biol 1009 chapter 6/7

Which of the following statements regarding integral membrane proteins is TRUE? Select one: a. They are usually transmembrane proteins. b. They serve only a structural role in membranes. c. They are loosely bound to the surface of the bilayer. d. They are not mobile within the bilayer.

a

An animal cell lacking oligosaccharides on the external surface of its plasma membrane would likely be impaired in which function? Select one: a. transporting ions against an electrochemical gradient b. cell-cell recognition c. attaching to the cytoskeleton d. maintaining the fluidity of the phospholipid bilayer

b

When a hydrogen ion (= a proton) enters a cell, it is Select one: a. moving down its electrochemical gradient because the outsides of cells are positively charged relative to the insides and that offsets the fact that the hydrogen ion concentration inside of cells is greater than outside of cells b. moving down its electrochemical gradient as the hydrogen ion concentration is greater outside of cells and the outsides of cells are positively charged relative to the insides c. moving down its electrochemical gradient as the hydrogen ion concentration is so much greater outside of cells than inside that this effect offsets the effect of the outsides of cells being negatively charged relative to the insides d. moving up its electrochemical gradient as the hydrogen ion concentration is lower outside of cells and the outsides of cells are negatively charged relative to the insides

b

Which of the following structures provide cytoplasmic channels between neighboring cells? Select one: a. tight junctions b. gap junctions c. extracellular matrix d. desmosomes

b

Why isn't the mitochondrion classified as part of the endomembrane system? Select one: a. It is not attached to the outer nuclear envelope. b. Its structure is not derived from the endoplasmic reticulum (ER). c. It is not involved in protein synthesis. d. It has two membrane layers.

b

Of the following functions, which is most important for the glycoproteins and glycolipids in animal cell membranes? Select one: a. Helping cells distinguish one type of neighboring cell from another. b. Maintaining membrane fluidity at low temperatures. c. Facilitated diffusion of molecules down their concentrations gradients. d. Active transport of molecules against their concentration gradients.

a

Which of the following factors would tend to increase membrane fluidity? Select one: a. a greater proportion of unsaturated phospholipids b. a lower temperature c. a relatively high protein content in the membrane d. a greater proportion of relatively large glycolipids compared with lipids having smaller molecular masses

a

Which of the following is a reasonable explanation for why unsaturated lipids help keep membranes more fluid at lower temperatures? Select one: a. The double bonds form kinks in the hydrocarbon chains, forcing adjacent lipid molecules to be further apart. b. Unsaturated lipids have a higher cholesterol content and therefore more cholesterol in the membranes. c. The double bonds result in shorter hydrocarbon chains and thinner membranes. d. Unsaturated lipids permit more water in the interior of the membrane.

a

Which of the following statements about cytoskeletons is TRUE? Select one: a. Microtubules are made of tubulins and microfilaments are made of actin b. Both microtubules and microfilaments are made of actin c. Microtubules are made of actin and microfilaments are made of tubulins d. Both microtubules and microfilaments are made of tubulins

a

Cotransporters Select one: a. transport molecules after binding to a molecule of ATP b. transport two different types of molecules, with one moving down its concentration or electrochemical gradient and the other moving up c. transport two molecules of the same type (e.g. two sucrose molecules) across the membrane simultaneously d. are transporter proteins that function in cooperative groups

b

Gap junctions function to Select one: a. create spaces between cells b. provide cytoplasmic channels between cells c. prevent leakage of extracellular fluid between neighboring cells d. fasten cells together into strong sheet

b

Ribosomes are composed of Select one: a. rRNA and membrane b. ribosomal proteins and rRNA c. ribosomal proteins and membrane d. ribosomal proteins, rRNA and membrane

b

Tight junctions function to Select one: a. fasten cells together into strong sheets b. prevent leakage of extracellular fluid between neighboring cells c. create spaces between cells d. provide cytoplasmic channels between cells

b

As material diffuses across a membrane from the side of higher concentration to the side of lower concentration, Select one: a. ATP is required for this diffusion. b. the free energy of the system decreases. c. the free energy of the system increases. d. osmotic pressure will not develop unless the membrane is equally permeable to the solvent and all the solutes.

b (This is a spontaneous process and the free energy of the system will decrease.)

In order for a protein to be a transmembrane protein it would have to be which of the following? Select one: a. hydrophobic b. amphipathic c. hydrophilic d. a glycoprotein

b (meaning that it has both hydrophilic and hydrophobic parts)

Which of the following structures acts to fasten together neighboring cells into sheets of tissue? Select one: a. extracellular matrix b. gap junctions c. desmosomes d. tight junctions

c

Which statement correctly characterizes bound ribosomes? Select one: a. All of these answers are correct. b. Bound and free ribosomes are structurally different. c. Bound ribosomes generally synthesize membrane proteins and secretory proteins. d. Bound ribosomes are enclosed in their own membrane.

c

Flagella and cilia Select one: a. all of these answers are correct b. are formed using intermediate filaments c. are formed using microfilaments d. are formed using microtubule

d

Which of the following components of the cytoskeleton is made from actin filaments? Select one: a. all of these answers are correct b. microtubules c. intermediate filaments d. microfilaments

d

Which of the following statements about ribosomes is TRUE? Select one: a. Free ribosomes are available to begin synthesizing new proteins whereas bound ribosomes are currently unavailable for synthesizing new proteins as they are already in the process of synthesizing a protein. b. Free ribosomes are free to diffuse around the cytosol and bound ribosomes are confined inside the nucleus. c. Bound ribosomes are attached to protein molecules whereas free ribosomes are NOT attached to protein molecules. d. Free ribosomes carry out protein synthesis while floating free in the cytosol and bound ribosomes carry out protein synthesis while attached to a membrane.

d