Rucete ✏ AP Biology In a Nutshell
3. Cell Organelles, Membranes, and Transport — Practice Questions
This chapter covers the structure and function of cell organelles, plasma membranes, and the processes of material transport critical for maintaining cellular homeostasis.
(Multiple Choice — Click to Reveal Answer)
1. Which of the following is found in both prokaryotic and eukaryotic cells?
(A) Nucleus
(B) Mitochondria
(C) Ribosomes
(D) Chloroplasts
Answer
(C) — Ribosomes are found in both prokaryotic and eukaryotic cells and function in protein synthesis.
2. Which organelle is primarily responsible for producing ATP in animal cells?
(A) Chloroplast
(B) Mitochondrion
(C) Ribosome
(D) Lysosome
Answer
(B) — Mitochondria are the sites of cellular respiration and ATP production in animal cells.
3. What type of molecules move most easily across the plasma membrane without assistance?
(A) Large and polar
(B) Small and nonpolar
(C) Large and nonpolar
(D) Small and polar
Answer
(B) — Small, nonpolar molecules like oxygen and carbon dioxide move easily through the lipid bilayer.
4. Which structure is responsible for packaging and modifying proteins for export from the cell?
(A) Nucleus
(B) Rough endoplasmic reticulum
(C) Golgi complex
(D) Smooth endoplasmic reticulum
Answer
(C) — The Golgi complex modifies, sorts, and packages proteins for secretion or delivery to other organelles.
5. What would happen if a cell’s lysosomes were damaged and became nonfunctional?
(A) Proteins would not be synthesized.
(B) The cell could not digest waste materials properly.
(C) The plasma membrane would lose its structure.
(D) The cell would stop performing photosynthesis.
Answer
(B) — Lysosomes contain digestive enzymes; if they fail, waste builds up and cellular recycling processes are disrupted.
6. Which organelle is primarily involved in lipid synthesis?
(A) Golgi apparatus
(B) Rough endoplasmic reticulum
(C) Smooth endoplasmic reticulum
(D) Ribosome
Answer
(C) — The smooth ER is responsible for synthesizing lipids and detoxifying harmful substances.
7. Which of the following processes does NOT require cellular energy (ATP)?
(A) Active transport
(B) Endocytosis
(C) Facilitated diffusion
(D) Exocytosis
Answer
(C) — Facilitated diffusion moves molecules down their concentration gradient without energy input.
8. Which organelle contains digestive enzymes for breaking down waste materials?
(A) Lysosome
(B) Ribosome
(C) Chloroplast
(D) Mitochondrion
Answer
(A) — Lysosomes digest waste materials and cellular debris.
9. What structure gives plant cells rigidity and structural support?
(A) Plasma membrane
(B) Cytoskeleton
(C) Cell wall
(D) Chloroplast
Answer
(C) — The cell wall, made primarily of cellulose, provides strength and protection for plant cells.
10. What is the primary function of the cytoskeleton?
(A) Store genetic information
(B) Produce proteins
(C) Provide structural support and aid in movement
(D) Digest worn-out organelles
Answer
(C) — The cytoskeleton maintains cell shape, anchors organelles, and enables movement.
11. The sodium-potassium pump is an example of which type of transport?
(A) Simple diffusion
(B) Facilitated diffusion
(C) Active transport
(D) Osmosis
Answer
(C) — The sodium-potassium pump uses ATP to move ions against their concentration gradients.
12. What structure separates the contents of the nucleus from the cytoplasm?
(A) Plasma membrane
(B) Nuclear envelope
(C) Nucleolus
(D) Rough ER
Answer
(B) — The nuclear envelope is a double membrane that surrounds the nucleus and controls what enters and exits.
13. Which organelle is abundant in muscle cells due to their high energy needs?
(A) Golgi apparatus
(B) Lysosome
(C) Mitochondrion
(D) Chloroplast
Answer
(C) — Mitochondria produce ATP needed for muscle contraction.
14. What type of transport moves water across a semipermeable membrane?
(A) Simple diffusion
(B) Facilitated diffusion
(C) Active transport
(D) Osmosis
Answer
(D) — Osmosis is the diffusion of water across a selectively permeable membrane.
