114年 - 114 台灣聯合大學系統_碩士班招生考試試題_化學類：生物化學#126447

1. Which carbohydrate polymer is the primary component of fungal cell walls? (A) Amylopectin (B) Glycogen (C) Chitin (D) Cellulose (E) Starch

2. Which interaction is unique to stabilizing quaternary protein structures? (A) Hydrogen bonds (B) Ionic bonds (C) Covalent bonds (D) Inter-subunit bonding (E) Peptide bonds

3. Which type of lipid is primarily involved in energy storage within cells? (A) Steroids (B) Glycolipids (C) Phospholipids (D) Sphingolipids (E) Triglycerides

4. What is the primary role of enzymes in biochemical reactions? (A) Stabilize products (B) Lower activation energy (C) Alter free energy (D) Change equilibrium (E) Consume reactants

5. Which characteristic distinguishes amphipathic lipids? (A) Possess both hydrophobic and hydrophilic regions (B) Only hydrophilic (C) Only hydrophobic (D) Contain glycerol backbones (E) Lack double bonds

6. Which is an example of a zero-order reaction in enzyme kinetics? (A) Enzyme saturation at high [S] (B) Allosteric effects on enzyme (C) When substrate concentration is low (D) Competitive inhibition (E) Inhibitor binding reduces [S]

7. Which of the following is an irreversible form of enzyme inhibition? (A) Noncompetitive (B) Covalent modification (C) Uncompetitive (D) Competitive (E) Allosteric

8. What is the effect of increasing substrate concentration on enzyme activity in competitive inhibition? (A) Overcomes inhibition (B) Enhances substrate binding (C) Reduces inhibitor binding (D) Reduces Vmax (E) Increases Km

9. Which glycosidic bond is typically found between two glucose molecules in maltose? (A) Alpha-1,2 (B) Beta-1,6 (C) Beta-1,4 (D) Alpha-1,6 (E) Alpha-1,4

10. What role do disulfide bonds play in proteins? (A) Maintain primary sequence (B) Increase hydrophilicity (C) Stabilize tertiary and quaternary structures (D) Enhance ionic interactions (E) Provide flexibility

11. Which factor is primarily responsible for enzyme specificity? (A) Temperature (B) Enzyme concentration (C) Coenzyme availability (D) pH (E) Active site structure

12. The side chain of which amino acid contains a guanidinium group? (A) Histidine (B) Glutamate (C) Arginine (D) Lysine (E) Cysteine

13. What is the main interaction stabilizing alpha-helices in proteins? (A) Covalent bonds (B) Hydrophobic effects (C) Ionic interactions (D) Van der Waals forces (E) Hydrogen bonds

14. The amino acid whose derivative is used in the urea cycle is: (A) Aspartate (B) Glutamate (C) Cysteine (D) Arginine (E) Serine

15. Which lipid derivative is a precursor to prostaglandins? (A) Phosphatidylcholine (B) Carotenoids (C) Sphingomyelin (D) Arachidonic acid (E) Cholesterol 頁 4

16. Which enzyme catalyzes the conversion of glucose-1-phosphate to UDP-glucose? (A) Hexokinase (B) Glycogen synthase (C) Glucokinase (D) UDP-glucose pyrophosphorylase (E) Phosphoglucomutase

17. Which test specifically detects starch in biological samples? (A) Tollen's test (B) Sudan III test (C) Iodine test (D) Benedict's test (E) Biuret test

18. What distinguishes lipids from carbohydrates in terms of energy density? (A) Lipids are less soluble in water (B) Lipids have higher oxidation potential (C) Lipids store energy more efficiently (D) Carbohydrates are more compact (E) Lipids store less energy per unit

19. What is the significance of the glycosidic bond in carbohydrate polymers? (A) Links monosaccharides in polysaccharides (B) Determines polymer solubility (C) Creates free aldehyde groups (D) Facilitates DNA synthesis (E) Prevents water absorption

20. Why are triglycerides considered a better energy storage form than carbohydrates? (A) They are hydrophilic (B) They store more energy per gram (C) They are water-soluble (D) They enhance oxygen utilization (E) They are rapidly metabolized

21. Acetyl-CoA plays a crucial role in the cellular metabolism. Which of the following best describes the primary function of acetyl-CoA? (A) To directly participate in the electron transport chain as an electron carrier. (B) To serve as a precursor for the synthesis of fatty acids, ketone bodies, and cholesterol. (C) To act as a structural component of the mitochondrial inner membrane. (D) To regulate gene expression by binding to specific DNA sequences. (E) To catalyze the hydrolysis of ATP for energy production.

