Lecture 5 Flashcards
Proteins functions
- Enzymes: catalyze specific reactions: ex DNA replication, cellular respiration, drug detoxification
- Transport proteins: hemoglobin, channel/carrier proteins in cell membranes
- Structural proteins: ex cytoskeleton
4 & 5. Hormonal proteins, receptor proteins
- Defensive proteins
Proteins are made of
Proteins are made of monomers called amino acids.
There are 20 common amino acids
Amino acids are held together by …
Amino acids are held together by peptide bonds
How do we get essential amino acids?
We can’t make or make enough of to meet our needs. Have to get from diet
4 levels of protein structure
Primary
Secondary
Tertiary
Quaternary: 2 or more polypeptides
All proteins have primary, secondary, & tertiary structures but quaternary structures only arise when a protein is made up of two or more polypeptide chains.
Protein shape essential to function
Primary structure
sequence of amino acids in a polypeptide chain (determined by the sequence of nucleotides in the gene)
Shape of protein ultimately depends on primary sequence.
Secondary Strucure
Coiling / folding of the 1° structure = secondary structure
AA of protein interact to form 2° structure through H-bonds
Coiled (α-helix): Flexible: H-bonds can be broken so polypeptide can stretch under tension. Release tension → H-bonds reform →polypeptide recoils
Folded (ß-pleated): strong
Tertiary Structure
Polypeptide with secondary structure folds on itself giving the protein a three-dimensional shape.
All polypeptides have this level
Quaternary Structure
Association of 2 or more polypeptide chains
Polypeptide vs Protein
A peptide is two or more amino acids joined together by peptide bonds
protein contains one or more polypeptides
Protein loss of proper function due to
Loss of proper shape→ loss of function
1. Mutation: change in primary structure
2. Denaturation: lose shape & therefore function in response to external conditions (no change in
primary structure)
Mutations in Proteins
Mutations: change in primary structure→∆/loss of function
Protein misfolding can occur due to mutations (primary structure), which can lead to changes in secondary & tertiary structure
Denaturation in proteins
Due to cellular conditions: Heat, pH, heavy metals (Hg), alcohol & salt change the shape of proteins
Disruption and possible destruction of both the secondary & tertiary structures of the polypeptide & possibly of quaternary structure if present
Inhibits protein function
Can be reversible or irreversible
How are peptides bonds formed
dehydration synthesis reaction
