What is the stroma of a chloroplast?

The stroma is the fluid-filled matrix surrounding the grana, in which the enzymes of the light-independent reactions are dissolved.

Which four components of the light-dependent reaction are held in the thylakoid membranes?

The light harvesting complexes, the photosystems, the electron transport chain and ATP synthase.

Where in the chloroplast is RuBisCO found, and why is that where it is needed?

RuBisCO is dissolved in the stroma, because the Calvin cycle reactions it catalyses take place there.

Explain the advantage of the thylakoid membranes being arranged in stacks.

Stacking packs a very large membrane surface area into a small volume, so many more light harvesting complexes and photosystems can be held for absorbing light.

OCR A-Level Biology B H422

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Photosynthesis, Food Production and Management of the Environment

Chloroplast ultrastructure and photosynthetic pigments

3 things to know
Components 01, 02 and 03

Overview

Recall questions on the chloroplast envelope, thylakoids, grana, stroma and intergranal lamellae, where the light-dependent components and RuBisCO sit, chloroplast DNA and ribosomes, and separating chlorophyll a, chlorophyll b, carotene and xanthophyll by paper chromatography with Rf values.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Describe the structures seen in a chloroplast, working from its outer boundary inwards.

Key term

What type of membrane encloses a chloroplast?

Key term

Name the flattened membrane sacs inside a chloroplast and the stacks they form.

Questions from this subtopic

Each one with the model answer underneath.

1
What type of membrane encloses a chloroplast?
Model answer
A double membrane called the chloroplast envelope, made of an inner and an outer membrane separated by a narrow intermembrane space.
2
Name the flattened membrane sacs inside a chloroplast and the stacks they form.
Model answer
The flattened sacs are thylakoids, and a stack of thylakoids is called a granum.
3
What is the stroma of a chloroplast?
Model answer
The stroma is the fluid-filled matrix surrounding the grana, in which the enzymes of the light-independent reactions are dissolved.
4
Which four components of the light-dependent reaction are held in the thylakoid membranes?
Model answer
The light harvesting complexes, the photosystems, the electron transport chain and ATP synthase.
5
Where in the chloroplast is RuBisCO found, and why is that where it is needed?
Model answer
RuBisCO is dissolved in the stroma, because the Calvin cycle reactions it catalyses take place there.
6
Explain the advantage of the thylakoid membranes being arranged in stacks.
Model answer
Stacking packs a very large membrane surface area into a small volume, so many more light harvesting complexes and photosystems can be held for absorbing light.

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