Cell types with full photosynthetic machinery — Antenna complexes (light-harvesting), photosynthetic electron transport chains, and carbon fixation (Calvin–Benson cycle) are all present together in which cells?
-
AAnimal cells
-
BBacterial cells (as a blanket category for all bacteria)
-
CPlant cells (chloroplast-containing)
-
DOnly as part of the citric acid cycle reactions
-
EArchaeal methanogens exclusively
Answer
Correct Answer: Plant cells (chloroplast-containing)
Explanation
Introduction / Context:Complete oxygenic photosynthesis requires three coordinated components: light capture (antenna), photochemical electron transfer (ETC), and carbon fixation. This combination is a hallmark of chloroplast-bearing plant cells and many algae.
Given Data / Assumptions:
- Plants possess chloroplasts with thylakoid membranes housing antenna and ETC complexes.
- Carbon fixation (Calvin–Benson cycle) occurs in the chloroplast stroma.
- Not all bacteria are photosynthetic; many lack these systems entirely.
Concept / Approach:Choose the cell type that generally and consistently contains all three systems. While some bacteria (for example, cyanobacteria) do have analogous components, the option “bacterial cells” as a blanket statement is overly broad and thus misleading. Animal cells do not photosynthesize, and the citric acid cycle is unrelated to the triad listed.
Step-by-Step Solution:
Identify universal presence of antenna + ETC + Calvin cycle → chloroplast-bearing plant cells.Exclude animals (no photosynthesis) and general bacteria category (not universally true).Select plant cells as the best, consistently correct answer.Verification / Alternative check:Chloroplast ultrastructure shows grana/thylakoids with photosystems and stroma enzymes for carbon fixation.
Why Other Options Are Wrong:
a) Animals lack photosystems and RuBisCO.b) Statement is not true for all bacteria; many are heterotrophs lacking photosystems and Calvin cycle.d) The citric acid cycle is a respiratory pathway, not photosynthetic.e) Methanogens are anaerobic archaea without oxygenic photosynthesis.Common Pitfalls:Generalizing from cyanobacteria to “all bacteria.”
Final Answer:Plant cells (chloroplast-containing).