BIO181 Exam 2 - Chapters 5-9

Critical thinking & Review Questions

Which plasma membrane component can be either found on its surface or embedded in the membrane structure?

1. protein

2. cholesterol

3. carbohydrate

4. phospholipid

1. protein

Which characteristic of a phospholipid contributes to the fluidity of the membrane?

1. its head

2. cholesterol

3. a saturated fatty acid tail

4. double bonds in the fatty acid tail

4. double bonds in the fatty acid tail

What is the primary function of carbohydrates attached to the exterior of cell membranes?

1. identification of the cell

2. flexibility of the membrane

3. strengthening the membrane

4. channels through membrane

1. identification of the cell

A scientist compares the plasma membrane composition of an animal from the Mediterranean coast with one from the Mojave Desert. Which hypothesis is most likely to be correct?

1. The cells from the Mediterranean coast animal will have more fluid plasma membranes.

2. The cells from the Mojave Desert animal will have a higher cholesterol concentration in the plasma membranes.

3. The cells’ plasma membranes will be indistinguishable.

4. The cells from the Mediterranean coast animal will have a higher glycoprotein content, while the cells from the Mojave Desert animal will have a higher lipoprotein content.

1. The cells from the Mojave Desert animal will have a higher cholesterol concentration in the plasma membranes.

Water moves via osmosis _________.

1. throughout the cytoplasm

2. from an area with a high concentration of other solutes to a lower one

3. from an area with a high concentration of water to one of lower concentration

4. from an area with a low concentration of water to higher concentration

3. from an area with a high concentration of water to one of lower concentration

The principal force driving movement in diffusion is the __________.

1. temperature

2. particle size

3. concentration gradient

4. membrane surface area

3. concentration gradient

What problem is faced by organisms that live in fresh water?

1. Their bodies tend to take in too much water.

2. They have no way of controlling their tonicity.

3. Only salt water poses problems for animals that live in it.

4. Their bodies tend to lose too much water to their environment.

1. Their bodies tend to take in too much water.

In which situation would passive transport not use a transport protein for entry into a cell?

1. water flowing into a hypertonic environment

2. glucose being absorbed from the blood

3. an ion flowing into a nerve cell to create an electrical potential

4. oxygen moving into a cell after oxygen deprivation

4. oxygen moving into a cell after oxygen deprivation

Active transport must function continuously because __________.

1. plasma membranes wear out

2. not all membranes are amphiphilic

3. facilitated transport opposes active transport

4. diffusion is constantly moving solutes in opposite directions

4. diffusion is constantly moving solutes in opposite directions

How does the sodium-potassium pump make the interior of the cell negatively charged?

1. by expelling anions

2. by pulling in anions

3. by expelling more cations than are taken in

4. by taking in and expelling an equal number of cations

3. by expelling more cations than are taken in

What is the combination of an electrical gradient and a concentration gradient called?

1. potential gradient

2. electrical potential

3. concentration potential

4. electrochemical gradient

4. electrochemical gradient

What happens to the membrane of a vesicle after exocytosis?

1. It leaves the cell.

2. It is disassembled by the cell.

3. It fuses with and becomes part of the plasma membrane.

4. It is used again in another exocytosis event.

3. It fuses with and becomes part of the plasma membrane.

Which transport mechanism can bring whole cells into a cell?

1. pinocytosis

2. phagocytosis

3. facilitated transport

4. primary active transport

2. phagocytosis

In what important way does receptor-mediated endocytosis differ from phagocytosis?

1. It transports only small amounts of fluid.

2. It does not involve the pinching off of membrane.

3. It brings in only a specifically targeted substance.

4. It brings substances into the cell, while phagocytosis removes substances.

3. It brings in only a specifically targeted substance.

Many viruses enter host cells through receptor-mediated endocytosis. What is an advantage of this entry strategy?

1. The virus directly enters the cytoplasm of the cell.

2. The virus is protected from recognition by white blood cells.

3. The virus only enters its target host cell type.

4. The virus can directly inject its genome into the cell’s nucleus.

3. The virus only enters its target host cell type.

Which of the following organelles relies on exocytosis to complete its function?

1. Golgi apparatus

2. vacuole

3. mitochondria

4. endoplasmic reticulum

1. Golgi apparatus

Imagine a cell can perform exocytosis, but only minimal endocytosis. What would happen to the cell?

