Biology-exam 2

Which part of the equation ΔG = ΔH - TΔS tells you if a process is spontaneous? (Concept 8.2) SHOW HINT ΔH ΔG TΔS ΔS All of these values reveal the direction in which a reaction will go.

ΔG

If, during a process, the system becomes more ordered, then __________. (Concept 8.2) SHOW HINT ΔS is negative ΔH is negative ΔG is positive ΔG is negative ΔH is positive

ΔS is negative

When one molecule is broken down into six component molecules, which of the following will always be true? (Concept 8.2) SHOW HINT An input of free energy is needed. ΔS is negative. ΔH is negative. ΔS is positive. ΔG is positive.

ΔS is positive.

The internal solute concentration of a plant cell is about 0.8 M. To demonstrate plasmolysis, it would be necessary to suspend the cell in what solution? 150 mM. 0.8 M 1.0 M 0.4 M distilled water

1.0 M

Green olives may be preserved in brine, which is a 30% salt solution. How does this method of preservation prevent microorganisms from growing in the olives? (Concept 7.3) SHOW HINT A 30% salt solution is hypotonic to the bacteria, so they gain too much water and burst. A 30% salt solution is hypertonic to the bacteria, so they lose too much water and undergo plasmolysis. High salt concentration raises the pH, thus inhibiting bacterial metabolism. Bacterial cells shrivel up in high salt solutions, causing the cell to burst. High salt concentration lowers the pH, thus inhibiting bacterial metabolism.

A 30% salt solution is hypertonic to the bacteria, so they lose too much water and undergo plasmolysis.

Which of the following is a correct difference between active transport and facilitated diffusion? Active transport involves transport proteins, and facilitated diffusion does not. Facilitated diffusion can move solutes against a concentration gradient, and active transport cannot. Facilitated diffusion requires carrier proteins, but active transport requires channel proteins. Active transport requires energy from ATP, and facilitated diffusion does not. Facilitated diffusion involves transport proteins, and active transport does not.

Active transport requires energy from ATP, and facilitated diffusion does not.

Which statements about the sidedness of the plasma membrane is correct? Parts of proteins that are exposed on the cytoplasmic side of the endoplasmic reticulum are also exposed on the cytoplasmic side of the plasma membrane. The two lipid layers may differ in specific lipid composition. The asymmetrical distribution of membrane proteins, lipids, and carbohydrates across the plasma membrane is determined as the membrane is being constructed. Every integral membrane protein has a specific orientation in the plasma membrane. All of the listed responses are correct.

All of the listed responses are correct.

Which of the following correctly states the relationship between anabolic and catabolic pathways? Energy derived from catabolic pathways is used to drive the breakdown of organic molecules in anabolic pathways. Degradation of organic molecules by anabolic pathways provides the energy to drive catabolic pathways. Anabolic pathways synthesize more complex organic molecules using the energy derived from catabolic pathways. The flow of energy between catabolic and anabolic pathways is reversible. Catabolic pathways produce usable cellular energy by synthesizing more complex organic molecules.

Anabolic pathways synthesize more complex organic molecules using the energy derived from catabolic pathways.

Cells A and B are the same size, shape, and temperature, but cell A is metabolically less active than cell B. and cell B is actively converting oxygen to water in cellular respiration. Oxygen will diffuse more rapidly into cell __________ because __________. B ... the oxygen molecules inside cell B have a higher kinetic energy B ... the diffusion gradient in cell B is steeper A ... its membrane transport proteins will not be saturated B ... the gradient of oxygen is oriented in the opposite direction compared to cell A A ... the concentration gradient there is shallower

B ... the diffusion gradient in cell B is steeper

Seawater is hypertonic to cytoplasm in vertebrate cells and in plant cells. If a red blood cell and a plant cell were placed in seawater, what would happen to the two types of cells? Both cells would lose water; the red blood cell would shrivel, and the plant plasma membrane would pull away from the cell wall. Both cells will gain water, but cell walls will prevent both cells from bursting. Both cells would gain water by osmosis; the red blood cell would burst, and the plant cell would increase in turgor pressure. The red blood cell would shrink, and the plant cell would gain water. The red blood cell would burst, and the plant cell would shrink.

Both cells would lose water; the red blood cell would shrivel, and the plant plasma membrane would pull away from the cell wall.

In what way do the membranes of a eukaryotic cell vary? -Only certain membranes are constructed from amphipathic molecules. -Phospholipids are found only in certain membranes. -Certain proteins are unique to each membrane. -Only certain membranes of the cell are selectively permeable.

