Membrane potential

Which of the following happens when a G-protein-coupled receptor activates a G protein? A. The GDP bound to the α subunit is phosphorylated to form bound GTP. B. The α subunit exchanges its bound GDP for GTP. C. It activates the α subunit and inactivates the βγ complex. D. The β subunit exchanges its bound GDP for GTP.

The α subunit exchanges its bound GDP for GTP.

Which of the statement is not true about genetically encoded fluorescent proteins like GFP? A. They enable fluorescent imaging of live cells. B. They can be used with recombinant DNA techniques to label any protein. C. They can only be used in fixed cells. D. They can be expressed in multiple organisms and cell types.

They can only be used in fixed cells.

What happens to the NADH and FADH2 produced in the citric acid cycle? A. They donate electrons to the electron transport chain. B. They are used to oxidize pyruvate to acetyl‑CoA. C. They act as electron acceptors in the electron transport chain. D. They are used to convert glucose to pyruvate in glycolysis.

They donate electrons to the electron transport chain.

Photosynthesis is a process that takes place in chloroplasts and uses light energy to generate high-energy electrons, which are passed along an electron-transport chain. Where are the proteins of the electron-transport chain located in chloroplasts? A. Thylakoid space B. Inner membrane C. Stroma D. Outer membrane E. Thylakoid membrane

Thylakoid membrane

The basal body is located at the base of the primary cilium, and functions as the microtubule organizing center (MTOC) to organize the microtubules in the cilium. Therefore, the plus ends of these microtubules are located at the ___________ of the cilium. Kinesins are frequently observed in the primary cilium; Kinesins transport the cargoes toward the _____________ of the cilium.

Tip; tip

True or False: CO2 and O2 are small molecules that diffuse freely across cell membranes.

True

True or False: During photosynthesis, energy is transferred between the chlorophyll in the antenna complex via resonance, until it reaches the special pair in the reaction center. The electrons in the special pair then donate their electrons to plastoquinone.

True

True or False: Glycolysis happens in cells under both aerobic and anaerobic conditions.

True

True or False: NADH produced in the cytosol during glycolysis uses shuttle to transport electrons to the mitochondria.

True

True or False: The permeability in artificial lipid bilayers is similar to cell membranes when considering the diffusion of small, non-polar molecules

True

True or False: Two kinases, K1 and K2, function sequentially in a signaling pathway. You generated a cell that contains K2 with the inactivating mutation and K1 with the activating mutation. You observe signaling response even in the absence of an extracellular signal. You concluded that in the normal signaling pathway, K2 activates K1.

True

What is the source of the electrons that replace the excited electrons lost from chlorophyll in photosystem II? A. Photosystem I B. NADPH C. Sunlight D. O2 E. Water

Water

Cyanide is a poisonous gas that binds irreversibly to Complex IV in the electron transport chain. Briefly describe cyanide's impact on the following three processes: 1. Electron transport chain. Make sure you specify how the redox status of the electron carriers changes, and what is the impact on ATP production. 2. Citric Acid Cycle. Will it speed up, slow down, stop, or be unchanged? Why? 3. Glycolysis, Will it speed up, slow down, stop, or be unchanged? Why?

When complex IV can not donate its electrons, it will stay in the reduced state. 1. The electron transport chain will stop/halt because all complexes and electron shuttles will stay in the reduced state, thus no protons are pumped and no ATP is produced (1 point). 2. The CAC will also halt as all NAD+'s are reduced to NADHs and FADs stay reduced to FADH2s. Thus, they cycle can not move forward. No ATPs are produced as the cycle is at a stand still. 3. Glycolysis will speed up because cells detect low ATP levels. As a feedback glycolysis speed up to produce more pyruvate.

Is ATP synthesis in chloroplasts light-dependent? Why? A. No, because ATP synthase can function in the dark. B. Yes, because oxidation of water by water-splitting enzyme is light-dependent. C. Yes, because light energizes the electrons that are used by ATP synthase to make ATP. D. Yes, because the light-dependent reactions set up the proton gradient that drives ATP synthesis. E. No, ATP synthesis and light-driven electron transport in chloroplasts are not coupled processes.

Yes, because the light-dependent reactions set up the proton gradient that drives ATP synthesis.

Select all true statements regarding membrane lipids and proteins. A. In Golgi apparatus, sugar moiety of a glycoprotein faces noncytosolic side (lumen). B. Sugar chains attached to membrane proteins and lipids always face cell surface. C. Sugar chains attached to membrane proteins and lipids always face cytosolic side. D. In Golgi apparatus, sugar moiety of a glycoprotein faces cytosolic side. E. In the plasma membrane, two leaflets have the same composition.

A and B

The receptor for adrenaline is a GPCR belonging to Gαs family. Activation of this receptor by adrenaline leads to cAMP production and PKA activation. Which of the following mutation in cells will enhance the effect of adrenaline? A. Cells that lack cAMP phosphodiesterase B. Mutations in α subunit that reduce its intrinsic GTPase activity C. Cells that lack adenylyl cyclase D. Cells that lack the GPCR receptor

A and B

You found a new protein that could participate in the transportation of a vesicle from the Golgi to the nucleus. Which of the following microscopies could you use to observe this protein in this transporting process in live cells? A. Fluorescence microscope B. Scanning EM C. Super-resolution microscope D. Confocal microscope

A and B

Which of the following structures is not organized by actin cytoskeleton? A. Mitotic spindles B. Lamellipodium C. Primary cilium D. Filopodium E. Contractile rings during mitosis

A and C

Which of the followings is true about genetic recombination during meiosis? A. Chiasmata hold homologous chromosomes together. B. Sister chromatids undergo crossing-over with each other. C. Genetic information exchanges between non-sister chromatids. D. Maximally, one crossover event may occur for each pair of chromosomes.

