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According to the competitive exclusion principle, two species cannot continue to occupy the same


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

They can move laterally along the plane of the membrane.

Which of the following statements correctly describes some aspect of protein excretion in prokaryotic cells?

Proteins that are excreted by prokaryotes are synthesized on ribosomes that are bound to the cytoplasmic surface of the plasma membrane

Which of the following is not one of the four major groups of macromolecules found in living organisms?


Use the diagram of the U-tube in the figure below to answer the following questions. 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. Initially, in terms of tonicity, the solution in side A with respect to that in side B is


A patient has had a serious accident and lost a lot of blood. In an attempt to replenish body fluids, distilled water, equal to the volume of blood lost, is transferred directly into one of his veins. What will be the most probable result of this transfusion?

The patient's red blood cells will swell because the blood fluid is hypotonic compared to the cells.

A cell whose cytoplasm has a concentration of 0.02 molar glucose is placed in a test tube of water containing 0.02 molar glucose. Assuming that glucose is not actively transported into the cell, which of the following terms describes the tonicity of the external solution relative to the cytoplasm of the cell?


After the system reaches equilibrium, what changes are observed?

The water level is higher in side A than in side B

Celery stalks that are immersed in fresh water for several hours become stiff and hard. Similar stalks left in a salt solution become limp and soft. From this we can deduce that the cells of the celery stalks are -

hypertonic to fresh water but hypotonic to the salt solution.

Which of the following statements about membrane structure and function is false?

The types of proteins that are exposed on one side of a membrane are nearly identical to those exposed on the other side of the membrane.

Which fact does not result from strong hydrogen bonding between water molecules?

Water is a universal solvent

The pH of blood

is normally close to 7.4.

Which of the following statements incorrectly describes common structural features of an animal secretory cell and a photosynthetic plant cell?

Both cells have chloroplasts

Which of the following is a reasonable explanation for why unsaturated fatty acids help keep any membrane more fluid at lower temperatures?

The double bonds form a kink in the fatty acid tail, forcing adjacent lipids to be further apart.

Of the following functions, which is most important for the glycoproteins and glycolipids of animal cell membranes?

a cell's ability to distinguish one type of neighboring cell from another

Glucose diffuses slowly through artificial phospholipid bilayers. The cells lining the small intestine, however, rapidly move large quantities of glucose from the glucose-rich food into their glucose-poor cytoplasm. Using this information, which transport mechanism is most probably functioning in the intestinal cells?

facilitated diffusion

Water passes quickly through cell membranes because

it moves through aquaporins in the membrane.

The chemical reactions involved in respiration are virtually identical between prokaryotic and eukaryotic cells. In eukaryotic cells, ATP is synthesized primarily on the inner membrane of the mitochondria. Where are the corresponding reactions likely to occur in prokaryotic respiration?

on the plasma membrane

Of the following, which is probably the most common route for membrane flow in the endomembrane system?

rough ER  vesicles  Golgi  plasma membrane

Which of the following is stored in the human liver for energy?


Which of these ecosystems has the highest net primary productivity per square meter?

tropical rain forest

Which of the following statements about the cytoskeleton is incorrect?

Microfilaments are structurally rigid and resist compression, while microtubules resist tension (stretching).

The high level of pesticides in birds of prey is an example of


In the fractionation of homogenized cells using centrifugation, the primary factor that determines whether a specific cellular component ends up in the supernatant or the pellet is

the size and weight of the component.

Which of the following lists the biomes as they appear as you move from the equator to the North Pole?

tropical rain forest - desert - temperate deciduous forest - taiga - tundra

The advantage of light microscopy over electron microscopy is that

light microscopy allows one to view dynamic processes in living cells.

You are working on a team that is designing a new drug. In order for this drug to work, it must enter the cytoplasm of specific target cells. Which of the following would not be a factor that determines whether the molecule enters the cell?

lipid composition of the target cells' plasma membrane

What is one of the functions of cholesterol in animal cell membranes?

maintains membrane fluidity

Which of the following incorrectly matches the type of cell, type of protein, and site of the protein's synthesis?

e. prokaryote, secreted protein, free cytoplasmic ribosome

After a membrane freezes and then thaws, it often becomes leaky to solutes. The most reasonable explanation for this is that

the integrity of the lipid bilayer is broken when the membrane freezes.

When a potassium ion () moves from the soil into the vacuole of a cell on the surface of a root, it must pass through several cellular structures. Which of the following correctly describes the order in which these structures will be encountered by the ion?

primary cell wall  plasma membrane  cytoplasm  tonoplast

A species of fish is found to require a certain water temperature, a particular oxygen content of the water, a particular depth, and a rocky substrate on the bottom to thrive. These requirements are part of its

ecological niche.

Which of the following statements is correct about diffusion?

It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration.

A biologist ground up some plant leaf cells and then centrifuged the mixture to fractionate the organelles. Organelles in one of the heavier fractions could produce ATP in the light, while organelles in the lighter fraction could produce ATP in the dark. The heavier and lighter fractions are most likely to contain, respectively,

chloroplasts and mitochondria.

Which of the following best summarizes the relationship between dehydration reactions and hydrolysis?

Dehydration reactions assemble polymers, and hydrolysis breaks down polymers.

Large numbers of ribosomes are present in cells that specialize in producing which of the following molecules?


The experimental approach taken in current biological investigations presumes that

living organisms can be understood in terms of the same physical and chemical laws that can be used to explain all natural phenomena.

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