membrane structure

B. It has both hydrophilic and hydrophobic regions.

Which statement best describes the amphipathic nature of a phospholipid?

A. It has hydrophobic heads and hydrophilic tails.
B. It has both hydrophilic and hydrophobic regions.
C. Both ends of the molecule are nonpolar.
D. It dissolves completely in water.
E. It repels all charged particles.

B. Phosphate head groups

2. Which region of a phospholipid interacts with the aqueous environment inside and outside the cell?

A. Fatty acid tails
B. Phosphate head groups
C. Sterol ring structure
D. Glycerol backbone
E. All parts equally

B. Freeze-fracture and electron microscopy

3. Evidence for the bilayer nature of membranes came from which technique?

A. Polymerase chain reaction
B. Freeze-fracture and electron microscopy
C. Northern blotting
D. Mass spectrometry
E. X-ray crystallography

C. Membrane proteins embedded in the bilayer

4. In the freeze-fracture experiment, bumps observed on the membrane surface correspond to:

A. Cholesterol molecules
B. Carbohydrate chains
C. Membrane proteins embedded in the bilayer
D. Peripheral cytoskeletal elements
E. Nucleic acids

C. Membranes are fluid and dynamic.

5. When a mouse cell and a human cell fuse, the intermixing of their membrane proteins provides evidence that:

A. Membranes are rigid and static.
B. Membranes contain carbohydrate rafts.
C. Membranes are fluid and dynamic.
D. Protein synthesis occurs at the membrane surface.
E. Cells cannot fuse under physiological conditions.

C. Energy storage

6. Which of the following is not a typical function of an integral membrane protein?

A. Enzyme catalysis
B. Cell-to-cell recognition
C. Energy storage
D. Signal reception
E. Transport of molecules

C. Cell-surface receptor

7. A protein that binds to a signaling molecule such as a hormone is called a:

A. Transporter
B. Enzyme
C. Cell-surface receptor
D. Cytoskeletal anchor
E. Identity marker

B. The presence of diverse proteins and lipids in the membrane.

8. The “mosaic” aspect of the fluid mosaic model refers to:

A. The random movement of phospholipids.
B. The presence of diverse proteins and lipids in the membrane.
C. The symmetrical bilayer arrangement.
D. The stacking of carbohydrates.
E. The role of cholesterol.

B. Proteins and lipids that move laterally.

9. The “fluid” aspect of the model refers to:

A. Water inside the bilayer.
B. Proteins and lipids that move laterally.
C. The movement of ions through pores.
D. The separation of the two leaflets.
E. The absence of hydrophobic regions.

A. The hydrophilic head cannot pass through the hydrophobic core.

10. The main reason lipids rarely flip-flop between membrane layers is because:

A. The hydrophilic head cannot pass through the hydrophobic core.
B. Cholesterol blocks their movement.
C. Membrane proteins prevent rotation.
D. Enzymes inhibit flipping.
E. The outer layer is thicker.

B. Flippase

11. The enzyme responsible for moving specific lipids from the outer to inner leaflet is:

A. Kinase
B. Flippase
C. Synthase
D. Ligase
E. Lipase

C. Increased fluidity

12. The presence of more unsaturated fatty acids in membrane phospholipids results in:

A. Increased rigidity
B. Decreased permeability
C. Increased fluidity
D. Formation of lipid rafts
E. Loss of amphipathic character

B. Buffer membrane fluidity against temperature changes

13. Cholesterol’s role in the plasma membrane is to:

A. Form channels for ions
B. Buffer membrane fluidity against temperature changes
C. Provide energy for diffusion
D. Anchor glycoproteins
E. Act as a cell-surface receptor

C. Lowering temperature

14. Which of the following would decrease membrane fluidity?

A. Replacing saturated with unsaturated fatty acids
B. Decreasing cholesterol in cold environments
C. Lowering temperature
D. Adding double bonds to fatty acids
E. Removing long hydrocarbon tails

B. The ER membrane is thinner with more unsaturated fatty acids.

15. The plasma membrane and the endoplasmic reticulum differ because:

A. The ER membrane is thicker with more cholesterol.
B. The ER membrane is thinner with more unsaturated fatty acids.
C. Both have identical composition.
D. The plasma membrane lacks proteins.
E. The ER has no phospholipids.

