Nokea
How is the plasma membrane arranged?
- A. In a single layer made of proteins
- B. In a double layer made of proteins
- C. In a single layer of phospholipids
- D. In a double layer of phospholipids
Correct Answer: D
Rationale: The plasma membrane is arranged in a double layer of phospholipids, known as a lipid bilayer. This structure consists of two layers of phospholipid molecules with their hydrophilic (water-attracting) heads facing outwards and their hydrophobic (water-repelling) tails facing inward. This lipid bilayer provides a barrier that separates the interior of the cell from the external environment, regulating the passage of substances in and out of the cell.
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Skin cells undergo what type of cellular division?
- A. Melosis.
- B. Binary fission.
- C. Sexual reproduction.
- D. Mitosis.
Correct Answer: D
Rationale: The correct answer is D: Mitosis. Skin cells undergo mitosis, a type of cellular division where a parent cell divides into two identical daughter cells. During mitosis, the genetic material is equally distributed between the daughter cells to ensure genetic stability. Melosis (A) is incorrect as it refers to the type of cell division that occurs during sexual reproduction to produce gametes. Binary fission (B) is incorrect as it is a form of asexual reproduction seen in prokaryotes. Sexual reproduction (C) is incorrect as it involves the fusion of gametes from two different parents to produce genetically diverse offspring, not the division of existing cells like in skin cells. In summary, mitosis is the correct choice for skin cell division as it maintains genetic continuity and ensures tissue growth and repair.
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.
What are the three types of muscle tissue?
- A. Cardiac, spinal, stomach
- B. Smooth, skeletal, cardiac
- C. Neuron, epithelial, collagen
- D. None of the above
Correct Answer: B
Rationale: The correct answer is B: Smooth, skeletal, cardiac. Muscle tissue in the body is classified into three main types: smooth muscle (found in hollow organs like the digestive tract), skeletal muscle (attached to bones, responsible for voluntary movement), and cardiac muscle (specific to the heart, responsible for its rhythmic contractions). Therefore, option B is the correct answer as it lists the three types of muscle tissue.
How are lipids different from other organic molecules?
- A. They are indivisible.
- B. They are not water-soluble.
- C. They contain zinc.
- D. They form long proteins.
Correct Answer: B
Rationale: Lipids are different from other organic molecules because they are not water-soluble, unlike carbohydrates and proteins. This property is due to their hydrophobic nature, which makes them insoluble in water but soluble in nonpolar solvents. Lipids play essential roles in energy storage, insulation, and cell membrane structure, making them distinct from other organic molecules. The statement 'They are indivisible' (Choice A) is not accurate as lipids can be broken down into fatty acids and glycerol. Choice C, 'They contain zinc,' is incorrect as lipids do not necessarily contain zinc. Choice D, 'They form long proteins,' is inaccurate as lipids do not form proteins; proteins are formed from amino acids.
What is the purpose of the mitochondria?
- A. Control the cell
- B. Generate energy
- C. Synthesize proteins
- D. Package waste for removal
Correct Answer: B
Rationale: The mitochondria's main function is to generate energy for the cell through the process of cellular respiration. This organelle is often referred to as the powerhouse of the cell due to its role in producing adenosine triphosphate (ATP), the cell's main energy currency. While other organelles are responsible for activities like controlling the cell (nucleus) or synthesizing proteins (ribosomes), the mitochondria's primary role is energy production.