15. Which part of the plasma membrane is hydrophobic?
(A) Phosphate heads
(B) Carbohydrate chains
(C) Fatty acid tails
(D) Protein channels
Answer
(C) — The fatty acid tails are nonpolar and hydrophobic, forming the membrane's interior.
16. What process allows a cell to engulf large particles or liquids into vesicles?
(A) Exocytosis
(B) Endocytosis
(C) Diffusion
(D) Osmosis
Answer
(B) — Endocytosis involves the plasma membrane wrapping around material to form a vesicle inside the cell.
17. Which organelle modifies and packages proteins for secretion?
(A) Rough ER
(B) Golgi apparatus
(C) Smooth ER
(D) Ribosome
Answer
(B) — The Golgi apparatus modifies, sorts, and packages proteins for export.
18. The movement of oxygen from an area of high concentration to an area of low concentration across a membrane is an example of:
(A) Active transport
(B) Facilitated diffusion
(C) Osmosis
(D) Simple diffusion
Answer
(D) — Simple diffusion moves small nonpolar molecules like oxygen directly across the membrane.
19. In which organelle are ribosomes most densely located?
(A) Smooth ER
(B) Golgi apparatus
(C) Rough ER
(D) Lysosome
Answer
(C) — The rough ER is studded with ribosomes that synthesize proteins.
20. Which organelle is the site of photosynthesis?
(A) Mitochondrion
(B) Ribosome
(C) Chloroplast
(D) Nucleus
Answer
(C) — Chloroplasts capture light energy to produce glucose through photosynthesis.
21. What happens to a cell placed in a hypertonic solution?
(A) Water enters the cell, causing it to swell
(B) Water leaves the cell, causing it to shrink
(C) No net water movement occurs
(D) The cell bursts
Answer
(B) — In a hypertonic solution, water exits the cell, leading to shrinkage (crenation in animal cells).
22. Which organelle is responsible for producing ribosomes?
(A) Nucleolus
(B) Smooth ER
(C) Golgi apparatus
(D) Lysosome
Answer
(A) — The nucleolus, located within the nucleus, assembles ribosomal RNA and proteins into ribosome subunits.
23. Which type of protein in the plasma membrane allows specific molecules to pass through?
(A) Structural protein
(B) Channel protein
(C) Glycoprotein
(D) Peripheral protein
Answer
(B) — Channel proteins facilitate the passage of specific ions or molecules across the membrane.
24. Which process removes large molecules from the cell using vesicles?
(A) Endocytosis
(B) Exocytosis
(C) Osmosis
(D) Diffusion
Answer
(B) — Exocytosis involves vesicles fusing with the plasma membrane to release their contents outside the cell.
25. What is the main component of the plasma membrane?
(A) Proteins
(B) Carbohydrates
(C) Phospholipids
(D) Nucleic acids
Answer
(C) — Phospholipids form the bilayer structure that is the basis of the plasma membrane.
26. Which of the following best explains why the plasma membrane is described as a "fluid mosaic"?
(A) It consists of a rigid structure of phospholipids only.
(B) Proteins and lipids can move laterally within the layer.
(C) Carbohydrates are fixed to a single location.
(D) It is impermeable to all molecules.
Answer
(B) — The fluid mosaic model describes the flexible structure of the membrane with movable proteins embedded in a phospholipid bilayer.
27. Which of the following organelles likely originated through endosymbiosis?
(A) Ribosome
(B) Mitochondrion
(C) Golgi apparatus
(D) Nucleolus
Answer
(B) — Mitochondria are thought to have evolved from free-living prokaryotes engulfed by ancestral eukaryotic cells.
28. What best describes the function of the rough ER?
(A) Lipid synthesis
(B) Detoxification of poisons
(C) Protein modification and transport
(D) DNA replication
Answer
(C) — The rough ER modifies and transports proteins synthesized by attached ribosomes.
29. If a cell is placed in a hypotonic solution, what will most likely happen?
(A) Water will move out, causing shrinkage.
(B) Water will move in, causing the cell to swell.
(C) Water will move equally in both directions.
(D) The cell membrane will collapse inward.
Answer
(B) — In a hypotonic solution, water enters the cell, potentially causing it to swell and even burst.
30. Which structure maintains turgor pressure in plant cells?
(A) Chloroplast
(B) Mitochondrion
(C) Central vacuole
(D) Ribosome
Answer
(C) — The central vacuole stores water and maintains internal pressure against the cell wall, supporting plant structure.
