Nokea
How does yeast reproduce?
- A. Binary fission
- B. Spore formation
- C. Budding
- D. Cloning
Correct Answer: C
Rationale: Yeast typically reproduces through a process called budding. During budding, a small outgrowth forms on the parent yeast cell, gradually enlarging in size until it separates to become a new, genetically identical daughter cell. This method of reproduction allows yeast to rapidly multiply and grow in favorable conditions. It is different from binary fission, spore formation, and cloning. Binary fission involves the division of a single organism into two genetically identical organisms. Spore formation is a method seen in certain fungi where specialized cells develop into spores for reproduction. Cloning involves producing genetically identical copies of an organism. Therefore, budding is the correct answer for how yeast reproduces.
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How do green plants use nitrates in the nitrogen cycle?
- A. To synthesize proteins
- B. To store food
- C. To decompose ammonia
- D. To break down nitrites
Correct Answer: A
Rationale: Green plants use nitrates in the nitrogen cycle to synthesize proteins. Nitrogen is an essential component of amino acids, which are the building blocks of proteins. Plants take up nitrates from the soil through their roots and incorporate nitrogen into their proteins through the process of protein biosynthesis. This helps in their growth, development, and overall health. Choice B, 'To store food,' is incorrect because nitrates are primarily used for protein synthesis, not food storage. Choice C, 'To decompose ammonia,' is incorrect as plants do not decompose ammonia but rather utilize it through nitrification. Choice D, 'To break down nitrites,' is incorrect as plants typically convert nitrites into nitrates through a process called nitrate assimilation for protein synthesis.
Which statement is true of enzymes?
- A. They are made from lipids.
- B. They are made from proteins.
- C. They form double chains of DNA.
- D. They bind with catalysts.
Correct Answer: B
Rationale: The correct answer is B: Enzymes are made from proteins. Enzymes are biological molecules that act as catalysts to speed up chemical reactions in living organisms. While the majority of enzymes are proteins, a few are made from RNA. The statement that enzymes are made from lipids (choice A) is incorrect. Enzymes do not form double chains of DNA (choice C) as their primary function is not related to DNA structure. Additionally, enzymes themselves do not bind with catalysts (choice D); instead, they act as catalysts to facilitate reactions.
In contrast with triglycerides, phospholipids are lacking one of which of the following components?
- A. Monosaccharide
- B. Glycerol
- C. Phosphates
- D. Fatty acid
Correct Answer: B
Rationale: Phospholipids are structurally similar to triglycerides but lack one of the fatty acid chains that triglycerides possess. Triglycerides consist of three fatty acid chains attached to a glycerol molecule, while phospholipids have two fatty acid chains and a phosphate group attached to a glycerol backbone. Therefore, phospholipids are lacking the third fatty acid chain found in triglycerides. Choice A (Monosaccharide) is incorrect because neither triglycerides nor phospholipids contain monosaccharides in their structure. Choice C (Phosphates) is incorrect because phospholipids actually contain phosphates, unlike triglycerides. Choice D (Fatty acid) is incorrect as both triglycerides and phospholipids contain fatty acids, but the number of fatty acid chains differs between the two.
How does an enzyme work on a chemical reaction that occurs in a substrate?
- A. An enzyme slows down the chemical reaction.
- B. An enzyme speeds up the chemical reaction.
- C. An enzyme has no effect on the chemical reaction.
- D. An enzyme stops most chemical reactions.
Correct Answer: B
Rationale: Enzymes are biological catalysts that facilitate chemical reactions by lowering the activation energy required for the reaction to occur. This allows the reaction to proceed more quickly and efficiently. Enzymes do not change the overall outcome of the reaction, but they significantly increase the rate at which it takes place. Therefore, choice B, 'An enzyme speeds up the chemical reaction,' is the correct answer. Choices A, C, and D are incorrect because enzymes do not slow down, have no effect, or stop chemical reactions; instead, they accelerate the process by lowering the activation energy.
What happens during anaphase?
- A. Chromosomes move to opposite ends of the spindle.
- B. Nuclear membrane and nucleoli disintegrate.
- C. Chromatids line up at the center of the spindle.
- D. Nuclear membrane and nucleoli form.
Correct Answer: A
Rationale: During anaphase, the sister chromatids, joined at the centromere, separate and move towards opposite ends of the spindle apparatus. This movement ensures that each daughter cell receives an identical set of chromosomes. Choice B is incorrect as the disintegration of the nuclear membrane and nucleoli occurs during prophase. Choice C is incorrect as chromatids align at the center of the spindle during metaphase, not anaphase. Choice D is incorrect as the formation of the nuclear membrane and nucleoli occurs during telophase, not anaphase.