1. The cell would secrete all its intracellular proteins.

2. The plasma membrane would increase in size over time.

3. The cell would stop expressing integral receptor proteins in its plasma membrane.

4. The cell would lyse.

2. The plasma membrane would increase in size over time.

Energy is stored long-term in the bonds of _____ and used short-term to perform work from a(n) _____ molecule.

1. ATP : glucose

2. an anabolic molecule : catabolic molecule

3. glucose : ATP

4. a catabolic molecule : anabolic molecule

3. glucose : ATP

DNA replication involves unwinding two strands of parent DNA, copying each strand to synthesize complementary strands, and releasing the parent and daughter DNA. Which of the following accurately describes this process?

1. This is an anabolic process.

2. This is a catabolic process.

3. This is both anabolic and catabolic.

4. This is a metabolic process but is neither anabolic nor catabolic.

1. This is an anabolic process.

Consider a pendulum swinging. Which type(s) of energy is/are associated with the pendulum in the following instances: i. the moment at which it completes one cycle, just before it begins to fall back towards the other end, ii. the moment that it is in the middle between the two ends, and iii. just before it reaches the end of one cycle (just before instant i.).

1. i. potential and kinetic, ii. potential and kinetic, iii. kinetic

2. i. potential, ii. potential and kinetic, iii. potential and kinetic

3. i. potential, ii. kinetic, iii. potential and kinetic

4. i. potential and kinetic, ii. kinetic iii. kinetic

3. i. potential, ii. kinetic, iii. potential and kinetic

Which of the following comparisons or contrasts between endergonic and exergonic reactions is false?

1. Endergonic reactions have a positive ∆G and exergonic reactions have a negative ∆G.

2. Endergonic reactions consume energy and exergonic reactions release energy.

3. Both endergonic and exergonic reactions require a small amount of energy to overcome an activation barrier.

4. Endergonic reactions take place slowly and exergonic reactions take place quickly.

4. Endergonic reactions take place slowly and exergonic reactions take place quickly.

Which of the following is the best way to judge the relative activation energies between two given chemical reactions?

1. Compare the ∆G values between the two reactions.

2. Compare their reaction rates.

3. Compare their ideal environmental conditions.

4. Compare the spontaneity between the two reactions.

2. Compare their reaction rates.

Which of the following is not an example of an energy transformation?

1. turning on a light switch

2. solar panels at work

3. formation of static electricity

4. none of the above

1. turning on a light switch

In each of the three systems, determine the state of entropy (low or high) when comparing the first and second: i. the instant that a perfume bottle is sprayed compared with 30 seconds later, ii. an old 1950s car compared with a brand new car, and iii. a living cell compared with a dead cell.

1. i. low, ii. high, iii. low

2. i. low, ii. high, iii. high

3. i. high, ii. low, iii. high

4. i. high, ii. low, iii. low

1. i. low, ii. high, iii. low

The energy released by the hydrolysis of ATP is____

1. primarily stored between the alpha and beta phosphates

2. equal to −57 kcal/mol

3. harnessed as heat energy by the cell to perform work

4. providing energy to coupled reactions

4. providing energy to coupled reactions

Which of the following molecules is likely to have the most potential energy?

1. sucrose

2. ATP

3. glucose

4. ADP

1. sucrose

Which of the following is not true about enzymes:

1. They increase ∆G of reactions.

2. They are usually made of amino acids.

3. They lower the activation energy of chemical reactions.

4. Each one is specific to the particular substrate(s) to which it binds.

1. They increase ∆G of reactions.

An allosteric inhibitor does which of the following?

1. Binds to an enzyme away from the active site and changes the conformation of the active site, increasing its affinity for substrate binding.

2. Binds to the active site and blocks it from binding substrate.

3. Binds to an enzyme away from the active site and changes the conformation of the active site, decreasing its affinity for the substrate.

4. Binds directly to the active site and mimics the substrate.

3. Binds to an enzyme away from the active site and changes the conformation of the active site, decreasing its affinity for the substrate.

Which of the following analogies best describes the induced-fit model of enzyme-substrate binding?

1. a hug between two people

2. a key fitting into a lock

3. a square peg fitting through the square hole and a round peg fitting through the round hole of a children’s toy

4. the fitting together of two jigsaw puzzle pieces

1. a hug between two people

The energy currency used by cells is ________.

1. ATP

2. ADP

3. AMP

4. adenosine

1. ATP

A reducing chemical reaction ________.

1. reduces the compound to a simpler form

2. adds an electron to the substrate

3. removes a hydrogen atom from the substrate

4. is a catabolic reaction

2. adds an electron to the substrate

During the second half of glycolysis, what occurs?

