Chloroplast Structure

Question 1

Function of chloroplasts:

Answer 1

• Site of photosynthesis
• Organelles found in some algae and plant cells
• Mainly found in mesophyll tissues of leaves

Question 2

Main roles of chloroplasts:

Answer 2

• Absorb light energy to drive photosynthesis
• Convert light energy into chemical energy

Question 3

Thylakoids:

Answer 3

These flattened sacs contain complexes of pigments like chlorophyll in their membranes to absorb light for the light-dependent reaction.

Question 4

Grana:

Answer 4

These are stacks of thylakoids.

Question 5

Lamella:

Answer 5

These are membranous extensions that connect thylakoids.

Question 6

Stroma:

Answer 6

This is a fluid surrounding the thylakoids where the light-independent reaction occurs.

Question 7

Starch grains:

Answer 7

These store sugars.

Question 8

Ribosomes:

Answer 8

These are for protein synthesis within the chloroplast

Question 9

Chloroplast DNA:

Answer 9

This has genes that code for proteins involved in photosynthesis.

Question 10

Main photosynthetic pigments:

Answer 10

• Chlorophyll a
• Chlorophyll b
• Xanthophylls and carotenoids

Question 11

Chlorophyll a

Answer 11

• Main pigment that absorbs red and blue light and reflects green light (so most of plant looks green)

Question 12

Chlorophyll b:

Answer 12

• Accessory pigment mostly found with chlorophyll a in light-harvesting complexes

Question 13

Xanthophylls and carotenoids:

Answer 13

• Absorbs different wavelengths than chlorophyll, broadening the spectrum of light that can drive photosynthesis

Question 14

Photosystems:

Answer 14

Chloroplasts contain clusters of pigments called photosystems embedded in the thylakoid membranes.

Question 15

Each photosystem has:

Answer 15

• A light-harvesting system
• A reaction centre

Question 16

A light-harvesting system:

Answer 16

This contains pigments like chlorophyll a, chlorophyll b, and carotenoids.

Question 17

A reaction centre:

Answer 17

This contains two chlorophyll a molecules.

Question 18

Role of photosystems:

Answer 18

• The light-harvesting system absorbs light energy.
• This energy is transferred to the reaction centre.
• The reaction centre then emits high-energy electrons to drive the light-dependent reactions.

Question 19

Chromatography:

Answer 19

• separate and identify the different photosynthetic pigments found in chloroplasts.
• Works because each type of pigment travels a different distance up the chromatography paper

Question 20

Rf values:

Answer 20

The Rf value allows us to identify the pigments, as each pigment has a characteristic Rf value.

Question 21

Order from greatest Rf value to smallest:

Answer 21

• Carotene
• Xanthophyll
• Chlorophyll a
• Chlorophyll b

Question 22

Rf value equation

Answer 22

distance moved by pigment / solvent front