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biology online quizzes, moodle quizzes, mastering biology quiz, and clicker questions

Which one of the following statements is true about diffusion?

It is a passive process

Which of the following statements is true about passive transport?

Passive transport permits the transported molecule to move in either direction, but the majority of transport occurs down the concentration gradient of the molecule.

Which of the following statements about the role of phospholipids in forming membranes is correct?

Phospholipids form a selectively permeable structure.

Cells A and B are the same size, shape, and temperature, but cell A is metabolically quiet and cell B is actively consuming oxygen. Oxygen will diffuse more quickly into cell _____ because _____.

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

Which statement(s) about the sidedness of the plasma membrane is (are) correct?

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 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 plasma membrane is referred to as a "fluid mosaic" structure. Which of the following statements is true?

The fluid component of the membrane is phospholipid, and the mosaic is protein.

Which of the following reactions would be endergonic?

glucose + fructose to sucrose

Which of the following states the relevance of the first law of thermodynamics to biology?

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

Organisms are described as thermodynamically open systems. Which of the following statements is consistent with this description?

Organisms acquire energy from their surroundings.

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

releases energy when proceeding in the forward direction

Which of the following is an example of the second law of thermodynamics as it applies to biological reactions?

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

Which is the most abundant form of energy in a cell?

chemical energy

Which of the following is not an example of the cellular work accomplished with the free energy derived from the hydrolysis of ATP?

the production of heat, which raises the temperature of the cell

Which of the following are examples of the cellular work accomplished with the free energy derived from the hydrolysis of ATP?

transport work, such as the active transport of an ion into a cell
chemical work, such as the synthesis of new protein
mechanical work, such as the beating of cilia

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

The products of the pathway become the reactants for a different reaction, and thus products are unable to accumulate.

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

The compound that regulates the pathway acts as a non-competitive inhibitor or a negative allosteric regulator.
Accumulation of the product of the pathway will tend to slow down further formation of that product.
The final product of a metabolic pathway is the compound that regulates the pathway.
The enzyme that is regulated by feedback inhibition is usually the first enzyme in the metabolic pathway.

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 incorrect?

The free energy lost to the system in this combustion is greater than the energy that appears as heat.

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) are correct?

The reverse reaction, making glucose from water and carbon dioxide, must be an endergonic reaction.
This reaction is spontaneous with the release of free energy.
The entropy of the universe increases as the result of this reaction.
The entropy of the products is greater than the entropy of the reactants.

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

The compound is a negative allosteric regulator.
The compound is a competitive inhibitor.
The compound causes a cofactor to be lost from the enzyme.

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

an energy-releasing pathway
a pathway in which the entropy of the system increases
a catabolic pathway

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

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

increase the rate of a reaction without being consumed by the reaction

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.

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

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

Which of the following statements correctly describe(s) the role(s) of heat and temperature in biological reactions?

Heat from the environment is necessary for substrates to get over the activation energy barrier.
Increasing temperature increases the kinetic energy of the substrates.

The mechanism of enzyme action is _____.

lowering the energy of activation for a reaction

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. Which of the following best explains these observations?

In the cell, the hydrolysis of ATP is coupled to other endergonic reactions.

Which of the following statements about enzymes is true?

Enzymes speed up the rate of the reaction without changing the Delta G for the reaction.

The formation of glucose-6-phosphate from glucose is an endergonic reaction and is coupled to which of the following reactions or pathways?

the hydrolysis of ATP

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

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

Which of the following statements about enzymes are correct?

Most enzymes are proteins.
An enzyme is not consumed by the catalytic process.
An enzyme lowers the activation energy of a chemical reaction.
An enzyme is very specific in terms of which substrate it binds to.

What best characterizes the role of ATP in cellular metabolism?

The free energy released by ATP hydrolysis may be coupled to an endergonic process via the formation of a phosphorylated intermediate.

Most of the energy that enters electron transport enters as

FADH2 and NADH.

Cells do not catabolize carbon dioxide because

CO2 is already completely oxidized.

Which statement about the citric acid cycle are correct?

The citric acid cycle oxidizes the products of glycolysis to carbon dioxide.
The last reaction in the citric acid cycle produces a product that is a substrate for the first reaction of the citric acid cycle.
The citric acid cycle produces most of the NADH that is subsequently used by the electron transport chain.
The citric acid cycle depends on the availability of NAD+, which is a product of the electron transport chain.

Glycolysis is an ________ reaction.

exergonic

A glucose molecule is completely broken down to carbon dioxide and water in glycolysis and the citric acid cycle, but together these two processes yield only a few molecules of ATP. What happened to most of the energy that the cell obtains from the oxidation of glucose?

