Enlighten Knowledge Sample Biology Questions and Answers For 2024 WAECE Candidates (set 1)


Enlighten Knowledge Sample Biology Questions and Answers For 2024 WAECE Candidates (set 1)

1. Anton van Leeuwenhoek made an important contribution to the development of the cell theory. How?

  • He articulated the pattern component of the theory that all organisms are made of cells.
  • He articulated the process component of the theory that all cells come from pre-existing.
  • He invented the first microscope and saw the first cell.
  • He invented more powerful microscopes and was the first to describe the diversity of cells.

2. Suppose that a proponent of the spontaneous generation hypothesis claimed that cells would appear in Pasteur’s swan-necked flask eventually. According to this view, Pasteur did not allow enough time to pass before concluding that life does not originate spontaneously. Which of the following is the best response?

  • The spontaneous generation proponent is correct: Spontaneous generation would probably happen eventually.
  • Both the all-cells-from-cells hypothesis and the spontaneous generation hypothesis could be correct.
  • If spontaneous generation happens only rarely, it is not important.
  • If spontaneous generation did not occur after weeks or months, it is not reasonable to claim that it would occur later.

3. What does the term evolution mean?

  • The strongest individuals produce the most offspring.
  • The characteristics of an individual change through the course of its life, in response to natural selection.
  • The characteristics of populations change through time.
  • The characteristics of species become more complex over time.

4. What does it mean to say that a characteristic of an organism is heritable?

  • The characteristic evolves.
  • The characteristic can be passed on to offspring.
  • The characteristic is advantageous to the organism.
  • The characteristic does not vary in the population.

5. In biology, what does the term fitness mean?

  • how well trained and muscular an individual is, relative to others in the same population
  • how slim an individual is, relative to others in the same population
  • how long a particular individual lives
  • the ability to survive and reproduce

6. Could both the food competition hypothesis and the sexual selection hypothesis explain why giraffes have long necks? Why or why not?

  • In science, only one hypothesis can be correct.
  • Observations have shown that the food competition hypothesis cannot be correct.
  • Long necks could be advantageous for more than one reason.
  • Al giraffes have been shown to feed at the highest possible height and fight for mates.

7. Which of the following occurs when a covalent bond forms?

  • The potential energy of electrons drops.
  • Electrons in valence shells are shared between nuclei.
  • lons of opposite charge interact.
  • Polar molecules interact.

8. If a reaction is exothermic, then which of the following statements is true?

  • The products have lower potential energy than the reactants.
  • Energy must be added for the reaction to proceed.
  • The products have higher entropy (are more disordered) than the reactants.
  • It occurs extremely quickly.

9. What is thermal energy?

  • a form of potential energy
  • the temperature increase that occurs when any form of energy is added to a system
  • mechanical energy
  • the kinetic energy of molecular motion, measured as heat

10. What determines whether a chemical reaction is spontaneous?

  • if it increases the disorder, or entropy, of the substances involved
  • if it decreases the potential energy of the substances involved
  • the temperature only-reactions are spontaneous at high temperatures and nonspontaneous at low temperatures
  • The combined effect of changes in potential energy and entropy

11. What two functional groups are present on every amino acid?

  • a carbonyl group and a carboxyl group
  • an amino group and a carbonyl group
  • an amino group and a hydroxyl group
  • an amino group and a carboxyl group

12. Twenty different amino acids are found in the proteins of cells. What distinguishes these molecules?

  • the location of their carboxyl group
  • the location of their amino group
  • the composition of their side chains, or R-groups
  • their ability to form peptide bonds

13. What determines the primary structure of a polypeptide?

  • its sequence of amino acids
  • hydrogen bonds that form between carboxyl and amino groups on different residues
  • hydrogen bonds and other interactions between side chains
  • the number, identity, and arrangement of polypeptides that make up a protein