C. Saturated fatty acids and cholesterol

16. Specialized lipid “rafts” in the plasma membrane are rich in:

A. Unsaturated fatty acids and cholesterol
B. Carbohydrates and nucleic acids
C. Saturated fatty acids and cholesterol
D. Glycerol and water channels
E. Enzymes for transcription

B. Lateral diffusion

17. Which process describes the movement of membrane proteins and lipids within the same layer?

A. Diffusion
B. Lateral diffusion
C. Osmosis
D. Endocytosis
E. Active transport

B. Maintaining cell shape and stability

18. Membrane proteins attached to the cytoskeleton are primarily responsible for:

A. Energy production
B. Maintaining cell shape and stability
C. Signal amplification
D. Ion pumping
E. Catalysis of lipid synthesis

B. Glycoproteins and glycolipids

19. Cell-surface identity markers are usually:

A. Phospholipids
B. Glycoproteins and glycolipids
C. Steroids
D. RNA fragments
E. Hydrophobic enzymes

A. Facilitate endocytosis by forming coated pits

20. The main function of clathrin proteins is to:

A. Facilitate endocytosis by forming coated pits
B. Catalyze reactions at the plasma membrane
C. Transport lipids across leaflets
D. Bind to cell-surface receptors
E. Strengthen the nuclear envelope

B. Secreted or inserted into membranes

21. The rough endoplasmic reticulum produces proteins that are:

A. Used only in the nucleus
B. Secreted or inserted into membranes
C. Stored in lysosomes indefinitely
D. Synthesized for energy
E. Formed outside the cell

B. Receives vesicles from the ER.

22. In the Golgi apparatus, the “cis” face:

A. Sends materials toward the plasma membrane.
B. Receives vesicles from the ER.
C. Produces ribosomes.
D. Breaks down old membranes.
E. Synthesizes lipids.

B. Secondary lysosome

23. When a phagosome fuses with a lysosome, the structure formed is a:

A. Primary lysosome
B. Secondary lysosome
C. Golgi vesicle
D. Transport raft
E. Secretory vesicle

D. The plasma membrane

24. The final destination for proteins meant for secretion is:

A. The cytoplasm
B. The Golgi trans face
C. The lysosome
D. The plasma membrane
E. The nucleus

C. Smooth ER

25. Which organelle contributes new membrane lipids to the plasma membrane?

A. Mitochondrion
B. Rough ER
C. Smooth ER
D. Ribosome
E. Lysosome

C. Cell recognition and communication

26. Glycolipids in the plasma membrane function mainly in:

A. Energy storage
B. Structural reinforcement
C. Cell recognition and communication
D. Protein synthesis
E. DNA repair

B. The membrane allows only certain molecules to cross.

27. The term “selective permeability” means:

A. All substances move freely across the membrane.
B. The membrane allows only certain molecules to cross.
C. Only water can cross.
D. Proteins block all movement.
E. Lipids move without restriction.

C. Channel

A protein that moves ions down their concentration gradient without energy use is a:

A. Pump
B. Carrier (facilitated diffusion)
C. Channel
D. Enzyme
E. Receptor

B. Only animal membranes contain cholesterol.

29. Which statement correctly compares plant and animal cell membranes?

A. Both contain cholesterol in equal amounts.
B. Only animal membranes contain cholesterol.
C. Plant membranes have no phospholipids.
D. Plant membranes are impermeable to water.
E. Both lack glycolipids.

A. Human-mouse cell fusion experiment

30. Which experiment best demonstrated that membrane proteins move freely within the bilayer?

A. Human-mouse cell fusion experiment
B. Gorter-Grendel lipid study
C. Freeze-fracture imaging
D. DNA replication analysis
E. Osmosis diffusion test

B. The membrane allows only some molecules to pass through based on size or charge.

1. Which statement best defines selective permeability?

A. The membrane blocks all molecules.
B. The membrane allows only some molecules to pass through based on size or charge.
C. The membrane allows everything to pass freely.
D. The membrane allows water but not gases.
E. The membrane is impermeable to nonpolar molecules.

