Biology Final Practice MC

The advantage of light microscopy over electron microscopy is that

C) light microscopy allows one to view dynamic processes in living cells.

If a modern electron microscope (TEM) can resolve biological images to the nanometer level, as opposed to the best light microscope, this is due to which of the following?

C) Electron beams have much shorter wavelengths than visible light.

Large numbers of ribosomes are present in cells that specialize in producing which of the following molecules?

proteins

Which structure is the site of the synthesis of proteins that may be exported from the cell?

Rough ER

The Golgi apparatus has a polarity or sidedness to its structure and function. Which of the following statements correctly describes this polarity?

All of the above correctly describe polar characteristics of the Golgi function.

The difference in lipid and protein composition between the membranes of the endomembrane system is largely determined by

function of the Golgi apparatus in sorting and directing membrane components

In animal cells, hydrolytic enzymes are packaged to prevent general destruction of cellular components. Which of the following organelles functions in this compartmentalization?

lysosomes

Which of the following statements correctly describes some aspect of protein disposal from prokaryotic cells?

Proteins that are excreted by prokaryotes are synthesized on ribosomes that are bound to the cytoplasmic surface of the plasma membrane.

Tay-Sachs disease is a human genetic abnormality that results in cells accumulating and becoming clogged with very large and complex lipids. Which cellular organelle must be involved in this condition?

lysosome

The liver is involved in detoxification of many poisons and drugs. Which of the following structures is primarily involved in this process and therefore abundant in liver cells?

Smooth ER

Which of the following produces and modifies polysaccharides that will be secreted?

Golgi apparatus

Which of the following contains enzymes that transfer hydrogen from various substrates to oxygen?

peroxisome

Motor proteins provide for molecular motion in cells by interacting with what types of cellular structures?

cytoskeletons

Of the following, which cell structure would most likely be visible with a light microscope that has been manufactured to the maximum resolving power possible?

mitochondrion

The differences among the three categories of cytoskeletal elements would suggest that each of the following has specialized roles. Which of the following is a correct match?

microtubules and chromosome movement

If an individual has abnormal microtubules, due to a hereditary condition, in which organs or tissues would you expect dysfunction?

sperm, larynx, and trachea: cells and tissues that contain flagella or cilia

Microfilaments are well known for their role in which of the following?

A, B, and C (ameboid movement, formation of cleavage furrows, and contracting of muscle cells)

Which structure is not part of the endomembrane system?

Chloroplast

The extracellular matrix is thought to participate in the regulation of animal cell behavior by communicating information from the outside to the inside of the cell via which of the following?

integrins

Cells of the pancreas will incorporate radioactively labeled amino acids into proteins. This "tagging" of newly synthesized proteins enables a researcher to track their location. In this case, we are tracking an enzyme secreted by pancreatic cells. What is its most likely pathway?

ER → Golgi → vesicles that fuse with plasma membrane

Which of the following is present in a prokaryotic cell?

ribosome

Which structure-function pair is mismatched?

microtubule; muscle contraction

Cyanide binds with at least one molecule involved in producing ATP. If a cell is exposed to cyanide, most of the cyanide would be found within the

mitochondria

Which of the following statements is a logical consequence of the second law of thermodynamics?

Every chemical reaction must increase the total entropy of the universe.

The mathematical expression for the change in free energy of a system is ΔG =ΔH - TΔS. Which of the following is (are) correct?

Δ is the change in free energy

Which of the following is true for all exergonic reactions?

The reaction proceeds with a net release of free energy.

Chemical equilibrium is relatively rare in living cells. Which of the following could be an example of a reaction at chemical equilibrium in a cell?

a chemical reaction in which both the reactants and products are not being produced or used in any active metabolic pathway

Which of the following best describes enthalpy?

the heat content of a chemical system

Sucrose is a disaccharide, composed of the monosaccharides glucose and fructose. The hydrolysis of sucrose by the enzyme sucrase results in

breaking the bond between glucose and fructose and forming new bonds from the atoms of water.

Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reaction's

activation energy

Which of the following statements regarding enzymes is true?

Enzymes increase the rate of a reaction.

Which curve represents the behavior of an enzyme taken from a bacterium that lives in hot springs at temperatures of 70°C or higher?

curve 3

Which curve was most likely generated from analysis of an enzyme from a human stomach where conditions are strongly acid?

curve 4

Increasing the substrate concentration in an enzymatic reaction could overcome which of the following?

competitive inhibition

invasive species

species that enter new ecosystems and multiply, harming native species and their habitats

Which of the following terms best describes the reaction?

exergonic

Which of the following represents the Δ of the reaction?

D

Which of the following is likely to lead to an increase in the concentration of ATP in a cell?

an increase in a cell's catabolic activity

Among enzymes, kinases catalyze phosphorylation, while phosphatases catalyze removal of phosphate(s). A cell's use of these enzymes can therefore function as an on-off switch for various processes. Which of the following is probably involved?

the change in a protein's charge leading to a conformational change.

Besides turning enzymes on or off, what other means does a cell use to control enzymatic activity?

compartmentalization of enzymes into defined organelles

Choose the pair of terms that correctly completes this sentence: Catabolism is to anabolism as \____

is to \____.

exergonic; endergonic

Which of the following metabolic processes can occur without a net influx of energy from some other process?

C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O

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

Nothing; the reaction would stay at equilibrium

Some bacteria are metabolically active in hot springs because

their enzymes have high optimal temperatures

Which of the following types of molecules are the major structural components of the cell

membrane?

phospholipids and proteins

The presence of cholesterol in the plasma membranes of some animals

enables the membrane to stay fluid more easily when cell temperature drops.