1. ATP is used up.

2. Fructose is split in two.

3. ATP is made.

4. Glucose becomes fructose.

3. ATP is made.

What is removed from pyruvate during its conversion into an acetyl group?

1. oxygen

2. ATP

3. B vitamin

4. carbon dioxide

4. carbon dioxide

What do the electrons added to NAD⁺ do?

1. They become part of a fermentation pathway.

2. They go to another pathway for ATP production.

3. They energize the entry of the acetyl group into the citric acid cycle.

4. They are converted to NADP.

2. They go to another pathway for ATP production.

GTP or ATP is produced during the conversion of ________.

1. isocitrate into α-ketoglutarate

2. succinyl-CoA into succinate

3. fumarate into malate

4. malate into oxaloacetate

2. succinyl-CoA into succinate

How many NADH molecules are produced on each turn of the citric acid cycle?

1. one

2. two

3. three

4. four

3. three

What compound receives electrons from NADH?

1. FMN

2. ubiquinone

3. cytochrome c₁

4. oxygen

1. FMN

Chemiosmosis involves ________.

1. the movement of electrons across the cell membrane

2. the movement of hydrogen atoms across a mitochondrial membrane

3. the movement of hydrogen ions across a mitochondrial membrane

4. the movement of glucose through the cell membrane

3. the movement of hydrogen ions across a mitochondrial membrane

Which of the following fermentation methods can occur in animal skeletal muscles?

1. lactic acid fermentation

2. alcohol fermentation

3. mixed acid fermentation

4. propionic fermentation

1. lactic acid fermentation

A major connection for sugars in glycolysis is ________.

1. glucose-6-phosphate

2. fructose-1,6-bisphosphate

3. dihydroxyacetone phosphate

4. phosphoenolpyruvate

1. glucose-6-phosphate

Beta-oxidation is ________.

1. the breakdown of sugars

2. the assembly of sugars

3. the breakdown of fatty acids

4. the removal of amino groups from amino acids

3. the breakdown of fatty acids

The effect of high levels of ADP is to ________ in cellular respiration.

1. increase the activity of specific enzymes

2. decrease the activity of specific enzymes

3. have no effect on the activity of specific enzymes

4. slow down the pathway

1. increase the activity of specific enzymes

The control of which enzyme exerts the most control on glycolysis?

1. hexokinase

2. phosphofructokinase

3. glucose-6-phosphatase

4. aldolase

1. phosphofructokinase

Which of the following components is not used by both plants and cyanobacteria to carry out photosynthesis?

1. chloroplasts

2. chlorophyll

3. carbon dioxide

4. water

1. chloroplasts

What two main products result from photosynthesis?

1. oxygen and carbon dioxide

2. chlorophyll and oxygen

3. sugars/carbohydrates and oxygen

4. sugars/carbohydrates and carbon dioxide

3. sugars/carbohydrates and oxygen

In which compartment of the plant cell do the light-independent reactions of photosynthesis take place?

1. thylakoid

2. stroma

3. outer membrane

4. mesophyll

2. stroma

Which statement about thylakoids in eukaryotes is not correct?

1. Thylakoids are assembled into stacks.

2. Thylakoids exist as a maze of folded membranes.

3. The space surrounding thylakoids is called stroma.

4. Thylakoids contain chlorophyll.

2. Thylakoids exist as a maze of folded membranes.

Predict the end result if a chloroplast’s light-independent enzymes developed a mutation that prevented them from activating in response to light.

1. G3P accumulation

2. ATP and NADPH accumulation

3. Water accumulation

4. Carbon dioxide depletion

2. ATP and NADPH accumulation

How are the NADPH and G3P molecules made during photosynthesis similar?

1. They are both end products of photosynthesis.

2. They are both substrates for photosynthesis.

3. They are both produced from carbon dioxide.

4. They both store energy in chemical bonds.

4. They both store energy in chemical bonds.

Which of the following structures is not a component of a photosystem?

1. ATP synthase

2. antenna molecule

3. reaction center

4. primary electron acceptor

1. ATP synthase

How many photons does it take to fully reduce one molecule of NADP⁺ to NADPH?

1. 1

2. 2

3. 4

4. 8

2. 2

Which complex is not involved in the establishment of conditions for ATP synthesis?

1. photosystem I

2. ATP synthase

3. photosystem II

4. cytochrome complex

2. ATP synthase

From which component of the light-dependent reactions does NADPH form most directly?