Certain proteins are unique to each membrane

Which of the following statements about cotransport of solutes across a membrane is correct? A cotransport protein is most commonly an ion channel. Cotransport proteins allow a single ATP-powered pump to drive the active transport of many different solutes. The sodium-potassium pump is an example of a cotransport protein. Cotransport involves the hydrolysis of ATP by the transporting protein. In cotransport, both solutes that are being transported are moving down their chemical gradients.

Cotransport proteins allow a single ATP-powered pump to drive the active transport of many different solutes.

Which of the following correctly describes a general property of all electrogenic pumps? Electrogenic pumps result in a cell with a high internal concentration of protons. Electrogenic pumps result in a cell with an interior that is positively charged relative to the outside of the cell. Electrogenic pumps can pump a large variety of solutes across a membrane against their concentration gradient. Electrogenic pumps create a voltage difference across the membrane. Electrogenic pumps pump sodium out of the cell and potassium into the cell.

Electrogenic pumps create a voltage difference across the membrane.

Which of the following states the relevance of the first law of thermodynamics to biology? (Concept 8.1) SHOW HINT Because living things consume energy, the total energy of the universe is constantly decreasing. Photosynthetic organisms produce energy in sugars from sunlight. Energy can be freely transformed among different forms as long as the total energy is conserved. Living organisms must increase the entropy of their surroundings.

Energy can be freely transformed among different forms as long as the total energy is conserved.

If the entropy of a living organism is decreasing, which of the following is most likely to be occurring simultaneously? (Concept 8.2) SHOW HINT The entropy of the organism's environment must also be decreasing. The first law of thermodynamics is being violated. In this situation, the second law of thermodynamics must not apply. Energy input into the organism must be occurring to drive the decrease in entropy. Heat is being used by the organism as a source of energy.

Energy input into the organism must be occurring to drive the decrease in entropy.

Which of these statements describes some aspect of facilitated diffusion? Facilitated diffusion of solutes may occur through channel or transport proteins in the membrane. Facilitated diffusion of solutes occurs through phospholipid pores in the membrane. There is only one kind of protein pore for facilitated diffusion. Facilitated diffusion is another name for osmosis. Facilitated diffusion requires energy to drive a concentration gradient.

Facilitated diffusion of solutes may occur through channel or transport proteins in the membrane.

Which of the following is FALSE in regard to facilitated diffusion? Facilitated diffusion can occur by means of transport proteins. Facilitated diffusion requires the hydrolysis of ATP. Facilitated diffusion requires a concentration gradient. Facilitated diffusion can move ions across membranes. Facilitated diffusion can occur through protein channels.

Facilitated diffusion requires the hydrolysis of ATP.

Which of the following statements about diffusion is true? It always requires integral proteins of the cell membrane. It involves only the movement of water molecules. It is a passive process. It requires expenditure of energy by the cell. It occurs when molecules move from a region of lower concentration to a region of higher concentration.

It is a passive process.

Which of the following statements concerning carbohydrates associated with the plasma membrane is correct? Carbohydrates are found associated with the membranes of prokaryotic cells only. Carbohydrates on the plasma membrane are typically long, complex chains of several dozen monosaccharides. The carbohydrate composition of most eukaryotic plasma membranes is quite similar. Membrane carbohydrates function primarily in cell-cell recognition. Carbohydrates associated with the plasma membrane are located on both surfaces of the membrane.

Membrane carbohydrates function primarily in cell-cell recognition.

Which of the following functions of membrane proteins is important in tissue formation during embryonic development in animals? ( Membrane proteins with short sugar chains form identification tags that are recognized by other cells. Membrane proteins attach the membrane to the cytoskeleton. Membrane proteins form channels, which move substances across the membrane. Membrane proteins possess enzymatic activity. All of the listed responses are correct.

Membrane proteins with short sugar chains form identification tags that are recognized by other cells.

A selectively permeable membrane separates two solutions. Water is able to pass through this membrane; however, sucrose (a disaccharide) and glucose (a monosaccharide) cannot pass. The membrane separates a 0.2-molar sucrose solution from a 0.2-molar glucose solution. With time, how will the solutions change? After the sucrose dissociates into two monosaccharides, water will move via osmosis to the side of the membrane that contains the dissociated sucrose. Water will enter the sucrose solution because the sucrose molecule is a disaccharide and, thus, larger than the monosaccharide glucose. Water will leave the sucrose solution because the sucrose molecule is a disaccharide and, thus, larger than the monosaccharide glucose. Nothing will happen, because the two solutions are isotonic to one another.

