Bio Test 2 191

Which of the following statements about diffusion is true?

It is a passive process.

What is the role of oxygen in the electron transport chain?

It is reduced to form water.

Which of the following statements is correct regarding kinetic and potential energy?

Kinetic energy is associated with the relative motion of objects, and potential energy is the energy that matter possesses because of its location or structure.

Which statement correctly describes the difference between alcohol fermentation and lactic acid fermentation?

Lactic acid fermentation produces lactate, and alcohol fermentation produces ethanol.

Which of the following statements concerning carbohydrates associated with the plasma membrane is correct?

Membrane carbohydrates function primarily in cell-cell recognition.

Which of the following is true regarding metabolic pathways?

Metabolic pathways consist of a series of reactions, each catalyzed by a different enzyme.

What organelle is indicated by the letter C?

Mitochondrion

______ is the compound that functions as the electron acceptor in glycolysis.

NAD+

After completion of the citric acid cycle, most of the usable energy from the original glucose molecule is in the form of __________.

NADH

The reduced form of the electron acceptor in glycolysis is______

NADH

During the energy payoff phase of glycolysis, __________.

NADH and ATP are produced

In what molecule(s) is the majority of the chemical energy from pyruvate transferred during the citric acid cycle?

NADH and FADH2

Which of the following is a correct description of the events of cellular respiration and the sequence of events in cellular respiration?

Oxidation of glucose to pyruvate; oxidation of pyruvate; oxidation of acetyl-coA; oxidative phosphorylation

All of the processes involved in cellular respiration produce ATP. Which of the following processes produces the most ATP?

Oxidative phosphorylation

What molecule is indicated by the letter D?

Oxygen

Which of the following statements about passive transport is correct?

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

Which of the following molecules are most abundant in the plasma membrane?

Phospholipids

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.

Which of the following cell structures exhibits selective permeability between a cell and its external environment?

Plasma membrane

What would the value of ΔS be for a chemical reaction in which a molecule is broken down into smaller components?

Positive

Which of the following structural arrangements of the components in biological membranes facilitates the cell membrane's property of selective permeability?

Proteins embedded in two layers of phospholipids

How does the "fluid mosaic model" describe the structure of the plasma membrane?

Proteins in the membrane contribute to the mosaic quality of the membrane while the lateral and rotational movements of phospholipids contribute to its fluidity.

In preparing pyruvate to enter the citric acid cycle, which of the following steps occurs?

Pyruvate is oxidized and decarboxylated, and the removed electrons are used to reduce an NAD+ to an NADH.

Most of the electrons removed from glucose by cellular respiration are used for which of the following processes?

Reducing NAD+ to NADH in glycolysis and the citric acid cycle AND producing a proton gradient for ATP synthesis in the mitochondria.

Which of these statements about enzyme inhibitors is true?

The action of competitive inhibitors may be reversible or irreversible.

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

The active reactants

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.

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.

Most of the NADH that delivers electrons to the electron transport chain comes from which of the following processes?

The citric acid cycle

What process occurs within Box B?

The citric acid cycle

Which part of the catabolism of glucose by cellular respiration requires molecular oxygen (O2) and produces CO2?

The combination of the citric acid cycle and electron transport

Which of the following metabolic pathways produce(s) the most ATP, per glucose molecule metabolized, during cellular respiration?

The electron transport chain and oxidative phosphorylation

Which of the following statements is correct regarding ATP?

The energy in an ATP molecule is released through hydrolysis of one of the phosphate groups.

At low pH, a particular enzyme catalyzes a reaction at a high rate. At neutral pH, the enzyme is completely inactive. What statement best explains the difference in how pH affects the function of this enzyme?

The enzyme is adapted for low pH but is denatured at neutral pH, leaving it nonfunctional.

The ATP synthase in a human cell obtains energy for synthesizing ATP directly from which of the following processes?

The flow of H+ across the inner mitochondrial membrane through the ATP synthase enzyme

What best characterizes the role of ATP in cellular metabolism?