14. In a polypeptide, what is most responsible for the secondary structure called an a-helix?

  • the sequence of amino acids
  • hydrogen bonds that form between carboxyl and amino groups on different residues
  • hydrogen bonds and other interactions between side chains
  • the number, identity, and arrangement of polypeptides that make up a protein

15. What is a transition state?

  • the complex formed as covalent bonds are being broken and reformed during a reaction
  • the place where regulatory molecules bind to an enzyme
  • a reactant with high potential energy created by phosphorylation
  • the shape adopted by an enzyme that has an inhibitory molecule bound at its active site

16. By convention, biologists write the sequence of amino acids in a polypeptide in which direction?

  • carboxy- to amino-terminus
  • amino- to carboxy-terminus
  • polar residues to nonpolar residues
  • charged residues to uncharged residues

17. What are the four nitrogenous bases found in RNA?

  • uracil, guanine, cytosine, thymine (U, G, C, T)
  • adenine, guanine, cytosine, thymine (A, G, C, T)
  • adenine, uracil, guanine, cytosine (A, U, G, C)
  • alanine, threonine, glycine, cysteine (A, T, G, C)

18. What determines the primary structure of an RNA molecule?

  • the sugar-phosphate backbone
  • complementary base pairing and the formation of hairpins
  • the sequence of deoxyribonucleotides
  • the sequence of ribonucleotides

19. DNA attains a secondary structure when hydrogen bonds form between the nitrogenous bases called purines and pyrimidines. What are the complementary base pairs that form in DNA?

  • A-T and G-C
  • A-U and G-C
  • A-G and T-C
  • A-C and T-G

20. In RNA, when does the secondary structure be called a hairpin form?

  • when hydrophobic residues coalesce
  • when hydrophilic residues interact with water
  • when complementary base pairing between ribonucleotides on the same strand creates a stem-and-loop structure
  • When complementary base pairing forms a double helix arrangement.

21. The secondary structure of DNA is called a double helix. Why?

  • Two strands wind around one another in a helical or spiral,
  • It is shaped like a ladder.
  • A single strand winds around itself in a helical or spiral, arrangement.
  • It stabilizes the molecule.

22. What is the difference between a monosaccharide, a disaccharide, and a polysaccharide?

  • the number of carbon atoms in the molecule
  • the type of glycosidic linkage between monomers
  • the spatial arrangement of the various hydroxyl residues in the molecule
  • the number of monomers in the molecule

23. What type of bond allows sugars to polymerize?

  • glycosidic linkage
  • phosphodiester bond
  • peptide bond
  • hydrogen bonds

24. What holds cellulose molecules together in bundles large enough to form fibres?

  • the cell walls
  • peptide bonds
  • hydrogen bonds
  • hydrophobic interactions between different residues in the cellulose helix

25. What are the primary functions of carbohydrates in cells?

  • energy storage, cell identity, structure, and building blocks for synthesis
  • catalysis, structure, and transport
  • information storage and catalysis
  • signal reception, signal transport, and signal response

26. Why is it unlikely that carbohydrates played a large role in the origin of life?

  • They cannot be produced by chemical evolution.
  • They have optical isomers.
  • More types of glycosidic linkages are possible than are observed in organisms.
  • They do not polymerize without the aid of enzymes.

27. What is a “quick and dirty” way to assess how much free energy an organic molecule has?

  • Count the number of oxygen atoms it contains.
  • Count the number of hydrogen atoms it contains.
  • Determine whether it contains an amino group.
  • Determine whether it contains a carbonyl group.

28. What does the term hydrophilic mean when it is translated literally?

  • “Oil loving
  • “Water-loving”
  • “Oil fearing”
  • “Water fearing”

29. If a solution surrounding a cell is hypotonic relative to the inside of the cell, how will water move?

  • It will move into the cell via osmosis.
  • It will move out of the cell via osmosis.
  • It will not move, because equilibrium exists.
  • It will evaporate from the cell surface more rapidly.

