🧬 MCAT Biochemistry Review - 1 Flashcards
(156 cards)
What is a tripeptide?
A peptide consisting of three amino acid residues
Tripeptides are a type of peptide that contains exactly three amino acids linked by peptide bonds.
What is the term used for relatively small peptides up to about 20 residues?
Oligopeptide
Oligopeptides are short chains of amino acids that are typically less than 20 residues long.
What is the functional group formed by the peptide bond?
-C(O)NH-
The peptide bond is a type of amide bond that forms between the carboxyl group of one amino acid and the amino group of another.
What type of reaction occurs during peptide bond formation?
Condensation or dehydration reaction
This reaction results in the removal of a water molecule when a peptide bond forms.
What is the main characteristic of amide groups in peptide bonds?
Exhibit resonance
Resonance gives the C-N bond in the amide partial double bond character, restricting rotation.
What is the N-terminus of a peptide?
The free amino end
The N-terminus is where the amino group is located, and it is conventionally drawn on the left.
What is the C-terminus of a peptide?
The free carboxyl end
The C-terminus is where the carboxyl group is located, and it is conventionally drawn on the right.
What is the role of trypsin in peptide bond hydrolysis?
Cleaves at the carboxyl end of arginine and lysine
Trypsin is a hydrolytic enzyme that specifically targets certain amino acids in peptide chains.
What is the primary structure of a protein?
The linear arrangement of amino acids
The primary structure is determined by the sequence of amino acids from the N-terminus to the C-terminus.
What stabilizes the primary structure of a protein?
Covalent peptide bonds
These bonds are formed between adjacent amino acids in the protein chain.
What are the two main secondary structures of proteins?
- α-helix
- β-pleated sheet
These structures are stabilized by hydrogen bonding between nearby amino acids.
Describe the structure of an α-helix.
A rodlike structure coiling clockwise around a central axis
Stabilized by hydrogen bonds between carbonyl oxygen and amide hydrogen atoms four residues apart.
What is the structure of β-pleated sheets?
Peptide chains lying alongside one another, forming rows held by hydrogen bonds
The R groups of amino acids point above and below the plane of the sheet.
What unique role does proline play in secondary protein structure?
Introduces a kink in the peptide chain
Proline is rarely found in α-helices but is often found in turns of β-pleated sheets.
What defines the tertiary structure of a protein?
The three-dimensional shape of the protein
Tertiary structure is determined by interactions between R groups of amino acids.
What type of bonds are important for stabilizing tertiary structure?
- Hydrophobic interactions
- Hydrogen bonds
- Disulfide bonds
These interactions help maintain the protein’s three-dimensional conformation.
What is denaturation in the context of proteins?
Loss of tertiary structure leading to loss of function
Denaturation can be caused by changes in temperature, pH, or chemical exposure.
What is the importance of the solvation layer in protein folding?
It affects the entropy of the system
Hydrophobic residues prefer to be inside proteins to minimize unfavorable interactions with water.
What happens to hydrophobic residues in an aqueous solution?
They prefer to be on the interior of the protein
This arrangement reduces their exposure to water, enhancing protein stability.
What happens to water molecules when a hydrophobic side chain is placed in aqueous solution?
Water molecules rearrange themselves into specific arrangements to maximize hydrogen bonding, resulting in a negative change in entropy (~S).
Negative changes in entropy represent increasing order (decreasing disorder) and are unfavorable.
What is the effect of hydrophilic residues on the solvation process?
Hydrophilic residues allow nearby water molecules more latitude in their positioning, increasing their entropy (~S > 0) and making the solvation process spontaneous.
How does a protein achieve maximum stability?
By moving hydrophobic residues away from water molecules and hydrophilic residues toward water molecules.
What is the primary structure of a protein compared to?
Letters.
What does the secondary structure of a protein resemble?
Words.