A and C

You are studying a signaling pathway called the Porcupine pathway. Upon ligand binding, the receptor is activated and the signaling eventually triggers the transcription and translation of protein Bird. Bird is released outside the cell to inhibit ligand-receptor binding. What is true about this pathway? A. Bird mediates negative feedback. B. Bird mediates positive feedback. C. The Porcupine signaling is a slow response. D. Bird will amplify the signaling intensity. E. The Porcupine signaling is a fast response.

A and C

After the receptor tyrosine kinase (RKT) is activated, it activates the monomeric G protein Ras. Active Ras triggers a signaling cascade that eventually leads to cell proliferation. Uncontrolled cell proliferation causes cancer. Which of the following mutations in Ras may cause cancer? A. Mutations that cause Ras to permanently associated with GTP B. Mutations that cause Ras to permanently associated with GDP C. Mutations that disable its binding with Ras-GEF D. Mutations that disable its binding with Ras-GAP

A and D

To achieve better resolution in fluorescence microscope, which of the following conditions is/are preferred? A. Ultra-violet light source B. Lens with lower numerical aperture C. Red light source D. Lens with higher numerical aperture

A and D

You are performing nuclear lamina assembly experiment with purified lamin molecules. Which of the following conditions do you predict would be most likely to block the assembly of the nuclear lamina? A. Phosphatase inhibitors B. Decreasing the ATP concentration C. Protein kinase inhibitors D. Increasing the ATP concentration

A and D

Given what we've learned about myosin, kinesin, and dynein, what are some "universal" properties of motor proteins? A. ATP loading and hydrolysis induce protein conformation changes that allow repeated binding and unbinding to cytoskeletal filaments. B. Motor proteins move directionally along cytoskeletal filaments. C. The motor proteins usually form homodimer to work. D. Motor proteins bind and hydrolyze nucleotide triphosphates.

A, B, and D

Intestinal epithelial cells use multiple types of transporters to transfer glucose from the gut lumen to the rest of the body. Identify all types of transport that take place during the transfer of glucose from the gut lumen into the blood. A. Passive transport - uniport of glucose from the basal side of epithelial intestinal cell to underlaying tissues and then into the blood B. Secondary active transport - symport of glucose and Na+ into the intestinal cell from the intestine lumen using Na+ electrochemical gradient. C. Primary active transport - symport of Na+ and K+ from basal side of epithelial intestinal cell to underlaying tissues and then into the blood. D. Primary active transport - ATP driven antiport of Na+ out of the cell and K+ into the cell. E. Passive transport - uniport of glucose into the epithelial intestinal cell from the intestinal lumen after a meal. F. Passive transport - symport of glucose and Na+ from basal side of epithelial intestinal cell to underlaying tissues and then into the blood. G. Secondary active transport - ATP driven antiport of Na+ out of the cell and K+ into the cell.

A, B, and D

You hypothesize that a new protein you discovered could participate in the transportation of a vesicle from the Golgi body to the cytoplasmic membrane. You want to test this hypothesis by imaging live cells. Which of the following microscopes will potentially fit your need? A. Confocal microscope B. Fluorescence microscope C. Transmission EM D. Scanning EM E. Phase contrast light microscrope

A, B, and E

Which of the following statements about lipids are true? A. Tails of lipid molecules can bend and flex. B. Margarine contains more unsaturated lipids than the vegetable oil from which it is made. C. Lipids in a lipid bilayer rapidly exchange position with one another in their own monolayer. D. To increase membrane fluidity, cells will incorporate phospholipids with short chain, unsaturated hydrocarbon tails into their membranes. E. Lipids in a lipid bilayer flip-flop readily from one lipid monolayer to the other.

A, C, and D

In relation to microtubules, what is dynamic instability? A. A technique used to study microtubule polymerization in vitro B. The formation of a short "seed" polymer from multiple monomers C. Cycling between periods of growth and rapid shrinking D. When a polymer has two distinct ends

Cycling between periods of growth and rapid shrinking

Which protein(s) is/are lipid-linked membrane protein(s)? Select all that apply. A. A B. B C. C D. D E. E

D

Actin and microtubules have many things in common. Which of the following does not describe something similar about actin and microtubules? A. Polymerization occurs faster at the plus end compared to the minus end. B. Depolymerization only occurs at the minus end. C. Nucleotide hydrolysis promotes depolymerization. D. Both actin and microtubules have associated motor proteins.

Depolymerization only occurs at the minus end.

During sexual reproduction, novel mixtures of alleles are generated. This is because ________________. A. Every gamete produced by a diploid individual has several different alleles of a single gene. B. In all diploid species, two alleles exist for every gene. C. During meiosis, the segregation of homolog chromosomes is random such that different gametes end up with different alleles of each gene. D. A diploid individual has two different alleles for every gene.

During meiosis, the segregation of homolog chromosomes is random such that different gametes end up with different alleles of each gene.

All microtubules in the axon point in the same direction, with their plus ends toward the axon terminal. What motor protein mediates the backward transport to the cell body? A. Myosin B. Kinesin C. Dynein D. ATP

Dynein

Which of the following statements is true? A. Intermediate filaments are required for cell movement. B. Dynein motors associated with the 9+2 microtubules in the cilium are involved in the movement of motile cilia and flagella. C. Microtubules provide structure to the nucleus. D. Actin filaments provide a mechanism to separate chromosomes during cell division.