C. Diffusion

2. Movement of molecules from a region of high concentration to low concentration is called:

A. Osmosis B. Active transport C. Diffusion D. Endocytosis E. Exocytosis

B. Diffusion moves solute; osmosis moves water.

3. Which statement correctly compares diffusion and osmosis?

A. Both require ATP.
B. Diffusion moves solute; osmosis moves water.
C. Osmosis occurs only in gases.
D. Diffusion moves water; osmosis moves ions.
E. Both move substances against their gradient.

B. Against their gradients using ATP.

4. The Na⁺/K⁺ pump moves ions:

A. With their gradients using facilitated diffusion.
B. Against their gradients using ATP.
C. Only when no ATP is present.
D. By osmosis.
E. Through ligand-gated channels.

C. Primary active transport

5. Which transport process requires energy directly from ATP?

A. Simple diffusion
B. Facilitated diffusion
C. Primary active transport
D. Osmosis
E. Symport

B. The movement of one solute down its gradient provides energy for another to move up its gradient.

6. In secondary active transport (coupled transport):

A. ATP directly drives both solutes.
B. The movement of one solute down its gradient provides energy for another to move up its gradient.
C. Both solutes move against their gradients.
D. Water movement drives both solutes.
E. Vesicles are required.

B. Two molecules in the same direction.

7. A symport transports:

A. Two molecules in opposite directions.
B. Two molecules in the same direction.
C. One molecule only.
D. Ions through gated channels.
E. Water molecules exclusively.

B. Moves substances in opposite directions.

8. An antiport differs from a symport because it:

A. Moves both substances the same way.
B. Moves substances in opposite directions.
C. Uses vesicles for transport.
D. Requires no membrane proteins.
E. Works only in plant cells.

C. It uses specific carrier or channel proteins.

9. Which statement about facilitated diffusion is true?

A. It requires ATP.
B. It moves molecules against the gradient.
C. It uses specific carrier or channel proteins.
D. It transports only water.
E. It is slower than simple diffusion.

D. Any of the above depending on channel type.

10. A gated channel opens in response to:

A. A change in membrane potential.
B. Mechanical stress.
C. Binding of a ligand.
D. Any of the above depending on channel type.
E. None of the above.

B. O₂, CO₂, and steroid hormones

11. Which molecules can diffuse freely through a membrane without assistance?

A. Glucose and ions
B. O₂, CO₂, and steroid hormones
C. H₂O and proteins
D. Na⁺ and Cl⁻
E. Large polar molecules

B. Osmosis

12. Water movement across a selectively permeable membrane is called:

A. Diffusion B. Osmosis C. Endocytosis D. Active transport E. Filtration

B. Swell and burst

13. A red blood cell placed in a hypotonic solution will:

A. Shrink
B. Swell and burst
C. Remain unchanged
D. Gain ions but lose water
E. Undergo crenation

C. Shrink as water leaves the cell

14. A red blood cell placed in a hypertonic solution will:

A. Swell
B. Burst
C. Shrink as water leaves the cell
D. Remain unchanged
E. Increase in internal pressure

B. Maintaining osmotic pressure (turgor)

15. In plant cells, the cell wall prevents lysis by:

A. Allowing water to escape freely
B. Maintaining osmotic pressure (turgor)
C. Releasing ATP
D. Destroying aquaporins
E. Reducing solute concentration

B. Strengthen the coated pit and form vesicles

16. During receptor-mediated endocytosis, clathrin functions to:

A. Pump ions through the membrane
B. Strengthen the coated pit and form vesicles
C. Bind directly to ligands
D. Digest unwanted proteins
E. Fuse vesicles with lysosomes

B. It expels materials from the cell.

17. Exocytosis differs from endocytosis because:

A. It uses less energy.
B. It expels materials from the cell.
C. It brings materials into the cell.
D. It occurs only in plants.
E. It requires receptor proteins.

A. Use carrier proteins.

18. Facilitated diffusion and active transport are similar because both:

A. Use carrier proteins.
B. Require ATP.
C. Move molecules against their gradient.
D. Involve vesicles.
E. Are restricted to ions.

