Cell Bio Exam 3

Liposomes are: a) not very useful to biological chemists as models for biomembranes. b) a drug-carrying vehicle for disease treatment c) enzymes that de-esterify cholesterol in late endosomes d) membranes of single layered phospholipids with hydrophobic regions attached at their tails

a drug-carrying vehicle for disease treatment

A peptide bond forms between which two functional groups? a) Hydroxyl and amino b) Hydroxyl and carboxyl c) Hydroxyl and methyl d) Carboxyl and amino

Carboxyl and amino

We can estimate the relative mobility of a population of molecules along the surface of a living cell by fluorescently labeling the molecules of interest, bleaching the label in one small area, and then measuring the speed of signal recovery as molecules migrate back into the bleached area. What is this method called? a) SDS b) SPT c) GFP d) FRAP

FRAP

A protein that spans the plasma membrane once: a) Has a hydrophobic extracellular domain b) Has a hydrophobic cytoplasmic domain c) Has hydrophobic extracellular and cytoplasmic domains separated by a hydrophilic transmembrane domain d) Has hydrophilic extracellular and cytoplasmic domains separated by a hydrophobic transmembrane domain e) Has a hydrophilic extracellular domain followed by hydrophobic transmembrane and cytoplasmic domains

Has hydrophilic extracellular and cytoplasmic domains separated by a hydrophobic transmembrane domain

What is a prion? a) Chaperone protein b) Protein that cleaves DNA c) Protein that converts normal protein into abnormal protein d) Enzyme

Protein that converts normal protein into abnormal protein

Enzymes catalyze the many reactions in a cell. There are hundreds of different enzymes in a cell—each with a unique three-dimensional shape. Why do cells have so many different enzymes? a) Each enzyme molecule can only be used once. b) The shape of enzyme's active site generally fits a specific substrate. c) The substrate molecules react with enzymes to create new enzymes. d) Enzymes are randomly produced. With thousands of different shapes—one is likely to work.

The shape of enzyme's active site generally fits a specific substrate.

The process of generating monoclonal antibodies is labor-intensive and expensive. An alternative is to use polyclonal antibodies. A subpopulation of purified polyclonal antibodies that recognize a particular antigen can be isolated by chromatography. Which type of chromatography is used for this purpose? a) affinity b) ion-exchange c) gel-filtration d) any of the above

affinity

Membrane proteins, like membrane lipids, can move laterally by exchanging positions with other membrane components. Which type of membrane proteins is expected to be the least mobile, based on their function? a) channels b) anchors c) receptors d) enzymes

anchors

You are asked to provide data that support the hypothesis that protein structure and function are correlated. The best set of data to support this hypothesis is _____. a) denatured proteins do not function normally b) enzymes tend to be globular in shape c) proteins function best at certain temperatures d) proteins have four distinct levels of structure and many functions

denatured proteins do not function normally

Haemoglobin has 4 identical subunits a) True b) False

false

Membrane proteins that pump ions in and out of the cell are classified as enzymes. a) True b) False

false

What maintains the secondary structure of a protein? a) peptide bonds b) hydrogen bonds between the amino group of one peptide bond and the carboxyl group of another peptide bond c) disulfide bonds d) hydrophobic interactions e) hydrogen bonds between the R groups

hydrogen bonds between the amino group of one peptide bond and the carboxyl group of another peptide bond

Which of the following is not true of the plasma membrane? a) contains receptors for communication b) forms intercellular connections c) is a rigid sheet of molecules with little flexibility d) regulates material movement into and out of the cell

is a rigid sheet of molecules with little flexibility

Cholesterol serves several essential functions in mammalian cells. Which of the following is not influenced by cholesterol? a) membrane permeability b) membrane fluidity c) membrane rigidity d) membrane thickness

membrane thickness

Which type of lipids are the most abundant in the plasma membrane? a) Phospholipids b) Glycolipids c) Cholesterol

phospholipids

You observe a cluster of intestinal cells under a microscope and notice that the ECM connecting the cells is crystalline and dry as opposed to being soft-gel like. Which ECM protein is mutated in these cells? a) Collagens b) Proteoglycans c) Fibronectins d) Laminins e) Integrins

proteoglycans

The bonding of two amino acid molecules to form a larger molecule requires which of the following? a) removal of a water molecule b) addition of a water molecule c) formation of a glycosidic bond d) formation of a hydrogen bond e) both removal of a water molecule and formation of a hydrogen bond

removal of a water molecule

When urea is removed from proteins dissolved in urea detergent, the protein a) Denatures b) Renatures c) Both denatures and renatures d) No effect

renatures

Membrane lipids are capable of many different types of movement. Which of these does not occur spontaneously in biological membranes? a) switching between lipid layers b) lateral movement c) rotation d) flexing of hydrocarbon chains

switching between lipid layers

An Antibody heavy and light chains are held together by di-sulfide bonds a) True b) False

true

Which of the following methods would be the most suitable to assess levels of expression of your target protein in different cell types? a) gel-filtration chromatography b) gel electrophoresis c) western blot analysis d) ion-exchange chromatography

western blot analysis