Unit 2 Practice Questions

Question 1

Catabolism is to anabolism as ____________ is to ____________.

Answer 1

exergonic; endergonic

Question 2

Most cells cannot harness heat to perform work because

Answer 2

temperature is usually uniform throughout a cell.

Question 3

If an enzyme in solution is saturated with substrate, the most effective way to obtain a faster yield of products is to

Answer 3

add more of the enzyme.

Question 4

Some bacteria are metabolically active in hot springs because

Answer 4

their enzymes have high optimal temperatures.

Question 5

If an enzyme is added to a solution where its substrate and product are in equilibrium, what will occur?

Answer 5

Nothing; the reaction will stay at equilibrium.

Question 6

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

Answer 6

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

Question 7

The synthesis of complex molecules in _____ pathways requires an input of energy from _____ pathways.

Answer 7

The synthesis of complex molecules in anabolic pathways requires an input of energy from catabolic pathways.

Question 8

_____ systems are those in which energy and materials can be exchanged between the system and its surroundings.

Answer 8

Open systems are those in which energy and materials can be exchanged between the system and its surroundings.

Question 9

_____ Systems: Organisms acquire energy from and lose energy to their surroundings.

Answer 9

Open

Question 10

_____ Systems: The metabolism of an organism is isolated from its surroundings.

Answer 10

Closed

Question 11

organisms constantly lose _____ to their environment as a consequence of being open systems.

Answer 11

Heat

Question 12

Growth of plants requires an input of ____. It is a ______ processes.

Answer 12

energy, non-spontaneous

Question 13

The growth of plants represents a ______ in entropy, which by the second law requires a corresponding _____ in entropy of the plant’s surroundings (the universe).

Answer 13

The growth of plants represents a decrease in entropy, which by the second law requires a corresponding increase in entropy of the plant’s surroundings (the universe).

Question 14

For plants, Energy is NOT produced by _______; it is converted from energy in the form of sunlight into energy in the form of ______.

Answer 14

Energy is NOT produced by photosynthesis; it is converted from energy in the form of sunlight into energy in the form of chemical bonds (sugars).

Question 15

According to the second law of thermodynamics, The ____ in entropy associated with life must be compensated for by _____ entropy in the environment in which life exists.

Answer 15

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

Question 16

The second law of thermodynamics demands that total entropy _____ with any reaction.

Answer 16

increase

Question 17

If the entropy of a living organism is decreasing,

Answer 17

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

Question 18

If the entropy is decreasing, this would tend to make the free energy change associated with this positive. Thus, an input of energy would be required to make this decrease in entropy occur.

Answer 18

If the entropy is decreasing, this would tend to make the free energy change associated with this positive. Thus, an input of energy would be required to make this decrease in entropy occur.

Question 19

Which part of the equation ΔG = ΔH – TΔS tells you if a process is spontaneous?

Answer 19

ΔG

In any spontaneous process, the free energy of a system decreases. The change in free energy equals the change in total energy minus the change in entropy times the temperature.

Question 20

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

Answer 20

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

Question 21

An exergonic (spontaneous) reaction is a chemical reaction that __________.

Answer 21

releases energy when proceeding in the forward direction

Question 22

_______ reactions proceed with a net release of free energy, and they occur spontaneously.

Answer 22

Exergonic

Question 23

Molecules A and B contain 110 kcal/mol of free energy, and molecules C and D contain 150 kcal/mol of energy. A and B are converted to C and D. What can be concluded?

Answer 23

The reaction that proceeds to convert A and B to C and D is endergonic; the products are more organized than the reactants.

Question 24

By subtracting the free energy of the reactants from the free energy of the products, the _____can be calculated, and the difference in these values determines the sign of the difference.

Answer 24

ΔG

Question 25

Metabolic pathways can be displaced from equilibrium either by adding_____ or by removal of the ______ of the pathway by other reactions.

Answer 25

free energy, products

Question 26

In general, the hydrolysis of ATP drives cellular work by __________.

Answer 26

releasing free energy that can be coupled to other reactions

Question 27

With the help of specific enzymes, the cell can couple the energy of ATP hydrolysis directly to _______ processes.

