BS 161 EXAM 2 LAUNCHPAD QUESTIONS

Disorders of which organelle are often associated with defects in transport from compartment to compartment, resulting in poor sorting of protein components within the cell?

the Golgi apparatus

Which part of a cholesterol molecule is polar?

the OH group The part of the cholesterol molecule with paired atoms of unequal electronegativity is polar; the electronegativity of carbon and hydrogen is similar.

What is glycosylation?

the addition of sugars to lipids or proteins

During which stages of cellular respiration is carbon dioxide released? Select all that apply.

the citric acid cycle and pyruvate oxidation

The energy required to drive the synthesis of the majority of the ATP generated during aerobic respiration comes most directly from:

the flow of protons through an ATP synthase complex.

During the pyruvate oxidation stage of cellular respiration, which of the following occurs?

the formation of NADH, the oxidation of pyruvate, the formation of CO2, the formation of acetyl-CoA

Which of the choices is an example of kinetic energy?

electricity

Of the choices, which can be a product of a catabolic reaction?

an amino acid like tryptophan An amino acid would be the product of protein degradation by protease enzymes in a catabolic reaction.

Which of the choices is an example of potential energy?

an electrochemical gradient across the cell membrane

The reactions in the pathways of glycolysis and the citric acid cycle break down glucose into smaller molecules. Therefore, these pathways:

are catabolic pathways

When chemical reactions occur the _____ but the _____.

atoms retain their identities; arrangement of bonds change

Where are the ribosomes that translate proteins to be secreted from the cell?

attached to the rough endoplasmic reticulum Secreted proteins must be produced in a way that allows them to be on the inside of the membrane making up a vesicle, so when that vesicle fuses with the plasma membrane, the protein is released through exocytosis.

The majority of the energy captured in the citric acid cycle is in the form of:

electrons donated to NAD+ and FAD.

The first phase of glycolysis requires the input of two ATP molecules. It is therefore:

endergonic

Synthesis of a protein is an example of a chemical reaction that is:

endergonic and anabolic

The synthesis of ATP from ADP and Pi is a(n) _____ reaction with ____ ΔG.

endergonic; a positive

The controlled release of cellular material stored in membrane-bound vesicles to the outside of the cell is an example of:

exocytosis.

Sodium ions (Na+) move through sodium channels in a synthetic membrane using

facilitated diffusion

_____ are organisms that derive energy from sunlight.

phototrophs

Organic molecules store _____ energy in their _____ bonds.

potential; covalent

The action of sodium-potassium pumps that hydrolyze ATP in order to move sodium ions (Na+) out of a cell and potassium ions (K+) into a cell is an example of:

primary active transport

When H2CO3 reacts to form CO2 and H2O, what is the net change in the number of shared electron pairs?

0

Nicotinamide adenine dinucleotide is an electron carrier in many important cellular reactions. It exists in an oxidized form (NAD+) and a reduced form (NADH). What is the missing component in the reaction: NAD+ + ____ + H+ → NADH?

2e-

Which best describes energy captured in ATP during aerobic cellular respiration?

A small amount of energy is captured in ATP by substrate-level phosphorylation; most is captured in ATP by oxidative phosphorylation.

Which protein would be synthesized on the rough endoplasmic reticulum and processed in the Golgi apparatus?

A sodium-potassium pump, which is an integral membrane protein in the plasma membrane

If one follows the respiratory energy transfers and transformations sequentially from glucose through glycolysis, pyruvate oxidation, and the citric acid cycle, but before the electron transport chain and oxidative phosphorylation, most of the free energy captured from the original glucose molecule is found in:

ATP

During the citric acid cycle

ATP is synthesized by substrate level phosphorylation.

Which of the statements is true of allosteric inhibitors of an enzyme?

Allosteric inhibitors decrease enzyme activity.

Complete oxidation of glucose to CO2 involves two different mechanisms for synthesizing ATP: oxidative phosphorylation and substrate-level phosphorylation. Which is true of substrate-level phosphorylation?

An enzyme catalyzes the transfer of a phosphate group to ADP from an organic molecule to form ATP.

How do eukaryotic plant and animal cells differ from one another?