1. photosystem II

2. photosystem I

3. cytochrome complex

4. ATP synthase

1. photosystem I

Three of the same species of plant are each grown under a different colored light for the same amount of time. Plant A is grown under blue light, Plant B is grown under green light, and Plant C is grown under orange light. Assuming the plants use only chlorophyll a and chlorophyll b for photosynthesis, what would be the predicted order of the plants from most growth to least growth?

1. A, C, B

2. A, B, C

3. C, A, B

4. B, A, C

1. A, C, B

Plants containing only chlorophyll b are exposed to radiation with the following wavelengths: 10nm (x-rays), 450nm (blue light), 670nm (red light), and 800nm (infrared light). Which plants harness the most energy for photosynthesis?

1. X-ray irradiated plants

2. Blue light irradiated plants

3. Red light irradiated plants

4. Infrared irradiated plants

2. Blue light irradiated plants

Which molecule must enter the Calvin cycle continually for the light-independent reactions to take place?

1. RuBisCO

2. RuBP

3. 3-PGA

4. CO₂

4. CO₂

Which order of molecular conversions is correct for the Calvin cycle?

1. RuBP + G3P → 3-PGA → sugar

2. RuBisCO → CO2⁢ → RuBP → G3P

3. RuBP + CO2⁢ → ⁢[RuBisCO]⁢ 3-PGA → G3P

4. CO2⁢ → 3-PGA → RuBP → G3P

3. RuBP + CO2⁢ → ⁢[RuBisCO]⁢ 3-PGA → G3P

Where in eukaryotic cells does the Calvin cycle take place?

1. thylakoid membrane

2. thylakoid lumen

3. chloroplast stroma

4. granum

3. chloroplast stroma

Which statement correctly describes carbon fixation?

1. the conversion of CO₂ into an organic compound

2. the use of RuBisCO to form 3-PGA

3. the production of carbohydrate molecules from G3P

4. the formation of RuBP from G3P molecules

5. the use of ATP and NADPH to reduce CO₂

1. the conversion of CO₂ into an organic compound

If four molecules of carbon dioxide enter the Calvin cycle (four “turns” of the cycle), how many G3P molecules are produced and how many are exported?

1. 4 G3P made, 1 G3P exported

2. 4 G3P made, 2 G3P exported

3. 8 G3P made, 1 G3P exported

4. 8 G3P made, 4 G3P exported

3. 8 G3P made, 1 G3P exported

What property prevents the ligands of cell-surface receptors from entering the cell?

1. The molecules bind to the extracellular domain.

2. The molecules are hydrophilic and cannot penetrate the hydrophobic interior of the plasma membrane.

3. The molecules are attached to transport proteins that deliver them through the bloodstream to target cells.

4. The ligands are able to penetrate the membrane and directly influence gene expression upon receptor binding.

2. The molecules are hydrophilic and cannot penetrate the hydrophobic interior of the plasma membrane.

The secretion of hormones by the pituitary gland is an example of _______________.

1. autocrine signaling

2. paracrine signaling

3. endocrine signaling

4. direct signaling across gap junctions

3. endocrine signaling

Why are ion channels necessary to transport ions into or out of a cell?

1. Ions are too large to diffuse through the membrane.

2. Ions are charged particles and cannot diffuse through the hydrophobic interior of the membrane.

3. Ions do not need ion channels to move through the membrane.

4. Ions bind to carrier proteins in the bloodstream, which must be removed before transport into the cell.

2. Ions are charged particles and cannot diffuse through the hydrophobic interior of the membrane.

Endocrine signals are transmitted more slowly than paracrine signals because ___________.

1. the ligands are transported through the bloodstream and travel greater distances

2. the target and signaling cells are close together

3. the ligands are degraded rapidly

4. the ligands don't bind to carrier proteins during transport

1. the ligands are transported through the bloodstream and travel greater distances

A scientist notices that when she adds a small, water-soluble molecule to a dish of cells, the cells turn off transcription of a gene. She hypothesizes that the ligand she added binds to a(n) ______ receptor.

1. Intracellular

2. Hormone

3. Enzyme-linked

4. Gated ion channel-linked

3. Enzyme-linked

Where do DAG and IP₃ originate?

