Nokea
Which of the following statements is not true about enzymes?
- A. They catalyze reactions
- B. They raise the activation energy needed
- C. They have an active site
- D. They are typically proteins
Correct Answer: B
Rationale: Enzymes function by lowering the activation energy required for a reaction to occur, not by raising it. This catalytic property allows enzymes to accelerate reactions without being consumed in the process. Enzymes are biological catalysts that are typically proteins and have specific active sites where substrates bind and reactions take place. The statement that enzymes raise the activation energy needed is incorrect as their role is to lower this energy barrier. Therefore, the correct answer is B.
You may also like to solve these questions
Why can animal cells use a contractile ring but plant cells cannot?
- A. Plant cells can use both methods to divide.
- B. Animal cells divide faster, requiring them to pinch apart.
- C. Plant cells are too rigid to utilize a contractile ring.
- D. Plant cells have a cell wall that hinders the formation of a contractile ring.
Correct Answer: D
Rationale: Plant cells have a rigid cell wall surrounding their cell membrane, which prevents the formation of a contractile ring during cell division. The contractile ring is a structure composed of actin filaments responsible for pinching the cell in two during cytokinesis. Since plant cells cannot form a contractile ring due to the presence of the cell wall, they rely on other methods such as cell plate formation to complete cell division.
What type of cells are without a true nucleus?
- A. Complex.
- B. Eukaryotic.
- C. Prokaryotic.
- D. Simple.
Correct Answer: C
Rationale: The correct answer is C: Prokaryotic. Prokaryotic cells lack a true nucleus and their genetic material is not enclosed within a membrane-bound nucleus. This is a defining characteristic of prokaryotic cells, distinguishing them from eukaryotic cells (choice B), which have a true nucleus. Complex cells (choice A) and simple cells (choice D) are vague terms that do not specifically address the presence or absence of a true nucleus. Prokaryotic cells, such as bacteria, have a simpler internal structure compared to eukaryotic cells, making them distinct in terms of genetic organization and cellular complexity.
Why do cells need to use exocytosis?
- A. To obtain energy
- B. To defend against invaders
- C. To eliminate waste
- D. To undergo cell division
Correct Answer: C
Rationale: Cells use exocytosis to eliminate waste from the cell. Exocytosis is the process by which cells expel waste materials or products outside the cell. This process helps maintain cellular cleanliness and proper functioning by preventing the accumulation of harmful substances inside the cell, ensuring the cell's health and survival.
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 term for movement of water across a cellular membrane?
- A. Osmosis.
- B. Facilitated diffusion.
- C. Diffusion.
- D. Active transport.
Correct Answer: A
Rationale: Correct Answer: A - Osmosis
Rationale:
1. Osmosis is the movement of water across a selectively permeable membrane from an area of low solute concentration to high solute concentration.
2. Water moves passively to equalize solute concentrations on both sides of the membrane.
3. Facilitated diffusion (B) involves the use of transport proteins, not specific to water movement.
4. Diffusion (C) is the movement of solutes, not specific to water.
5. Active transport (D) requires energy to move molecules against their concentration gradient, different from osmosis.