It is stored in NADH.

In fermentation, ________ is ________.

NADH; oxidized

How many ATP molecules are produced (total) by glycolysis?

4

Pyruvate is formed

in the cytosol

Most CO2 from catabolism is released during

the citric acid cycle.

In the absence of oxygen, what is the net gain of ATP for each glucose molecule that enters glycolysis?

2 ATP

In the combined processes of glycolysis and cellular respiration, what is consumed and what is produced?

Glucose is consumed, and carbon dioxide is produced.

Which of the following statements about the redox reactions of the electron transport chain is correct?

The redox reactions of the electron transport chain are directly coupled to the movement of protons across a membrane.

When light strikes chlorophyll molecules, they lose electrons, which are ultimately replaced by _____.

splitting water

Which of the following is not a product of the light reactions of photosynthesis?

sugar

Which of the following are products of the light reactions of photosynthesis?

oxygen, NADPH, high-energy electrons, ATP

Plants are photoautotrophs. What does this mean?

They are in the same category as algae and cyanobacteria.
They use light energy to drive the synthesis of organic molecules.
They make their own food from inorganic materials.
They are among the producers of the biosphere.

The photosynthetic membranes are found in the _____ in plant cells.

chloroplasts

In the electromagnetic spectrum, the type of radiation that we call visible light occurs between _____.

ultraviolet radiation and infrared radiation

Photosynthesis is an _____ process of carbon _____, while respiration is an _____ process of carbon _____.

endergonic ... reduction ... exergonic ... oxidation

The overall function of the Calvin-Benson cycle is _____.

making sugar

C4 plants occur more commonly in desert conditions because _____.

they can fix carbon at the lower CO2 concentrations that develop when the stomata are closed

The ultimate source of energy to support most life on Earth is _____.

sunlight

Which of the following is produced by the light reactions of photosynthesis and consumed by the Calvin-Benson cycle?

NADPH

Which of the following statements about the role of phospholipids in forming membranes is correct?

Phospholipids form a selectively permeable structure.

The plasma membrane is referred to as a "fluid mosaic" structure. Which of the following statements is true?

The fluid component of the membrane is phospholipid, and the mosaic is protein

Which of the following types of information is (are) most likely to be derived from freeze-fracture of biological samples?

proteins imbedded in membrane bilayers

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

in the interior of the membrane

Which of the following functional processes result(s) from the presence of proteins in or on the plasma membrane?

enzymatic activity, cell-cell recognition, intercellular joining, cell-cell communication

What are functions of membrane proteins?

Membrane proteins attach the membrane to the cytoskeleton.
Membrane proteins provide receptors for chemical messengers.
Membrane proteins form channels, which move substances across the membrane.
Membrane proteins with short sugar chains form identification tags that are recognized by other cells.

Select the correct statement concerning carbohydrates associated with the plasma membrane.

Membrane carbohydrates function primarily in cell-cell recognition.

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

on the outside (external) surface of the membrane

Which statement(s) about the sidedness of the plasma membrane is (are) 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 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 specific orientation in the plasma membrane.

Which one of the following molecules is most likely to diffuse freely across the lipid bilayer of the plasma membrane without the involvement of a transport protein?

carbon dioxide

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

a large polar molecule

Which of the following structures is most consistent with the selective permeability property of biological membranes?

proteins embedded in two layers of phospholipid

Which of the following statements is true about passive transport?

Passive transport permits the transported molecule to move in either direction, but the majority of transport occurs down the concentration gradient of the molecule.

Cells A and B are the same size, shape, and temperature, but cell A is metabolically quiet and cell B is actively consuming oxygen. Oxygen will diffuse more quickly into cell _____ because _____.

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

Which one of the following statements is true about diffusion?

It is a passive process.

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?

1.0 M

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?

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

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.

Which of these statements describes some aspect of facilitated diffusion?

Facilitated diffusion of solutes may occur through protein pores in the membrane.

Which one of the following is not in some way involved in facilitated diffusion?

an outside energy source

Movement of phospholipids from one side of a membrane to the other does occur under appropriate circumstances. Based on your understanding of membrane structure and transport, which of the following is likely to describe this movement of phospholipids between the two sides of a membrane?

None of the above could facilitate movement of phospholipids from one side of the membrane to the other

Imagine two solutions separated by a selectively permeable membrane that allows water to pass, but not sucrose or glucose. The membrane separates a 0.2-molar sucrose solution from a 0.2-molar glucose solution. With time, how will the solutions change?

Nothing happens because the two solutions are isotonic to one another.

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?

a hypertonic sucrose solution

Green olives may be preserved in brine, which is a 30% salt solution. How does this method of preservation prevent contamination by microorganisms?