Dynein motors associated with the 9+2 microtubules in the cilium are involved in the movement of motile cilia and flagella.

Which of the statements below about intermediate filaments is false? A. They can sustain high tensions of stretch and bend. B. Each filament is about 10 μm in diameter. C. They can stay intact in cells treated with concentrated salt solutions. D. They can be found in the cytoplasm and the nucleus.

Each filament is about 10 μm in diameter.

Which of the following statements is false? A. The tendency for a redox pair to donate or accept electrons can be determined experimentally by measuring its redox potential. B. Electrons will move spontaneously from a redox pair with a higher redox potential, to a redox pair with a low redox potential. C. Electrons will move spontaneously from a redox pair with a low redox potential, to a redox pair with a high redox potential. D. NADH is an excellent molecule to donate electrons to the respiratory chain, while O2 is well suited to act as an electron "sink" at the end of the pathway.

Electrons will move spontaneously from a redox pair with a higher redox potential, to a redox pair with a low redox potential.

Which of the following statements about enzymes is false? A. Enzymes speed up chemical reactions. B. The enzyme remains unchanged at the end of reaction. C. Enzymes lower activation energy for the reactions they catalyze. D. Enzymes lower free energy change for the reactions they catalyze.

Enzymes lower free energy change for the reactions they catalyze.

In which tissue would you find the enrichment of keratin and vimentin, respectively? A. Connective tissues, epithelial cells B. Nerve cells, connective tissues C. Epithelial cells, connective tissues D. Muscle cells, epithelia cells

Epithelial cells, connective tissues

Which statement about membrane proteins is false? A. Membrane proteins can act as enzymes. B. Membrane proteins can act as receptors. C. Membrane proteins can be involved in transport of molecules and ions across the membrane. D. Every membrane protein must be covalently attached to the membrane.

Every membrane protein must be covalently attached to the membrane.

Na+/K+ ATPase (sodium potassium pump) is found in the plasma membrane and catalyzes the exchange of sodium and potassium ions across the membrane. Which of the following statements about this transport system is false? A. Exchanges 3K+ ions for 2Na+ ions B. Exchanges 3Na+ ions for 2K+ ions C. Pumps K+ ions into the cell D. Pumps Na+ ions out of the cell E. ATP is required for its function.

Exchanges 3K+ ions for 2Na+ ions

Which of the following changes represents oxidation? A. Fe3+ to Fe2+ B. FAD to FADH2 C. FADH2 to FAD D. NAD+ to NADH

FADH2 to FAD

True or False: Transporters are similar to channels in terms of energy consumption, except that they are larger, allowing folded proteins as well as smaller organic molecules to pass through them.

False

True or False: Two out of the 10 glycolysis steps are irreversible.

False

True or False: When an amphipathic compound is mixed with water, the polar regions cluster together to present the smallest hydrophobic area to the aqueous solvent (water), and the nonpolar regions are arranged to maximize their interactions with water, a phenomenon called the hydrophobic effect.

False

Which of the following amino acid sequences listed below in the single-letter amino acid code is the most likely candidate to form a transmembrane region (α helix) of a transmembrane protein? Figure below is given for reference. A. L L L I F F G V M A L V I V V I L L I A B. I T L I Y F G N M S S V T Q T I L L I S C. L L K K F F R D M A A V H E T I L E E S D. L L L I F F G V

L L L I F F G V M A L V I V V I L L I A

When cholesterol is incorporated into membranes that contain phospholipids with unsaturated hydrocarbon tails, membrane will become _________________. A. Less fluid B. More fluid

Less fluid

In transmission electron microscopy (TEM), areas where electrons pass through easily appear ________________. A. Darker B. Lighter

Lighter

Pyruvate dehydrogenase complex converts pyruvate to acetyl-CoA. Additional product of this reaction is ______________. A. NADH B. NAD+ C. CoA D. ATP

NADH

The reactions of the citric acid cycle are shown in the image. As labeled in the diagram, reactions 1, 3, and 4 are regulation points in the citric acid cycle. Which molecule inhibits reaction 1? A. FAD B. NADH C. ADP D. NAD+

NADH

Which statement about energy carriers is false? A. NADH, NADPH and FADH2 can donate electrons to other molecules. B. ATP is a molecule that stores energy as a transferrable chemical group. C. NADH, NADPH and FADH2 are molecules that store energy as transferrable chemical groups. D. Hydrolysis of ATP is strongly exergonic (thermodynamically favorable).

NADH, NADPH and FADH2 are molecules that store energy as transferrable chemical groups.

In the light reactions of plant photosynthesis, the initial electron donor is _______ and the final electron acceptor _______.

NADH; H2S

Amino acids are taken up by animal cells using a symport in the plasma membrane. What is the most likely ion whose electrochemical gradient drives the import? Is ATP consumed in the process? A. K+; Yes B. Na+; No C. Na+; Yes D. Cl-; No

Na+; No

The plasma membrane is a semi-permeable barrier. Which molecule is most likely to diffuse through the lipid bilayer unaided by proteins? A. Cl- B. The amino acid glutamate C. Glucose D. O2 E. Na+

O2

In nerve cells, upon depolarization, the Na+ channel is ____________ open . Then during the refractory period, the Na+ channel is _______________ inactive for a short period of time, then the Na+ channel is _______________ closed in the absence of stimuli.