22. Within the citric acid cycle (Krebs cycle), what is the direct role of acetyl-CoA? (A) It acts as the final electron acceptor in the electron transport chain. (B) It directly catalyzes ATP formation via substrate-level phosphorylation. (C) It serves as the initial substrate that combines with oxaloacetate to initiate the citric acid cycle. (D) It regulates the activity of key enzymes within the citric acid cycle through allosteric modulation. (E) It transports protons across the inner mitochondrial membrane to generate the proton motive force.

23. What is the role of acetyl-CoA in glycolysis? (A) It is the final product of glycolysis, directly yielding ATP. (B) It directly participates in the phosphorylation of glucose to glucose-6-phosphate. (C) It is a crucial intermediate formed during the conversion of glucose to pyruvate. (D) It directly reduces NAD+ to NADH through the glycolytic pathway. (E) It is not directly involved in glycolysis itself but links glycolysis to the citric acid cycle.

24. What is the primary function of glycolysis? (A) To synthesize glucose from non-carbohydrate precursors. (B) To completely oxidize glucose to carbon dioxide and water. (C) To convert glucose into pyruvate, generating ATP and NADH. (D) To produce fatty acids from acetyl-CoA. (E) To synthesize proteins from amino acids. 頁 6

25. Cancer cells often exhibit an increased rate of glycolysis, even in the presence of oxygen (a phenomenon known as the Warburg effect). How does this enhanced glycolysis contribute to the ability of cancer cells to thrive? (A) It produces metabolic intermediates that are used for the biosynthesis of macromolecules that are required for cell growth and proliferation. (B) It generates excess oxygen, counteracting the hypoxic conditions often found in tumors. (C) It directly provides the large amounts of ATP required for rapid cell division. (D) It prevents the accumulation of reactive oxygen species (ROS), protecting cancer cells from oxidative damage. (E) It increases the efficiency of oxidative phosphorylation in the mitochondria.

26. Cancer tissue microenvironments are often observed to be more acidic than normal tissues. Which of the following is the primary reason for this acidification? (A) Decreased blood flow to the tumor leading to reduced oxygen delivery and accumulation of carbon dioxide. (B) Increased activity of the electron transport chain in cancer cells, leading to increased production of protons. (C) Enhanced oxidative phosphorylation in cancer cell mitochondria, consuming bicarbonate buffers. (D) Increased rate of glycolysis in cancer cells, leading to increased production of lactic acid and protons. (E) Reduced activity of proton pumps on the cell membrane of cancer cells, inhibiting proton export.

27. What is the fundamental relationship between phosphorylation and ATP (adenosine triphosphate)? (A) Phosphorylation is the process of hydrolyzing ATP to release energy. (B) Phosphorylation is the process of adding a phosphate group to a molecule, often using ATP as the phosphate donor. (C) Phosphorylation is the process of synthesizing ATP from ADP and inorganic phosphate using energy released from other reactions. (D) Both B and C. (E) Phosphorylation is the process of removing a phosphate group from a molecule, releasing energy in the form of ATP.

28. What is the crucial role of ATP in active transport? (A) ATP hydrolysis provides the energy required to move substances against their concentration gradient. (B) ATP provides the energy required to move substances down their concentration gradient. (C) ATP acts as a structural component of transport proteins, facilitating their movement within the membrane. (D) ATP binds directly to the transported substance, altering its chemical properties to facilitate its passage across the membrane. (E) ATP regulates the fluidity of the cell membrane, allowing for easier diffusion of substances.

