Proteins - AP Biology

Flashcards reviewing protein structure, amino acid chemistry, folding levels, functions, lipoproteins, denaturation, and prion diseases based on the AP Biology macromolecule lecture.

What six primary functions do proteins perform in cellular processes?

Structure, nutrition, enzymes, transport, communication, and cellular defense.

What are the monomers of proteins, and what basic structural parts compose them?

Amino acids are the monomers of proteins. Each amino acid consists of an amine group, a carboxyl group, and one or more variable groups (R groups).

What is the function of R groups in amino acids?

R groups (or functional groups) give each amino acid unique chemical properties, such as being polar, non-polar, or acidic.

What is a polypeptide, and what bond links its monomers together?

A polypeptide is a linear chain of amino acids held together by peptide bonds (covalent bonds) formed through condensation reactions.

How many different amino acids exist, and what accounts for protein diversity?

There are 20 different amino acids. The order of amino acids and the overall length of the polypeptide account for the wide diversity of proteins.

How do the functional groups of adjacent amino acids connect to form a chain?

The carboxyl end of one amino acid links together with the amine end of a different amino acid, behaving like interlocking lego bricks.

What defines the primary structure of a protein?

The primary structure is the unique linear sequence of amino acids in a polypeptide chain, linked by peptide bonds.

What causes secondary structure in proteins, and what two main shapes can form?

Secondary structure arises when a polypeptide chain twists and forms hydrogen bonds between amino acids, creating Alpha Helices (coils) or Beta Sheets (flat sheets).

What characterizes the tertiary structure of a protein?

Tertiary structure occurs when the polypeptide chain folds up into structurally stable units called domains (such as barrels or pockets), creating a fully functional protein.

Which four types of R-group interactions stabilize a protein's tertiary structure?

Hydrogen bonds, hydrophobic interactions, disulfide bridges, and ionic bonds.

What is quaternary structure in proteins?

Quaternary structure occurs when two or more folded polypeptide chains associate as one molecule, held together by hydrogen bonds, disulfide bridges, hydrophobic interactions, or ionic bonds.

What are the subunits and non-protein components of a hemoglobin molecule?

Hemoglobin consists of four globin protein chains (subunits), each containing a non-protein iron-holding heme group.

What are glycoproteins, and what role do they play in the body?

Glycoproteins are proteins that contain sugars; they allow the body to recognize its own cells for immune responses.

What are lipoproteins, and how do LDL and HDL differ in function?

Lipoproteins are proteins containing lipids. Low-density lipoprotein (LDL) transports cholesterol out of the liver to cells, whereas High-density lipoprotein (HDL) carries cholesterol released from dead cells back to the liver.

What does it mean for a protein to denature, and what factors trigger this?

Denaturation occurs when a protein loses its three-dimensional shape and can no longer function correctly. It is caused by heat, pH, salts, and detergents disrupting hydrogen bonds.

What chemical changes occur to albumin in egg whites when cooked?

Cooking destroys the hydrogen bonds maintaining albumin's shape, causing it to denature and turn opaque, while leaving the covalent bonds of its primary structure intact.

What is a prion, and what diseases does it cause?

A prion is a disease-causing misfolded protein. Examples include Mad Cow Disease (bovine spongiform encephalitis), Creutzfeldt- Jakob Disease in humans, and Scrapie in sheep.

How does PrPC cause brain damage when converted into a prion?

Misfolded PrPC acts as an infectious prion that causes other PrPC proteins to misfold, forming long fibers that accumulate in the brain and kill brain cells, leaving holes behind.

Why can prions pass from infected animals to humans through consumption of meat?

Prions cannot be destroyed by heat, allowing the misfolded protein to survive cooking and infect humans.