Answer 27

With the help of specific enzymes, the cell can couple the energy of ATP hydrolysis directly to endergonic processes.

Question 28

Much of the suitability of ATP as an energy intermediary is related to the instability of the bonds between the phosphate groups. These bonds are unstable because __________.

Answer 28

the negatively charged phosphate groups vigorously repel one another and the terminal phosphate group is more stable in water than it is in ATP

Question 29

When 1 mole of ATP is hydrolyzed in a test tube without an enzyme, about twice as much heat is given off as when 1 mole of ATP is hydrolyzed in a cell.

Answer 29

In the cell, the hydrolysis of ATP is coupled to other endergonic reactions. ***The coupling of ATP to other endergonic processes in cells means that less of the free energy is released as heat. When ATP is hydrolyzed without this coupling, all of the energy is released as heat.

Question 30

The role of ATP in cellular metabolism: The free energy released by ATP hydrolysis may be coupled to an ______ process via the formation of a phosphorylated intermediate.

Answer 30

The free energy released by ATP hydrolysis may be coupled to an endergonic process via the formation of a phosphorylated intermediate. This is one way a cell can use an exergonic reaction to drive an endergonic reaction.

Question 31

A chemical reaction is designated as exergonic rather than endergonic when __________.

Answer 31

the potential energy of the products is less than the potential energy of the reactants

Question 32

If a reaction is _____, the formation of new bonds releases more energy than was invested in breaking the old bonds.

Answer 32

exergonic

Question 33

What is changed by the presence of an enzyme in a reaction?

Answer 33

The activation energy An enzyme lowers the amount of energy required to get the reactants to the transition state.

Question 34

What do the sign and magnitude of the ΔG of a reaction tell us about the speed of the reaction?

Answer 34

Neither the sign nor the magnitude of ΔG has anything to do with the speed of a reaction. The speed of a reaction is determined by the activation energy barrier of the reaction and the temperature (which determines how many reactants have the energy to overcome the barrier).

Question 35

Enzymes speed up reactions by lowering the activation energy barrier for the reaction. Enzymes cannot change the DG for the reaction.

Answer 35

Enzymes speed up reactions by lowering the activation energy barrier for the reaction. Enzymes cannot change the DG for the reaction.

Question 36

Enzymes can lower the activation energy of reactions, but they cannot change the equilibrium point because they cannot change the net energy output.

Answer 36

Enzymes lower the activation energy barrier of a reaction but do not change the free energy of the products.

Question 37

The environment usually supplies activation energy in the form of ____. The lower the temperature, the less energy that is available to overcome the activation energy barrier.

Answer 37

heat

Question 38

Enzyme facts: An enzyme ____ the activation energy of a chemical reaction. Most enzymes are ____. Enzymes can be used to accelerate both ____ and ____ reactions. An enzyme is very specific in terms of the ____ to which it binds.

Answer 38

*An enzyme lowers the activation energy of a chemical reaction. *Most enzymes are proteins. *Enzymes can be used to accelerate both anabolic and catabolic reactions. *An enzyme is very specific in terms of the substrate to which it binds.

Question 39

The ____ site for an enzyme may resemble a groove or pocket in the surface of a protein into which the _____ fits.

Answer 39

The active site may resemble a groove or pocket in the surface of a protein into which the substrate fits.

Question 40

What is meant by the "induced fit" of an enzyme?

Answer 40

the enzyme changes its shape slightly as the substrate binds to it. **The enzyme changes slightly to bind to the substrate and catalyze the reaction.

Question 41

The role or roles of heat in biological reactions? Heat from the environment is necessary for substrates to get over the activation energy barrier. The kinetic energy of the substrates is increased as the amount of heat in the system is increased.

Answer 41

Heat from the environment is necessary for substrates to get over the activation energy barrier. The kinetic energy of the substrates is increased as the amount of heat in the system is increased.

Question 42

As the heat energy in a system increases, so does the _____ energy of the reactants. As the ____energy of the reactants increases, the reactants are more likely to interact (with each other directly, or with the active site of an enzyme). Subsequently, the reaction rate would increase.