A 30% salt solution is hypertonic to the bacteria, so they lose too much water and cannot survive.

Active transport requires a cell to expend energy. Which of the following statements is not true?

Active transport usually moves solutes down the concentration gradient.

Glucose is a six-carbon sugar that diffuses slowly through artificial membranes. The cells lining the small intestine, however, rapidly move glucose from the gut into their cytoplasm. This occurs whether the gut concentrations of glucose are higher or lower than the glucose concentrations in intestinal cell cytoplasm. Using this information, which transport mechanism is most likely responsible for the glucose transport in intestinal cells?

active transport

Which of the following is a difference between active transport and facilitated diffusion?

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

Which of the following statements about the sodium-potassium pump are correct?

The sodium-potassium pump transports Na+ and K+ ions across the plasma membrane in opposite directions at the expense of ATP hydrolysis.
The sodium-potassium pump creates an electrochemical gradient.
The sodium-potassium pump is electrogenic.
The sodium-potassium pump creates concentration gradients of both Na+ and K+ across the plasma membrane

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

Which of the following correctly describes a general property of all electrogenic pumps?

creates a voltage difference across the membrane

Which of the following statements about cotransport of solutes across a membrane is correct?

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

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, don't protons move back into the cell through the sucrose-proton cotransport protein?

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

Which of the following enables a cell to pick up and concentrate a specific kind of molecule?

receptor-mediated endocytosis

Which of the following processes, normally associated with membrane transport, must occur in order to account for the increase in the surface area of a cell?

exocytosis

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?

endocytosis

The transmission of nerve impulses between adjacent nerve cells requires the release of a neurotransmitter (a molecule or small peptide) by exocytosis. Which of the following processes would most likely follow the release of neurotransmitter to bring the cell back to its original state?

receptor-mediated endocytosis

Which one of the following pairs matches the name of a membrane transport process with the primary function of that process?

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

Which of the following correctly states the relationship between anabolic and catabolic pathways?

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

Which of the following situations does represent a transformation of one type of energy to another?

the burning of gasoline in a car engine to move a car
the production of sugar by photosynthesis
the production of electrical power by damming a river
playing music by putting new batteries in your CD player

Organisms are described as thermodynamically open systems. Which of the following statements is consistent with this description?

Organisms acquire energy from their surroundings.

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 laws of thermodynamics?

In order to obey the first law, the crop must represent an open system.

Which of the following states the relevance of the first law of thermodynamics to biology?

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

Which is the most abundant form of energy in a cell?

chemical energy

Which of the following is an example of the second law of thermodynamics as it applies to biological reactions?

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?

The decrease in entropy associated with life must be compensated for by an increase in entropy in the environment that life occurs in.

If the entropy of a living organism is decreasing, which of the following is most likely to be occurring simultaneously?

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

Which one of the following has the most free energy per molecule?

a starch molecule

Which part of the equation DG = DH - TDS tells you if a process is spontaneous?

DG

If, during a process, the system becomes more ordered, then _____.

DG is negative

When one molecule is broken down into six component molecules, which one of the following will always be true?

DS is positive

From the equation DG = DH - TDS it is clear that _____.

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
increasing the temperature of a system will increase the probability of spontaneous change

What must be true if the reaction AB + CD ® AC + BD occurs spontaneously?

The difference between DH and TDS must be negative.

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

releases energy when proceeding in the forward direction

Which of the following reactions would be endergonic?

glucose+fructose=surcrose

Metabolic pathways in cells are typically far from equilibrium. Which of the following processes tend to keep these pathways away from equilibrium?

the continuous removal of the products of a pathway to be used in other reactions
an input of free energy from outside the pathway

Which of the following is are examples of the cellular work accomplished with the free energy derived from the hydrolysis of ATP?

mechanical work, such as the beating of cilia
transport work, such as the active transport of an ion into a cell
chemical work, such as the synthesis of new protein

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

releasing free energy that can be coupled to other reactions

Which of the following statements correctly describes some aspect of ATP hydrolysis being used to drive the active transport of an ion into the cell against the ion's concentration gradient?

This is an example of energy coupling.

Which compound could be most easily modified to form ATP?
the RNA nucleotide adenosine

the RNA nucleotide adenosine

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 _____.

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

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. Which of the following best explains these observations?

In the cell, the hydrolysis of ATP is coupled to other endergonic reactions.

What best characterizes the role of ATP in cellular metabolism?

The free energy released by ATP hydrolysis may be coupled to an endergonic process via the formation of a phosphorylated intermediate.