B. 3 Na⁺ out and 2 K⁺ in

19. The Na⁺/K⁺ pump transports how many ions per cycle?

A. 2 Na⁺ out and 3 K⁺ in
B. 3 Na⁺ out and 2 K⁺ in
C. 2 Na⁺ in and 3 K⁺ out
D. 1 Na⁺ out and 1 K⁺ in
E. 3 Na⁺ in and 2 K⁺ out

D. It equalizes ion concentrations on both sides.

20. Which statement about the Na⁺/K⁺ pump is false?

A. It makes the inside of the cell negative relative to the outside.
B. It requires ATP hydrolysis.
C. It moves Na⁺ out and K⁺ in.
D. It equalizes ion concentrations on both sides.
E. It helps establish an electrochemical gradient.

C. Endocytosis

21. Which type of transport requires vesicle formation?

A. Simple diffusion
B. Osmosis
C. Endocytosis
D. Facilitated diffusion
E. Ion channel transport

B. The CO₂ concentration gradient

22. The rate of CO₂ diffusion into a cell depends mainly on:

A. ATP levels
B. The CO₂ concentration gradient
C. Number of carrier proteins
D. Cell size
E. Clathrin availability

E. Both A and C are correct.

23. A patient receives an IV of 0.85 % NaCl because:

A. It is isotonic to red blood cells.
B. Distilled water would shrink cells.
C. Distilled water would cause cells to burst.
D. Saline supplies nutrients.
E. Both A and C are correct.

B. Osmotic pressure

24. Which term describes the force driving water movement during osmosis?

A. Hydrostatic pressure
B. Osmotic pressure
C. Turgor pressure
D. Electrochemical gradient
E. Kinetic force

A. Potential energy

25. The energy stored in an ion gradient across a membrane is called:

A. Potential energy
B. Kinetic energy
C. Chemical equilibrium
D. Heat energy
E. Activation energy

A. Carrier – binds and moves molecules through conformational change

26. Which of the following correctly pairs a transport protein and its function?

A. Carrier – binds and moves molecules through conformational change
B. Channel – uses ATP for every molecule
C. Pump – moves ions with gradient
D. Receptor – carries glucose inside the cell
E. Clathrin – channels ions across bilayer

A. Na⁺/K⁺ pump

27. An example of an antiporter is:

A. Na⁺/K⁺ pump
B. Na⁺/glucose cotransporter
C. Cl⁻ channel
D. Proton pump
E. Aquaporin

B. Direction of movement relative to gradient

28. Which feature distinguishes active from passive transport?

A. Requirement for a membrane protein
B. Direction of movement relative to gradient
C. Requirement for carbohydrate chain
D. Occurrence only in animal cells
E. Dependence on osmotic pressure

A. Ligand

29. In receptor-mediated endocytosis, the molecule that binds to the receptor is called the:

A. Ligand
B. Cargo
C. Clathrin
D. Channel
E. Transporter

B. Exocytosis

30. Which process requires the fusion of a vesicle with the plasma membrane?

A. Endocytosis B. Exocytosis C. Pinocytosis D. Diffusion E. Osmosis

B. Energy in the universe is constant.

1. The first law of thermodynamics states that:

A. Energy can be created and destroyed.
B. Energy in the universe is constant.
C. The universe’s total energy is increasing.
D. Organisms can make their own energy.
E. Energy in chemical bonds never changes.

A. Energy transformations increase entropy.

2. The second law of thermodynamics states that:

A. Energy transformations increase entropy.
B. Energy can be perfectly conserved.
C. Living organisms can avoid disorder.
D. Heat energy is completely usable.
E. Energy cannot change form.

D. Covalent bonds in a molecule

3. Which of the following is not a form of kinetic energy?

A. Atoms diffusing across a membrane
B. Electrical current through a wire
C. Sunlight traveling through space
D. Covalent bonds in a molecule
E. Flowing water

C. It has a ΔG of +7.3 kcal/mol.

4. Which of the following is not true about ATP hydrolysis?

A. The phosphate bonds are high energy.
B. It releases large amounts of free energy.
C. It has a ΔG of +7.3 kcal/mol.
D. The phosphate bonds are unstable.
E. ATP hydrolysis powers many reactions.

C. Chemical bonds represent potential energy.

5. Which statement about energy types is correct?

A. Kinetic energy is stored energy.
B. Potential energy is energy of motion.
C. Chemical bonds represent potential energy.
D. Entropy is a type of kinetic energy.
E. Energy cannot change forms.