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

The energy from the electrons in NADH and FADH2 fuel what process in the electron transport chain?

The pumping of H+ across the cristae of the mitochondrion

A cell is placed into a solution and the cell shrinks. Which of the following is true regarding the solution?

The solution is hypertonic

Which of the following is correct regarding integral proteins?

These proteins exhibit both hydrophilic and hydrophobic properties.

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

What is the total production of ATP, NADH, and FADH2 in the citric acid cycle from one molecule of glucose?

Two ATP, six NADH, and two FADH2

A molecule becomes more oxidized when it __________.

When it loses an electron

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

In facilitated diffusion, __________ proteins provide openings in the plasma membrane for substances to flow through without changing structure, and __________ proteins allow passage of substances through the plasma membrane after undergoing a subtle change in shape.

channel; carrier

Fermentation is essentially glycolysis plus an extra step in which pyruvate is reduced to form lactate or alcohol and carbon dioxide. This last step_______.

enables the cell to recycle the reduced NADH to oxidized NAD+

The function of cellular respiration is to __________.

extract usable energy from glucose

ATP allosterically inhibits enzymes in ATP-producing pathways. The result of this is called __________.

feedback inhibition

In glycolysis, the carbon-containing compound that functions as the electron donor is ______.

glucose

During the energy investment phase of glycolysis, __________.

glucose is phosphorylated before it is split into two three-carbon molecules

What process occurs in Box A?

glycolysis

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

All cells have voltages across their membranes. This voltage is called a(n) __________ and is often maintained by __________.

membrane potential; electrogenic pumps

When a compound donates (loses) electrons, that compound becomes _________. Such a compound is often referred to as an electron donor.

oxidized

What process occurs in structure H?

photosynthesis

Once the electron donor in glycolysis gives up its electrons, it is oxidized to a compound called _______.

pyruvate

When a compound accepts (gains) electrons, that compound becomes ____. Such a compound is often referred to as an electron acceptor.

reduced

Muscle tissues make lactate from pyruvate to do which of the following?

regenerate NAD+

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

releases energy when proceeding in the forward direction

An exergonic reaction __________ free energy, and an endergonic reaction __________ free energy.

releases; absorbs

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

releasing free energy that can be coupled to other reactions

The plasma membrane exhibits selective permeability. This means that __________.

the plasma membrane allows some substances to flow through it more easily than others

The sodium-potassium pump __________.

transports sodium ions out of the cell and transports potassium ions into the cell

Which of the following statements is true of the bonds in a water molecule?

-Oxygen holds electrons more tightly than hydrogen does, and the net charge is zero.

Among the products of glycolysis, which compounds contain energy that can be used by other biological reactions?

-Pyruvate, ATP, NADH

Red blood cells contain approximately a 2% concentration of solutes. A red blood cell is placed into a solution that contains a 4% concentration of solutes to which the cell is not permeable. What will happen to the red blood cell?

-The cell will decrease in size as water flows out of it.

Which of the following is correct regarding peripheral proteins?

-These proteins are found only on the surface of the plasma membrane.

Which terms describe two atoms when they form a bond in which electrons are completely transferred from one atom to the other?

-anion and cation

Which term describes the degree to which an element attracts electrons?

-electronegativity

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

1.0 M

Which of the following plant cells would exhibit the most turgor pressure?

A cell placed in a hypotonic solution

Which of the following statements is not true of most cellular redox reactions?

A hydrogen atom is transferred to the atom that loses an electron.

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 substances would be most likely to pass through the plasma membrane without the help of a transport protein?

A nonpolar molecule, such as a hydrocarbon

As ATP begins to build up in a cell, metabolism slows down. How does this happen?

ATP acts as an allosteric inhibitor to many of the enzymes involved in metabolism, thus slowing their function.

Cells use ATP constantly, but ATP is considered a renewable resource. What process makes this possible?

ATP can be regenerated by the addition of a phosphate group to ADP.

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

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

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.

