Chapter 7 & 8 Reviews.

If a red blood cell is placed in a salt solution and bursts, what is the tonicity of the solution relative to the interior of the cell?

Hypotonic

Which of the following statements about feedback regulation of a metabolic pathway is correct?

The final product of a metabolic pathway is usually the compound that regulates the pathway. It is quite common that the end product of the pathway controls the overall rate of the pathway

You know that this cell is in a(n) _____ solution because it _____.

hypertonic ... lysed

Which of the following molecules can cross the lipid bilayer of a membrane directly, without a transport protein or other mechanism? Select all that apply.

water, oxygen, carbon dioxide, lipids

Which of the following statements about equilibrium of chemical reactions is correct?

A reaction that is at equilibrium is not capable of doing any work. The ΔG for a reaction at equilibrium is zero, which means that there is no free energy available to do any work.

The competitive inhibitor competes with the substrate for what on the enzyme?

Active Site

Active and passive transport of solutes across a membrane typically differ in which of the following ways?

Active transport always involves the utilization of cellular energy, whereas passive transport does not require cellular energy. Active and passive transport can be distinguished by whether or not they use cellular energy.

You have an enzymatic reaction proceeding at the optimum pH and optimum temperature. You add a competitive inhibitor to the reaction and notice that the reaction slows down. What can you do to speed the reaction up again?

Add more substrate; it will outcompete the inhibitor and increase the reaction rate

In what way do the membranes of a eukaryotic cell vary?

Certain proteins are unique to each membrane

Consider a situation in which the enzyme is operating at optimum temperature and pH, and has been saturated with substrate. What is your best option for increasing the rate of the reaction?

Increase the enzyme concentration.

Usually, a(n) inhibitor forms a covalent bond with an amino acid side group within the active site, which prevents the substrate from entering the active site or prevents catalytic activity.

Irreversible Inhibitor

Select the correct statement about chemical energy, a term used by biologists to refer to potential energy available for release in a chemical reaction.

Light energy is converted to chemical energy during photosynthesis.

Which of the following statements about osmosis is correct?

Osmosis is the diffusion of water from a region of lower water concentration to a region of higher water concentration.

Select the correct statement about osmosis. Select the correct statement about osmosis. Osmotic equilibrium cannot be reached unless solute concentrations equalize across the membrane. Osmosis is the diffusion of water molecules across a selectively permeable membrane. If a dead cell is placed in a solution hypotonic to the cell contents, osmosis will not occur.

Osmosis is the diffusion of water molecules across a selectively permeable membrane.

Which of the following particles could diffuse easily through a cell membrane?

Oxygen (O2)

A semipermeable membrane is placed between the following solutions. Which solution will decrease in volume?

Solution A: 1.4% (m/v) starch

A semipermeable membrane is placed between the following solutions. Which solution will increase in volume?

Solution D: 12.4% (m/v) NaCl

Enzyme inhibitors disrupt normal interactions between the enzyme and _.

Substrate

Which of the following is NOT a way in which an enzyme can speed up the reaction that it catalyzes?

The active site can provide heat from the environment that raises the energy content of the substrate. An enzyme cannot extract heat from the environment to speed a reaction. It can only lower the activation energy barrier so that more substrates have the energy to react.

The binding of a compound to an enzyme is observed to slow down or stop the rate of the reaction catalyzed by the enzyme. Increasing the substrate concentration reduces the inhibitory effects of this compound. Which of the following could account for this observation?

The compound is a competitive inhibitor.

Which of the following statements about ATP (adenosine triphosphate) is correct?

The cycling between ATP and ADP + Pi provides an energy coupling between catabolic and anabolic pathways. Catabolic pathways provide the energy needed to make ATP from ADP and Pi. The hydrolysis of ATP to ADP + Pi releases the same amount of energy.

Which of the following statements about the role of ATP in cell metabolism is true?

The energy from the hydrolysis of ATP may be directly coupled to endergonic processes by the transfer of the phosphate group to another molecule.

Which of the following statements about the combustion of glucose with oxygen to form water and carbon dioxide (C6H12O6 + 6 O2 → 6 CO2 + 6 H2O) is correct?