Animal cells do not have chloroplasts and cell walls, and plant cells do. Because both plants and animals must perform cellular respiration, they both require mitochondria.

Some bacteria run the citric acid cycle in reverse. Without any other modifications to the cycle, what inputs would be required to do this?

CO2, FADH2, NADH, and ATP Running the citric acid cycle in reverse would require a source of energy, and if the cycle is unmodified, as suggested, then that energy would be acquired from FADH2, NADH, and ATP. The starting carbon substrate would be CO2.

One unifying feature of prokaryotic and eukaryotic cells is the presence of:

DNA

Imagine a cell that has a membrane composed mostly of lipids with saturated fatty acid tails, and that this membrane also has low cholesterol content. What are the characteristics of this cell membrane?

Due to its low cholesterol content, the cell membrane would lose its fluidity at cold temperatures. Remember that cholesterol is a bulky nonpolar molecule with multiple ring structures that prevent tight packing of the phospholipids' tails and that cholesterol increases membrane fluidity at low temperatures.

Insulin is a protein hormone that helps to control the level of glucose in the blood. It is secreted from specialized cells in the pancreas. Based on this information, which path does insulin take out of the cell?

ER → Golgi apparatus → vesicle → exterior of cell

The diagram shown represents the four stages of aerobic cellular respiration as four simple boxes. Many of the "inputs" and "outputs" are shown as arrows. Open arrows (→) represent "energy management molecules" (ATP and electron carriers), and closed arrows (→) represent other inputs and outputs, such as substrates and products. Use this diagram to answer the questions.

From left to right, the boxes represent glycolysis, pyruvate oxidation, the citric acid cycle, and the electron transport chain/oxidative phosphorylation. The correct answer will be known by considering the inputs and outputs of each stage of cellular respiration and their interconnections.

What happens when glucose is phosphorylated during phase 1 of glycolysis?

Glucose is destabilized so that it can be broken apart in phase 2

Human blood types A, B, AB, and O differ by the sugars attached to the proteins and lipids found in in the red blood cell plasma membrane. The attachment of these sugars, called glycosylation, occurs in which organelle?

Golgi

Which of the following best describes how ATP synthase converts the potential energy of the proton gradient to the chemical energy of ATP?

Kinetic energy from the flow of protons is converted to the kinetic energy of rotation of the Fo subunit; the rotation of the Fo subunit leads to rotation of the F1 subunit, which can then catalyze ATP synthesis.

A researcher has devised a technique that allows her to label all the integral membrane proteins with a fluorescent tag. She uses a laser to bleach the fluorescence in a specific area of the cell membrane. After 24 hours, she notices that fluorescence has returned to the bleached area. What can she deduce from this experiment?

Integral membrane proteins are able to move laterally within the cell membrane. Consider how integral membrane proteins that were not bleached at the start of the experiment might be able to return to the previously bleached area by lateral movement in the fluid mosaic of the membrane.

Which statement describes the proton gradient generated by the electron transport chain?

It is an electrochemical gradient.

Why is the transporter in the figure considered to be an example of "secondary transport"?

It is driven by the proton gradient that was created by energy from ATP

What happens to pyruvate during fermentation?

It is reduced to ethanol or lactic acid.

Which of the following correctly characterizes the F1 subunit of ATP synthase?

It is the catalytic unit that synthesizes ATP.

If oxygen is unavailable, predict what will happen to the citric acid cycle.

It will stop because the supplies of NAD+ and FAD will become depleted. Production of reduced electron carriers, NADH and FADH2, during the citric acid cycle depends upon an input of oxidized forms, NAD+ and FAD. When oxygen is absent, it means that the electron carriers cannot be oxidized and returned to the citric acid cycle from the electron transport chain.

Which statement about mitochondria is true?

Mitochondria generate ATP.

In glycolysis, high energy electrons in glucose are used to reduce ___________ and _____________.

NAD+; FAD

Which example is an electron carrier in its reduced form?

NADH

Which example represents the reduced forms of the two major electron carriers?

NADH and FADH2

The immediate source of electrons for the electron transport chain is:

NADH and FADH2.