Open; inactive; closed

The receptor for VEGF is a receptor tyrosine kinase (RTK). Determine the sequence of the signaling cascade by filling in the following space. Step 1: VEGF binds to VEGFR. Step 2: _______________________ Step 3: _______________________ Step 4: _______________________ Step 5: _______________________ Step 6: mTOR pathways is activated to promote cell growth.

PI3 kinase is activated. PIP2 is converted to PIP3. Protein Kinase 1 and Akt are recruited to the cytoplastic membrane. Akt is phosphorylated by mTOC2 and Protein Kinase 1.

Which one is the substrate of PI 3 Kinase? A. DAG B. PIP3 C. IP3 D. PIP2

PIP2

After receptor tyrosine kinase is activated, Akt is recruited to the cytoplasmic membrane by which molecule? A. The phosphorylated tyrosine residue in the receptor cytosolic domain. B. PIP2 C. PIP3 D. Protein kinase 1

PIP3

Which of the following statements about phagocytic cells in animals is false? A. Phagocytic cells are important in the gut to take up large particles of food. B. Phagocytic cells scavenge dead and damaged cells and cell debris. C. Phagocytic cells can engulf invading microorganisms and deliver them to their lysosomes for destruction. D. Phagocytic cells extend pseudopods that surround the material to be ingested.

Phagocytic cells are important in the gut to take up large particles of food.

Glycolysis consists of 10 biochemical reactions, each with a distinct ∆G. Based on your understanding of ∆G, which of the following reactions is the most energetically favorable? A. 1,3-bisphospoglycerate + ADP --> 3- phosphoglycerate + ATP (∆G = -18.8 kJ/mole) B. Glucose + Pi --> Glucose-6-phosphate (∆G = +14.3 kJ/mole) C. Glucose-6-phosphate --> Fructose-6- phosphate (∆G = +1.7 kJ/mole) D. Phosphoenolpyruvate + ADP --> Pyruvate + ATP (∆G = -31.4 kJ/mole)

Phosphoenolpyruvate + ADP --> Pyruvate + ATP (∆G = -31.4 kJ/mole)

Phospholipids can spontaneously assemble into enclosed lipid bilayers. Which of the following processes do not contribute to this assembly? A. Phospholipids are covalently linked to a cell cortex. B. Hydrophobic tails cluster together to avoid contact with water. C. Polar heads form electrostatic interactions and hydrogen bonds with water. D. The lipid bilayer self seals into a sphere to achieve an energetically favorable structure.

Phospholipids are covalently linked to a cell cortex.

________________ molecules such as glucose will move through the membrane from the area of high concentration to the area of low concentration via ____________________.

Polar uncharged; facilitated diffusion

A polypeptide chain usually crosses the lipid bilayer as an α helix, because _____________ peptide bonds are shielded from the ____________ core of the lipid bilayer by the _____________ side chains.

Polar; hydrophobic; non-polar

Classify the phrases based on whether they describe or give an example of simple diffusion, facilitated diffusion (transport), primary active transport or secondary active transport. Transport of H+ into the lysosome driven by hydrolysis of ATP --> _________________ Transport of glucose into the cell down the concentration gradient --> _________________ Transport of O2 into the cell --> ____________________ Transport of lactose into the cell driven by H+ gradient --> ______________________

Primary active transport; facilitated diffusion; simple diffusion; secondary active transport

During glycolysis, one molecule of glucose is split into 2 molecules of _______________. In addition to it, the net products are __________ molecule(s) of ATP and two molecules of ________________.

Pyruvate; 2; NADH

Two reactions that take place in a cell are coupled. The reaction 1 has a standard free energy change of +3 kJ/mol and reaction 2 has a standard free energy change of -10 kJ/mol. Based on the given information select a true statement? A. Reaction 2 proceeds quickly. B. Reaction 2 is thermodynamically favorable. C. Reaction 1 is thermodynamically favorable. D. The overall reaction is unfavorable. E. Reaction 2 is thermodynamically unfavorable.

Reaction 2 is thermodynamically favorable.

Which of the following statements about actin is false? A. ATP hydrolysis decreases actin filament stability. B. Actin at the cell cortex helps govern the shape of the plasma membrane. C. The dynamic instability of actin filaments is important for cell movement. D. Actin filaments is nucleated at the side of existing actin filaments in lamellipodia.

The dynamic instability of actin filaments is important for cell movement.

Which of the following statements about secretion is true? A. Proteins destined for constitutive exocytosis aggregate as a result of the acidic pH of the trans Golgi network. B. Coating proteins like clathrin will help vesicles fuse with the target compartment. C. The membrane of a secretory vesicle will fuse with the plasma membrane when it discharges its contents to the cell's exterior. D. Vesicles for regulated exocytosis will not bud off the trans Golgi network until the appropriate signal has been received by the cell.

The membrane of a secretory vesicle will fuse with the plasma membrane when it discharges its contents to the cell's exterior.

Which of the following phenomena will be observed if a cell's membrane is pierced? A. A tear is formed. B. The membrane expands. C. The membrane reseals. D. The membrane collapses.

The membrane reseals.

Microtubules have a plus and minus end. How are the two ends different from each other? A. The plus end binds GTP and the minus end binds ATP. B. The plus end is hydrophilic and the minus end is hydrophobic. C. The plus end is positively charged and the minus end is negatively charged. D. The plus end grows faster than the minus end.

The plus end grows faster than the minus end.

In the heart peacemaker cells, acetylcholine binds to its receptor and the signaling pathway eventually slows down the heart beating rate. In this process, the ___________ subunit of the acetylcholine receptor opens the ______________ channel to hyperpolarize the cell.