Which of the following is one of the ways that the membranes of winter wheat are able to remain

fluid when it is extremely cold?

by increasing the percentage of unsaturated phospholipids in the membrane

Which of these are attached to the extracellular matrix?

integrins

Which of these often serve as receptors or cell recognition molecules on cell surfaces?

glycoproteins

The formulation of a model for a structure or for a process serves which of the following purposes?

It functions as a testable hypothesis.

Which of the following is true of the evolution of cell membranes?

All components of membranes evolve in response to natural selection.

Which of the following is a characteristic feature of a carrier protein in a plasma membrane?

It exhibits a specificity for a particular type of molecule.

After a membrane freezes and then thaws, it often becomes leaky to solutes. The most reasonable explanation

for this is that

the integrity of the lipid bilayer is broken when the membrane freezes.

Initially, in terms of tonicity, the solution in side A with respect to that in side B is

isotonic

After the system reaches equilibrium, what changes are observed?

The water level is higher in side A than in side B.

Celery stalks that are immersed in fresh water for several hours become stiff and hard. Similar stalks left in a salt solution become limp and soft. From this we can deduce that the cells of the celery stalks are

hypertonic to fresh water but hypotonic to the salt solution

If you examine side A after 3 days, you should find

a decrease in the concentration of NaCl and a decrease in the water level

You are working on a team that is designing a new drug. In order 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 enters the cell?

similarity of the drug molecule to other molecules transported by the target cells

When a plant cell, such as one from a peony stem, is submerged in a very hypotonic solution, what is likely to occur?

the cell will become turgid

Which of the following membrane activities require energy from ATP hydrolysis?

Na+ ions moving out of the cell

What is the voltage across a membrane called?

membrane potential

What mechanisms do plants use to load sucrose produced by photosynthesis into specialized cells in

the veins of leaves?

A, B, and C: an electrogenic pump, a proton pump, a contransport protein

The sodium-potassium pump in animal cells requires cytoplasmic ATP to pump ions across the

plasma membrane. When the proteins of the pump are first synthesized in the rough ER, what side of the ER membrane will the ATP binding site be on?

It will be on the cytoplasmic side of the ER.

Proton pumps are used in various ways by members of every kingdom of organisms. What does this

most probably mean?

Cells with proton pumps were maintained in each Kingdom by natural selection

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

embedded in a lipid bilayer

Why does the oxidation of organic compounds by molecular oxygen to produce CO2 and water release free energy?

Electrons are being moved from atoms that have a lower affinity for electrons (such as C) to atoms with a higher affinity for electrons (such as O).

The ATP made during glycolysis is generated by

substrate-level phosphorylation

A molecule that is phosphorylated

has an increased chemical potential energy; it is primed to do cellular work.

Which kind of metabolic poison would most directly interfere with glycolysis?

an agent that closely mimics the structure of glucose but is not metabolized

Why is glycolysis described as having an investment phase and a payoff phase?

It uses stored ATP and then forms a net increase in ATP.

During cellular respiration, acetyl CoA accumulates in which location?

mitochondrial matrix

How many molecules of carbon dioxide would be produced by five turns of the citric acid cycle?

10

Which of the following describes the sequence of electron carriers in the electron transport chain, starting with the least electronegative?

FMN, Fe•S, ubiquinone, cytochromes (Cyt)

During aerobic respiration, which of the following directly donates electrons to the electron transport chain at the lowest energy level?

FADH2

The primary role of oxygen in cellular respiration is to

act as an acceptor for electrons and hydrogen, forming water

When hydrogen ions are pumped from the mitochondrial matrix across the inner membrane and into the intermembrane space, the result is the

creation of a proton gradient

Where is ATP synthase located in the mitochondrion?

inner mitochondrial membrane

Recall that the complete oxidation of a mole of glucose releases 686 kcal of energy (ΔG = -686 kcal/mol). The phosphorylation of ADP to form ATP stores approximately 7.3 kcal per mole of ATP. What is the approximate efficiency of cellular respiration for a "mutant" organism that produces only 29 moles of ATP for every mole of glucose oxidized, rather than the usual 36-38 moles of ATP?

30%

After the first disruption, when electron transfer and ATP synthesize still occur, what must be

present?

all of the electron transport proteins as well as ATP synthase

The accompanying figure shows the electron transport chain. Which of the following is the combination of substances that is initially added to the chain?

NADH, FADH2, and electrons

The parts of the figure labeled with Roman numerals symbolize what concept?

multimeric groups of proteins in 4 complexes

Which metabolic pathway is common to both cellular respiration and fermentation?

glycolysis

Why is glycolysis considered to be one of the first metabolic pathways to have evolved?

It is found in the cytosol, does not involve oxygen, and is present in most organisms.

Muscle cells, when an individual is exercising heavily and when the muscle becomes oxygen deprived, convert pyruvate to lactate. What happens to the lactate in skeletal muscle cells?

It is taken to the liver and converted back to pyruvate.

In mitochondria, exergonic redox reactions

provide the energy that establishes the proton gradient.

When electrons flow along the electron transport chains of mitochondria, which of the following changes occurs?

The pH of the matrix increases.

Which of the following are products of the light reactions of photosynthesis that are utilized in the

Calvin cycle?

ATP and NADPH

What are the products of the light reactions that are subsequently used by the Calvin cycle?

ATP and NADPH

When oxygen is released as a result of photosynthesis, it is a byproduct of which of the following?

splitting water molecules

What wavelength of light in the figure is most effective in driving photosynthesis?

420 mm

In the thylakoid membranes, what is the main role of the pigment molecules?

harvest photons and transfer light energy to the reaction-center chlorophyll