Nothing will happen, because the two solutions are isotonic to one another.

Organisms are described as thermodynamically open systems. Which of the following statements is consistent with this description? (Concept 8.1) SHOW HINT Heat produced by the organism is conserved in the organism and not lost to the environment. Organisms acquire energy from, and lose energy to, their surroundings. The metabolism of an organism is isolated from its surroundings. Because energy must be conserved, organisms constantly recycle energy and thus need no input of energy. All of the listed responses are correct.

Organisms acquire energy from, and lose energy to, their surroundings.

Which of the following statements about passive transport is correct? Passive transport does not occur in the human body. Passive transport operates independently of diffusion. Passive transport operates independently of the concentrations of the moving solute. Passive transport permits the solute to move in either direction, but the net movement of solute molecules occurs down the concentration gradient of the molecule. In passive transport, solute movement stops when the solute concentration is the same on both sides of the membrane.

Passive transport permits the solute to move in either direction, but the net movement of solute molecules occurs down the concentration gradient of the molecule.

Which of the following statements about the role of phospholipids in the structure and function of biological membranes is correct? Phospholipids form a selectively permeable structure. They are triacylglycerols, which are commonly available in foods. Phospholipids form a structure in which the hydrophobic portion faces outward. Phospholipids are completely unable to interact with water. Phospholipids form a single sheet in water.

Phospholipids form a selectively permeable structure.

Which of the following is an example of the second law of thermodynamics as it applies to biological reactions? (Concept 8.1) SHOW HINT The aerobic respiration of one molecule of glucose produces six molecules each of carbon dioxide and water. All types of cellular respiration produce ATP. Cellular respiration releases some energy as heat. The first and second choices are correct. The first, second, and third choices are correct.

The aerobic respiration of one molecule of glucose produces six molecules each of carbon dioxide and water.

According to the second law of thermodynamics, which of the following is true? (Concept 8.1) SHOW HINT The decrease in entropy associated with life must be compensated for by increased entropy in the environment in which life exists. All reactions produce some heat. The entropy of the universe is constantly decreasing. Energy conversions increase the order in the universe. The total amount of energy in the universe is constant.

The decrease in entropy associated with life must be compensated for by increased entropy in the environment in which life exists.

Which of the following is a reasonable explanation for why unsaturated fatty acids help keep any membrane more fluid at lower temperatures? -Unsaturated fatty acids are more polar than saturated fatty acids. -Unsaturated fatty acids have a higher cholesterol content and therefore more cholesterol in membranes. -The double bonds result in shorter fatty acid tails and thinner membranes. -The double bonds block interaction among the hydrophilic head groups of the lipids. -The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly.

The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly.

The plasma membrane is referred to as a "fluid mosaic" structure. Which of the following statements about that model is true? The fluid aspect of the membrane is due to the behavior of phospholipids, and the mosaic aspect is due to the presence of carbohydrates. The fluid aspect of the membrane is due to the lateral and rotational movement of phospholipids, and embedded proteins account for the mosaic aspect. The mosaic aspect of the membrane is due to the glycosylation of phospholipids on the cytoplasmic side of the membrane. The fluid aspect of the membrane describes its structure at normal temperatures, and the mosaic aspect describes the behavior of the membrane as the temperature is lowered. Only phospholipids are capable of moving in the membrane.

The fluid aspect of the membrane is due to the lateral and rotational movement of phospholipids, and embedded proteins account for the mosaic aspect.

Consider the transport of protons and sucrose into a plant cell by the sucrose-proton cotransport protein. Plant cells continuously produce a proton gradient by using the energy of ATP hydrolysis to pump protons out of the cell. Why, in the absence of sucrose, do protons not move back into the cell through the sucrose-proton cotransport protein? Protons, unlike other substances, do not diffuse down their electrochemical gradient. Protons are freely permeable through the phospholipid bilayer, so no transport protein is needed for protons. The movement of protons through the cotransport protein cannot occur unless sucrose moves at the same time. In the absence of sucrose, the ATP-powered proton pump does not function, so there is no proton gradient. Protons cannot move through membrane transport proteins.

The movement of protons through the cotransport protein cannot occur unless sucrose moves at the same time.

Active transport requires an input of energy and can also generate voltages across membranes. Based on this information, which of the following statements is true? Active transport uses channel proteins and ensures that the interior of the cell is always positive compared to the exterior of the cell. Active transport moves solutes down their concentration gradients and always uses ATP as the source of energy to do this. Active transport can use ATP as its energy source and ensures that there is no voltage across the cell membrane. The source of energy for active transport of a solute up its gradient can be ATP or a concentration gradient of a second solute. This second gradient of solutes maintains no net difference in voltage across the membrane. The sodium-potassium pump hydrolyzes ATP and results in a net positive change outside the cell membrane.