βγ; potassium

________________ allows new actin filaments to grow from the side of pre-existing filaments; __________ promotes the addition of actin monomer to straight, unbranced actin filament.

Arp2/3 complex; formin

Determine whether each phrase describes ligand‑gated ion channels, voltage‑gated ion channels, both or neither.

1. Change of conformation in response to changing membrane potential --> 2. Conversion of chemical signal to electrical signal --> 3. Is a form of passive transport --> 4. Change of conformation in response to a signal molecule binding --> 5. Is a form of active transport --> 6. An example is the acetylcholine receptor -->

The chemical 2,4-Dinitrophenol (DNP) was once used to treat obesity, but was banned because of its severe side effects. DNP is known to uncouple the two states of chemiosmosis. 1. Briefly explain how DNP uncouples chemiosmosis. In your answer, make sure you specify the organelle and location where DNP acts, its impact on ATP production and the impacted enzyme and ions, if any. 2. Briefly explain the impact of DNP on the electron transport chain. Will it be accelerated or slowed down? Why?

1. DNP allow H+ to flow from mitochondria intermembrane space to the matrix, bypassing ATP synthase. As a result, the H+ gradient is dissipated, ATP synthase stops and no ATP is produced. 2. DNP accelerates ETC. When the cell senses reduced ATP levels and low H+ gradient in the mitochondria, the ETC will speed up in order to pump more H+ into the mitochondria intermemebrace space.

Plasma membranes are extremely thin and fragile, requiring an extensive support network of fibrous proteins. This network is called the ____________. A. Attachment complex B. Glycocalyx C. Cortex D. Spectrin

Cortex

Substrate-level phosphorylation takes place in steps 7 and 10 in glycolysis. Which of the following classes of enzymes can catalyze these reactions? A. Kinases B. Dehydrogenases C. Isomerases D. Isomerases

Kinases

During photosynthesis, plant cells capture energy from sun light to produce organic molecules. Describe the light reaction process of photosynthesis while answering the following questions: 1. Where and how do plant cells capture the energy from sunlight and produce high-energy electrons? Make sure you specify the organelle and molecules involved, and describe how energy is transferred, and the initial electron donor. 2. Following the path of electron flow, list at least 4 complexes that host the electrons, and the final electron acceptor. 3. Name a proton pump that contributes to the proton gradient, then specify the location of the proton gradient within the organelle. 4. Name two products of the light reaction that are then used in the dark reaction.

1. The molecule chlorophyll in chloroplast (or thylakoid membrane) captures the energy from sun light. in this process, energy from sunlight excites electrons in chlorophyll and the energy is transferred in the antenna via resonance until it reaches the special pair in the reaction center. the electrons in the special pair are passed to plastoquinone, leaving the reaction center positively charged. to replace the lost electrons from the special pair, H2O is split and donates electrons to the special pair, thus water is the electron donor. 2. Any of these 4: PSII, plastoquinone, cytochrome B6-f complex, plastocyanin, PSI, Ferredoxin, Ferredoxin-NADP reductase (FNR). the final electron acceptor is NADP+. 3. Cytochrome B6-f complex is the proton pump contributing to the proton gradient. A proton gradient is formed from the pumping of 4 protons to the thylakoid space. 4. NADPH and ATP

You discovered a new fluorophore. You have determined that this fluorophore is excited by 647 nm light. Which of the following cannot be the emission wavelength of this fluorophore? A. 510 nm B. 702 nm C. 690 nm D. 750 nm

510 nm

Which of the following is not part of the process known as oxidative phosphorylation? A. FADH2 and NADH become oxidized as they transfer a pair of electrons to the electron-transport chain. B. Molecular oxygen serves as a final electron acceptor. C. ATP molecules are produced in the cytosol as glucose is converted into pyruvate. D. The electron carriers in the electron-transport chain switch between reduced and oxidized states as electrons are passed along.

ATP molecules are produced in the cytosol as glucose is converted into pyruvate.

The carbon-fixation cycle requires energy in the form of ___________ and reducing power in the form of _________________.

ATP; NADPH

What activates trimeric G Protein, PKA and PKC? A. Activated GPCR, cAMP, phospholipase C B. GEF, cAMP, DAG and Ca2+ C. Activated GPCR, cAMP, DAG and Ca2+ D. GAP, cAMP, DAG

Activated GPCR, cAMP, DAG and Ca2+

Which of the following statement represents the cell theory? A. All cells are formed by the growth and division of existing cells. B. All cells require a continual input of energy to sustain life. C. All cells can be seen using a microscope. D. All cells resemble square or rectangular chambers.

All cells are formed by the growth and division of existing cells.

The formation of a bivalent during meiosis ensures that _____________. A. The sex chromosomes, which are not identical, will line up separately at the metaphase plate during meiosis I. B. Recombination will occur between identical sister chromatids. C. All four sister chromatids remain together until the cell is ready to divide. D. One chromatid from the mother and one chromatid from the father will segregate together during meiosis I.

All four sister chromatids remain together until the cell is ready to divide.

Signals travel along the axon in nerve cells from the dendrites (receiving end) to the axon terminal (end of neuron where signal triggers action), in what is called an action potential. Along the axon, there are voltage-gated Na+ channels and K+ channels. Based on your understanding of action potential, answer the questions below: What are the major roles of voltage-gated Na+ channels during an action potential? In your answer, make sure you specify its three conformational states, and how it contributes to the unidirectionality of signals, and shape of an action potential.