29. While other nucleoside triphosphates (NTPs), such as TTP, CTP, and GTP exist within cells, ATP is the primary energy currency. Which of the following explains why ATP is favored in this role? (A) ATP has a unique chemical structure that allows it to store significantly more energy per phosphate bond than other NTPs do. (B) ATP is the most abundant NTP in cells, making it readily available for energy-intensive processes. (C) ATP hydrolysis releases an optimal amount of energy that is sufficient to drive most cellular reactions, but not so much that energy is wasted as heat. (D) ATP is the only NTP that can be readily synthesized from ADP through both substrate-level and oxidative phosphorylation. (E) ATP has a higher affinity for energy-coupling enzymes than other NTPs, making it a more efficient energy donor.

30. GTP is preferentially used over ATP during protein synthesis (translation) at several key steps. Which of the following factors best explains this preference? (A) GTP hydrolysis releases more energy per phosphate bond than ATP hydrolysis, making it more suitable for the energy-intensive process of translation. (B) GTP is more readily available in the ribosome environment than ATP, due to its higher concentration in the cytoplasm. (C) GTP has a unique chemical structure that allows it to form stronger interactions with ribosomal RNA (rRNA) than ATP. (D) The use of GTP in translation prevents interference with other cellular processes that rely on ATP as their primary energy source. (E) GTP hydrolysis is coupled with conformational changes in translation factors and the ribosome, providing precise timing and control of the translation process.

31. During the process of protein synthesis (translation), various types of RNA molecules play distinct and essential roles. Which of the following best describes the function of transfer RNA (tRNA) in this process? (A) It serves as the template carrying the genetic code from DNA to the ribosomes. (B) It forms the structural and catalytic core of the ribosomes, facilitating peptide bond formation. (C) It regulates gene expression by binding to messenger RNA (mRNA) and inhibiting translation. (D) It carries specific amino acids to the ribosome and matches them to the corresponding codons on the mRNA. (E) It is a precursor molecule that is processed into mature messenger RNA (mRNA) by removing introns.

32. Lipids and amino acids serve as important sources of energy for the human body. Which of the following best describes how these molecules are utilized to generate ATP? (A) Lipids are primarily broken down through β-oxidation to generate acetyl-CoA, which enters the citric acid cycle. Amino acids, after deamination, can be converted to intermediates of the citric acid cycle or glycolysis. (B) Lipids are directly converted into glucose through gluconeogenesis, which then enters glycolysis. Amino acids are directly incorporated into proteins for structural purposes, with minimal contribution to ATP production. (C) Lipids are stored as glycogen in the liver and muscles, and are readily converted to glucose for immediate energy needs. Amino acids are primarily used for neurotransmitter synthesis and do not contribute significantly to ATP production. (D) Lipids are broken down through fermentation in the cytoplasm, producing small amounts of ATP. Amino acids are converted to fatty acids and stored as triglycerides for long-term energy storage. (E) Lipids are directly transported into the mitochondria to undergo oxidative phosphorylation. Amino acids are converted to ketone bodies in the liver and used as an alternative fuel source for the brain.

33. Cholesterol plays a crucial role in maintaining the fluidity and stability of cell membranes. Which of the following best describes how cholesterol contributes to membrane stability under varying temperature conditions? (A) Cholesterol forms strong covalent bonds with phospholipids, rigidifying the membrane at all temperatures. (B) Cholesterol intercalates between phospholipids, preventing them from packing too tightly at low temperatures and preventing excessive fluidity at high temperatures. (C) Cholesterol increases the hydrophobicity of the membrane, reducing water permeability and stabilizing the bilayer. (D) Cholesterol interacts with membrane proteins, anchoring them to the membrane and preventing lateral movement. (E) Cholesterol directly regulates the activity of membrane transport proteins, influencing the movement of ions and molecules across the membrane.

34. Cell membrane fluidity is essential for various cellular processes, including cell division (mitosis). Which of the following best describes the role of membrane fluidity in mitosis? (A) Membrane fluidity is crucial for the condensation of chromosomes during prophase. (B) Membrane fluidity facilitates the attachment of spindle fibers to the kinetochores. (C) Membrane fluidity allows for the dynamic remodeling of the cell membrane during cytokinesis. (D) Membrane fluidity is necessary for the proper functioning of the nuclear pores during mitosis. (E) Membrane fluidity prevents the formation of membrane blebs during cell rounding in prophase.