How does cholesterol affect membrane fluidity?

At body temperature, it makes the membrane less fluid.

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

At low temperatures, there is not enough free energy for the enzyme to function at a high rate, and at high temperatures, the enzyme is denatured, leaving it nonfunctional.

During aerobic respiration, molecular oxygen (O2) is used for which of the following purposes?

At the end of the electron transport chain to accept electrons and form H2O

Cells A and B are the same size, shape, and temperature, but cell A is metabolically less active than cell B; cell B is actively converting oxygen to water in cellular respiration. Oxygen will diffuse more rapidly into the cell __________ because __________.

B; the diffusion gradient in cell B is steeper

Why is energy required for active transport?

Because it moves solutes against their concentration gradient

Which of the following statements correctly describes cofactors and coenzymes?

Both are nonprotein enzyme helpers; but most cofactors are metal ions, and coenzymes are organic molecules that are a specific type of cofactor.

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.

How does ATP drive mechanical work inside a cell?

By binding to motor proteins

How does ATP drive transport work inside a cell?

By phosphorylating a transport protein

Which of the following molecules is most likely to passively diffuse across the plasma membrane?

Carbon dioxide

What molecules belong in spaces E and F?

Carbon dioxide and water

What function do carbohydrates fulfill in the plasma membrane?

Cell-to-cell recognition

Which of the following pairs of pathways and their location in the cell is incorrectly matched?

Citric acid cycle: cytosol

Which of the following statements is correct regarding competitive and noncompetitive enzyme inhibitors?

Competitive inhibitors bind to the active site of an enzyme while noncompetitive inhibitors bind to an enzyme away from the active site.

Sort the statements into the appropriate bin depending on whether or not they correctly describe some aspect of substrate-level phosphorylation in glycolysis.

Correct: -One of the substrates is a molecule derived from the breakdown of glucose -An enzyme is required in order for the reaction to occur -A bond must be broken between an organic molecule and phosphate before ATP can form. Incorrect: -The phosphate group added to ADP to make ATP comes from free inorganic phosphate ions. -The enyzmes involved in ATP synthesis must be attached to a membrane to produce ATP.

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

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.

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 to drive the decrease in entropy.

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.

Which of the following statements about enzymes is true?

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

The primary manner in which cells manage their energy resources in order to do work is called energy coupling. Which of the following statements accurately defines energy coupling?

Exergonic reactions drive endergonic reactions.

Which of the following processes and organelle(s) accounts for the replacement of lipids and proteins lost from the plasma membrane?

Exocytosis and smooth and rough ER

Which of these statements describes some aspect of facilitated diffusion?

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

Glucose is the primary fuel for cellular respiration. Which of the following molecules can also be used by cellular respiration to generate ATP?

Fatty Acids, Amino Acids, Glycerol

Cells must regulate their metabolic pathways so that they do not waste resources. What is the most common mechanism that regulates cellular respiration in most cells?

Feedback inhibition of glycolysis

Fermentation by itself produces no ATP but keeps glycolysis going, which produces a small amount of ATP. How does fermentation do this?

Fermentation oxidizes NADH to NAD+, which facilitates the production of ATP in glycolysis.

Which of the following reactions would be endergonic?

Glucose + fructose → sucrose

16. What molecules belong in space A and B?

Glucose and oxygen

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

Glucose, oxygen

In which process is glucose oxidized to form two molecules of pyruvate?

Glycolysis

Which metabolic pathway is common to both fermentation and cellular respiration of a glucose molecule?

Glycolysis

Most of the ATP in cellular respiration is produced by the process of chemiosmosis. How does this process produce ATP?

H+ flows across the inner mitochondrial membrane through the enzyme ATP synthase.

Gaseous hydrogen burns in the presence of oxygen to form water: 2H2 + O2 → 2H2 O + energy. Which molecule is oxidized and what kind of bond is formed?

Hydrogen, polar

What kind of bond is formed when lithium and fluorine combine to form lithium fluoride?

Ionic