The formation of glucose-6-phosphate from glucose is an endergonic reaction and is coupled to which of the following reactions or pathways?

the hydrolysis of ATP

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

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

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

Neither the sign nor the magnitude of DG have anything to do with the speed of a reaction.

The mechanism of enzyme action is _____.

lowering the energy of activation for a reaction

Which of the following statements about enzymes is true?

Enzymes speed up the rate of the reaction without changing the DG for the reaction.

Which of the following statements about enzyme function is correct?

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

32 . A plot of reaction rate (velocity) against temperature for an enzyme indicates little activity at 10°C and 45°C, with peak activity at 35°C. The most reasonable explanation for the low velocity at 10°C is that _____.

there is too little activation energy available

Which of the following statements about enzymes are correct?

Most enzymes are proteins.
An enzyme is not consumed by the catalytic process.
An enzyme is very specific in terms of which substrate it binds to.
An enzyme lowers the activation energy of a chemical reaction.

Which of the following statements about the active site of an enzyme is correct?

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

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

The enzyme changes its shape slightly as the substrate binds to it.

Which of the following statements correctly describe(s) the role(s) of heat and temperature in biological reactions?

Heat from the environment is necessary for substrates to get over the activation energy barrier.
Increasing temperature increases the kinetic energy of the substrates.

Above a certain substrate concentration, the rate of an enzyme-catalyzed reaction drops as the enzymes become saturated. Which of the following would lead to a faster conversion of substrate into product under these saturated conditions?

an increase in concentration of enzyme
increasing the temperature by a few degrees

Which of the following environments or actions does not affect the rate of an enzyme reaction?
heating the enzyme
cooling the enzyme
substrate concentration
pH
all of the above

all of the above

Enzyme activity is affected by pH because _____.

high or low pH may disrupt hydrogen bonding or ionic interactions and thus change the shape of the active site

Which of these statements about enzyme inhibitors is true?

The action of competitive inhibitors may be reversible or irreversible.

Succinylcholine is structurally almost identical to acetylcholine. If succinylcholine is added to a mixture that contains acetylcholine and the enzyme that hydrolyzes acetylcholine (but not succinylcholine), the rate of acetylcholine hydrolysis is decreased. Subsequent addition of more acetylcholine restores the original rate of acetylcholine hydrolysis. Which of the following correctly explains this observation?

Succinylcholine must be a competitive inhibitor with acetylcholine.

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

allosteric regulation

Which, if any, of the following statements is not true about allosteric proteins?

They can bind to a range of substrates.

The binding of an allosteric inhibitor to an enzyme causes the rate of product formation by the enzyme to decrease. Which of the following best explains why this decrease occurs?

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

Under most conditions, the supply of energy by catabolic pathways is regulated by the demand for energy by anabolic pathways. Considering the role of ATP formation and hydrolysis in energy coupling of anabolic and catabolic pathways, which of the following statements is most likely to be true?

High levels of ADP act as an allosteric activator of catabolic pathways

A molecule becomes more oxidized when it _____.

loses an electron

In the overall process of glycolysis and cellular respiration, _____ is oxidized and _____ is reduced.

glucose ... oxygen

Most of the ATP produced in cellular respiration comes from which of the following processes?

oxidative phosphorylation

Oxygen gas (O2) is one of the strongest oxidizing agents known. The explanation for this is that _____.

the oxygen atom is very electronegative

The function of cellular respiration is to _____.

extract usable energy from glucose

During the reaction C6H12O6 + 6 O2 ® 6 CO2 + 6 H2O, which compound is reduced as a result of the reaction?

oxygen

Which of the following statements provides the best explanation for why the oxidation of organic compounds by molecular oxygen (O2) yields so much energy?

The oxygen atom has a higher affinity for electrons than the carbon atom.

Each ATP molecule contains about 1% of the amount of chemical energy available from the complete oxidation of a single glucose molecule. Cellular respiration produces about 38 ATP from one glucose molecule. What happens to the rest of the energy in glucose?

it is converted to heat

A small amount of ATP is made in glycolysis by which of the following processes?

transfer of a phosphate group from a fragment of glucose to ADP by substrate-level phosphorylation

A chemist has discovered a drug that blocks phosphoglucoisomerase, an enzyme that catalyzes the second reaction in glycolysis. He wants to use the drug to kill bacteria in people with infections. But he can't do this because _____.

human cells must also perform glycolysis; the drug might also poison them

In glycolysis, there is no production of carbon dioxide as a product of the pathway. Which of the following is the best explanation for this?

The two pyruvate molecules produced from each glucose molecule each contain three carbon atoms.

Of the following molecules in the glycolytic pathway (the process of glycolysis), the one with the most chemical energy is _____.

fructose-1,6-bisphosphate

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