3. Light Dependent Reaction

Question 1

where does photosynthesis take place?

Answer 1

within the chloroplasts of plant cells

Question 2

what are thylakoids stacked to make?

Answer 2

grana

Question 3

Grana are ________ by ________

Answer 3

1. linked
2. lamallae

Question 4

define a photosynthetic pigment

Answer 4

a coloured substance that absorbs light energy needed for photosynthesis

Question 5

name an example of a photosynthetic pigment

Answer 5

chlorophyll

Question 5

where is chlorophyll and other photosynthetic substances held?

Answer 5

thylakoid membrane

Question 6

what are photosystems

Answer 6

where a protein and a photosynthetic pigment are linked

Question 7

name the two photosystems

Answer 7

PS1 and PS2

Question 8

where are photosystems found?

Answer 8

within the thylakoid membrane

Question 9

what is the best wavelength of the PS1?

Answer 9

700

Question 10

what is the best wavelength of the PS2?

Answer 10

680

Question 11

what is stroma?

Answer 11

a gel like substance within the chloroplast

Question 12

what can the stroma contain?

Answer 12

enzymes, sugars and organic acids

Question 13

what are excess carbohydrates stored as?

Answer 13

starch grains within the stroma

Question 14

name the equation for breaking a water molecule

Answer 14

H20 –> 2H+ + 2e- + 1/202

Question 15

where does the light dependent reaction take place?

Answer 15

within the thylakoid membrane

Question 16

what does the LDR do?

Answer 16

• produces oxygen from water
• produces ATP
• produces NADPH

Question 17

photosystems absorb __________

Answer 17

light from the sun

Question 18

what are photosystems joined by?

Answer 18

electron transport carriers

Question 19

describe the process of the light dependent reaction

Answer 19

1. photolysis breaks a water molecule down into protons and electrons
2. the electron enters the chlorophyll replacing the previous one
3. light is absorbed in the chlorophyll via PSII and photosynthetic pigments
4. this absorption excites the electron
5. this boosts the electron to a higher energy level, as the chlorophyll releases it from the cell
6. the electron travels down the electron transport chain to PS1, releasing energy as it reaches each electron carrier, slowly reducing its energy levels
7. the H+ ions from photolysis are moved into the thylakoid membrane via the proton pump to cause a high concentration in the thylakoid than stroma
8. they reach ATP synthase, where it diffuses down via chemiosmosis, down an electrochemical gradient.
9. either side of the ATP synthase there is ADP and Pi (Pi was added using energy from the electron)
10. a protein spins ATP synthase which combines together ADP and Pi forming ATP
11. PSI absorbs more light energy boosting the electrons to a high energy level again, the electrons and protons are transferred to NADP to form NADPH

Question 20

what is the energy released from the electron used for?

Answer 20

• be used to add a phosphate group to ATP synthase to turn ADP to ATP
• be used to transfer NADP to NADPH
• used to give energy for the proton pump

Question 21

what is the role of the proton pump?

Answer 21

it moves H+ ions into the thylakoid membrane, using energy from the electrons

Question 22

what does photolysis produce?

Answer 22

• protons
• electrons
• oxygen

Question 23

what happens to the oxygen?

Answer 23

it is released instantly

Question 24

The LDR is ______-_______ photophosphorylation

Answer 24

non-cyclic

Question 25

How many turns of the cycle to make one hexose sugar?

Answer 25

Six (as 1/6 t-3-p each cycle leave to make a hexose)