BASI M01L03 - Amino Acids, Protein Structure, and Enzymes

How many amino acids are there?

20

What are amino acids classified by?

The properties of their side chain (aka R groups)

Are non-polar molecules hydrophobic or hydrophilic?

Hydrophobic

What is hydrophobic interaction?

Polar groups are not very soluble in water so they aggregate together in groups (ex: oil in water

What does hydrophobic interaction contribute to in proteins?

Protein folding

In an aqeous solution, where are non-polar amino acids located? Why?

Inside of proteins. To limit interaction with water (hydrophobic)

Are polar molecules hydrophobic or hydrophilic?

Hydrophilic

Polar uncharged molecules participate in what kind of bonds?

Hydrogen Bonds and Disulfide bonds (CYSTEINE ONLY)

What types of bonds do polar charged molecules participate in?

Hydrogen and ionic

Which polar charged amino acids are acidic (R groups are negatively charged at physiological pH)?

Aspartic acid and Glutamic acid

Which polar charged amino acids are basic (R groups are positively charged at physiological pH)?

Histidine, Arginine, and Lysine

What are the non-polar amino acids?

Glycine

Alanine

Valine,

Leucine

Isoleucine

Phenylalalnine

Tryptophane

Methionine

Proline

What are the polar uncharged amino acids?

Serine

Threonine

Tyrosine

Cysteine

Asparagine

Glutamine

What are the four classifications of amino acids?

Non-polar

Polar uncharged

Polar charged acidic

Polar charged basic

What is the bond that only cysteine can form?

Disulfide bond

What are the four levels of protein structure?

Primary

Secondary

Tertiary

Quarternary

What is the primary structure of a protein?

A linear sequence of amino acids (polypeptide chain)

What is the secondary structure of a protein?

The local folding of a polypeptide chain

What is the tertiary structure of a protein?

The protein’s specific, overall 3D shape

What is the quarternary structure of a protein?

An arrangement of polypeptides that consists of more than one chain

What bond joins amino acids together?

Peptide bond

What are the major secondary structures of proteins?

α-Helix and β-Sheet

What is a domain?

a distinct, stable structural element within a protein that has its own function

The quarternary structure is found in proteins with…

more than one polypeptide chain

In sickle cell anemia, which amino acid is converted due to mutation?

Glutamate (polar, charged)

In sickle cell anemia, which amino acid is the result of the mutation?

Valine (non-polar)

At which position of hemoglobin does the mutation occur?

6th

When oxygen is low, what happens to the mutant hemoglobin?

It polymerizes and forms fibers that change the shape of the red blood cell

How many days can an RBC resulting from sickle cell anemia survive? How about a normal RBC?

Sickle Cell - 20 days

Normal RBC - 120 days

What is an enzyme?

a protein catalyst that increases velocity of a reaction

How does an enzyme increase reaction rate?

Binds to a substrate so that it is positioned correctly in the active site and reduces energy of activation

What curve does a Michaelis-Menten enzyme form?

Hyperbolic

What curve does an Allosteric enzyme form?

Sigmoidal

What is Vmax?

Maximum velocity

What is Km?

Michaelis-Menten constant, represents the substrate concentration [S] where the initial velocity is half that of Vmax

What does Km measure?

Binding affinity of the enzyme for the substrate

An enzyme with a low Km has a _____ affinity for the substrate.

high

An enzyme with a high Km has a _____ affinity for the substrate.

low

What are the two types of Michaelis-Menten enzymes?

Competitive Inhibitors

Non-competitive Inhibitors

What does a competitive inhibitor do?

Competes with the substrate to bind to the active site, increases Km but leaves Vmax unchanged (lowers enzyme affinity for substrate)

What does a non-competitive inhibitor do?

Binds to the enzyme outside of the substrate-binding site (structurally different from the substrate), decreases Vmax and leaves Km unchanged (doesn’t necessarily prevent binding)

What are the two functions of allosteric enzymes?

Inhibitor - stabilizes the enzyme in a low-affinity form, decreases activity

Activator - stabilizes enzyme in high-affinity form, increases activity