30. If a solution surrounding a cell is hypertonic relative to the inside of the cell, how will water move?

  • It will move into the cell via osmosis.
  • It will move out of the cell via osmosis.
  • It will not move, because equilibrium exists.
  • It will evaporate from the cell surface more rapidly.

31. When does a concentration gradient exist?

  • when the membranes rupture
  • when solute concentrations are high
  • when solute concentrations are low
  • when solute concentrations differ on the two sides of a membrane

32. Which of the following must be true for osmosis to occur?

  • Water must be at room temperature or above.
  • Solutions with the same concentration of solutes must be separated by a selectively permeable membrane.
  • Solutions with different concentrations of solutes must be separated by a selectively permeable membrane.
  • Water must be under pressure.

33. Why are the lipid bilayers in cells called “selectively permeable”?

  • They are not all that permeable.
  • Their permeability changes with their molecular composition.
  • Their permeability is temperature dependent.
  • They are permeable to some substances but not others.

34. Which of the following best describes the nuclear envelope?

  • It is continuous with the endomembrane system.
  • It is continuous with the nucleolus.
  • It is continuous with the plasma membrane.
  • It contains a single membrane and nuclear pores.

35. What is a nuclear localization signal?

  • a stretch of amino acids that directs proteins from the nucleus to the ER
  • A molecule that is attached to nuclear proteins so that they are retained inside the nucleus
  • a signal built into a protein that directs it to the nucleus
  • a component of the nuclear pore complex

36. Which of the following is not true of secreted proteins?

  • They are synthesized in ribosomes.
  • They are transported through the endomembrane system in membrane-bound transport organelles.
  • They are transported from the Golgi apparatus to the ER.
  • They contain a signal sequence that directs them into the ER.

37. To find the nuclear localization signal in the protein nucleoplasmin, researchers separated the molecule’s core and tail segments, labelled both with a radioactive atom, and injected them into the cytoplasm. Why did the researchers conclude that the signal is in the tail region of the protein?

  • The protein reassembled and folded into its normal shape spontaneously.
  • Only the tail segments appeared in the nucleus.
  • With a confocal microscope, tail segments were visible in the nucleus.
  • The tail and head segments appeared together in the nucleus.

38. Molecular zip codes direct molecules to particular destinations in the cell. How are these signals read?

  • They bind to receptor proteins.
  • They enter transport vesicles.
  • They bind to motor proteins.
  • They are glycosylated by enzymes in the Golgi apparatus.

39. The number and size of organelles in a cell correlate with that cell’s function. Propose a function for cells that contain extensive rough ER.

  • rapid cell division in growing bones or muscle tissues
  • production and processing of fatty acids and other lipids
  • movement via cell crawling
  • production of proteins that are secreted from the cell

40. Which of the following represents a fundamental difference between the fibres found in the extracellular layers of plants and those of animals?

  • Plant fibres are thicker; they are also stronger because they have more cross-linkages.
  • Animal fibres consist of proteins; plant fibres consist of polysaccharides instead.
  • Plant extracellular fibres never move; animal fibres can slide past one another.
  • Cellulose microfibrils run parallel to each other; collagen filaments crisscross.

41. In plants and animals, where are most components of the extracellular material synthesized?

  • smooth ER
  • the rough ER and Golgi apparatus
  • in the extracellular layer itself
  • adjacent cells

42. Treating dissociated cells with certain antibodies makes the cells unable to reaggregate. Why?

  • The antibodies bind to cell adhesion proteins called cadherins.
  • The antibodies bind to the fibre component of the extracellular matrix.
  • The antibodies bind to receptors on the cell surface.
  • The antibodies act as enzymes that break down desmosomes.

43. What does it mean to say that a signal is transduced?

  • The signal enters the cell directly and binds to a receptor inside.
  • The physical form of the signal changes between the outside of the cell and the inside.
  • The signal is amplified, such that even a single molecule evokes a large response.
  • The signal triggers a sequence of phosphorylation events inside the cell.

