PHOTOSYNTHESIS

Question 1

Grana

Answer 1

a stack of 100 disc shaped substance called thyllakoids.

Question 2

where does ldr occur

Answer 2

thyllakoids

Question 3

where does lir occur

Answer 3

stroma

Question 4

stroma

Answer 4

fluid filled matrix containing enzyme for lir.

Question 5

light dependent reaction

Answer 5

the light dependent reaction requires light and it occurs on the thyllakoid membranes.

Question 6

stages of light dependent reaction

Answer 6

1. photolysis
2. photoionisation of chlorophyll
3. chemiosmosis
4. production of atp and reduced nadp.

Question 7

photolysis

Answer 7

light energy is absorbed by the chlorophyll and splits water into electrons, H+ and oxygen. the h+ atoms are picked up by NADP to form reduced NADP. the electrons are transported along a chain of electron carrier proteins and oxygen is either used for respiration or diffused through stomata.

Question 8

photoionisation

Answer 8

light energy is absorbed by chlorophyll and the energy results in electrons becoming excited and raise their levels so that they leave the chlorophyll. here the chlorophyll has been ionised by light. some of the energy released from the electron is used to make atp and reduced nadp in chemiosmosis.

Question 9

chemiosmosis

Answer 9

the electrons that gained energy and left the chlorophyll now move across a series of embedded protein across the thyllakoid membrane. as they move they re;lease energy which can be used to pump protons across the chloroplast membranes.
an electrochemical gradient is formed which means that the protons can be transported by facilitated diffusion through atp synthase from the thyllakoid lumen to the stroma. as the protons attatch to the enzyme atp synthase, it phosphorylates adp into atp. when the protons reach the stroma, the co-enzyme NADP picks up an electron from the end of the electron transport chain and proton that has been passed through the atp synthase and reduces NADP to NADPH.

Question 10

light independent reaction or kevins cycle

Answer 10

the cavin cycle occurs in the stroma and this fluid contains the enzyme rubisco which catalyses the reaction. this stage is temperature sensitive because of the fact that it involves enzymes.

Question 11

cavins cycle

Answer 11

the cavin cycle uses carbon dioxide, atp and reduced nadp from the LDR to form a hexose sugar. atp is hydrolysed to provide energy for this reaction and reduced nadp donates hydrogen to reduce molecules GP within the cycle.

Question 12

process of cavins cycle

Answer 12

• the carbon dioxide reacts with ribulose bi phosphate RuBP ( a 5 carbon compound) to form 2 molecules of GP(glycerate-3 phosphate) and this reaction is catalysed by an enzyme called rubisco. the GP is then reduced to triose phosphate TP by using energy from the ATP and accepting a H from reduced NADP. some of the carbon from TP leaves the cycle and frms useful organic substance while the rest is used to regenerate RuBP.

Question 13

what makes atp a good energy source

Answer 13

• atp stores or releases only a small amount of energy at a time.
• atp is a small soluble molecule, so it is easily transported around the cell.
• atp can make other molecules active by the process of phosphorylation.
• atp can not pass out of the cell, so cell always have an immediate supply of energy.

Question 14

co enzyme

Answer 14

a molecule that aids the functioning of an enzyme. nad, nadp, fad and co enzyme a

Question 15

co - enzyme used in photosynthesis

Answer 15

NADP

Question 16

co- enzyme used in respiration

Answer 16

nad, fad and co-enzyme a

Question 17

products of ldr

Answer 17

atp and reduced nadp
- atp transfers energy and reduced nadp transfers hydrogen to the light independent reactions.
- also h20 is oxidised to 02

Question 18

in ldr energy from photoionisation is used for 3 things

Answer 18

1. photophosphorylation- making atp from adp and pi
2. making reduced nadp from nadp.
3. photolysis - splitting water into protons, electrons and oxygen.

Question 19

chloroplast adaptation for photosynthesis

Answer 19

• thylakoid membrane provides larger surface area.
• proteins hold grana for maximum light absorption
• atp synthase and selectively permemable membrane for atp synthesis.
• dna and ribosomes for synthesis of required proteins.

Question 20

process of light dependent reaction

Answer 20

• photoionisation, photolysis, electron transfer chain, reduced nadp and phosphorylation and chemi osmosis

Question 21

photoionisation

Answer 21

• light energy is absorbed by the chlorophyll and this light energy is then transferred into the electrons within the chlorophyll.
• the electrons then go into an exciting state and is released from the chlorophyll.

Question 22

photolysis

Answer 22

• since the electrons leave the chlorophyll, it soon needs to be replaced by other electrons.
• light energy splits water into electrons, proton and oxygen.
• electron is replaced and transported along a chain of electron transfer protein and oxygen is diffused out of the cell for the process of respiration.

Question 23

electron transfer chain

Answer 23

the electrons then moves along a series of proteins called the electron transfer chain which is controlled by a series of reaction called the oxidation reduction reactions. the energy released by these reactions helps in the active transport of protons from the stroma into the thyllakoid spaces.

Question 24

reduced nadp

Answer 24

at the end of the electron transfer chain, the electrons reacts with a co enzyme called NADP and a proton to form reduced NADP.

Question 25

chemiosmosis and phosphorylation

Answer 25

as we know there is a higher concentration of protons in the thyllakoid spaces rather than in the stroma, an electro chemical gradient is established. so now the protons move down the concentration gradient via an enzyme called atp synthase embedded in the thyllakoid membrane. the energy released from this movement creates atp from adp and pi(phosphorylation).