Proteins and Protein Structure – Video Notes Review

A set of practice flashcards covering proteins, their structure, functions, and examples from the lecture notes.

What is a protein?

A long-chain polymer made of amino acids; the primary functional molecules in cells.

What is a peptide bond?

A covalent bond linking the amino group of one amino acid to the carboxyl group of the next amino acid.

What is an amino acid?

The monomer of proteins, consisting of an amino group, a carboxyl group, and a variable R-group.

What is the R-group (side chain) of an amino acid?

The variable side chain that determines the amino acid’s properties (polar, non-polar, acidic, basic).

What are the four levels of protein structure?

Primary, secondary, tertiary, and quaternary.

What is primary structure?

The linear sequence of amino acids in a polypeptide.

What is secondary structure?

Local folding patterns such as alpha helices and beta sheets formed by hydrogen bonds.

What is an alpha helix?

A spiral region of a polypeptide stabilized by hydrogen bonds.

What is a beta sheet?

A sheet-like arrangement formed when parts of the polypeptide align and hydrogen bonds stabilize the structure.

What is tertiary structure?

The overall three-dimensional shape of a single polypeptide, stabilized by ionic, hydrogen, and covalent bonds, including disulfide bridges.

What is quaternary structure?

The arrangement of multiple polypeptide subunits into a functional protein.

Hemoglobin is an example of which kind of protein?

A transport protein.

What is collagen?

A structural protein that provides tissue and connective tissue support (bones, joints, ligaments).

What are immunoglobulins?

Defense proteins (antibodies) that attack pathogens.

What are myosin and actin?

Motor proteins that enable movement and muscle contraction.

What are amylase, pepsin, trypsin, and lipase?

Enzymes that break down foods during digestion.

What is prolamine?

A storage protein found in plant seeds that provides nutrients for the embryo.

What is ACE2?

A receptor protein on cell surfaces that binds external molecules; viruses like COVID-19 exploit it to enter cells.

What is insulin?

A protein hormone produced by the pancreas that regulates glucose uptake via insulin receptors.

How many standard amino acids exist?

Twenty standard amino acids.

What is the average length of a protein?

About 500 amino acids.

What bonds link amino acids together in a protein chain?

Peptide bonds connect the amino group of one amino acid to the carboxyl group of the next.

What stabilizes secondary structures like alpha helices and beta sheets?

Hydrogen bonds between polar amino acids in the chain.

What is a disulfide bridge?

A covalent bond between cysteine residues that can stabilize the tertiary structure.

What roles do proteins serve besides enzymes?

Structural support, energy storage, transport, hormones, receptors, movement, and defense.

What is the role of storage proteins?

Store energy in covalent bonds within the protein; energy is released by breaking those bonds.

What is the role of defense proteins?

Proteins that protect the organism from pathogens (e.g., antibodies).

What is the role of transport proteins?

Move substances through the body or across membranes (e.g., hemoglobin).

What is the role of protein hormones?

A hormone that coordinates an organism’s activities; many hormones are proteins.

What is the role of receptor proteins?

Bind specific chemicals and relay information into the cell.

Do individual proteins perform all roles in a cell?

No. Most proteins perform 1–3 roles; other molecules (carbohydrates, lipids, etc.) also participate.

What does hydrophobic vs hydrophilic mean in amino acids?

Hydrophobic = nonpolar; hydrophilic = polar or charged.

What is a secondary structural feature formed by hydrogen bonds?

Alpha helices and beta sheets.

What is a disulfide bridge and why is it important?

A covalent bond between cysteine residues that helps stabilize the tertiary structure.

What is the general purpose of polysaccharide and protein energy storage in seeds?

Storage proteins in seeds (like prolamine) provide nutrients for the embryo until photosynthesis begins.

What percentage of the body’s proteins is collagen?

About 25–35%.