31. Which of the following movements across a membrane requires energy input from the cell?
(A) Facilitated diffusion
(B) Osmosis
(C) Simple diffusion
(D) Active transport
Answer
(D) — Active transport moves substances against their concentration gradient using ATP energy.
32. Which feature is shared by mitochondria and chloroplasts that supports the endosymbiotic theory?
(A) Presence of a single membrane
(B) Inability to divide
(C) Presence of their own DNA and ribosomes
(D) Lack of a lipid bilayer
Answer
(C) — Both mitochondria and chloroplasts contain their own circular DNA and ribosomes, similar to prokaryotes.
33. Which part of the plasma membrane serves primarily as a barrier to large, polar molecules?
(A) Protein channels
(B) Hydrophilic heads
(C) Hydrophobic core
(D) Carbohydrate side chains
Answer
(C) — The hydrophobic core of the membrane repels polar molecules and large ions without the help of proteins.
34. Which type of transport protein changes its shape to move substances across the membrane?
(A) Channel protein
(B) Carrier protein
(C) Glycoprotein
(D) Peripheral protein
Answer
(B) — Carrier proteins undergo conformational changes to transport molecules across membranes.
35. Which organelle would be particularly abundant in white blood cells that engulf bacteria?
(A) Chloroplast
(B) Smooth ER
(C) Lysosome
(D) Ribosome
Answer
(C) — Lysosomes contain hydrolytic enzymes needed to digest engulfed pathogens.
36. Describe the main function of ribosomes in the cell.
Answer
Ribosomes are responsible for synthesizing proteins by translating messenger RNA (mRNA) sequences into amino acid chains.
37. Explain why the phospholipid bilayer is critical to the function of the plasma membrane.
Answer
The bilayer creates a selectively permeable barrier, allowing certain substances to pass while blocking others, maintaining internal homeostasis.
38. Why are lysosomes considered essential for cellular health?
Answer
Lysosomes digest damaged organelles, pathogens, and cellular debris, preventing buildup of waste inside the cell.
39. Which type of molecule typically requires a transport protein to cross the plasma membrane, and why?
Answer
Large or polar molecules need transport proteins because they cannot pass through the hydrophobic core of the lipid bilayer.
40. Describe the difference between passive and active transport across a membrane.
Answer
Passive transport moves substances down a concentration gradient without energy input, while active transport requires ATP to move substances against the gradient.
41. How does the structure of the rough ER relate to its function?
Answer
The rough ER’s ribosome-studded surface allows it to efficiently synthesize and transport proteins destined for membranes or secretion.
42. What is the primary role of the Golgi apparatus in protein processing?
Answer
The Golgi apparatus modifies, sorts, and packages proteins into vesicles for transport within or outside of the cell.
43. Why is the fluidity of the plasma membrane important for cell function?
Answer
Membrane fluidity allows proteins and lipids to move, facilitating processes like endocytosis, exocytosis, and cell signaling.
44. Identify one similarity between mitochondria and chloroplasts.
Answer
Both have a double membrane structure and their own DNA, allowing them to produce some of their own proteins independently.
45. How does facilitated diffusion differ from simple diffusion?
Answer
Facilitated diffusion uses membrane proteins to move substances across the membrane, while simple diffusion involves direct movement through the lipid bilayer.
46. Why are plant cells generally more rigid than animal cells?
Answer
Plant cells have a cell wall made of cellulose that provides rigidity and protection beyond the plasma membrane.
47. What is the function of the nucleolus inside the nucleus?
Answer
The nucleolus assembles ribosomal RNA (rRNA) and proteins to form ribosome subunits.
48. Define turgor pressure and its importance for plant cells.
Answer
Turgor pressure is the force exerted by stored water in the central vacuole, maintaining plant rigidity and upright growth.
49. What role does cholesterol play in the plasma membrane?
Answer
Cholesterol maintains membrane fluidity, stabilizing it at different temperatures by preventing tight packing or excessive looseness.
50. How do channel and carrier proteins differ in membrane transport?
Answer
Channel proteins create open pores for passive transport, while carrier proteins bind specific molecules and undergo shape changes to move them across the membrane.