Component 1 - Photosynthesis

Question 1

What is photosynthesis?

Answer 1

The process by which autotrophic organisms use light energy to make sugar and oxygen gas from carbon dioxide and water

Question 2

Why are plants green?

Answer 2

Different wavelengths of visible light are seen by the human eye as different colours
Thylakoid membrane of the chloroplast is impregnated with photosynthetic pigments

Question 3

What are the adaptations of leaves for photosynthesis?

Answer 3

Large surface area - capture maximum amount of light
Thin - Light penetrates right through the leaf and creates a short diffusion pathway for carbon dioxide
Permeable - stomatal pores - allow carbon dioxide to diffuse into leaf
Air spaces - allow carbon dioxide to diffuse to all cells
Cuticle and epidermis are transparent

Question 4

What are the adaptions of palisade cells for photosynthesis?

Answer 4

Large vacuole - chloroplasts for a single layer at periphery of each cell and do not shade one another
Cylindrical, elongated and at right angles to the leaf surface - light only has to pass through epidermal cell walls and one palisade cell wall before reaching a chloroplast
Contain a large amount of chloroplasts - maximise amount of light energy trapped

Question 5

What do chloroplasts do with light energy?

Answer 5

Absorb light energy and convert it to chemical energy

Question 6

Label the structure of a chloroplast

Answer 6

Question 7

Where does photosynthesis occur in plants?

Answer 7

Primarily in the leaves in the chloroplasts

Question 8

What does a chloroplast contain structurally?

Answer 8

Stroma, a fluid
Grana, stacks of thylakoids

Question 9

What do thylakoids contain?

Answer 9

Chlorophyll - green pigment that captures light for photosynthesis

Question 10

How is the stacking of the thylakoids an adaptation to a chloroplast?

Answer 10

Maximises light catchment

Question 11

What is the function of the starch grains and lipid droplets in chloroplasts?

Answer 11

Store the products of photosynthesis

Question 12

What is the purpose of the grana?

Answer 12

Contain chlorophyll
Contain different pigments absorb different wave lengths of light

Question 13

What is the function of the stroma?

Answer 13

Site of light independent reactions

Question 14

What is the function of thylakoids?

Answer 14

Site of light dependent reactions
Chlorophyll absorbs light energy
ATP and NADPH2 produced

Question 15

What is the function of the granum?

Answer 15

Stacks of thylakoids - SA for absorption of light eneergy

Question 16

What is the function of the starch grain?

Answer 16

Excess carbohydrate stored as a starch grain
Starch does not affect the water potential

Question 17

What is the function of double membrane?

Answer 17

Controls movement of substances in and out of the chloroplasts

Question 18

What are the 3 main pigments in chloroplasts?

Answer 18

Chlorophyll a
Chlorophyll b
Carotenoids - absorb the light from the blue - violet region of the spectrum

Question 19

What are the two main types of carotenoids?

Answer 19

Carotenes and xanthophylls

Question 20

What is chromatography?

Answer 20

Is a separation technique first used to separate pigments in plant leaves

Question 21

What does an Rf value show?

Answer 21

How far a component has travelled compared with the solvent front

Question 22

What is the absorption spectra?

Answer 22

A graph showing the degree of absorption of different wavelengths of light by an individual pigment is referred to as the absorption spectrum for that pigment
Chlorophylls absorb strongly in the blue-violet and red regions of the spectrum
Carotenoids absorb in the blue and green regions

Question 23

What is the action spectrum?

Answer 23

A graph showing the degree to which different wavelengths affect the rate of photosynthesis
The action spectrum for photosynthesis is closely correlated with the absorption spectra for chlorophylls a and b and the carotenoids
This suggests that these are the main pigments involved in harvesting light energy used in photosynthesis

Question 24

What are the products of the Calvin cycle?

Answer 24

Makes sugar from carbon dioxide
ATP generated by the light reactions provide the energy for sugar synthesis
The NADPH produced by the light reactions provides the electrons for the reduction of carbon dioxide to glucose

Question 25

What is the function of the coenzyme - NADP?

Answer 25

Accept H atoms from molecules and become reduced Work with dehydrogenase enzymes and carry out oxidation reactions Carry H to Calvin cycle reactions from thylakoid membrane to stroma, where the H reduce GP to TP

Question 26

What are antenna complexes?

Answer 26

Photosynthetic pigments which are grouped in clusters

Question 27

How are photons of light transferred to the primary pigment? (chlorophyll a)

Answer 27

Through the antenna complex

Question 28

In photosystem 1 what is the reaction centre called and why?

Answer 28

p700 As it contains chlorophyll a molecule with a maximum absorption at a wavelength of 700nm

Question 29

In photosystem 2 what is the reaction centre called and why?

Answer 29

p680 Contains chlorophyll a molecule with a maximum absorption at a wavelength of 680nm

Question 30

What is cyclic photophosphorylation?

Answer 30

Process for ATP generation associated with some photosynthetic bacteria Reaction centre = 700nm

Question 31

Describe the process of cyclic photophosphorylation

Answer 31

Involves photosystem I Light energy is absorbed by the accessory pigments and passed to chlorophyll a at the reaction centre Electrons are emitted and passed to a high energy level where they are received by electron acceptors Electrons pass along a chain of electron carriers, generating sufficient energy to synthesis ATP by chemiosmosis Electron returns to reaction centre of PSI No reduced NADP is produced

Question 32

What is Noncyclic photophosphorylation?

Answer 32

Photosystem II regains electrons by splitting water leaving O2 gas a by-product

Question 33

Describe the process of non-cyclic photophosphorylation

Answer 33

Causes the displacement of two excited electrons from PS2 which are emitted to a higher energy level where they are picked up by an electron acceptor Electrons pass along a series of electron carriers and then to PSI The energy lost by electrons is used to pump protons from the stroma into the thylakoid space. This produces ATP through chemiosmosis PSII receives replacement electrons from the photolysis off water In photolysis ,water molecules dissociate into hydrogen ions, electrons and oxygen gas