Photosynthesis

Question 1

What is photosynthesis

Answer 1

• the process by which energy (in the form of light from the sun) is used to build complex organic molecules

Question 2

Word equation for photosynthesis

Answer 2

carbon dioxide + water = glucose + oxygen

Question 3

What are autotrophs

Answer 3

Organisms that can photosynthesis to produce their own complex molecules

Question 4

What are heterotrophs

Answer 4

have to obtain complex organic molecules by eating other organisms

Question 5

Key structural features of chloroplasts

Answer 5

• double membrane
• very flat- increases surface area to absorb light
• thylakoids
• grana/ granum
• lamellae
• stroma

Question 6

What is a granum

Answer 6

A stack of thylakoids (fluid filled sacs formed by membranes)

Question 7

What are lamellae

Answer 7

• join grana together
• bits of thylakoid membranes, membranous channels

Question 8

What is the stroma

Answer 8

• the fluid enclosed in a chloroplast
• site of many chemical reactions

Question 9

What is chlorophyll

Answer 9

• pigment molecule that absorb different wavelengths of light
• absorbs red and blue, reflects green

Question 10

What are 4 main photosynthetic pigments

Answer 10

• chlorophyll A
• chlorophyll B
• carotenoids
• xanthophyll

Question 11

Differences in roles of photosynthetic pigments

Answer 11

• chlorophyll A is in the reaction centre where photosynthesis occurs
• chlorophyll B, carotenoids, xanthophyll embedded in thylakoid membranes, joined to proteins, form light harvesting system

Question 12

What is a photosystem

Answer 12

-the light harvesting system and reaction centre
- proteins and pigments collectively

Question 13

Summary of the light dependent stage

Answer 13

• occurs in thylakoid membranes
• energy from sunlight is absorbed and used to form ATP
• hydrogen from water is used to reduce NADP
• Produces NADPH, ATP, oxygen

Question 14

non-cyclic phosphorylation

Answer 14

• involves PSI + PSII
• electrons travel from PSII to PSI, losing electrons as they do so
• electrons lost from PSII are replaced by photolysis
• electrons from PSI pass down electron transport chain, form reduced NADP
• electrons lost from PSI replaced with electrons from PSII

Question 15

What is photolysis, what is the equation

Answer 15

• light energy is used to split water
• water => hydrogen + electrons + oxygen

Question 16

Cyclic phosphorylation

Answer 16

• involves PSI only
• electrons leaving PSI return via electron carriers
• ATP produced

Question 17

What cycle is involved in the light independent stage

Answer 17

Calvin cycle

Question 18

Where does the light independent stage occur

Answer 18

Stroma

Question 19

3 key molecules involved in the light independent stage

Answer 19

• Triose phosphate (TP)
• Ribulose phosphate (RuBp)
• Glycerate 3 phosphate (GP)

Question 20

Overall products of the light independent stage

Answer 20

• ADP + P
• NADP
• carbs/ sugars/ amino acids/ lipids
• regeneration of RuBp

Question 21

Factors affecting photosynthesis

Answer 21

• light intensity
• carbon dioxide concentration
• temperature

Question 22

How does light intensity affect photosynthesis

Answer 22

• If light intensity is high, more ATP and NADPH are produced in the light dependent stage, so more ATP and NADPH enter the calvin cycle
• Results in high GP, low TP and RuBp

Question 23

How does carbon dioxide concentration affects photosynthesis

Answer 23

• increases the rate of carbon fixation in the Calvin cycle
• results in less GP , less TP, increases RuBp

Question 24

How does temperature affect photosynthesis

Answer 24

• at high temperatures, enzymes may denature, stomata may close causing less photosynthesis as less CO2, potential damage to all the membranes, resulting in less photosynthesis