D. Organisms can decrease entropy in the universe.

6. Which of the following is false?

A. Kinetic energy is energy of motion.
B. Chemical bonds contain potential energy.
C. Energy is the capacity to do work.
D. Organisms can decrease entropy in the universe.
E. Free energy drives biological work.

C. Free energy (ΔG)

7. Which term represents usable energy available to do work?

A. Entropy B. Enthalpy C. Free energy (ΔG) D. Heat E. Potential energy

C. The disorder or randomness of energy.

8. Entropy refers to:

A. Total energy of a system.
B. Energy lost as heat.
C. The disorder or randomness of energy.
D. Energy stored in bonds.
E. Kinetic energy from movement.

B. Life requires constant energy input to maintain order.

9. How does the second law apply to organisms?

A. Living cells do not follow it.
B. Life requires constant energy input to maintain order.
C. Organisms reverse entropy naturally.
D. It prevents photosynthesis.
E. It causes ATP to spontaneously form.

B. ΔG = ΔH - TΔS

10. The relationship between free energy, enthalpy, and entropy is shown by:

A. ΔG = ΔH + TΔS
B. ΔG = ΔH - TΔS
C. ΔG = ΔS - TΔH
D. ΔG = ΔH × TΔS
E. ΔG = ΔS / TΔH

B. ΔG is negative and energy is released.

11. In an exergonic reaction:

A. ΔG is positive and energy is absorbed.
B. ΔG is negative and energy is released.
C. Products contain more energy than reactants.
D. The reaction requires constant ATP input.
E. It can never occur spontaneously.

C. Are endergonic and require ATP.

12. Anabolic reactions (building molecules):

A. Are exergonic.
B. Release energy.
C. Are endergonic and require ATP.
D. Decrease potential energy.
E. Occur spontaneously.

C. Release energy (exergonic).

13. Catabolic reactions (breaking molecules):

A. Are endergonic.
B. Require ATP input.
C. Release energy (exergonic).
D. Always form proteins.
E. Have a positive ΔG.

E. All of the above

14. Which of the following represents a form of potential energy?

A. Chemical bonds
B. Concentration gradients
C. Electric charge imbalances
D. Both A and B
E. All of the above

B. Exergonic

15. The hydrolysis of ATP is:

A. Endergonic B. Exergonic C. Nuclear D. Photosynthetic E. Unfavorable

B. –7.3 kcal/mol

16. ATP + H₂O → ADP + Pi + energy has a ΔG of:

A. +7.3 kcal/mol B. –7.3 kcal/mol C. 0 kcal/mol D. +14.6 kcal/mol E. –14.6 kcal/mol

C. It hydrolyzes quickly and cannot be stored.

17. ATP is not suitable for long-term energy storage because:

A. It contains weak bonds.
B. It is too stable.
C. It hydrolyzes quickly and cannot be stored.
D. It contains little free energy.
E. It cannot be regenerated.

A. Has two phosphate groups.

18. ADP differs from ATP because it:

A. Has two phosphate groups.
B. Contains more energy.
C. Is produced by endergonic reactions.
D. Cannot be phosphorylated.
E. Contains three phosphate groups.

B. ATP hydrolysis drives an endergonic reaction.

19. In coupled reactions:

A. Both reactions are exergonic.
B. ATP hydrolysis drives an endergonic reaction.
C. Energy is transferred from heat to work.
D. Both reactions require energy input.
E. ΔG is always positive.

B. Potential energy

20. The chemical energy stored in glucose is an example of:

A. Kinetic energy
B. Potential energy
C. Thermal energy
D. Mechanical energy
E. Electrical energy

B. To lower activation energy

1. What is the main function of an enzyme in a chemical reaction?

A. To increase activation energy
B. To lower activation energy
C. To increase ΔG
D. To provide energy to the system
E. To change the products of the reaction

D. Type of buffer used in lab

2. Which of the following does not affect enzyme activity?

A. Temperature
B. pH
C. Substrate concentration
D. Type of buffer used in lab
E. Cofactor presence

C. Lowering activation energy barrier

3. Enzymes speed up reactions by:

A. Adding heat to the system
B. Providing free energy
C. Lowering activation energy barrier
D. Making endergonic reactions exergonic
E. Breaking substrates directly