1. They are formed by phosphorylation of cAMP.

2. They are ligands expressed by signaling cells.

3. They are hormones that diffuse through the plasma membrane to stimulate protein production.

4. They are the cleavage products of the inositol phospholipid, PIP₂.

4. They are the cleavage products of the inositol phospholipid, PIP₂.

What property enables the residues of the amino acids serine, threonine, and tyrosine to be phosphorylated?

1. They are polar.

2. They are non-polar.

3. They contain a hydroxyl group.

4. They occur more frequently in the amino acid sequence of signaling proteins.

3. They contain a hydroxyl group.

Histamine binds to the H1 G-protein-linked receptor to initiate the itchiness and airway constriction associated with an allergic response. If a mutation in the associated G-protein’s alpha subunit prevented the hydrolysis of GTP how would the allergic response change?

1. More severe allergic response compared to normal G-protein signaling.

2. Less severe allergic response compared to normal G-protein signaling.

3. No allergic response.

4. No change compared to normal G-protein signaling.

1. More severe allergic response compared to normal G-protein signaling.

A scientist observes a mutation in the transmembrane region of EGFR that eliminates its ability to be stabilized by binding interactions during dimerization after ligand binding. Which hypothesis regarding the effect of this mutation on EGF signaling is most likely to be correct?

1. EGF signaling cascades would be active for longer in the cell.

2. EGF signaling cascades would be active for a shorter period of time in the cell.

3. EGF signaling cascades would not occur.

4. EGF signaling would be unaffected.

3. EGF signaling cascades would not occur.

What is the function of a phosphatase?

1. A phosphatase removes phosphorylated amino acids from proteins.

2. A phosphatase removes the phosphate group from phosphorylated amino acid residues in a protein.

3. A phosphatase phosphorylates serine, threonine, and tyrosine residues.

4. A phosphatase degrades second messengers in the cell.

2. A phosphatase removes the phosphate group from phosphorylated amino acid residues in a protein.

How does NF-κB induce gene expression?

1. A small, hydrophobic ligand binds to NF-κB, activating it.

2. Phosphorylation of the inhibitor Iκ-B dissociates the complex between it and NF-κB, and allows NF-κB to enter the nucleus and stimulate transcription.

3. NF-κB is phosphorylated and is then free to enter the nucleus and bind DNA.

4. NF-κB is a kinase that phosphorylates a transcription factor that binds DNA and promotes protein production.

2. Phosphorylation of the inhibitor Iκ-B dissociates the complex between it and NF-κB, and allows NF-κB to enter the nucleus and stimulate transcription.

Apoptosis can occur in a cell when the cell is ________________.

1. damaged

2. no longer needed

3. infected by a virus

4. all of the above

4. all of the above

What is the effect of an inhibitor binding an enzyme?

1. The enzyme is degraded.

2. The enzyme is activated.

3. The enzyme is inactivated.

4. The complex is transported out of the cell.

3. The enzyme is inactivated.

How does PKC’s signaling role change in response to growth factor signaling versus an immune response?

1. PKC interacts directly with signaling molecules in both cascades, but only exhibits kinase activity during growth factor signaling.

2. PKC interacts directly with signaling molecules in growth factor cascades, but interacts with signaling inhibitors during immune signaling.

3. PKC amplifies growth factor cascades, but turns off immune cascades.

4. PKC is activated during growth factor cascades, but is inactivated during immune response cascades.

2. PKC interacts directly with signaling molecules in growth factor cascades, but interacts with signaling inhibitors during immune signaling.

A scientist notices that a cancer cell line fails to die when they add an inducer of apoptosis to his culture of cells. Which hypothesis could explain why the cells fail to die?

1. The cells have a mutation that prevents the initiation of apoptosis signaling.

2. The cells have lost expression of the receptor for the apoptosis-inducing ligand.

3. The cells overexpress a growth factor pathway that inhibits apoptosis.

4. All of the above.

4. All of the above.

Which type of molecule acts as a signaling molecule in yeasts?

1. steroid

2. autoinducer

3. mating factor

4. second messenger

3. mating factor

Quorum sensing is triggered to begin when ___________.

1. treatment with antibiotics occurs

2. bacteria release growth hormones

3. bacterial protein expression is switched on

4. a sufficient number of bacteria are present

4. a sufficient number of bacteria are present

A doctor is researching new ways to treat biofilms on artificial joints. Which approach would best help prevent bacterial colonization of the medical implants?

1. Increase antibiotic dosing

2. Create implants with rougher surfaces

3. Vaccinate patients against all pathogenic bacteria

4. Inhibit quorum sensing

4. Inhibit quorum sensing