45. Why are tight junctions found in only certain types of tissues, while desmosomes are found in a wide array of cells?

  • Tight junctions are required only in cells where communication between adjacent cells is particularly important.
  • Tight junctions are not as strong as desmosomes.
  • Tight junctions have different structures but the same functions.
  • Tight junctions are found only in epithelial cells that must be watertight.

46. What physical event represents the receipt of an intercellular signal?

  • the passage of ions through a desmosome
  • the activation of the first protein in a phosphorylation cascade
  • the binding of a hormone to a signal receptor, which changes a conformation in response
  • the activation of a G protein associated with a signal receptor

46. When does feedback inhibition occur?

  • when lack of an appropriate electron acceptor makes an electron transport chain stop
  • When an enzyme that is active early in a metabolic pathway is inhibited by a product of the pathway
  • when ATP synthase reverses and begins pumping protons out of the mitochondrial matrix
  • when cellular respiration is inhibited and fermentation begins

47. Where does the Krebs cycle occur in eukaryotes?

  • in the cytoplasm
  • in the matrix of mitochondria
  • in the inner membrane of mitochondria
  • in the intermembrane space of mitochondria

48. What does the chemiosmotic hypothesis claim?

  • Substrate-level phosphorylation occurs in the electron transport chain.
  • Substrate-level phosphorylation occurs in glycolysis and the Krebs cycle.
  • The electron transport chain is located in the inner membrane of mitochondria.
  • Electron transport chains generate ATP indirectly, by the creation of a proton-motive force.

49. What is the function of the reactions in a fermentation pathway?

  • to generate NADH from NAD, so electrons can be donated to the electron transport chain
  • to synthesize pyruvate from lactate
  • to generate NAD* from NADH, so glycolysis can continue
  • to synthesize electron acceptors, so that cellular respiration can continue

50. When do cells switch from cellular respiration to fermentation?

  • when electron acceptors are not available
  • when the proton-motive force runs down
  • when NADH and FADH, supplies are low
  • when pyruvate is not available

51. Why are NADH and FADH, said to have “reducing power?”

  • They are the reduced forms of NAD and FAD.
  • They donate electrons to components of the ETC, reducing those components.
  • They travel between the cytoplasm and the mitochondrion.
  • They have the power to reduce carbon dioxide to glucose.

52. What is the stroma of a chloroplast?

  • the inner membrane
  • the pieces of membrane that connect grana
  • the interior of a thylakoid
  • the fluid inside the chloroplast but outside the thylakoids

53. Why is chlorophyll green?

  • It absorbs all wavelengths in the visible spectrum, transmitting ultraviolet and infrared light.
  • It absorbs wavelengths only in the red and far-red portions of the spectrum (680 nm, 700 nm).
  • It absorbs wavelengths in the blue and red parts of the visible spectrum and transmits wavelengths in the green part.
  • It absorbs wavelengths only in the blue part of the visible spectrum and transmits all other wavelengths.

54. What does it mean to say that CO2, becomes fixed?

  • It becomes bonded to an organic compound.
  • It is released during cellular respiration.
  • It acts as an electron acceptor.
  • It acts as an electron donor.

55. What do the light-dependent reactions of photosynthesis produce?

  • RuBP
  • G3P
  • ATP and NADPH
  • plastoquinone

56. Why do the absorption spectrum for chlorophyll and the action spectrum for photosynthesis coincide?

  • Photosystems I and II are activated by different wavelengths of light.
  • Wavelengths of light that are absorbed by chlorophyll trigger light-dependent reactions.
  • Energy from wavelengths absorbed by carotenoids is passed onto chlorophyll.
  • The rate of photosynthesis depends on the amount of light received.

57. What happens when an excited electron is passed to an electron acceptor n a photosystem?

  • It drops back down to its ground state, resulting in the phenomenon known as fluorescence.
  • The chemical energy in the excited electron is released as heat.
  • The electron acceptor is oxidized.
  • Energy in sunlight is transformed to chemical energy.


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