine, Isoleucine, Methionine, and Proline
Aromatic
Tryptophan, Phenylalanine, and Tyrosine
Polar
,Serine, Theronine, Asparagine, Glutamine, and Cysteine
Negatively Charged (Acidic)
Aspartic Acid and Glutamic Acid
Positively Charged (Basic)
Lysine, Arginine, and Histidine
Amino Acid Chemistry
-Amphoteric
-Protonated at low pH
-Zwitterion at neutral pH
-Fully deprotonated at high pH
pL
Determine by averaging pKa values that refer to protonation and deprotonation of the zwitterion
Peptide Bonds
Formed through condensation (dehydration) reaction with a nucleophilic amino group attacking an
electrophilic carbonyl. Broken through hydrolysis.
,Protein Structure
Primary, Secondary, Tertiary, and Quaternary
Primary Structure
Linear sequence of amino acids
Secondary Structure
Local structure, stabilized by hydrogen bonding:
α-helices and β-pleated sheets
Tertiary Structure
Three-dimensional structure stabilized by hydrophobic interactions, acid-base interactions (salt bridges),
hydrogen bonding, and disulfide bonds
Quaternary Structure
Interactions between subunits, heat and solutes cause denaturation
Structural Proteins
Generally fibrous, include collagen, elastin, keratin, actin, and tubulin
, Motor Proteins
Capable of force generation through a conformational change. Include myosin, kinesin, and dyenin
Binding Proteins
Bind a specific substrate, either to sequester it in the body or hold its concentration at a steady state
Cell Adhesion Molecules (CAMs)
Bind cells to other cells or surfaces. Include cadherins, integrins, and selectins
Antibodies (immunoglobulins/Ig)
Target a specific antigen, which may be a protein on a surface of a pathogen (invading organism) or a
toxin
Ion Channels
Can be used for regulating ion flow into or out of a cell. There are three main types of ion channels:
ungated, voltage-gated, and ligand-gated channels
Enzyme-linked Receptors
Participate in cell signaling through extracellular ligand binding and initiation of second messenger
cascades