It is often stated that the phosphate-phosphate bonds in ATP are "high energy," but in fact, they are not notably high in energy. Rather, they are easy to break, and the ΔG of hydrolysis is a "useful" quantity of energy. What makes the phosphate bonds easy to break?

Negative charges on phosphate groups repel each other.

What would happen if complexes I-IV of the electron transport chain pumped protons in the opposite direction?

No ATP would be synthesized.

Very low concentrations of detergent make membranes leaky to small molecules and ions without damaging proteins. In isolated mitochondria exposed to detergent, the molecules of the electron transport chain and of ATP synthase remain intact. Do you expect ATP synthesis to continue in the presence of low concentrations of detergent?

No, because with a leaky membrane, the proton gradient cannot be maintained.

Considering the amino acids that are found in various domains of transmembrane proteins, which statement would be true?

Nonpolar amino acids would be prevalent in the transmembrane domain, in contact with the environment of the inner membrane.

Which of the following statements is true regarding pyruvate oxidation?

Pyruvate oxidation forms the same number of NADH (per glucose molecule) as glycolysis.

Brown fat is a specialized tissue found especially in infants and hibernating mammals. Brown fat mitochondria have proton channels located in their inner membranes that allow protons to flow from the intermembrane space into the mitochondrial matrix without passing through ATP synthase. What does the flow of protons through these channels mean for the organism?

Rather than producing ATP, much more of the energy of metabolism would be lost as heat. Recall that channels allow flow of substances through membranes down their concentration gradients. The proton channels of brown fat mitochondria would dissipate the proton gradient formed by the electron transport chain and reduce the production of ATP. Cells of the brown fat type consume fuel molecules like glucose or fats but produce much less ATP, and much of the energy from the fuel molecules ends up being released as heat, often as a thermoregulatory response.

Which of the factors accounts for the higher potential energy of C-C and C-H bonds compared to C-O and H-O bonds?

The C-C and C-H bonds are weak, thus requiring a lot of energy to hold together.

In a FRAP experiment, after bleaching, cells were moved from the warm incubator to the refrigerator. How would this affect the fluorescence recovery time (compared to cells that remain in the incubator) and why?

The bleached spot will recover fluorescence more slowly, because the decrease in temperature decreases the fluidity of the membrane and therefore decreases protein movement.

Which statement best summarizes cellular respiration?

The chemical potential energy stored in organic molecules is converted to chemical energy that can be used to do the work of the cell.

Paramecium is a unicellular organism that lives in fresh water. Suppose you are studying two populations of this organism. One population lives in a pond in a cold environment, and the other lives in a pond in a warm environment. If you examined the fatty acids in plasma membranes of both of these populations, what difference would you expect to find?

The fatty acid tails from the cold environment would generally be shorter and less saturated compared to fatty acids from the warm environment.

In active mitochondria, what is the free energy change when protons move from the inner mitochondrial space to the matrix?

The free energy change is negative meaning movement of protons in this direction is favorable

Refer to Animation: Fluid Mosaic Model. Although the phospholipid molecules can be in constant lateral movement, they very rarely flip from one side of the bilayer to the other. Which of the answer choices could explain this?

The head groups are repelled by the hydrophobic membrane interior.

A proton pump is needed in the lysosomal membrane because:

The lysosomal proton pumps move protons into the interior of the lysosome to lower the pH.protons are being moved from low to high concentration.protons cannot move across a membrane on their own.the interior of the lysosome needs to be acidic.

Scientists often try to answer the same question using different techniques to gain confidence in their interpretations and conclusions. In a related experiment, a mouse cell and human cell were fused to create a single hybrid cell. The mouse and human cells were labeled with different antibodies (proteins) that bind to membrane proteins. Based on the conclusion of the FRAP experiment, what would you expect to see in this experiment?

The mouse and human proteins would slowly mix over time in the hybrid cell.

Predict how phospholipids would arrange if they were placed in a nonpolar solution rather than a polar solution like water.

The phospholipid tails would orient toward the solution, and the heads would cluster away from the solution. Remember that nonpolar chemical groups interact with each other and avoid polar groups.

Which of the statements about the formation of a peptide bond are true? Select all that apply.