The entropy of the products is greater than the entropy of the reactants. A large molecule (glucose) has been converted into several smaller molecules (water and carbon dioxide); thus, the products have more disorder (greater entropy) than the reactants.

Which of the following would be unlikely to contribute to the substrate specificity of an enzyme?

The enzyme has an allosteric regulatory site. The allosteric site is distinct from the active site, and does not affect the substrate specificity of the enzyme.

Which of the following factors does not affect membrane permeability?

The polarity of membrane phospholipids

Which factors affect the rate of osmotic movement of water?

The rate of osmosis increases with increasing differences in solute concentrations between two solutions separated by a selectively permeable membrane.

Which of the following statements about a typical plasma membrane is correct?

The two sides of the plasma membrane have different lipid and protein composition.

Which part of the adenosine triphosphate molecule is released when it is hydrolyzed to provide energy for biological reactions?

The γ-phosphate is the primary phosphate group on the ATP molecule that is hydrolyzed when energy is needed to drive anabolic reactions. Located the farthest from the ribose sugar, it has a higher energy than either the α- or β-phosphate.

In facilitated diffusion, what is the role of the transport protein?

Transport proteins provide a hydrophilic route for the solute to cross the membrane.

True or false? Osmosis is a type of diffusion.

True

True or false? The water-soluble portion of a phospholipid is the polar head, which generally consists of a glycerol molecule linked to a phosphate group.

True

What happens when two solutions separated by a selectively permeable membrane reach osmotic equilibrium?

Water molecules move between the two solutions, but there is no net movement of water across the membrane.

Which statement about the binding of enzymes and substrates is correct?

When substrate molecules bind to the active site of the enzyme, the enzyme undergoes a slight change in shape.

The process of cellular respiration, which converts simple sugars such as glucose into CO2 and water, is an example of _____.

a catabolic pathway. Cellular respiration is a catabolic pathway.

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

a greater proportion of unsaturated phospholipids

If you are going to bake potatoes, and your potatoes are soft and dehydrated, they can be soaked in __________ to make them more firm before baking.

a hypotonic solution such as tap water

A substrate binds to an enzyme at the , where the reaction occurs.

active site

If the concentration of phosphate in the cytosol is 2.0 mM and the concentration of phosphate in the surrounding fluid is 0.1 mM, how could the cell increase the concentration of phosphate in the cytosol?

active transport For the cell to accumulate phosphate, it must move calcium against the concentration gradient. This process requires energy.

A cell that neither gains nor loses water while sitting in a solution is probably sitting in

an isotonic environment.

An enzyme is considered a because it speeds up chemical reactions without being used up.

catalyst

In your body, what process converts the chemical energy found in glucose into the chemical energy found in ATP?

cellular respiration..... This is the name given to the process by which the body converts food energy to energy stored in ATP.

A , such as a vitamin, binds to an enzyme and plays a role in catalysis.

cofactor

A (n) inhibitor has a structure that is so similar to the substrate that it can bond to the enzyme just like the substrate.

competitive

When properly aligned, the enzyme and substrate form an enzyme-substrate (ES)

complex

The movement of glucose into a cell against a concentration gradient is most likely to be accomplished by which of the following?

cotransport of the glucose with a proton or sodium ion that was pumped across the membrane using the energy of ATP hydrolysis Movement of most solutes against their concentration gradient couples the movement of one solute down its concentration gradient to the movement of another (glucose in this case) against its concentration gradient.

An enzyme is when it loses its native conformation and its biological activity.

denatured

Catabolism is to anabolism as _______ is to _______

exergonic; endergonic

Paramecium is a genus of protists that lives in water. It has organelles called contractile vacuoles that continually eliminate the excess water gained through osmosis. Knowing that Paramecia gain water through osmosis, we can deduce that they normally live in

freshwater lakes and ponds

What type of reaction breaks the bonds that join the phosphate groups in an ATP molecule?

hydrolysis

Enzymes are described as catalysts, which means that they _____.

increase the rate of a reaction without being consumed by the reaction. This permits enzyme molecules to be used repeatedly.

