Lecture 4 Proteins Flashcards
(24 cards)
What is an enzyme?
Protein that speeds up (catalyzes) chemical reactions.
Example: Salivary amylase breaks down starch in your mouth.
What is a storage protein?
Protein that stores nutrients for later use.
Example: Casein in milk stores amino acids for baby mammals.
What is a hormonal protein?
Protein that carries chemical signals between body parts.
Example: Insulin regulates blood sugar.
What is a contractile (motor) protein?
Protein involved in movement of cells or muscles.
Example: Actin and myosin slide past each other to make muscles contract.
What is a defensive protein?
Protein that protects the body against disease.
Example: Antibodies bind to pathogens to neutralize them.
What is a transport protein?
Protein that moves substances in or out of cells or through the body.
Example: Hemoglobin carries oxygen in red blood cells.
What is a receptor protein?
Protein on a cell’s surface that detects chemical signals.
Example: Nerve cell receptors bind neurotransmitters.
What is a structural protein?
Protein that supports and shapes cells or tissues.
Example: Keratin strengthens hair and nails.
What is an amino acid?
Building block (monomer) of proteins, each has a central carbon bonded to an amino group (–NH₂), a carboxyl group (–COOH), a hydrogen (H), and an R-group (side chain) that varies.
What is a peptide bond?
Covalent link between the carboxyl group of one amino acid and the amino group of another, formed by removing water (dehydration synthesis).
What is a protein?
One or more polypeptides folded into a specific three-dimensional shape to do work in the cell.
What is a fibrous protein?
Long, rope-like proteins mainly for support or strength.
Example: Collagen in connective tissue.
What is a globular protein?
Spherical proteins that are often enzymes, transporters, or hormones.
Example: Hemoglobin transports oxygen.
What is the primary structure of a protein?
The exact sequence of amino acids in a polypeptide chain.
What is the secondary structure of a protein?
Local coils (α-helices) and folds (β-pleated sheets) formed by hydrogen bonds along the backbone.
What is the tertiary structure of a protein?
The overall 3D shape of a single polypeptide, formed by interactions among R-groups.
What is the quaternary structure of a protein?
Shape formed when two or more polypeptide chains (subunits) join together.
What is an R-group (side chain)?
The variable part of an amino acid that gives it unique chemical properties.
What is a nonpolar R-group?
Hydrophobic side chain that avoids water.
Example: Leucine.
What is a polar R-group?
Hydrophilic side chain that can form hydrogen bonds.
Example: Serine.
What is an acidic R-group?
Side chain with a negative charge at cellular pH.
Example: Aspartic acid.
What is a basic R-group?
Side chain with a positive charge at cellular pH.
Example: Lysine.
What is the hydrophobic effect?
Tendency of nonpolar R-groups to cluster away from water in the protein’s interior.
What is a disulfide bridge?
Strong covalent bond between two cysteine side chains (–S–S–) that helps stabilize tertiary structure.