The sodium-potassium pump hydrolyzes ATP and results in a net positive change outside the cell membrane.

Consider the growth of a farmer's crop over a season. Which of the following correctly states a limitation imposed by the first or second law of thermodynamics? (Concept 8.1) SHOW HINT To obey the first law, the crops must represent an open system. The entropy of the universe must decrease to account for the increased entropy associated with plant growth. The process of photosynthesis produces energy that the plant uses to grow. Growth of the crops must occur spontaneously. All of the listed responses are correct.

To obey the first law, the crops must represent an open system.

Glucose can be moved into cells via an active transport mechanism when the concentration of glucose inside the cell is higher than the concentration of glucose outside of the cell. This active transport mechanism moves glucose and sodium into the cell at the same time. The glucose moves up its gradient and the sodium moves down its gradient. Which of the following statements about this mechanism is accurate? -The distribution of sodium ions across the membrane forms an electrochemical gradient that drives this mechanism. -To pump glucose up its concentration gradient, sodium moves down its concentration gradient. -Sodium and glucose move together into the cell via facilitated diffusion. -Sodium and glucose move together into the cell via facilitated diffusion, and to pump glucose up its concentration gradient, sodium moves down its concentration gradient. -To pump glucose up its concentration gradient, sodium moves down its concentration gradient, and the distribution of sodium ions across the membrane forms an electrochemical gradient that drives this mechanism.

To pump glucose up its concentration gradient, sodium moves down its concentration gradient, and the distribution of sodium ions across the membrane forms an electrochemical gradient that drives this mechanism.

A single plant cell is placed in an isotonic solution. Salt is then added to the solution. Which of the following would occur as a result of the salt addition? The added salt would enter the cell, causing the cell to take up water and swell. There would be no osmotic movement of water in response to the added salt. Water would leave the cell by osmosis, causing the volume of the cytoplasm to decrease. Water would enter the cell by osmosis, and the cell would swell. The added salt makes the solution hypotonic compared to the cell. Water will enter the cell by osmosis.

Water would leave the cell by osmosis, causing the volume of the cytoplasm to decrease.

From the equation ΔG = ΔH - TΔS it is clear that __________. (Concept 8.2) SHOW HINT -a decrease in the system's total energy will increase the probability of spontaneous change -increasing the temperature of a system will increase the probability of spontaneous change -increasing the entropy of a system will increase the probability of spontaneous change -a decrease in the system's total energy will increase the probability of spontaneous change, and increasing the entropy of a system will increase the probability of spontaneous change -a decrease in the system's total energy will increase the probability of spontaneous change, increasing the entropy of a system will increase the probability of spontaneous change, and increasing the temperature of a system will increase the probability of spontaneous change

a decrease in the system's total energy will increase the probability of spontaneous change, increasing the entropy of a system will increase the probability of spontaneous change, and increasing the temperature of a system will increase the probability of spontaneous change

Which of the following factors would tend to increase membrane fluidity? -a lower temperature -a relatively high protein content in the membrane -a greater proportion of saturated phospholipids -a greater proportion of unsaturated phospholipids

a greater proportion of unsaturated phospholipids

The cell membranes of Antarctic ice fish might have which of the following adaptations? -very long chain fatty acids no cholesterol -branched isoprenoid lipids -a high percentage of polyunsaturated fatty acids -a higher percentage of trans-fatty acids

a high percentage of polyunsaturated fatty acids

The concentration of solutes in a red blood cell is about 2%, but red blood cells contain almost no sucrose or urea. Sucrose cannot pass through the membrane, but water and urea can. Osmosis would cause red blood cells to shrink the most when immersed in which of the following solutions? pure water a hypertonic sucrose solution a hypotonic urea solution a hypotonic sucrose solution a hypertonic urea solution

a hypertonic sucrose solution

which of the following would be LEAST likely to diffuse through a plasma membrane without the help of a transport protein? dissolved gases such as oxygen or carbon dioxide a large, polar molecule a large, nonpolar molecule a small, nonpolar molecule Any of the listed molecules would easily diffuse through the membrane.

