KeyExam1versionABIos352Spring2020

Hemoglobin

A protein in red blood cells that carries oxygen.

True or False: O₂ binding triggers a conformational change in hemoglobin

True

True or False: Positive cooperativity

When the first binding event increases the affinity at remaining sites.

True or False: Negative cooperativity

When the first binding event reduces affinity at remaining sites.

Toxicity of Carbon monoxide (CO)

It binds to the Fe atom in hemoglobin and prevents the binding of O2.

Lock and Key Model

A model that describes enzyme-substrate interaction without conformational change.

True or False: A beta-sheet is an example of quaternary structure

False

True or False: Proteins can be denatured by extremes of pH

True

True or False: An independently stable part of a protein is called a domain

True

True or False: O2 dissolves easily in water

False

Anfinsen's experiment

Showed that the amino acid sequence determines the native conformation.

Beta turn

A secondary structure that often includes Proline and Glycine.

pH calculation of weak acid

When the molar ratio of proton acceptor to donor is high, the pH is calculated using pKa and log values.

Noncovalent interactions

Include Electrostatic interactions, Hydrogen bonds, Hydrophobic effect, and Van der Waals interactions.

Gel filtration column

A chromatography method that separates molecules based on size.

Weak interactions in proteins

Include hydrogen bonds, hydrophobic interactions, and van der Waals forces, but not peptide bonds.

Western blot procedure

Involves immobilizing protein samples on a membrane and detecting them with antibodies.

Beer’s Law

A relation between absorbance and concentration, used in spectrophotometry.

Purification steps in chromatography

Can help identify and isolate a protein based on properties like size and charge.

Planar bonds in polypeptide backbone

C-N bonds, which cannot rotate.

Keratin

A fibrous protein with alpha-helices that have many disulfide bonds.

Bicarbonate reaction

CO2 acts as a conjugate base in the bicarbonate buffer system.

Pentapeptide

A peptide consisting of five amino acids.

Modification in amino acid residues

Steps can include adding functional groups or changing side chains.

Amino acids

Organic compounds composed of an amino group, a carboxyl group, and a distinctive side chain (R group), which determines the properties of the amino acid.

Nonpolar amino acids

Amino acids with hydrophobic side chains, generally do not interact favorably with water. Examples include Alanine (Ala), Valine (Val), Leucine (Leu), and Isoleucine (Ile).

Polar amino acids

Amino acids with hydrophilic side chains that can form hydrogen bonds with water. Examples include Serine (Ser), Threonine (Thr), Asparagine (Asn), and Glutamine (Gln).

Charged amino acids

Amino acids that have side chains with a positive or negative charge, making them hydrophilic. Examples include Lysine (Lys), Arginine (Arg), Aspartate (Asp), and Glutamate (Glu).

Aromatic amino acids

Amino acids with an aromatic ring in their side chains; generally hydrophobic. Examples include Phenylalanine (Phe), Tyrosine (Tyr), and Tryptophan (Trp).

Three-letter codes for amino acids

Each amino acid is represented by a three-letter abbreviation, which is standard in biochemistry. For example, Glycine is Gly, Alanine is Ala, etc.

Hydrophobic effect

The tendency of nonpolar substances to aggregate in aqueous solution to minimize exposure to water, significantly influencing protein folding.

Peptide bond

The covalent bond formed between the carboxyl group of one amino acid and the amino group of another, resulting in the release of a water molecule.

Protein structure levels

Proteins have four levels of structure: primary (amino acid sequence), secondary (alpha helices and beta sheets), tertiary (3D shape), and quaternary (assembly of multiple polypeptide chains).

Denaturation

The process in which proteins lose their native structure due to factors such as extreme pH, temperature, or chemical agents, leading to a loss of function.

Enzyme specificity

The ability of an enzyme to select for a particular substrate among multiple substrates, often modeled by the Lock and Key or Induced Fit models.

Isoelectric point (pI)

The pH at which an amino acid carries no net electrical charge, impacting its solubility and behavior in electrophoresis.

Zwitterion form

The dipolar ion form of amino acids at physiological pH, which possesses both a positive and negative charge but is overall neutral.

Functional groups in amino acids

The R group in amino acids can include functional groups such as hydroxyl (-OH), carboxyl (-COOH), amino (-NH2), and thiol (-SH), influencing properties.

Side chain variability

The side chains (R groups) of amino acids vary in size, shape, charge, and polarity, which affects protein structure and function.