biology test- 2

What is the function of the nuclear pore complex found in eukaryotes?

It regulates the movement of proteins and RNAs into and out of the nucleus.

Lysosomes

Asbestos is a material that was once used extensively in construction. One risk from working in a building that contains asbestos is the development of asbestosis caused by the inhalation of asbestos fibers. Cells will take up asbestos by phagocytosis, but are not able to degrade it. As a result, asbestos fibers accumulate in ________.

Which component in the accompanying figure is a protein fiber of the extracellular matrix?

E

Which of the following is a major difference between prokaryotic cells and eukaryotic cells?

Eukaryotic cells have membrane-bound organelles, while prokaryotic cells do not.

components of the cytoskeleton

Motor proteins provide for molecular motion in cells by interacting with what types of cellular structures?

Which of the following statements about the cytoskeleton is true?

Movement of cilia and flagella is the result of motor proteins causing microtubules to move relative to each other.

A phospholipid bilayer with equal amounts of saturated and unsaturated fatty acids displays a specific permeability to glucose. What effect will increasing the proportion of unsaturated fatty acids in the bilayer have on the membrane's permeability to glucose?

Permeability to glucose will increase.

The solutions in the two arms of this U-tube are separated by a membrane that is permeable to water and glucose but not to sucrose. Side A is half-filled with a solution of 2 M sucrose and 1 M glucose. Side B is half-filled with 1 M sucrose and 2 M glucose. Initially, the liquid levels on both sides are equal. Which of the following will be true when the system illustrated above reaches equilibrium?

The water level will be higher in side A than in side B.

phagocytic white blood cell

Which cell would be best for studying lysosomes?

competitive inhibition

Which of the following conditions may be overcome by increasing the substrate concentration in an enzymatic reaction with a fixed amount of enzyme?

plasmodesmata

Which of the following structures form cytoplasmic channels that connect adjacent plant cells through the cell walls?

scanning electron microscopy

Which of the following would be most appropriate method to observe the three-dimensional structure and organization of microvilli on an intestinal cell?

Chloroplast

Which structure below is independent of the endomembrane system?

Chemical equilibrium is relatively rare in living cells because metabolic pathways are interconnected. Which of the following statements describes an example of a reaction that may be at chemical equilibrium in a cell?

a chemical reaction in which neither the reactants nor the products are being produced or consumed in any metabolic pathway at that time in the cell

Which of the following factors would tend to increase membrane fluidity?

a greater proportion of unsaturated phospholipids

Which of the following is an example of potential rather than kinetic energy?

a molecule of glucose

Which of the following molecules is most similar in structure to ATP?

an RNA nucleotide

Which of the following molecules dramatically increases the rate of diffusion of water across cell membranes?

aquaporins

How does a noncompetitive inhibitor decrease the rate of an enzyme-catalyzed reaction?

by binding to an allosteric site, thus changing the shape of the active site of the enzyme

Human immunodeficiency virus (HIV) infects cells that have both CD4 and CCR5 cell surface molecules. The viral nucleic acid molecules are enclosed in a protein capsid, and the protein capsid is itself contained inside an envelope consisting of a lipid bilayer membrane and viral glycoproteins. One hypothesis for viral entry into cells is that binding of HIV membrane glycoproteins to CD4 and CCR5 initiates fusion of the HIV membrane with the plasma membrane, releasing the viral capsid into the cytoplasm. An alternative hypothesis is that HIV gains entry into the cell via receptor-mediated endocytosis, and membrane fusion occurs in the endocytotic vesicle. To test these alternative hypotheses for HIV entry, researchers labeled the lipids on the HIV membrane with a red fluorescent dye .In an HIV-infected cell producing HIV virus particles, the viral glycoprotein is expressed on the plasma membrane. How do the viral glycoproteins get to the plasma membrane? They are synthesized ________.

by ribosomes in the rough ER and arrive at the plasma membrane in the membrane of secretory vesicles

Choose the pair of terms that correctly completes this sentence: Catabolism is to anabolism as ________ is to ________.

exergonic; endergonic

In plant cells, the middle lamella ________.

glues adjacent cells together

Celery stalks that are immersed in fresh water for several hours become stiff. Similar stalks left in a 0.15 M salt solution become limp. From this we can deduce that the fresh water ________.

is hypotonic and the salt solution is hypertonic to the cells of the celery stalks

A sodium-potassium pump ________.

moves three sodium ions out of a cell and two potassium ions into a cell using energy from ATP hydrolysis

The difference between pinocytosis and receptor-mediated endocytosis is that ________.

pinocytosis is nonselective in the molecules it brings into the cell, whereas receptor-mediated endocytosis offers more selectivity

The solutions in the two arms of this U-tube are separated by a membrane that is permeable to water and glucose but not to sucrose. Side A is half-filled with a solution of 2 M sucrose and 1 M glucose. Side B is half-filled with 1 M sucrose and 2 M glucose. Initially, the liquid levels on both sides are equal. In the U-tube illustrated above, ________.

side A is isotonic to side B