The reaction has a positive ΔG. The reaction is endergonic. The reaction is spontaneous.

A container is divided into two compartments by a membrane that is fully permeable to water but not to larger molecules. Water is added to one side of the membrane (side A), and an equal volume of a 5% solution of glucose is added to the other (side B). What would you predict will happen?

The water level on side B will increase and on side A will decrease.

A beaker is divided by a membrane that is permeable to water and glucose, but not to sucrose. Equal volumes of solutions are added to side A and B with the initial concentrations as shown below. Initially, the liquid levels on both sides are the same. After the system described above reaches equilibrium, what can you predict about the water levels?

The water will be higher on side A than on side B.

Which of the answer choices correctly describes the movement of water across a selectively permeable membrane during osmosis?

The water will move from low solute concentration to high solute concentration. The water will move from high water concentration to low water concentration.

The defining characteristics of active transport are that this category of transport moves substances _________ their concentration gradient and requires _____

against; energy

A beaker contains two solutions of salt dissolved in water. The two solutions have different concentrations of salt (measured by molarity, M) and are separated by a membrane that is permeable to water but not salt. Which statement is true about the movement of these molecules?

There will be a net movement of water from side A to side B and no movement of salt.

Which of the statements describes catabolic reactions?

They are exergonic and have a negative change in free energy.

When the mitochondrial uncoupling protein (UCP1) is added to active mitochondria, protons move from the inner membrane space to the matrix. Which statement best describes the structure and function of UCP1?

UCP1 is an integral membrane protein that allows protons to move across the membrane from the intermembrane space to the matrix by facilitated diffusion.

Which choice is considered an integral membrane protein?

a protein with its amino-terminus in the cytoplasm and its carboxy-terminus in the extracellular space Integral membrane proteins are irreversibly embedded in the membrane. Some span the membrane with a hydrophobic bridge that connects the domains on either side of the membrane.

Energy released by transferring electrons along the electron transport chain is stored as potential energy in the form of:

a proton gradient.

A transmembrane protein is a protein that spans the entire lipid bilayer. Which of the following amino acids would likely be found the hydrophobic region that is embedded in the membrane?

alanine

Beta-oxidation does not produce any ATP directly, but it does produce

acetyl-CoA, NADH, and FADH2.

Fatty acid oxidation (also called beta-oxidation) does not produce any ATP directly, but it does produce:

acetyl-CoA, NADH, and FADH2.

In the example illustrated here, the molecule indicated by the diamond shapes is moved _______ its concentration gradient using the energy of _____

against; an electrochemical gradient

The breakdown of fatty acids takes place by a process called:

beta-oxidation.

What happened to individual in Masayuki Saito's study when brown fat was activated by cold temperature?

body mass fat decreased

The transition state is that portion of the progress of a chemical reaction with a large amount of energy found in _______ reactions

both endergonic and exergonic

Some diseases result from defective transport across the membrane. For example, cystic fibrosis results when a chloride ion transporter does not function. What is affected when this transporter does not function?

both the chloride concentration gradient and the electrical gradient of the cell If chloride ions cannot move across the membrane, they cannot form a gradient, and because they are negatively charged, that would alter the electric gradient as well.

When NADH accumulates in the cell, how and why does this impact cellular respiration?

cellular respiration slows because high levels of NADH inhibit pyruvate oxidation

Organisms that derive both their energy and carbon from organic compounds are:

chemoheterotrophs

The plasma membrane is composed of a phospholipid bilayer and associated proteins. What else is commonly found in the plasma membranes of animal cells?

cholesterol

An amphipathic molecule is one that

contains both polar and nonpolar regions.