At the depolarizing (or rising) phase, voltage gated Na+ channel opens in response to the depolarizing stimulus (or to increased membrane potential, or influx of Ca2+) to allow Na+ ion flow into the cell. This further depolarizes the cell and triggers an action potential. At the repolarizing phase, voltage gated Na+ channel switches to inactivate state, allowing cells to repolarize or to reduce the membrane potential, graph going down into the negative, and making this channel insensitive to the change in membrane voltage. This inactive state ensures unidirectionality of the signal, so that the signal only propagates in one direction. After the refractory period (inactive state), the channels goes into the closed state, and it is ready to open upon new stimulus.

Based on the hydropathy plot below, which protein, A or B, is most likely to have transmembrane regions?

B

Which of the following statements about apoptosis is true? A. Binding of Fas to its receptor triggers the formation of death-inducing signaling complex (DISC), which then activates caspase 9. B. Cells that constitutively express Bcl2 will be more resistant to undergo apoptosis. C. Apoptosis is induced by the release of cytochrome c into the cytosol from mitochondria. D. Bax and Bak promote apoptosis by binding to procaspases in the apoptosome.

B and

In the signaling pathway below, the chemokine CXCL8 is a chemoattractant for neutrophils. CXCL8 binds to its receptor CXCR8 and the signaling pathway eventually activates Prex1, a Guanine exchange factor (GEF) for Rac. A mutation in Prex1 causes its reduced interaction with Rac1, and neutrophils with this mutation fail to chase invading pathogens. Which is the following conditions could potentially rescue this defects in neutrophils? A. Expressing an overactive CXCR8-specific G𝝱𝛄 subunit B. Inactivating the Rac1-specific GAP (GTPase activating protein) C. Expressing the Arp2/3 whose activating conformation lasts longer than usual D. Expressing a constitutively active CXCR8 at the surface of the neutrophil

B and C

The basal level of Ca2+ concentration in the cytosol is extremely low. Why do you suppose cells need to keep cytosolic Ca2+ concentration so low? A. To save the Ca2+ bank in the cell B. This allows rapid response to an extracellular signal. C. To ensure that a small increase of Ca2+ leads to a large change in cytosolic Ca2+ concentration D. To keep the membrane potential at a negative level

B and C

Which of the following proteins regulate the intrinsic pathway of apoptosis? A. FAS B. Bax C. Caspase 9 D. BAD

B and C

Protein phosphorylation is an example of how protein function can be altered by chemically modifying a protein. What is true about protein phosphorylation? A. Kinase can remove a phosphate from an enzyme, inactivating it. B. Kinase can add a phosphate to an enzyme, inactivating it. C. Phosphatase can add a phosphate to an enzyme resulting in enzyme activation. D. Phosphatase can remove a phosphate from a protein, activating it.

B and D

Select the true statements about the citric acid cycle. A. The citric acid cycle occurs in the cytoplasm of the cell. B. The citric acid cycle operates only when O2 is present. C. One turn of the cycle produces 6 NADH, 2 FADH2 and 2 GTP (ATP). D. One turn of the cycle produces 3 NADH, 1 FADH2 and 1 GTP (ATP). E. The citric acid cycle occurs in most cells, including anaerobic microorganisms.

B and D

The members of the steroid hormone receptor family __________________. A. Are cell-surface receptors B. May enter the nucleus and act as a transcription factor C. Do not undergo conformational changes D. Interact with signal molecules that diffuse through the plasma membrane

B and D

Which is/are true statement/s about Notch signaling? A. Notch signaling usually mediates fast response. B. The effector protein is Notch Intracellular Domain that activates gene transcription. C. The activation of Notch signaling pathway involves signal amplification. D. Notch signaling usually mediates slow response.

B and D

Which of the following glycolytic intermediates can donate phosphoryl group to ADP, forming ATP? A. Fructose 1,6 bisphosphate B. 1,3 bisphosphoglycerate C. Glucose 6-phosphate D. Phosphoenolpyruvate E. 3-phosphoglycerate

B and D

Which of the following monomeric G proteins are not involved in vesicle budding or docking? A. Dynamin B. Ran-GTPase C. Rab1 D. Ras

B and D

Which of the following statement is true? A. M-Cdk must be phosphorylated by an activating kinase before it is activated. B. Binding of a cyclin to Cdk is required but not sufficient to activate the Cdk. C. Cdk is activated as soon as its corresponding cyclin binds to it. D. The concentration of M cyclin increases markedly during M phase.

Binding of a cyclin to Cdk is required but not sufficient to activate the Cdk.

Desmosomes are subcellular structures __________________. A. By which intermediate filaments in two adjacent cells are indirectly linked with each other B. By which epithelial cells attach to the basal lamina (basement membrane) instead of to each other C. Through which actin filament can be linked to the extracellular matrix D. Where intermediate filaments attach to microtubules via plectin

By which intermediate filaments in two adjacent cells are indirectly linked with each other

Acetylcholine can reduce heart rate in pacemaker cells, or trigger muscle contraction in skeleton muscle cells. Which of the following are true statements about these two actions of acetylcholine? A. Both are slow responses. B. The action on peacemaker cells is fast response, and on muscle cells is slow response. C. The responses differ because different downstream transducers are used in these two types of cells. D. The responses differ because acetylcholine binds to different receptors on these two types of cells.

C and D

Which of the following conditions could prevent a skin cell from passing the G1 checkpoint? A. The cell has not completed DNA replication. B. The chromosomes of the cell are not properly attached to spindle fibers. C. The cell's DNA is damaged. D. The cell is lacking nutrients.