Answer 42

kinetic

Question 43

Changes in temperature, substrate concentration, and pH are all likely to affect enzyme activity.

Answer 43

Changes in temperature, substrate concentration, and pH are all likely to affect enzyme activity.

Question 44

Each enzyme has an optimal pH at which it is most active, and variations in pH can alter the enzyme's structure, changing activity.

Answer 44

Each enzyme has an optimal pH at which it is most active, and variations in pH can alter the enzyme's structure, changing activity.

Question 45

A _______ competes with the substrate for binding at the active site.

Answer 45

competitive inhibitor The action of competitive inhibitors may be reversible or irreversible.

Question 46

Competitive inhibitors that bind covalently to the enzyme would be irreversible, and those that bind weakly would be reversible.

Answer 46

Competitive inhibitors that bind covalently to the enzyme would be irreversible, and those that bind weakly would be reversible.

Question 47

The process of stabilizing the structure of an enzyme in its active form by the binding of a molecule outside the active site is an example of __________.

Answer 47

allosteric activation

Question 48

Binding of a ______ inhibitor would stabilize the enzyme in a form that is less active

Answer 48

Binding of a noncompetitive inhibitor would stabilize the enzyme in a form that is less active, not more active

Question 49

a molecule similar to the substrate blocks the active site.

Answer 49

competitive inhibition

Question 50

In _____ inhibition, accumulating product inhibits one of the early enzymes in the metabolic pathway.

Answer 50

In feedback inhibition, accumulating product inhibits one of the early enzymes in the metabolic pathway.

Question 51

allosteric proteins is/are:

Answer 51

*They are sensitive to environmental conditions. *They exist in active and inactive conformations. *They are acted on by inhibitors.

Question 52

The binding of an allosteric inhibitor to an enzyme causes the rate of product formation by the enzyme to decrease. Why?

Answer 52

The allosteric inhibitor causes a structural change in the enzyme that prevents the substrate from binding at the active site.

Question 53

What does the term "fluid mosaic" refers to?

Answer 53

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

Question 54

Consider the currently accepted fluid mosaic model of the plasma membrane. Where in the plasma membrane would cholesterol most likely be found?

Answer 54

In the interior of the membrane The steroid cholesterol, wedged between phospholipid molecules in the plasma membranes of animals, helps stabilize the membrane.

Question 55

According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly

Answer 55

embedded in a lipid bilayer.

Question 56

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

Answer 56

a greater proportion of unsaturated phospholipids

Question 57

Which of the following processes includes all the others? osmosis diffusion of a solute across a membrane passive transport transport of an ion down its electrochemical gradient

Answer 57

passive transport

Question 58

Functions of membrane proteins? (Concept 7.1)

Answer 58

*Intercellular joining *Cell-cell recognition *Transport *Enzymatic activity

Question 59

Present in biological membranes to act as stores of energy, carbon, and nitrogen.

Answer 59

Lipids

Question 60

Plasma Membrane carbohydrates function primarily in

Answer 60

cell-cell recognition. Variations in carbohydrate structure distinguish one species from another, one individual from another, and even one cell type from another.

Question 61

The primary location of carbohydrates is on the ______ of the plasma membrane, where they can contribute to cell-cell recognition.

Answer 61

outer surface

Question 62

The carbohydrates on cell surfaces are generally branched chains of fewer than 15 sugars.

Answer 62

The carbohydrates on cell surfaces are generally branched chains of fewer than 15 sugars.

Question 63

Consider the currently accepted fluid mosaic model of the plasma membrane. Where in the membrane would carbohydrates most likely be found?

Answer 63

On the outside (external) surface of the membrane

Question 64

Membrane ________ are covalently bonded to lipids or proteins and extend out from the external side of the plasma membrane as a means of cell identification.

Answer 64

Membrane carbohydrates are covalently bonded to lipids or proteins and extend out from the external side of the plasma membrane as a means of cell identification.

Question 65

Which statement about the sidedness of the plasma membrane is correct? Every integral membrane protein has a specific orientation in the plasma membrane. 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.

