Photosynthesis

Question 1

what does life depend on

Answer 1

the continuous transfer of energy

Question 2

in plants what is light energy absorbed by

Answer 2

the chlorophyll and then transferred into the chemical energy of the molecules formed during photosynthesis

Question 3

site of photosynthesis

Answer 3

• the leaf in eukaryotic plants
• chloroplast are the cellular organelle where photosynthesis takes place

Question 4

structure of the leaf

Answer 4

• large surface ares to absorb as much sunlight as possible
• arrangement on plants that minimises leaves overshadowing each other
• thin so short diffusion pathway
• transparent cuticle and epidermis that lets light through to the photosynthetic mesophyll cells
• land narrow upper mesophyll cells packed with chloroplast
  numerous stomata for gas exchange

Question 5

photosynthesis equation

Answer 5

6co2 + 6h20 = c6h12o6 + 6o2

Question 6

3 stages of photosynthesis

Answer 6

1. capturing light energy
2. light dependent reaction
3. light independent reaction

Question 7

what captures light energy

Answer 7

chloroplast pigments (chlorophyll)

Question 8

what happens during light dependent reaction

Answer 8

• light energy absorbed is conserved in chemical bonds
• water splits (photolysis) into protons, electrons, NADP, ATP and oxygen

Question 9

what happens during the light independent reaction (simple)

Answer 9

protons (hydrogen ions) are used to produce sugar

Question 10

structure of chloroplast

Answer 10

• disc shaped
• 2- 10 um long
• 1 um in diameter
• surrounded by double membrane

Question 11

role of chloroplast

Answer 11

• grana are stacks of up to 100 disc like structures called thylakoids where the light dependent stage of photosynthesis takes place
• within the thylakoids is chlorophyll

Question 12

stroma

Answer 12

• fluid filled matrix where the light independent stage takes place
• has starch grains

Question 13

photosynthesis involves the capture of light energy for

Answer 13

1. add inorganic phosphate to ADP to make ATP
2. split water into h + ions (protons) and OH - ions (photolysis)

Question 14

what is oxidation

Answer 14

• a substance gains oxygen
• losses hydrogen
• loses electrons
• losses energy

Question 15

what is reduction

Answer 15

• a substance loses oxygen
• gains hydrogen
• gains electron
  gains energy

Question 16

how is ATP made in photosynthesis

Answer 16

1. when a chlorophyll molecule absorbs light energy it boosts the energy of a pair of electrons within the chlorophyll raising then to a higher energy state where they leave the chlorophyll molecule
2. the chlorophyll molecule becomes ionised (photoionisation)
3. the electron are taken up by the electron carrier
4. chlorophyll is oxidised and electron carrier is reduced
5. electrons are passed along electron carrier in oxidisation reduction reactions
6. each new carrier is at a lower electron level than the previous one in the chain so energy is lost at each stage
7. this energy is used to combine an inorganic phosphate with ADP to make ATP

Question 17

what is the chemiosmotic theory

Answer 17

• each thylakoid is an enclosed chamber with protons (H +) are pumped from the stroma using protein carriers in the thylakoid membrane (protein pumps)
• energy is supplied by the water splitting by light
• the photolysis of water also produces protons which further increase their concentration inside the thylakoid space
• this creates and maintains a concentration gradient which a high concentration of protons inside the thylakoid space and a low concentration in the stroma
• the proteins cross the thylakoid membrane through ATP sythases channel proteins
• as the protons passes the protein channel they cause changes to the structure of the enzyme which catalyses the combination of ADP and Pi to form ATP

Question 18

what is the process for the photolysis of water

Answer 18

• the replacements electrons for the chlorophyll molecules are provided from water molecules that are split using light energy
• these protons pass out of the thylakoid space through the ATP synthase channels and are taken up by NADP which becomes reduced NADPH

Question 19

equation for the photolysis of water

Answer 19

2H2O –>4H+ + 4E- +O2

Question 20

how is chlophyll structiually adapted to its function

Answer 20

1. thylakoid membrane provides a large surface area for the attachment of chlorophyll, electrons carriers and enzymes
2. granna has chlorophyll in a precise manner for maximum light absorption
3. granal membranes have ATP synthase channels which catalyses the production of ATP
4. chloroplast contains DNA and ribosomes so can manufacture some proteins involved in light dependent reactions

Question 21

what is chlorophylls function

Answer 21

capture sunlight and carry out the light dependent reaction of photosynthesis

Question 22

where does the light independent stage of photosynthesis take place

Answer 22

the stroma of the chloroplast

Question 23

brief outline of the calvin cycle

Answer 23

RuBP + co2 = 2 GP + NADPh = 3 TP + ATP = RuBP

Question 24

how is the chloroplast adapted to carry out the light independent reaction

Answer 24

1. the fluid of the stoma contains all the enzymes needed to carry out the reaction
2. stoma fluid surrounds the the grana and so the product of the light dependent reaction in the grana can readily diffuse into the stroma
3. contains both dna and ribose so it can quickly manufacture some of the proteins involved