Nokea
Which DNA strand would complement this segment: ACTTGCA?
- A. TGAACGT
- B. GACCATG
- C. ACTTGCA
- D. None of the above
Correct Answer: A
Rationale: To find the complementary DNA strand, you need to pair each nucleotide with its complementary base: A with T, C with G, T with A, and G with C. Therefore, the correct match for ACTTGCA is TGAACGT. Only Choice A follows this complementary base pairing rule, making it the correct answer.
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What action does an enzyme perform that increases the rate of a biological reaction?
- A. Lowers the activation energy.
- B. Removes the energy barrier.
- C. Changes the substrate.
- D. Alters the active site.
Correct Answer: A
Rationale: Correct Answer: A - Lowers the activation energy.
Rationale:
1. Enzymes lower activation energy needed for a reaction to occur by stabilizing the transition state.
2. This accelerates the reaction rate without being consumed in the process.
3. Choice B is incorrect as enzymes do not physically remove the energy barrier.
4. Choice C is incorrect as enzymes do not change the substrate but rather facilitate the reaction.
5. Choice D is incorrect as enzymes do not alter their active sites during reactions; the sites remain unchanged.
Why is the nucleus important in a cell?
- A. It stores the DNA.
- B. It provides structural support.
- C. It synthesizes proteins.
- D. It produces energy from food.
Correct Answer: A
Rationale: The correct answer is A. The nucleus is crucial in a cell because it stores the DNA, which contains the genetic information necessary for directing the cell's activities and determining its characteristics. The nucleus does not provide structural support, synthesize proteins, or produce energy from food; these functions are carried out by other cell organelles. Therefore, the main role of the nucleus is to safeguard and regulate the genetic material of the cell, ensuring proper cell function and inheritance of traits.
What is the characteristic of the cell membrane consisting of a bilayer of phospholipids with proteins, cholesterol, and glycoproteins that creates a hydrophobic region between two layers of lipids?
- A. Impermeable
- B. Permeable
- C. Selectively permeable
- D. Selectively impermeable
Correct Answer: C
Rationale: The correct answer is 'C: Selectively permeable.' The cell membrane is selectively permeable because it allows certain molecules to pass through while restricting the passage of others. The hydrophobic region formed by the lipid bilayer makes it selectively permeable by controlling the movement of substances in and out of the cell. This selective permeability is vital for cellular functions, as it regulates the transport of essential molecules and maintains the internal environment required for proper cell operation and overall cellular homeostasis.
Which statement is an inference related to scientific methodology?
- A. Flowers open in the sun.
- B. Homosapiens use tools.
- C. The skin is yellow.
- D. Nutrients are needed for growth.
Correct Answer: D
Rationale: Correct Answer: D
Rationale:
1. Inference: Nutrients are needed for growth implies a scientific methodology (cause and effect relationship).
2. This statement is based on scientific evidence and experimentation.
3. It aligns with the fundamental principles of biology and nutrition.
4. It demonstrates the importance of empirical evidence in scientific research.
Summary:
Choice D is correct as it directly relates to a fundamental aspect of scientific methodology by establishing a causal relationship based on evidence. Choices A, B, and C lack the scientific methodology aspect and do not involve an inference based on empirical evidence.
Which organelle is responsible for protein synthesis?
- A. Ribosome
- B. Chloroplast
- C. Lysosome
- D. Mitochondria
Correct Answer: A
Rationale: The correct answer is A, Ribosome. Ribosomes are the organelles responsible for protein synthesis in a cell. They are the site where amino acids are assembled into proteins based on the genetic information carried by mRNA. Chloroplasts are responsible for photosynthesis in plant cells, Lysosomes contain enzymes for digestion and waste removal, and Mitochondria are known as the powerhouse of the cell, responsible for generating energy.