Answer 65

All is correct

Question 66

Which of the following molecules is most likely to passively diffuse across the plasma membrane? Sodium ion DNA Glucose Hemoglobin Carbon dioxide

Answer 66

Hydrophobic molecules, such as hydrocarbons, carbon dioxide, and oxygen, can dissolve in the membrane and cross it with ease.

Question 67

What would be least likely to diffuse through a plasma membrane without the help of a transport protein?

Answer 67

A large, polar molecule The combination of being polar and large means that this molecule will be the slowest one from the choices to move across the membrane.

Question 68

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

Answer 68

down the

Question 69

_____ is the tendency of molecules to spread out in the available space. A substance will ____ from an area of higher concentration to an area of lower concentration without energy input. It is a ______ process.

Answer 69

Diffusion, diffuse, passive

Question 70

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?

Answer 70

Water would leave the cell by osmosis, causing the volume of the cytoplasm to decrease The added salt makes the solution hypertonic compared to the cell. Water will leave the cell by osmosis.

Question 71

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?

Answer 71

Both cells would lose water; the red blood cell would shrivel, and the plant plasma membrane would pull away from the cell wall. **Hypertonic: more solutes outside of the cell than inside

Question 72

Facilitated diffusion of solutes may occur through ________ in the membrane.

Answer 72

channel or transport proteins The passageways for facilitated diffusion may be either protein pores or carrier proteins.

Question 73

- can move ions across membranes. - requires a concentration gradient. -can occur by means of transport proteins. - can occur through protein channels.

Answer 73

Facilitated diffusion

Question 74

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?

Answer 74

A hypertonic sucrose solution When a cell is placed in a hypertonic environment, water will leave the cell, causing it to shrink.

Question 75

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?

Answer 75

A 30% salt solution is hypertonic to the bacteria, so they lose too much water and undergo plasmolysis. If a cell is placed in a hypertonic solution, it will lose water to its environment, shrivel, and probably die.

Question 76

If a cell is placed in a _____ solution, it will lose water to its environment, shrivel, and probably die.

Answer 76

If a cell is placed in a hypertonic solution, it will lose water to its environment, shrivel, and probably die.

Question 77

Active transport requires an input of energy and can also generate voltages across membranes. Based on this information, The sodium-potassium pump hydrolyzes ATP and results in a net positive change outside the cell membrane.

Answer 77

This is how the sodium-potassium pump generates voltage across the cell membrane.

Question 78

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 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.

Answer 78

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.

Question 79

What is the difference between active transport and facilitated diffusion?

Answer 79

Active transport requires an input of energy, and facilitated diffusion does not. Both systems depend on specific membrane transport proteins.

Question 80

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

Answer 80

Cotransport proteins The electrochemical gradient created by a single ATP-dependent pump can drive the transport of many different solutes using cotransport proteins.

Question 81

In receptor-mediated_____, only a specific molecule, called a ligand, can bind to the receptor. Without receptor binding occurring first, _____ does not proceed.

Answer 81

endocytosis

Question 82

In ______, vesicles derived from the endomembrane system fuse with the plasma membrane, thus increasing the number of phospholipids in the plasma membrane and increasing its surface area. The smooth ER is largely responsible for production of ____ destined for the membrane, and the rough ER produces _____ destined for the plasma membrane.

Answer 82

In exocytosis, vesicles derived from the endomembrane system fuse with the plasma membrane, thus increasing the number of phospholipids in the plasma membrane and increasing its surface area. The smooth ER is largely responsible for production of lipids destined for the membrane, and the rough ER produces proteins destined for the plasma membrane.

Question 83

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?

Answer 83

Endocytosis is the procedure that cells use to import large molecules across their plasma membrane.

Question 84

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

Answer 84

Pinocytosis is the uptake of liquid and the solutes dissolved in the liquid.

Question 85

_____: secretion of large particles from the cell by fusion of vesicles with the plasma membrane

Answer 85

Phagocytosis is a type of endocytosis, so it involves bringing material into the cell by englufing solid particles, forming pockets, enclosing it forming a vesicle within the cell

Question 86

_____: passive diffusion of water and small solutes across a membrane

Answer 86

Osmosis