Nokea
Why does cellular respiration occur?
- A. Cells can copy DNA
- B. Cells can breathe
- C. Cells can convert nutrients to energy
- D. Cells can divide
Correct Answer: C
Rationale: Cellular respiration is the metabolic process in which cells convert nutrients, such as glucose, into energy in the form of ATP (adenosine triphosphate). This energy is crucial for the cell to perform its various functions and maintain life processes. Options A, B, and D do not accurately describe the purpose of cellular respiration, which is primarily about energy production to support cellular activities.
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Lipids are better known as fats, but what are they specifically? (Select one that doesn't apply.)
- A. Fatty acids
- B. Phospholipids
- C. Ketones
- D. Steroids
Correct Answer: C
Rationale: Lipids are a diverse group of molecules that include fatty acids, phospholipids, and steroids. Ketones, while important in metabolism, are not typically classified under lipids. Ketones are produced during the breakdown of fatty acids or amino acids, but they are not themselves lipids. Therefore, option C, Ketones, is the correct answer as it does not specifically fall under the category of lipids.
Which of the following is not a product of the Krebs cycle?
- A. carbon dioxide
- B. oxygen
- C. adenosine triphosphate (ATP)
- D. energy carriers
Correct Answer: B
Rationale: The correct answer is B, 'oxygen.' The Krebs cycle, also known as the citric acid cycle, is a series of chemical reactions that produce energy-rich molecules like ATP, carbon dioxide, and energy carriers such as NADH and FADH2. Oxygen is not a direct product of the Krebs cycle but is essential for the electron transport chain, which follows the Krebs cycle and is where oxygen is used as the final electron acceptor.
Which of the following statements is false regarding cell structures?
- A. Animal cells use lysosomes to break down old cells
- B. Animal cells use chloroplasts to gain energy
- C. Plant cells have a cell wall to maintain structure
- D. All of the above are true
Correct Answer: B
Rationale: The statement in option B is false because animal cells do not use chloroplasts to gain energy. Chloroplasts are found in plant cells and are responsible for photosynthesis, a process where plants convert light energy into chemical energy. Animal cells rely on mitochondria to produce energy through cellular respiration. Options A and C are true statements as lysosomes are responsible for breaking down old cells in animal cells, and plant cells have a cell wall to provide structural support.
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.
What molecules are unmetabolized by the body, but are used to increase reaction rates?
- A. Sugars.
- B. Proteins.
- C. Enzymes.
- D. Lipids.
Correct Answer: C
Rationale: The correct answer is C: Enzymes. Enzymes are molecules that increase reaction rates by acting as catalysts in biochemical reactions. They are not metabolized by the body, meaning they remain unchanged after facilitating the reactions. Sugars (choice A), proteins (choice B), and lipids (choice D) are all metabolized by the body to provide energy or building blocks for various cellular functions, unlike enzymes which remain unchanged. Therefore, enzymes are the only choice that fits the description of being unmetabolized molecules used to increase reaction rates.