a large, polar molecule

Which of the following is an example of potential rather than kinetic energy? -light flashes emitted by a firefly -a crawling beetle foraging for food -water rushing over Niagara Falls -a molecule of glucose

a molecule of glucose

For a protein to be an integral membrane protein, it would have to be ________. -hydrophilic -hydrophobic -amphipathic, with at least one hydrophobic region -exposed on only one surface of the membrane

amphipathic, with at least one hydrophobic region

Which of the following molecules is most likely to passively diffuse across the plasma membrane? glucose hemoglobin DNA sodium ion carbon dioxide

carbon dioxide

A nursing infant is able to obtain disease-fighting antibodies, which are large protein molecules, from its mother's milk. These molecules probably enter the cells lining the baby's digestive tract via which process? active transport osmosis exocytosis endocytosis passive transport

endocytosis

Which of the following is NOT a function of membrane proteins? transport enzymatic activity intercellular joining cell-cell recognition energy, carbon, and nitrogen storage

energy, carbon, and nitrogen storage

Which of the following processes and organelles account for the replacement of lipids and proteins lost from the plasma membrane? endocytosis and Golgi flip-flop of phospholipids from one side of the plasma membrane to the other and the Golgi active transport and the rough ER exocytosis and smooth ER and rough ER receptor-mediated endocytosis and smooth ER and Golgi

exocytosis and smooth ER and rough ER

A cell has a membrane potential of -100 mV (more negative inside than outside) and has 1,000 times more calcium ions outside the cell than inside. Which of the following best describes a mechanism by which Ca2+ enters the cell? facilitated diffusion of Ca2+ into the cell down its electrochemical gradient movement of Ca2+ into the cell through an ion channel down its concentration gradient passive diffusion of Ca2+ into the cell down its electrochemical gradient movement of Ca2+ into the cell through a carrier protein down its electrical gradient cotransport of Ca2+ into the cell with Cl-

facilitated diffusion of Ca2+ into the cell down its electrochemical gradient

Consider the currently accepted fluid mosaic model of the plasma membrane. Where in the plasma membrane would cholesterol most likely be found? on the inside (cytoplasmic) surface in the interior of the membrane in the interior and on the inside surface, but not on the outside surface on either surface of the membrane, but not in the interior of the membrane on the outside (external) surface of the membrane

in the interior of the membrane

A sodium- potassium pump -moves three potassium ions out of a cell and two sodium ions into a cell using energy from ATP hydrolysis moves three sodium ions out of a cell and two potassium ions into a cell using energy from ATP hydrolysis -moves three potassium ions out of a cell and two sodium ions into a cell while producing ATP for each cycle -move three sodium ions out of a cell and two potassium ions into a cell and generates an ATP in each cycle

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

Consider the currently accepted fluid mosaic model of the plasma membrane. Where in the membrane would carbohydrates most likely be found? on both hydrophilic surfaces of the membrane but not in the hydrophobic interior on the outside (external) surface of the membrane in the interior of the membrane on the inside (cytoplasmic) surface of the membrane Carbohydrates are rarely associated with plasma membranes.

on the outside (external) surface of the membrane

White blood cells engulf bacteria using -pinocytosis -phagocytosis -osmosis -receptor-mediated exocytosis

phagocytosis

Which of the following types of molecules are the major structural components of the cell membrane? -proteins and cellulose -glycoproteins and cholesterol -nucleic acids and proteins -phospholipids and proteins -phospholipids and cellulose

phospholipids and proteins

Which of the following pairs correctly matches a membrane transport process to its primary function? phagocytosis: secretion of large particles from the cell by fusion of vesicles with the plasma membrane exocytosis: the movement of water and solutes out of the cell by passage through the plasma membrane osmosis: passive diffusion of water and small solutes across a membrane pinocytosis: the uptake of water and small solutes into the cell by formation of vesicles at the plasma membrane None of the listed responses is correct.

pinocytosis: the uptake of water and small solutes into the cell by formation of vesicles at the plasma membrane

Which of the following enables a cell to pick up and concentrate a specific kind of molecule? channel proteins passive transport receptor-mediated endocytosis facilitated diffusion osmosis

receptor-mediated endocytosis

An exergonic (spontaneous) reaction is a chemical reaction that __________. (Concept 8.2) SHOW HINT releases energy when proceeding in the forward direction cannot occur outside of a living cell is common in anabolic pathways leads to a decrease in the entropy of the universe occurs only when an enzyme or other catalyst is present

releases energy when proceeding in the forward direction

Which of the following are least likely to diffuse through the phospholipid bilayer of a cell membrane? -carbon dioxide -small ions -large hydrophobic molecules -small hydrophobic molecules

small ions