Bio Midterm

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

A) A

Five dialysis bags constructed of membrane, which is permeable to water and impermeable to sucrose, were filled with various concentrations of sucrose and then placed in separate beakers containing an initial concentration of 0.6 M sucrose solution. At 10-minute intervals, the bags were massed (weighed) and the percent change in mass of each bag was graphed. Which line in the graph represents the bag with the highest initial concentration of sucrose?

A) A (highest line)

According to the fluid mosaic model of cell membranes, which of the following is a true statement about membrane phospholipids?

A) They can move laterally along the plane of the membrane

Proteins that allow the diffusion of ions across membranes in the direction of their concentration gradients are most likely

A) channel proteins

How do unsaturated fatty acids keep any membrane more fluid at lower temperatures?

A) the double bonds form kinks in the fatty acid tails that prevent adjacent lipids from packing tightly together

Mammalian blood contains the equivalent of 0.15M NaCl. Seawater contains the equivalent of 0.45 M NaCl. What will happen if red blood cells are transferred to seawater?

A) water will leave the cells causing them to shrivel and collapse

A protein that spans the phospholipid bilayer one or more times is

A)a transmembrane protein

Which component in the figure plays an important role in cell-to-cell recognition?

B) B (glycolipid)

Five dialysis bags constructed of membrane, which is permeable to water and impermeable to sucrose, were filled with various concentrations of sucrose and then placed in separate beakers containing an initial concentration of 0.6 M sucrose solution. At 10-minute intervals, the bags were massed (weighed) and the percent change in mass of each bag was graphed. Which line or lines in the graph represent(s) bags that contain a solution that is hypertonic at 50 minutes?

B) B (second highest line that does not level off)

The fluid mosaic model of the membrane proposed that membranes:

B) consist of protein molecules embedded in a fluid bilayer of phospholipids

The solutions in the arms of a U-tube are separated at the bottom of the tube by a selectively permeable membrane. The membrane is permeable to sodium chloride but not to glucose. Side A is filled with a solution of 0.4 M glucose and 0.5 M sodium chloride (NaCl), and side B is filled with a solution containing 0.8 M glucose and 0.4 M sodium chloride. Initially, the volume in both arms is the same.. Refer to the figure. At the beginning of the experiment, side A in the figure

B) is hypotonic to side B

Which of the following is a characteristic feature of a carrier protein in a plasma membrane?

B) it exhibits a specificity for a particular type of molecule

A bacterium engulfed by a white blood cell through phagocytosis will be digested by enzymes contained in

B) lysosomes

A primary funtion of polysaccharides attached to glycoproteins and glycolipids of animal cell membranes is to

B) mediate cell-to-cell recognition

In receptor- mediated endocytosis, receptor molecules are intially localized on the outer surface of the plasma membrane. Where do the receptors end up following endocytosis?

B) on the inside surface of the vesicle

The primary structural components of the cell membrane are

B) phospholipids and proteins

What kinds of molecules pass through a cell membrane most easily?

B) small hydrophobic

After the system depicted in the figure reaches equilibrium, what changes are observed with respect to the concentrations of sugars?

B) the concentrations of glucose and sucrose are equal in sides A and B

After the system depicted in the figure reaches equilibrium, what changes are observed?

B) the water level is higher in side A than in side B

If you examine side A in the figure after three days, the concentration of glucose and NaCl should be

C) 0.6M glucose, 0.45 M NaCl

Which component in the figure is a micro filament of the cytoskeleton?

C) C

Five dialysis bags constructed of membrane, which is permeable to water and impermeable to sucrose, were filled with various concentrations of sucrose and then placed in separate beakers containing an initial concentration of 0.6 M sucrose solution. At 10-minute intervals, the bags were massed (weighed) and the percent change in mass of each bag was graphed. Which line in the graph represents the bag that contained a solution isotonic to the 0.6 M solution at the beginning of the experiment?

C) C (middle line)

Which of the following would diffuse through the lipid bilayer of a plasma membrane most rapidly?

C) O2

Proton pumps are used in various ways by members of every domain of organisms: bacteria, archea, and eukarya. What does this most prolly mean?

C) Proton gradients across a membrane were used by cells that were common ancestor of all three domains of life

Which of the following is true of integral membrane proteins

C) They are usually transmembrane proteins

The cell membranes of Antartic ice fish might have which of the following adaptations?

