Nokea
Which of the following statements best defines an organelle?
- A. Layer of polysaccharides outside the plasma membrane of cells.
- B. Abnormal infectious proteins.
- C. Specialized structures within a cell.
- D. Collection of tissues used to serve a specific function.
Correct Answer: C
Rationale: The correct answer is C: 'Specialized structures within a cell.' An organelle is a specialized subunit within a cell that has a specific function. Organelles are membrane-bound structures found within the cytoplasm of eukaryotic cells, each performing distinct roles that contribute to the overall functioning of the cell. Choices A, B, and D are incorrect. Option A describes the glycocalyx, which is a layer of polysaccharides outside the plasma membrane of cells. Option B refers to prions, abnormal infectious proteins. Option D defines an organ, a collection of tissues used to serve a specific function, rather than an organelle within a cell.
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The chemical equation below is unbalanced. When it is properly balanced, how many molecules of carbon dioxide (CO2) are produced for each molecule of propane (C3H8) in the reaction? 3C3H8 + 5O2 → 3CO2 + 4H2O
- A. One Half.
- B. Two.
- C. Three.
- D. Five.
Correct Answer: B
Rationale: The balanced chemical equation for the combustion of propane is: 3C3H8 + 5O2 → 3CO2 + 4H2O. This equation shows that for every 3 molecules of propane (C3H8) consumed, 3 molecules of carbon dioxide (CO2) are produced. Therefore, when properly balanced, 3CO2 are produced for each molecule of propane used. Thus, the correct answer is B: Two. Choices A, C, and D are incorrect because they do not reflect the correct stoichiometry as determined by the balanced equation.
What is the process by which simple cells become highly specialized cells?
- A. Cellular complication
- B. Cellular specialization
- C. Cellular differentiation
- D. Cellular modification
Correct Answer: C
Rationale: The correct answer is 'Cellular differentiation'. Cellular differentiation is the process by which simple cells become highly specialized cells. During cellular differentiation, cells acquire specific structures and functions that allow them to perform particular roles within an organism. This process involves the activation and silencing of specific genes, leading to the development of various cell types with distinct characteristics and functions. 'Cellular complication' (Choice A) is incorrect as it does not describe the specific process of cells becoming specialized. 'Cellular specialization' (Choice B) is not the most precise term for the process, as it does not capture the transformation from simple cells to specialized cells. 'Cellular modification' (Choice D) is incorrect as it is a vague term that does not specifically refer to the process of cellular specialization.
Which of these body parts does not contain melanin?
- A. Hair
- B. Nails
- C. Skin
- D. Iris
Correct Answer: D
Rationale: The iris is the colored part of the eye that determines the eye's color. Melanin is not present in the iris, unlike hair, nails, and skin. Melanin gives color to hair, nails, and skin, but not to the iris. Therefore, the correct answer is the iris (Choice D). Choices A, B, and C contain melanin and are incorrect.
Which statement is true regarding the process of digestion?
- A. Digestion of starch begins in the mouth.
- B. Amylase is produced by the stomach to help break down food in the upper intestine.
- C. The di- and tri-saccharides produced in early digestion are absorbed through the intestinal wall.
- D. Proteases are responsible for breaking down starches.
Correct Answer: A
Rationale: The statement 'Digestion of starch begins in the mouth' is correct. Salivary amylase, an enzyme produced in the salivary glands, initiates the breakdown of starch into simpler sugars like maltose in the mouth before further digestion in the stomach. This initial breakdown of starch is crucial in the digestion of carbohydrates, marking the beginning of the digestive process. Choice B is incorrect because amylase is produced in the salivary glands, not the stomach. Choice C is incorrect because di- and tri-saccharides are further broken down into monosaccharides before absorption. Choice D is incorrect because proteases are enzymes that break down proteins, not starches.
What is the control, if any, in this experiment?
- A. There is no control in this experiment
- B. The control is the water
- C. The control is the diet soda
- D. The control is the amount of sunlight provided to the plants
Correct Answer: B
Rationale: The correct answer is B: 'The control is the water.' In a scientific experiment, the control group is used as a baseline comparison to evaluate the effects of the variables being tested. Here, the water serves as the control group against which the effects of other substances like diet soda or different amounts of sunlight can be compared. Choice A is incorrect as every experiment should have a control group for comparison. Choice C and D are incorrect as they are not the standard control in this scenario.