B. Active site

4. The substrate binds to the enzyme at the:

A. Regulatory site
B. Active site
C. Allosteric site
D. Binding pocket
E. Cofactor domain

B. Induced fit model

5. The model where the enzyme changes shape slightly after substrate binding is called:

A. Lock-and-key model
B. Induced fit model
C. Transition model
D. Activation model
E. Regulatory fit

B. A nonprotein molecule (like metal ions) required for enzyme activity

6. Which of the following best describes a cofactor?

A. A protein required to complete enzyme folding
B. A nonprotein molecule (like metal ions) required for enzyme activity
C. A small peptide that inhibits enzymes
D. A carbohydrate that binds to substrates
E. A lipid that transports enzymes

B. Is an organic molecule (like NAD⁺ or FAD)

7. A coenzyme differs from a cofactor because it:

A. Is made of metal ions
B. Is an organic molecule (like NAD⁺ or FAD)
C. Is permanently bound to the enzyme
D. Functions only at high temperatures
E. Acts only as an inhibitor

B. They can be catabolic or anabolic sequences of enzyme-catalyzed steps.

8. Which of the following statements about metabolic pathways is correct?

A. They consist of a single enzyme reaction.
B. They can be catabolic or anabolic sequences of enzyme-catalyzed steps.
C. They require DNA to proceed.
D. They are not regulated.
E. They occur only in mitochondria.

B. Break down molecules and release energy.

9. Catabolic pathways:

A. Build molecules and require energy.
B. Break down molecules and release energy.
C. Use ATP to drive biosynthesis.
D. Are always endergonic.
E. Increase molecular complexity.

B. Build larger molecules and require ATP.

10. Anabolic pathways:

A. Break down glucose into pyruvate.
B. Build larger molecules and require ATP.
C. Are spontaneous and exergonic.
D. Occur only in plants.
E. Involve fermentation.

B. A product binds to an enzyme and slows or stops its activity.

11. Feedback inhibition occurs when:

A. A product activates an earlier enzyme in the pathway.
B. A product binds to an enzyme and slows or stops its activity.
C. ATP enhances enzyme activity.
D. Substrate concentration increases enzyme activity.
E. An inhibitor competes with the substrate.

A. The active site

12. A competitive inhibitor binds to:

A. The active site
B. The allosteric site
C. A cofactor
D. The product molecule
E. The regulatory enzyme

B. A separate site and changes enzyme conformation

13. A noncompetitive inhibitor binds to:

A. The active site
B. A separate site and changes enzyme conformation
C. The substrate directly
D. The product molecule
E. The coenzyme

B. A separate regulatory site that can activate or inhibit the enzyme

14. An allosteric enzyme has:

A. One active site only
B. A separate regulatory site that can activate or inhibit the enzyme
C. No regulatory control
D. Only one substrate
E. Permanent inhibition

B. R (relaxed) state

15. The active form of an enzyme stabilized by an allosteric activator is known as the:

A. T (tense) state
B. R (relaxed) state
C. Z state
D. M state
E. Transition state

C. ATP

16. Which molecule is the universal energy currency of cells?

A. NADH
B. Glucose
C. ATP
D. Pyruvate
E. FADH₂

B. Cytoplasm

17. Glycolysis takes place in the:

A. Mitochondrial matrix
B. Cytoplasm
C. Nucleus
D. Inner mitochondrial membrane
E. Peroxisome

A. 2 ATP, 2 NADH, and 2 pyruvate

18. The end products of glycolysis are:

A. 2 ATP, 2 NADH, and 2 pyruvate
B. 4 ATP, 4 NADH, and 4 pyruvate
C. 2 CO₂ and 2 H₂O
D. Glucose and NAD⁺
E. Acetyl-CoA and FADH₂

B. 2 ATP

19. Glycolysis requires an initial investment of:

A. 1 ATP
B. 2 ATP
C. 3 ATP
D. 4 ATP
E. None

B. 2 ATP

20. The net gain of ATP from glycolysis is:

A. 1 ATP
B. 2 ATP
C. 3 ATP
D. 4 ATP
E. 6 ATP