C and D

Dehydrogenases are enzymes that A. Catalyze the addition of phosphate group to molecules B. Catalyze oxidation-reduction reactions C. Catalyze the rearrangement of bonds within a single molecule D. Catalyze the shifting of a chemical group from one position to another within a molecule

Catalyze oxidation-reduction reactions

Based on the diagram below, which molecule, Cation X or Anion Y, has the steeper electrochemical gradient? Assume the cell has a membrane potential of -60 mV. A. Cation X B. Anion Y

Cation X

Classify each phrase based on whether it describes or is an example of transporter, channel, both, or neither. Can only facilitate passive transport --> ___________________ Na+/K+ pump --> _____________________ Is integral membrane protein --> ____________________ Involved in transport of nonpolar gases --> ________________________

Channel; transporter; both; neither

Which of the following is needed for light-dependent reactions? A. CO2 B. NADPH C. ATP D. Chlorophyll E. H2O

Chlorophyll

Select the process in which the highest amount of reduced electron carriers is produced. A. Conversion of pyruvate to acetyl-CoA B. Glycolysis C. Citric acid cycle D. All processes yield equal amount of reduced electron carriers.

Citric acid cycle

Which of the following statements about vesicle budding from the Golgi is false? A. Clathrin molecules are important for binding to and selecting cargoes for transport. B. Clathrin molecules act at the cytosolic surface of the Golgi membrane. C. Adaptins interact with clathrin. D. After vesicle budding completes, clathrin molecules are released from the vesicle.

Clathrin molecules are important for binding to and selecting cargoes for transport.

Botulinum toxin is a neurotoxin that causes paralysis of the muscles. This is accomplished by cleavage of SNARE proteins contained within the presynaptic compartment of the neuron. Given this information, which of the following best describes how botulinum toxin causes paralysis? A. The toxin prevents the SNAREs from stimulating proper synthesis of neurotransmitters in the neuron. B. Disruption of SNAREs reverses the transport direction of vesicles, taking them away from the muscle and towards the cell soma. C. Cleavage of SNAREs disrupts the propagation of the action potential. D. Cleavage of SNAREs inhibits vesicles containing neurotransmitters from fusing to the membrane and stimulating the post-synaptic muscle.

Cleavage of SNAREs inhibits vesicles containing neurotransmitters from fusing to the membrane and stimulating the post-synaptic muscle.

Cells can pause in G1 when DNA is damaged, and can pause in S when there are replication errors. Which cell cycle arrest is mediated by p53 activated transcription of the CDK inhibitor p21? A. G1 B. G2 C. S D. M

G1

Which of the following glycolytic steps is oxidation-reduction reaction? A. Glucose + Pi --> Glucose-6-phosphate B. Glucose-6-phosphate --> Fructose-6-phosphate C. 1,3-bisphospoglycerate + ADP --> 3- phosphoglycerate + ATP D. Glyceraldehyde 3-phosphate + Pi + NAD+ --> 1,3 bisphosphoglycerate + NADH

Glyceraldehyde 3-phosphate + Pi + NAD+ --> 1,3 bisphosphoglycerate + NADH

Which of the following processes occurs in the cytoplasm? A. Glycolysis B. Oxidative phosphorylation C. Citric acid cycle D. Breakdown of large molecules into subunits (digestion)

Glycolysis

Which statement about glycolysis is true? A. All glycolytic steps are reversible. B. Oxygen is required for glycolysis. C. Abundant ATP will stimulate glycolysis. D. Glycolysis occurs in most cells, including anaerobic microorganisms.

Glycolysis occurs in most cells, including anaerobic microorganisms.

Which mechanism best describes the process by which neutrophils are recruited by endothelial cells? A. Glycoproteins are tethered to the proteins on the surface of another cell. B. Proteins are tethered to the extracellular matrix. C. Protein movement is limited by the presence of a diffusion barrier. D. Proteins are tethered to the cell cortex. E. Proteins are components of lipid rafts.

Glycoproteins are tethered to the proteins on the surface of another cell.

The concentration of the 2nd messenger is kept low in the cytosol so that cell signaling can be faithfully transduced. What mechanisms reduce the cAMP and Ca2+ levels immediately after they are produced? A. High constitutive activity of PDE; Ca2+ channels in the ER and cytoplasmic membrane B. High constitutive activity of PDE; Ca2+ bump in the ER and cytoplasmic membrane C. High PKA activity; Ca2+ channels in the ER and cytoplasmic membrane D. Inactivation of adenylyl cyclase; Ca2+ Ca2+ bump in the ER and cytoplasmic membrane

High constitutive activity of PDE; Ca2+ bump in the ER and cytoplasmic membrane

When a signal needs to be sent to most cells throughout a multicellular organism, the signal most probably is a __________________. A. Neurotransmitter B. Diffusible small molecules C. Dissolved gas D. Hormone

Hormone

Which of the following statements is false? A. In yeast growing anaerobically, pyruvate is converted to ethanol. B. In anaerobic muscle, pyruvate is converted to lactate in order to regenerate NAD+ that will be used again in glycolysis. C. In anaerobic muscle, pyruvate is converted to lactate in order to regenerate NADH that will be used again in glycolysis. D. Under aerobic conditions pyruvate is converted to acetyl-CoA that enters the citric acid cycle.

In anaerobic muscle, pyruvate is converted to lactate in order to regenerate NADH that will be used again in glycolysis.

