Nokea
Which type of passive transport uses proteins that change shape to move a target molecule through the membrane?
- A. Diffusion
- B. Carrier proteins
- C. Channel proteins
- D. None of the above
Correct Answer: B
Rationale: Carrier proteins are involved in facilitated diffusion, a type of passive transport where molecules move across the cell membrane with the help of specific carrier proteins that change shape to transport the molecules across. Channel proteins, on the other hand, form pores or channels to allow specific molecules to pass through the membrane via passive transport. Diffusion, while a passive transport process, does not involve proteins changing shape to facilitate the movement of molecules.
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What type of bond in the DNA nucleotide base holds the strands together?
- A. Hydrogen
- B. Sodium chloride
- C. Copper
- D. Potassium bromide
Correct Answer: A
Rationale: Hydrogen bonds are the type of bonds that hold the two strands of DNA together by connecting complementary nitrogenous bases (adenine with thymine and cytosine with guanine). These weak bonds allow the DNA strands to separate during replication and transcription while providing stability to the overall structure of the DNA molecule.
Which of the following describes how a bacterium reproduces?
- A. Mitosis
- B. Meiosis
- C. Binary fission
- D. Cytokinesis
Correct Answer: C
Rationale: Binary fission is the correct answer. Bacteria reproduce asexually through binary fission, where a single cell divides into two identical daughter cells. Mitosis and meiosis are processes that occur in eukaryotic cells, not bacteria. Cytokinesis is the physical division of the cytoplasm that follows nuclear division, which is a part of the cell cycle in both eukaryotic and prokaryotic cells but not specific to bacterial reproduction.
What part of a plant cell acts as a barrier and provides support to the cell?
- A. cell membrane.
- B. Xylem.
- C. chloroplast
- D. Cell wall.
Correct Answer: D
Rationale:
Which of the following cell parts are present in plant cells but not animal cells (there may be more than one answer):
- A. Cell membrane
- B. Cell wall
- C. Ribosome
- D. Chloroplast
Correct Answer: D
Rationale: The correct answer is 'D - Chloroplast' because it is a unique cell part found only in plant cells and is responsible for photosynthesis. Animal cells do not possess chloroplasts. Both plant and animal cells have cell membranes, which are essential for cellular function. The cell wall is a structural component specific to plant cells, providing support and protection. Ribosomes, responsible for protein synthesis, are organelles present in both plant and animal cells.
Why is homeostasis necessary?
- A. It maintains temperature.
- B. It maintains pH.
- C. It maintains glucose levels.
- D. All of the above.
Correct Answer: D
Rationale: Homeostasis is essential for maintaining the internal balance and stability of the body. It regulates various factors, such as temperature, pH levels, and glucose levels, to ensure optimal physiological function. Therefore, all the choices (temperature, pH, and glucose levels) are correct as they are all essential components of homeostasis, working together to keep the body's internal environment stable and functioning properly.