C) a high percentage of unsaturated fatty acids

An integral membrane protein would have to be

C) amphipathic, with at least one hydrophobic region

The sodium-potassium pump is called an electrogenic pump because it

C) contributes to the membrane potential

The movement of the hydrophobic gas nitrous laughing gas into a cell is an example of

C) diffusion through the lipid bilayer

Initially in term of tonicity in the figure, the solution in side A with respect to that in side B is

C) isotonic

Which of the folliwng statements about diffusion is correct?

C) it is a passive process in which molecules move from a region of higher concentration to a region of lower concentration

The sodium-potassium pump generates the following concentration gradients across the plasma membrane:

C) low [Na+] and high [K+] inside the cell and high [Na+] and low [Na+] outside

Which of the following membrane activities requires energy from ATP through hydrolysis?

C) movement of sodium ions from a lower concentration in a mammalian cell to a higher concentration in the extracellular fluid

Which of the following tend to lack hydrophobic regions on their surface?

C) peripheral proteins

Which of the following are localized on the exterior of a phospholipid bi layer

C) phosphate groups

When biological membranes are frozen and then fractured, they tend to break along the middle of the bi layer. The best explanation for this is that

C) the hydrophobic interactions between the fatty acid tails of the two phospholipid monolayers are the weakest interactions in the membrane

The difference between pinocytosis and receptor mediated endocytosis is that

C)pinocyotsis is nonselective in the molecules it brings into the cell, whereas receptor-mediated endocytosis is highly selective

Which component in the figure is a peripheral protein?

D) D

If you examine side A in the figure after three days, you should find

D) a decrease in the concentration of NaCl and a decrease in the water level

Which of the following is one of the ways that the membranes of winter wheat are able to remain fluid when its extremely cold?

D) by increasing the percentage of unsaturated phospholipids in the membrane

The phosphate transport system in bacteria imports phosphate into the cell even when the concentration of phosphate outside the cell is much lower than the cytoplasmic phosphate concentration. Phosphate import depends on a pH gradient across the membrane- more acidic outside the cell than inside the cell. Phosphate transport is an example of

D) co transport (but technically it could be active transport too)

A primary function of cholesterol in the plasma membranes of some animals is to

D) enable the membrane to stay fluid more easily when the temperature drops

Glucose diffuses slowly through artifcial phospholipid bilayers. The cells lining the small intestine, however, rapdily move large quanities of glucose from the glucose-rich food into their glucose poor cytoplasm. Based on this information, which transport mechanism is most likely responsible for glucose transport in the intestinal cells?

D) facilitated diffusion

Familial hypercholesterolemia is characterized by extremely high levels of cholesterol in the blood, which results from

D) nonfunctional or missing LDL receptors on cell membranes

Submerging a red blood cell in distilled water will result in

D) the cell becoming flaccid

Submerging a plant cell in distilled water will result in

D) the cell becoming turgid

Which of the following is true for the evolution of cell membrane?

D) the evolution of cell membranes is driven by the evolution of all membrane components as a result of natural selection

Celery stalks are immersed in fresh water for several hours become turgid (stiff). Celery stalks left in a 0.15M salt solution become flaccid (limp). From this we can deduce that

D) the fresh water is hypotonic and the salt solution is hypertonic to the cells of the celery stalks

Which of the following provides the most likely explanation for why cell membranes are asymmetrical?

D) the two sides of cell membrane face different environments and carry out different functions

Which of the following is most likely true of a protein that cotransports glucose and sodium ions into the intestinal cells of an animal?

D) transport of sodium ions down their electrochemical gradient facilitates the transport of glucose against it concentration gradient

Why are lipids and proteins free to move laterally in membranes?

D) weak hydrophobic interaction in the interior of the membrane are easily disrupted

Which component in the figure is cholesterol?

E) E

Which component in the figure helps membranes resist changes in fluidity at high and low temperatures?

E) E (cholesterol)

Transport of potassium ions into an animal cell by the sodium-potassium pump requires

E) energy from ATP

Cystic fibrosis is a genetic disease in humans in which the CFTR protein, which functions as a chloride ion channel, is missing or nonfunctional in cell membranes. The CFTR protein belongs to what category of membrane protein?

E) hydrophillic channels

Water passes quickly through cell membranes because

E) it moves through aquaporin channel proteins

Which of the following would diffuse through the lipid bilayer of a plasma membrane most slowly if at all?

amino acids (glucose too but amino acids is the better answer)

Submerging a red blood cell in a hypertonic solution will result in

plasmolysis or lysis of the cell????