Where does most new membrane synthesis take place in a eukaryotic cell? A. In the plasma membrane B. On ribosomes C. In the Golgi apparatus D. In the endoplasmic reticulum E. In the mitochondria

In the endoplasmic reticulum

Signals travel along the axons in nerve cells from the dendrites (receiving end) to the axon terminal (end of neuron where signal prompts an action), in what is called action potential. Along the axon, there are voltage gated Na+ channels and K+ channels. Based on your understanding of action potential, answer the questions below: Dendrotoxin (DTX) is another neurotoxin that is produced by the mamba snake. Based on the graph below, describe the effects of DTX and propose a mechanism of action.

In this graph, application of dendrotoxin delays repolarization of the membrane potential. Dendrotoxin does this by inhibiting voltage-gated K+ channels. When K+ channels remain closed, K+ ions cannot leave the cell, keeping the membrane potential depolarized.

Signals travel along the axon in nerve cells from the dendrites (receiving end) to the axon terminal (end of neuron where signal triggers action), in what is called an action potential. Along the axon, there are voltage-gated Na+ channels and K+ channels. Based on your understanding of action potential, answer the questions below: Tetrodotoxin (TTX) is a potent neurotoxin found in pufferfish (Takifugu). Based on the graph below, describe the effects of TTX and propose a mechanism of action for this toxin.

In this graph, application of tetrodotoxin reduces the amplitude of depolarization and blocks the firing of action potentials. Tetrodotoxin does this by blocking voltage-gated Na+ channels; since fewer Na+ ions can come into the cell, the cell does not depolarize to same extent as a control cell.

The Retinoblastoma (Rb) protein blocks cells from entering the cell cycle by _____________________. A. Inhibiting transcription of cyclins B. Marking cyclins for destruction by proteolysis C. Phosphorylating CDK D. Activating apoptosis

Inhibiting transcription of cyclins

Receptors for the neurotransmitter GABA (gamma-aminobutyric acid) are ligand-gated Cl- (chloride) channels. Assuming the electrochemical gradient for Cl-draws Cl- ions into the cell, would you classify GABA as an excitatory or inhibitory neurotransmitter? A. Neither B. Excitatory C. Inhibitory

Inhibitory

Which statement is true about the primary cilium? A. It functions like an antenna to sense signaling molecules from the environment. B. It has dynein associated with the microtubule arrays. C. It functions to move fluid over the surface of the cell. D. It has 9+2 array of microtubules inside.

It functions like an antenna to sense signaling molecules from the environment.

What is true about monomeric G proteins? A. GEF(Guanine nucleotide exchange factor) proteins inhibits monomeric G protein. B. It has one subunit that binds to GTP or GDP. C. It has intrinsic GTPase activity, thereby hydrolyzing its bond GTP into GDP. D. G protein is usually activated by a kinase that phosphorylates its bond GDP into GTP. E. GAP (GTPase-activating protein) activates monomeric G protein.

It has one subunit that binds to GTP or GDP.

Which of the following statements about the glycocalyx is false? A. It can play a role in cell-cell adhesion. B. Specific oligosaccharides can be involved in cell-cell recognition. C. It protects and lubricates the cell. D. It is found on the extracellular side of the membrane. E. It is found on the cytosolic side of the membrane.

It is found on the cytosolic side of the membrane.

The electron microscope improves image resolution because A. It can produce a series of optical sections (Z-stack) through the sample. B. It uses lens with high numerical aperture (NA). C. Samples are sliced into ultrathin sections. D. It uses short wavelength light sources (electron beams). E. None of the above

It uses short wavelength light sources (electron beams).

What is not true about lysosome? A. The high levels of glycosylation in the lysosome transmembrane proteins protected them from being digested by the proteases in the lysosome lumen. B. The protein localization signal is M6P. C. Lysosome is important for cholesterol absorption into cells. D. Its high pH is required for the enzymatic activities in the lumen.

Its high pH is required for the enzymatic activities in the lumen.

The activation of MPF (M-phase promoting complex) at the beginning of mitosis is due to ________________. The decline of MPF activity at the end of mitosis is due to __________________.

Removal of the inhibitory phosphate group from the corresponding Cdk; the degradation of cyclin

In the carbon-fixation process in chloroplasts, carbon dioxide is initially added to the sugar ________________. The final product of carbon fixation in chloroplasts is the three-carbon compound ___________________.

Ribulose 1,5-bisphosphate; glyceraldehyde 3-phosphate

Actin and acting binding proteins allow muscle to contract. At the cellular levels, which of the following structures shorten during muscle contraction? A. Actin filaments B. Myosin filaments C. Flagella D. Sacromeres

Sacromeres

Which of the following steps in the citric acid cycle is substrate-level phosphorylation? A. Isocitrate + NAD+ --> alpha-ketoglutarate + NADH B. Acetyl-CoA + oxaloacetate --> citrate + CoA C. Succinyl-CoA + GDP --> succinate + GTP + CoA D. Succinate + FAD --> fumarate + FADH2

Succinyl-CoA + GDP --> succinate + GTP + CoA

Glucose is transported from the intestine across the intestinal cell into the blood via three transmembrane transport steps (shown below). A. Uniport of glucose from the intestinal cell to the intestine B. Symport of glucose and Na+ into the intestinal cell from the lumen of intestines C. Uniport of glucose into the intestinal cell from the intestine D. Symport of glucose and Na+ from the intestinal cell into the blood

Symport of glucose and Na+ into the intestinal cell from the lumen of intestines