Nokea
In a phospholipid, the head:
- A. Is hydrophilic
- B. Is hydrophobic
- C. Faces the outer side of the layer
- D. Both A and C
Correct Answer: D
Rationale: The head of a phospholipid is hydrophilic, meaning it is water-loving, and faces the outer side of the lipid bilayer. This arrangement allows the hydrophilic head to interact with water while the hydrophobic tails are shielded from it. Therefore, option D, 'Both A and C,' is the correct answer as the head is hydrophilic and faces the outer side of the layer.
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What is the term for a statement predicting the outcome of an experiment?
- A. Experiment.
- B. Hypothesis.
- C. Conclusion.
- D. Observation.
Correct Answer: B
Rationale: The correct answer is B: Hypothesis. A hypothesis is a statement that predicts the outcome of an experiment based on prior knowledge or observations. It serves as the foundation for the experiment and guides the research process.
A: Experiment - This choice refers to the actual process of conducting a test or investigation, not the prediction of the outcome.
C: Conclusion - This choice pertains to the final result or summary drawn from the experiment after analyzing the data collected, not the initial prediction.
D: Observation - This choice involves gathering and recording data through direct sensory experience, not making a prediction about the experiment's outcome.
Cells reproduce by different processes, all of which fall into what two categories?
- A. Sexual reproduction and binary fission
- B. Sexual reproduction and asexual reproduction
- C. Asexual reproduction and binary fission
- D. Asexual reproduction and mitosis
Correct Answer: B
Rationale: Cells can reproduce through sexual reproduction, involving the fusion of gametes, and asexual reproduction, which does not involve the fusion of gametes. Binary fission is a specific type of asexual reproduction where a cell divides into two identical cells. Therefore, the correct answer is B as it encompasses the broad categories of cellular reproduction processes, covering both sexual and asexual reproduction.
Which of the following is always true about molecules?
- A. They can travel through all cell membranes
- B. They move from low concentration to high concentration without using energy
- C. They move from high concentration to low concentration without using energy
- D. They cannot move
Correct Answer: C
Rationale: The correct answer is C: 'They move from high concentration to low concentration without using energy.' This statement aligns with the concept of passive transport, where molecules naturally move from areas of higher concentration to lower concentration to reach equilibrium. This process does not require energy input. Option A is incorrect because not all molecules can freely pass through all cell membranes due to factors like size and charge. Option B describes active transport, which involves the movement of molecules against their concentration gradient, requiring energy. Option D is incorrect as molecules are in constant motion.
In the human life cycle, only sperm and eggs have which number of chromosomes?
- A. Diploid
- B. Polyploid
- C. Monoploid
- D. Haploid
Correct Answer: D
Rationale: In humans, sperm and egg cells are haploid, meaning they contain half the number of chromosomes (23) compared to diploid cells (46). This reduction in chromosome number is essential for sexual reproduction, allowing the formation of a diploid zygote upon fertilization. Haploid cells carry only one set of chromosomes, which is necessary for genetic diversity and the fusion of genetic material during fertilization.
Which of the following DNA strands would complement the segment: ACTTGCA?
- A. TGAACGT
- B. GACCATG
- C. ACTTGCA
- D. None of the above
Correct Answer: A
Rationale: In DNA, adenine pairs with thymine (A-T) and cytosine pairs with guanine (C-G). To find the complementary strand, you need to match each base with its complementary base. The segment ACTTGCA consists of bases A, C, T, T, G, C, A, which would pair with T, G, A, A, C, G, T, respectively. Therefore, the complementary strand would be TGAACGT. Thus, option A (TGAACGT) is the correct choice as it follows the base-pairing rules in DNA.