In eukaryotes, fermentation takes place:

cytoplasm

In eukaryotic cells, glycolysis occurs in:

cytoplasm

Which sequence accurately describes the path traveled by a new protein from when it first starts to be translated to its release from the cell?

cytosol → ER → Golgi → vesicle → plasma membrane → external environment

DNP (2,4-dinitrophenol) is an effective weight loss agent that was used in diet pills in the 1930s. It has since been removed from the market because of serious side effects such as fever, cataracts, rashes, and sometimes death. DNP inserts into the inner mitochondrial membrane and allows the flow of protons from the intermembrane space to the matrix. Based on this information, what effects might you observe? Select all that apply.

decreased difference in pH between the matrix and intermembrane space reduced ATP production dissipation of the proton gradient

Sodium ions move randomly around a solution of sodium chloride in water, frequently colliding with other sodium ions and chloride ions. This is an example of

diffusion

Many cellular processes represent work that requires the expenditure of energy. Which of the actions is not a cellular process that requires the cell to expend energy?

diffusion of water into cells

A cellular reaction with a ΔG of 8.5 kcal/mol could be effectively coupled to the hydrolysis of a single molecule of ATP.

false

Fermentation produces nearly twice as much ATP as aerobic respiration, which explains why it is a preferred pathway for bacteria

false

If a molecule can freely cross the membrane, then at equilibrium there will be no further movement of molecules across the membrane

false

Oxidation is the gain of electrons

false

Simple diffusion of a molecule down its concentration gradient requires an input of energy to the system

false

Which molecule has the greatest chemical potential energy?

fructose 1,6 bisphosphate Fructose 1,6 bisphosphate has more energy because it is derived from glucose by reactions that transfer energy from two ATP molecules by phosphorylation. All of the other molecules are derived from energy releasing oxidation events from fructose 1,6 bisphosphate.

Proteins can be broken down to extract energy. They are typically broken down into amino acids, which then enter cellular respiration via:

glycolysis or the citric acid cycle.

The summary equation for cellular respiration is: glucose + oxygen --> carbon dioxide + water. During which stages of cellular respiration is oxygen directly required? Select all that apply.

glycolysis; the Krebs cycle; and electron transport phosphorylation.

To which of the substances is ATP most closely chemically related?

guanine

Entropy is often increased by:

heat

Suppose that three critical amino acids in the active site of a specific enzyme are arginine, lysine, and histidine. Which of the characteristics would you predict the substrate to possess, in order to bind the active site of this enzyme?

hydrophilic w a negative charge

In water, phospholipids can spontaneously form lipid bilayer structures. What bonds/forces/interactions are most influential in formation of the lipid bilayer?

hydrophobic exclusion of nonpolar fatty acid tailshydrogen bond interactions among water molecules and polar phospholipid heads

The interior region of a phospholipid bilayer is characterized as

hydrophobic.

Molecules that are _____________ and _____________ are able to move across the cell membrane via simple diffusion.

hydrophobic; small

Consider a protein that is targeted to be released from the cell (secreted). Where would this protein be located in the endoplasmic reticulum?

in the lumen (inside) of the E.R.

Consider a protein that is targeted to be released from the cell (secreted). Where would this protein be located in the Golgi?

in the lumen (inside) of the Golgi

which of the following would increase PFK-1 activity?

increased concentration of AMP Notice how the allosteric regulation works. An increase in enzyme activity could result from either increasing the activators or decreasing the inhibitors. From the choices here only increased AMP achieves the requirement.

Certain complexes of the mitochondrial electron transport chain pump protons. Protons are pumped across the _____ mitochondrial membrane, from the _____ to the _____.

inner; matrix; intermembrane space

Due to the pumping action of the electron transport chain, protons have a high concentration in the _____ and a low concentration in the _____.

intermembrane space; mitochondrial matrix

According to the article, what does mitochondrial uncoupling protein 1 do?

it causes mitochondria to produce heat instead of ATP

Pyruvate oxidation is an important stage in cellular respiration because:

it links glycolysis with the citric acid cycle.

In human cells, such as those in muscle tissue, the product of fermentation is:

lactic acid.

Oligomycin is an antibiotic that binds ATP synthase, blocking the flow of protons through the enzyme's proton channel. In addition to preventing synthesis of ATP, what additional effect might you expect in response to the presence of oligomycin?

lower pH in the intermembrane space If protons are blocked from flowing back through the ATP synthase, there would be an accumulation of protons in the intermembrane space, and higher proton concentration equals lower pH.

