**** this Biochem ****

Lineweaver-Burk plot y-intercept

1/Vmax

Which of the following cell-cell junctions would help skin cells withstand mechanical stress by directly anchoring the intermediate filaments of adjacent cells? Desmosomes Gap junctions Tight junctions A.I only B.II only C.I and III only D.II and III only

A.I only Desmosomes provide tensile strength to epithelial cell sheets by anchoring the cytoskeletons, specifically the intermediate filaments, of two cells together. Gap junctions are cell-cell junctions that mediate communication between cells. Tight junctions are cell-cell junctions that prevent water and solutes from diffusing between cells and across the epithelial cell layer.

An enzyme kinetics assay reveals that Vmax = 100 nmol/s and Km = 10 μM. For this assay, what substrate concentration is required for a reaction rate V0 of 75 nmol/s? A.20 μM B.30 μM C.50 μM D.75 μM

B.30 μM using the Michaelis-Menten equation V0 = Vmax[S] / (Km+[S])

Acetylation of lysine residues in histones increases gene expression because: A.DNA is tightly bound to negatively charged amino acids on histones. B.the carboxyl oxygen atoms in acetyl groups form hydrogen bonds with nitrogenous bases. C.the salt bridges between charged amino acids and phosphate groups are disrupted. D.lysine residues in histones associate with positively charged phosphate groups in DNA.

C.the salt bridges between charged amino acids and phosphate groups are disrupted.

K+ ______________ neural membrane potential Na+ _________________ neural membrane potential

K+ decreases Na+ increases

Lineweaver-Burk plot slope

Km/Vmax

Protease vs proteasome

Protease - an enzyme which breaks down proteins and peptides Proteasome - a protein complex in cells containing proteases; it breaks down proteins that have been tagged by ubiquitin.

The Michaelis-Menten equation describes the velocity V0 of any enzyme-catalyzed reaction as a function of substrate concentration [S]. V0 =

V0 = Vmax[S] / (Km+[S])

Find Vmax of an enzyme given Kcat (number of substrate molecules converted to product per second by each enzyme in solution under saturating conditions) Vmax =

Vmax = Kcat [Enzyme]

p values are expressed as decimals between 0 and 1. What does p-value = 0.5 indicate?

a 50% chance that an observed difference is merely due to random chance

Antibodies are ________________ that function in the immune system to recognize foreign particles known as _____________

antibodies are proteins antigens

Each antibody contains a variable region that binds to a specific chemical structure within an antigen, known as the ____________, which is a sequence of amino acids within a protein or peptide

epitope

Phosphorylation occurs at serine, threonine, and tyrosine residues, each of which contains a _____________ group in its side chain

hydroxyl

When an axon hillocks reaches threshold, an excitatory stimulus causes several nearby voltage-gated Na+ channels to open, allowing Na+ ions to rush ____(into or out of)_____ the cell.

into

Degradation is typically induced by targeting proteins to the _________________ or the _____________________.

lysosome or proteasome

For a peptide of known composition, in which each amino acid is different from every other amino acid, the number of possible arrangements is ___________

n! where n is the number of amino acids in the peptide.

Antibodies bind their epitopes through _________________ binding

noncovalent interactions (H-bonding or electrostatic interactions)

a p-value < ________ is accepted as statistically significant

p < 0.05 (ie, 95% chance of a true difference).

Specific activity measures protein __________________ Specific activity =

purity Specific activity = Total activity / total protein (g)

The lower the p-value,.....

the lower probability of random chance, and therefore a higher probability that the observed difference is real (ie, due to experimental differences)

Which is smaller: bacteria or virus?

virus

Lineweaver-Burk plot x-intercept

−1/Km