Biology 1113: Lecture 4 (proteins) Flashcards
What are proteins made of?
Long strings of amino acids (monomers linked together).
How do the type and arrangement of monomers affect proteins?
They determine the molecule’s shape, which in turn determines its function.
How many amino acids are used in human proteins?
20 amino acids.
What is the basic structure of an amino acid?
A central carbon bonded to:
- A hydrogen atom (H)
- An amino group (NH₂)
- A carboxyl group (COOH)
- A variable R group (side chain).
What determines the properties of an amino acid?
Its R group (hydrophilic, hydrophobic, acidic, basic, etc.).
What happens to hydrophobic R groups in water?
They cluster toward the protein’s interior.
What are the four levels of protein structure?
Primary: Sequence of amino acids.
Secondary: 3D shapes like α-helix and β-pleated sheets formed by hydrogen bonds.
Tertiary: Overall 3D shape formed by interactions between R groups.
Quaternary: Structure formed by multiple polypeptides.
What bonds are involved in secondary and tertiary structures?
Secondary: Hydrogen bonds.
Tertiary: Hydrogen bonds, ionic bonds, disulfide bonds, hydrophobic interactions, van der Waals forces.
What is a peptide bond?
A covalent bond between the carboxyl group of one amino acid and the amino group of another.
What distinguishes proteins, polypeptides, and peptides?
Peptides: Short chains (<50 amino acids).
Polypeptides: Longer chains (≥50 amino acids).
Proteins: Fully functional molecules, sometimes consisting of multiple polypeptides.
What happens when a protein denatures?
It loses its 3D shape and function, usually due to heat or chemical changes.
List the main functions of proteins.
Structural (e.g., hair, cartilage).
Protection/Defense (e.g., antibodies).
Signaling/Regulation (e.g., hormones).
Movement/Contraction (e.g., muscle proteins).
Transport (e.g., hemoglobin).
Catalysis (e.g., enzymes).
What is an enzyme?
A protein that speeds up biological reactions by reducing activation energy.
What is the active site of an enzyme?
The location where substrates bind and reactions occur.
Why are enzymes specific?
Their active site’s shape and chemical properties match specific substrates.
Why is the amino acid sequence important?
It determines the protein’s 3D shape and function.
What can a single amino acid change do to a protein?
It can drastically affect the protein’s shape and function, especially if the replacement is dissimilar (e.g., polar vs. nonpolar).
How do proteins fold into their functional shapes?
Through interactions between amino acids (e.g., hydrogen bonds, ionic bonds).
What are molecular chaperones?
Proteins that help other proteins fold correctly by preventing inappropriate interactions.
What causes protein misfolding diseases like prion diseases?
Misfolded proteins that induce other proteins with the same sequence to misfold.
What are essential amino acids?
Amino acids that the human body cannot produce and must be obtained through diet.
What is a complete protein?
A food containing adequate amounts of all essential amino acids.
How can you meet your essential amino acid needs without complete proteins?
By combining complementary foods (e.g., rice and beans).
How do enzymes speed up reactions?
By lowering the activation energy required for the reaction.
What suffix do most enzymes have?
“-ase” (e.g., lactase, cellulase).
What happens if an enzyme is missing or defective?
The reaction it catalyzes cannot proceed (e.g., lactose intolerance).
What makes peptide bonds unique?
They are stable and inflexible, giving proteins structural integrity.
What are α-helix and β-pleated sheets?
Common shapes in secondary structure due to hydrogen bonding.
How does denaturation affect bonds in proteins?
It disrupts weaker bonds (e.g., hydrogen bonds) but not the sequence of amino acids.
