Chloroplast Structure and Function

00:00 8 marks

The diagram shows a transmission electron micrograph of a chloroplast.
[VISUALIZATION: Transmission electron micrograph of a chloroplast clearly showing outer membrane, inner membrane, stroma, thylakoids stacked into grana, and starch grains. Label I points to a granum. Label II points to the stroma.]
(a) Identify the structures labelled I and II. [2]
I: ……………………………………………
II: …………………………………………..
(b) State the process that occurs in structure I. [1]
(c) State the process that occurs in structure II. [1]
(d) Explain how the structure of the chloroplast is adapted for photosynthesis. [4]
***(Total: 8 marks)***

Part a

2 minutes 2 marks

Question

(a) Identify the structures labelled I and II. [2]
I: ……………………………………………
II: …………………………………………..

Hint Hint

Hint

Structure I is a stack of flattened membrane sacs. Structure II is the fluid-filled space surrounding these stacks.

Answer Answer
Mark Scheme Mark Scheme
Explanation Explanation

Answer Answer

Complete Answer

I: Granum / stack of thylakoids; II: Stroma

Mark Scheme Mark Scheme

Answer Explanation Answer Explanation

Part b

1 minutes 1 marks

Question

(b) State the process that occurs in structure I. [1]

Hint Hint

Hint

Structure I (granum) contains chlorophyll and other pigments embedded in its membranes. What stage of photosynthesis directly uses light energy?

Answer Answer
Mark Scheme Mark Scheme
Explanation Explanation

Answer Answer

Complete Answer

Light-dependent reactions / photolysis / ATP synthesis / NADP reduction

Mark Scheme Mark Scheme

Answer Explanation Answer Explanation

Part c

1 minutes 1 marks

Question

Hint Hint

Hint

Structure II (stroma) is the fluid-filled space containing enzymes, ribosomes, and chloroplast DNA. What stage of photosynthesis uses the ATP and NADPH produced in the first stage to fix carbon dioxide?

Answer Answer
Mark Scheme Mark Scheme
Explanation Explanation

Answer Answer

Complete Answer

Light-independent reactions / Calvin cycle / carbon fixation

Mark Scheme Mark Scheme

Answer Explanation Answer Explanation

Part d

6 minutes 4 marks

Question

(d) Explain how the structure of the chloroplast is adapted for photosynthesis. [4]

Hint Hint

Hint

Think about the different parts of the chloroplast (membranes, thylakoids, stroma) and how their specific features facilitate either the light-dependent or light-independent reactions.

Answer Answer
Mark Scheme Mark Scheme
Explanation Explanation

Answer Answer

Complete Answer

Any four of: Large surface area of thylakoids/grana for light absorption/light-dependent reactions; Stroma contains enzymes (e.g., Rubisco) for Calvin cycle/light-independent reactions; Double membrane isolates chloroplast contents from cytoplasm; Presence of ribosomes/DNA allows synthesis of some proteins/enzymes within the chloroplast; Starch grains store products of photosynthesis; Small space within thylakoids allows rapid proton gradient build-up; Lamellae connect grana allowing movement of substances.

Mark Scheme Mark Scheme

Answer Explanation Answer Explanation