35. Hemoglobin is a protein responsible for oxygen transport in the blood. Which of the following best describes the role of the metal ion in hemoglobin's function? (A) The metal ion provides structural stability to the protein by forming disulfide bonds between different subunits. (B) The metal ion acts as a cofactor, directly catalyzing the binding of oxygen to the protein. (C) The metal ion directly binds oxygen, facilitating its transport from the lungs to the tissues. (D) The metal ion regulates the pH of the blood, indirectly influencing oxygen binding to hemoglobin. (E) The metal ion is involved in the synthesis of heme, a prosthetic group essential for hemoglobin function.

36. As discussed, hemoglobin is crucial for oxygen transport. Which specific metal ion is directly bound by the heme group within hemoglobin, enabling oxygen binding? (A) Magnesium (Mg2+) (B) Zinc (Zn2+) (C) Copper (Cu2+) (D) Iron (Fe2+) (E) Calcium (Ca2+)

37. As previously discussed, a specific metal ion is essential for hemoglobin's oxygen-carrying capacity. If there is a deficiency of this metal ion, which of the following conditions is most likely to result? (A) Decreased oxygen transport in the blood, leading to fatigue and tissue hypoxia. (B) Impaired blood clotting due to a deficiency in coagulation factors. (C) Reduced bone density and increased risk of osteoporosis. (D) Impaired nerve impulse transmission and muscle weakness. (E) Reduced immune function and increased susceptibility to infections.

38. Myelin sheaths play a crucial role in accelerating nerve impulse transmission. Which of the following best describes the composition, structure, and mechanism by which myelin sheaths enhance the speed of nerve impulse conduction? (A) Myelin sheaths are composed of collagen fibers that provide structural support to nerve axons, increasing their diameter and thus conduction speed. (B) Myelin sheaths are composed of lipids and proteins produced by Schwann cells (in the peripheral nervous system) or oligodendrocytes (in the central nervous system), forming an insulating layer that enables saltatory conduction. (C) Myelin sheaths are formed by glial cells wrapping around nerve axons, creating an insulating layer that allows for continuous conduction of action potentials. (D) Myelin sheaths are made of tightly packed microtubules that facilitate the rapid transport of ions along the axon, increasing the speed of action potential propagation. (E) Myelin sheaths are formed by a network of interconnected gap junctions between adjacent neurons, allowing for direct electrical transmission of signals and bypassing the need for chemical synapses.

39. Exosomes are extracellular vesicles involved in intercellular communication. Which of the following best describes the structure and biochemical functions of the exosomes? (A) Exosomes are membrane-bound organelles within the cytoplasm that synthesize proteins and lipids for cellular export. (B) Exosomes are large, multilayered vesicles formed by the fusion of multiple cells, facilitating the direct exchange of cytoplasmic contents. (C) Exosomes are small membrane-bound vesicles that originate from the endosomal pathway and carry various biomolecules for intercellular signaling. (D) Exosomes are fragments of the cell membrane that are shed during apoptosis and contain primarily degraded cellular components. (E) Exosomes are specialized structures composed of nucleic acids and proteins that directly transfer genetic material between cells via membrane fusion.

40. Oxytocin is a hormone involved in various physiological processes including uterine contractions during childbirth and milk ejection during lactation. Which of the following best describes the feedback mechanism that regulates oxytocin release during childbirth? (A) Oxytocin release is regulated by a negative feedback loop; as oxytocin levels rise, they inhibit the release of prostaglandins, which further reduces uterine contractions. (B) Oxytocin release is controlled by a negative feedback mechanism: increased oxytocin levels stimulate the release of corticotropin-releasing hormone (CRH), which further suppresses oxytocin secretion. (C) Oxytocin secretion is controlled by a negative feedback loop: high levels of oxytocin directly inhibit neurons in the hypothalamus, which is responsible for its synthesis and release. (D) Oxytocin release is independent of any feedback mechanism and is determined solely by hormonal signals from the placenta. (E) Oxytocin release during childbirth is a classic example of a positive feedback loop; uterine contractions stimulate the release of oxytocin, which in turn intensifies contractions, leading to a self-reinforcing cycle until childbirth is complete. After birth, the stimulus (cervical stretching) is removed, and oxytocin levels decline.