Which of the following is an organelle within an organelle?

Step 16: Analyze Question 16. An organelle within an organelle refers to a structure that is itself an organelle, but is located inside another organelle. Ribosomes are found in the cytoplasm, on the endoplasmic reticulum, and also within mitochondria and chloroplasts. Mitochondria and chloroplasts are organelles, making ribosomes an organelle within an organelle. A. Peroxisome: A single-membrane-bound organelle. B. ER: A network of membranes. C. Mesosome: An invagination of the plasma membrane in prokaryotes. D. Ribosome: Found inside mitochondria and chloroplasts, which are themselves organelles. The final answer is D Step 17: Analyze Question 17. This question asks for the correct description of a cellular part. A. Centrioles - Site of active RNA synthesis: Incorrect. Centrioles are involved in cell division. RNA synthesis occurs in the nucleus, mitochondria, and chloroplasts. B. Ribosomes - Those on chloroplasts are larger (80S) while those in the cytoplasm are smaller (70S): Incorrect. Eukaryotic cytoplasmic ribosomes are 80S, while chloroplast and mitochondrial ribosomes are 70S. C. Lysosomes - Optimally active at a pH of about 8.5: Incorrect. Lysosomal enzymes are optimally active at acidic pH (around 4.5-5.0). D. Thylakoids - Flattened membranous sacs forming the grana of chloroplasts: Correct. Thylakoids are the flattened sacs within chloroplasts that stack to form grana, where light-dependent reactions of photosynthesis occur. The final answer is D Step 18: Analyze Question 18. The diagram shows a duplicated chromosome. Label A points to the constricted region where the two sister chromatids are joined. This region is called the centromere. A. Chromosomes: A is a part of a chromosome. B. Centromere: The constricted region of a chromosome that holds sister chromatids together. C. Kinetichore: A protein structure on the centromere, not the centromere itself. D. Acrocentric: A type of chromosome based on centromere position, not the label for the centromere. The final answer is B Step 19: Analyze Question 19. The nuclear envelope is a double membrane surrounding the nucleus. The outer membrane of the nuclear envelope is structurally continuous with the endoplasmic reticulum (ER). A. ER: Correct. The outer nuclear membrane is continuous with the ER. B. Golgi body: The Golgi apparatus is a separate organelle, though it receives vesicles from the ER. C. Lysosome: Lysosomes are distinct membrane-bound organelles. D. All of these: Incorrect. The final answer is A Step 20: Analyze Question 20. Plastids are a group of organelles found in plant cells and some eukaryotic algae. They are involved in the synthesis and storage of food. A. Chloroplast: A type of plastid containing chlorophyll, responsible for photosynthesis. B. Chromoplast: A type of plastid containing pigments other than chlorophyll, giving color to fruits and flowers. C. Leucoplast: A type of plastid that is colorless and primarily involved in storage (e.g., starch, oil, protein). D. All of these: Since chloroplasts, chromoplasts, and leucoplasts are all types of plastids, this option is correct. The final answer is D Step 21: Analyze Question 21. Ptyalin is another name for salivary amylase, an enzyme found in saliva. Its function is to break down complex carbohydrates (starch) into simpler sugars by adding water molecules. This type of reaction is called hydrolysis. Enzymes that catalyze hydrolysis reactions are classified as hydrolases. A. Oxidoreductase: Catalyzes oxidation-reduction reactions. B. Transferase: Catalyzes the transfer of a functional group. C. Hydrolase: Catalyzes the hydrolysis of a chemical bond. D. Ligase: Catalyzes the joining of two large molecules. The final answer is C Step 22: Analyze Question 22. The figure shows an energy diagram for a chemical reaction, illustrating the effect of an enzyme. B represents the initial energy level of the substrate*. The higher curve represents the uncatalyzed reaction, and the lower curve represents the enzyme-catalyzed reaction. C represents the transition state energy* of the uncatalyzed reaction. A represents the activation energy* of the uncatalyzed reaction (the energy difference between the substrate and the uncatalyzed transition state). D represents the activation energy* of the enzyme-catalyzed reaction (the energy difference between the substrate and the catalyzed transition state). Since the options (a to d) for this question are not visible in the provided image, I cannot select a specific letter. However, based on the diagram: A is the activation energy of the uncatalyzed reaction*. B is the energy of the substrate*. C is the transition state energy of the uncatalyzed reaction*. D is the activation energy of the catalyzed reaction*.