Photosynthesis

Question 1

what is an autotrophic organism?

Answer 1

organisms that can photosynthesise.

Question 2

what is a heterotrophic organism?

Answer 2

an organism which obtains complex organic molecules by eating other organisms.

Question 3

where does photosynthesis take place?

Answer 3

in chloroplasts.

Question 4

what are thylakoids?

Answer 4

flattened sacs formed by membranes present within the chloroplast.

Question 5

what are grana?

Answer 5

stacks of thylakoids.

Question 6

what are lamellae?

Answer 6

membranous channels which join grana.

Question 7

where are pigments contained?

Answer 7

thylakoid membranes.

Question 8

what is the stroma?

Answer 8

the fluid enclosed in the chloroplast (cytoplasm)

Question 9

why are different plants different colours?

Answer 9

different pigments absorb and reflect different wavelengths of light

Question 10

what is an example of a primary pigment?

Answer 10

chlorophyll a

Question 11

what are examples of accessory pigments?

Answer 11

carotenoids and chlorophyll b.

Question 12

what is the role of a light harvesting system?

Answer 12

absorb light energy of diifferent wavelengths and transfer this energy quickly and efficiently to the reaction centre.

Question 13

what is a photosystem composed of?

Answer 13

a light harvesting system and reaction centre

Question 14

where is the primary pigment located?

Answer 14

in the reaction centre

Question 15

where are the accessory pigments located?

Answer 15

in the light harvesting system - along with proteins.

Question 16

why do leaves turn orange in autumn?

Answer 16

chlorophyll a is broken down in sunlight but not produced if there is little to no sunlight. orange and yellow accessory pigments are not usually seen as they are masked by green chlorophyll colour.

Question 17

what are the two stages of photosynthesis?

Answer 17

1. the light dependent stage.
2. the light-independent stage.

Question 18

what happens during the light dependent stage?

Answer 18

energy from sunlight is absorbed and used to form ATP. Hydrogen from water is used to reduce coenzyme NADP to reduced NADP.

Question 19

what happens during the light independent stage?

Answer 19

hydrogen from reduced NADP and carbon dioxide is used to build organic molecules. ATP supplies the required energy.

Question 20

how many photosystems are involved in non-cyclic photophosphorylation?

Answer 20

2

Question 21

what wavelength of light does photosystem 1 absorb?

Answer 21

700nm

Question 22

what wavelength of light does photosystem 2 absorb?

Answer 22

680nm

Question 23

what are the electrons lost from ps2 reaction centre replaced from?

Answer 23

water molecules broken down using energy from the sun. (photolysis.)

Question 24

what are water molecules split into?

Answer 24

hydrogen ions, electrons, and oxygen molecules.

Question 25

what is the equation for the photolysis reaction?

Answer 25

water –> (2) protons + (2) electrons + (0.5) oxygen

Question 26

where are protons released into after photolysis?

Answer 26

into the lumen of the thylakoids, increasing the proton concentration across the membrane.

Question 27

how is reduced NADP formed?

Answer 27

hydrogen ions are returned to the stroma and combine with NADP and an electron from ps1.

Question 28

what leads to cyclic phosphorylation?

Answer 28

electrons leaving electron transport chain after ps1 can be returned to ps1.

Question 29

what does cyclic phosphorylation mean?

Answer 29

PS1 can lead to the production of ATP without being supplied electrons from PS2. Reduced NADP is not produced when this happens.

Question 30

where does the light independent reaction take place?

Answer 30

the stroma of chloroplasts.