In eukaryotic cells, the oxidation of pyruvate occurs in:

matrix of the mitochondria

Individuals with a condition known as exercise intolerance lack sufficient ATP and suffer extreme fatigue from minimal exertion. Defects in which structures are most likely responsible for this condition?

mitochondria

Which of the answer choices is NOT considered to be a part of the endomembrane system?

mitochondria

Which statements are true regarding redox reactions? Select all that apply.

molecule that has gained H atoms is said to be reduced.b. If a molecule accepts electrons, it has been reduced.e. Oxidizing agents accept electrons.

Translation of a protein destined to function in the nucleus occurs:

on free ribosomes in the cytosol.

Water molecules move into the cytosol of a cell placed in a hypotonic solution using

osmosis

Most of the ATP produced during cellular respiration is generated through:

oxidative phosphorylation.

During the metabolism of glucose (the cellular fuel molecule) by the process of aerobic cellular respiration, glucose is _____ to CO2 via _____ reactions.

oxidized; redox

When an electron is transferred from NADH to CoQ of the electron transport chain, NADH is _____ and CoQ is _____.

oxidized; reduced

Which substance could most easily cross a synthetic membrane composed of phospholipids but not proteins?

oxygen (O2)

The final (terminal) electron acceptor of the electron transport chain is:

oxygen.

Which lipid composition option has the least membrane fluidity?

phospholipids with long-chain, saturated fatty acids Remember that saturated fatty acid chains are straight and pack together well with robust van der Waals interactions, whereas unsaturated fatty acids have bends or kinks that prevent tight stacking.

What type of molecule is sometimes found spanning a cell's plasma membrane with part of the molecule on one side of the membrane, part embedded in the membrane, and part on the other side?

protein Membranes have a polar environment, hydrophilic on both sides, separated by a nonpolar, hydrophobic inner environment. Among the 20 different amino acids, some are polar and could interact with charges in a polar environment, whereas others are nonpolar and can interact with nonpolar environments.

Redox reactions are always paired. Therefore, when one molecule is oxidized, another molecule is __________

reduced

The _____ forms of the electron carriers NAD+/NADH and FAD/FADH2 have high potential energy.

reduced

In the absence of oxygen, fermentation:

regenerates NAD+ from the reduction of pyruvate.

To move a specific molecule across a membrane, carrier proteins

require that the molecule specific to the carrier bind and cause a change in conformation.

All of the following are synthesized at the endoplasmic reticulum EXCEPT:

ribosomal proteins

Glucose molecules move into cells lining the intestine by moving up/against their concentration gradient. This movement of glucose is driven by the movement of sodium ions (Na+) into the cells down/with their concentration gradient. The above describes an example of:

secondary active transport

Which substance could LEAST easily cross a synthetic membrane composed of phospholipids but not proteins?

sodium ions (Na+)

Reactions in which there is a negative change in free energy (-ΔG) are:

spontaneous and exergonic

Glucose is stored in plants as _____ and in animals as _____.

starch; glycogen

Which eukaryotic cell structure plays a role in protein trafficking and sorting?

the gogli apparatus

Which choice describes the hydrophilic component of cholesterol?

the hydroxyl head group

We can tell from their structure that fatty acids are a good source of energy because of:

the large number of carbon-carbon and carbon-hydrogen bonds they contain.

Most proteins containing a signal sequence that binds signal recognition particle at their amino-terminal ends are sorted to:

the rough endoplasmic reticulum. The signal recognition particle (SRP) binds to the SRP receptor and allows translation of the protein through a membrane.

Diffusion is best described as the random movement of molecules influenced by:

the thermal energy of the environment and energy transferred from molecular collisions in the cell.

At equilibrium, there will be no net movement of molecules across the cell membrane

true

At the end of glycolysis, the carbon originally found in the starting glucose molecule is now present in

two pyruvate molecules. By the time pyruvate is formed, most of the energy contained in glucose has been released.

Most elements of the endomembrane system are connected by:

vesicular trafficking.

In the absence of carbohydrates, what can maintain production of NADH and FADH2 by the citric acid cycle?

β-oxidation of fatty acids The breakdown of fatty acids by β-oxidation results in acetyl-CoA, which enters the citric acid cycle, where NADH and FADH2 are produced.