Endocytosis moves materials _____ a cell via _____.

into ... membranous vesicles

An enzyme _____.

is an organic catalyst

As a result of its involvement in a reaction, an enzyme _____.

is unchanged

A human cell placed into a hypertonic solution is likely to

lose water by osmosis.

An inhibitor that binds to a site on the enzyme that is not the active site.

noncompetitive

What name is given to the process by which water crosses a selectively permeable membrane?

osmosis

Facilitated diffusion is a type of _______.

passive transport

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

passive transport

A white blood cell engulfing a bacterium is an example of _____.

phagocytosis

Chemical energy is a form of _____ energy

potential

In general, enzymes are what kinds of molecules?

proteins

Enzymes work by ____

reducing EA

When a person is dehydrated, his or her IV fluids

should be hypotonic, because if dehydrated, he or she needs as much water as possible.

Energy is observed in two basic forms: potential and kinetic. Which of the following correctly matches these forms with a source of energy?

the covalent bonds of a sugar molecule: potential energy. Bonds are a form of potential energy because the energy arises from the relative positions of the atoms that form the bond.

You are working on a team that is designing a new drug. For this drug to work, it must enter the cytoplasm of specific target cells. Which of the following would be a factor that determines whether the molecule selectively enters the target cells?

the similarity of the drug molecule to other molecules that are transported into the target cells

The permeability of a biological membrane to a specific polar solute may depend on which of the following?

the types of transport proteins in the membrane

Some bacteria are metabolically active in hot springs because

their enzymes have high optimal temperatures.

Which of the following best describes the structure of a biological membrane?

two layers of phospholipids with proteins either crossing the layers or on the surface of the layers

Which of these are by-products of cellular respiration?

ATP, carbon dioxide, and water

What property of dishwashing liquid (detergent) makes it useful to wash grease from pans?

Amphipathic nature

How does an enzyme increase the rate of the chemical reaction it catalyzes?

An enzyme reduces the free energy of activation (EA) of the reaction it catalyzes. (An enzyme catalyzes a reaction by lowering EA, enabling the reactant molecules to absorb enough energy to reach the transition state even at moderate temperatures.)

Which of the following metabolic processes can occur without a net influx of energy from some other process? Which of the following metabolic processes can occur without a net influx of energy from some other process? glucose + fructose → sucrose ADP + P i → ATP + H2O 6 CO2 + 6 H2O → C6H12O6 + 6 O2 amino acids → protein C6H12O6 + 6 O2 → 6 CO2 + 6 H2O

C6H12O6 + 6 O2 → 6 CO2 + 6 H2O

Which of the following correctly describes some aspect of exocytosis or endocytosis?

Exocytosis and endocytosis change the surface area of the plasma membrane-the fusion or budding of transport vesicles at the plasma membrane either adds or removes proteins and phospholipids, thus changing the surface area.

How can a lipid be distinguished from a sugar?

Lipids are mostly nonpolar.

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

Nothing; the reaction will stay at equilibrium.

You have added an irreversible inhibitor to a sample of enzyme and substrate. At this point, the reaction has stopped completely. What can you do to regain the activity of the enzyme?

The enzyme is inactive at this point. New enzyme must be added to regain enzyme activity.

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

add more of the enzyme.

Which of the following is least likely to be important in holding the components of a biological membrane together?

covalent interactions between the phospholipid and protein components of the membrane

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

embedded in a lipid bilayer.

"Conservation of energy" refers to the fact that _____.

energy cannot be created or destroyed but can be converted from one form to another

When the noncompetitive inhibitor is bonded to the enzyme, the shape of the is distorted.

enzyme

An enzyme is considered because of its ability to recognize the shape of a particular molecule.

specific

In a catalyzed reaction a reactant is often called a .

substrate

What name is given to the reactants in an enzymatically catalyzed reaction?

substrate

A human cell placed in a hypotonic environment would

take up water through osmosis.

Most cells cannot harness heat to perform work because

temperature is usually uniform throughout a cell.

Many bacteria and fungi have a difficult time surviving on our food if the food is very salty. The best explanation for this is

that the salt in the food creates a hypertonic environment for the bacteria and fungi