Photosynthesis Chloroplast Structure 3 — Questions and Answers
Question 1: Chloroplasts are thought to have originated through a process called:
- Mitosis
- Meiosis
- Endosymbiosis (Correct answer)
- Conjugation
Correct answer: Endosymbiosis
The endosymbiotic theory proposes that chloroplasts evolved from ancient cyanobacteria engulfed by a eukaryotic host cell.
Question 2: Which evidence supports the endosymbiotic origin of chloroplasts?
- They lack DNA entirely
- They have a single surrounding membrane
- They contain their own ribosomes and circular DNA (Correct answer)
- They are produced only during mitosis
Correct answer: They contain their own ribosomes and circular DNA
Chloroplasts possess prokaryote-like circular DNA and 70S ribosomes, supporting an endosymbiotic ancestry.
Question 3: Stroma lamellae connect adjacent:
- Outer and inner envelope membranes
- Grana to each other (Correct answer)
- Thylakoids to the outer membrane
- Ribosomes within the stroma
Correct answer: Grana to each other
Stroma lamellae are flattened membrane tubes that interconnect individual grana stacks.
Question 4: Which pigment is found in the thylakoid membrane and is primarily responsible for absorbing light in plants?
- Phycoerythrin
- Bacteriorhodopsin
- Chlorophyll a (Correct answer)
- Cytochrome c
Correct answer: Chlorophyll a
Chlorophyll a is the primary photosynthetic pigment embedded in the thylakoid membrane of plant chloroplasts.
Question 5: The double membrane surrounding the chloroplast is collectively called the:
- Thylakoid system
- Chloroplast envelope (Correct answer)
- Granal membrane
- Plastid cortex
Correct answer: Chloroplast envelope
The chloroplast envelope consists of the outer and inner membranes that together bound the organelle.
Question 6: Which of the following molecules is synthesized in the chloroplast stroma during the Calvin cycle?
- ATP from ADP
- Glucose (G3P) from CO2 (Correct answer)
- Water from O2
- NADP+ from NADPH
Correct answer: Glucose (G3P) from CO2
The Calvin cycle in the stroma uses CO2, ATP, and NADPH to produce glyceraldehyde-3-phosphate (G3P).
Question 7: In which part of the chloroplast does the splitting of water (photolysis) occur?
- Stroma
- Outer membrane
- Thylakoid lumen (Correct answer)
- Intermembrane space
Correct answer: Thylakoid lumen
Water is oxidized by the oxygen-evolving complex on the lumen side of Photosystem II, releasing O2 into the lumen.
Photosynthesis Chloroplast Structure 3
Chloroplasts are thought to have originated through a process called: