e'q Photosynthesis

Question 1

suggest why soda lime was not placed in the respirometer with the seedling grown in the light

Answer 1

• removing CO2 would prevent photosynthesis
• CO2 would be a limiting factor for photosynthesis

Question 2

outline the structural differences the chromista cholorplast + the chloroplasts found in flowering plants

Answer 2

• chromista has fewer thylakoids
• chromista has no inter- granal lamellae
• plants have thylakoids in groups of more than three
• plants have strach grains

Question 3

suggest why having a high conc of chlorophyll D is an advantage for Acaryochloris marina

Answer 3

• absorbs wider range of WL
• absorbs light at diff WL compared to aquatic plant species
• little light avaliable

Question 4

what can you conclude about the composition of pigment A to D

Answer 4

• pigment A contains 2 molecules (2 spots above each other)
• pigment B and D contain 1 molecule (1 spot above line)
• pigment C contains 3 molecules ( 3 spots above)
• pigments A and C share molecules ( next to each other)
• all pigments are soluble

Question 5

outline the importance of photosynthetic pigments in photosynthesis

Answer 5

• pigment absorb light
• electrons excited
• accessory pigments pass energy to primary pigments
• primary pigments loses electrons
• for light dependent reaction ( photophosphorylation)

Question 6

suggest why chromista needs pigment that are different from those of other photosynthetic organisms

Answer 6

that they have to absorb light of short WL
that some WL doesnt reach them

Question 7

state a material that can be used as the stationary phase in thin layer chromatography

Answer 7

silica gel

Question 8

state the precise location of photosynthtic pigments in a choroplast

Answer 8

photosystem in the thylakoid membrane

Question 9

on a chromotogram, how would you know what spot (pigment) is the most non polar

Answer 9

it would be the most soluble in moblie phase

Question 10

why it is important to hold the TLC plate carefully by the edges + avoid damaging the surface of the plate

Answer 10

so that the movement of spots not affected by damage

Question 11

why is it important to make sure the plate doesn’t touch the sides of the jar anywhere else

Answer 11

to avoid spots travelling in the wrong direction

Question 12

suggest an advantage of working quickly as possible in step 1 (extraction of pigments) in TLC

Answer 12

to prevent contamination of the pigments
to reduce evaporation of solvent

Question 13

state the name of the final electron accepter in the light dependent stage of PS

Answer 13

NADP

Question 14

DCPIP is reduced in the Hill reaction. suggest + explain the function of DCPIP in the Hill reaction

Answer 14

• final electron acceptor
• replaces NADP - the usual electron acceptor
• allows photolysis to continue

Question 15

explain why it was important that the pellet (sediment) was suspended in buffer solution + why it did not contain sucrose

Answer 15

buffer maintain the optimum pH
if theres no sucrose, no need to prevent damage to choloplast

Question 16

suggest and explain 2 improvements that would increase the validity of the method ( the hill reaction)

Answer 16

use ice cold solution = prevents damage to components
use a water bath = so that temp of all tubes is controlled

Question 17

explain why temperature has a greater effect on the rate of the light independent stage

Answer 17

light independent stage is controlled by enzymes
high temp will increase ESC’s formed
enzymes may be denatured at high temperatures

Question 18

describe 2 ways in which the structure of granum is adapted to its function

Answer 18

large SA for increase in absorption of light
contain photosystems
contain electron carriers

Question 19

w/ referece to the biochemistry of photosynthesis, explain why the theoretical rate of PS is not achieved at higher light intensities

Answer 19

at incr light intensity other factor becomes limiting
temp becomes limiting as calvin cycle invloves enzymes
CO2 conc becomes limiting as it is required for calvin cycle

Question 20

which species would be bettter adapted to living in shady conditions

Answer 20

one that starts PS at low light intensity
one that reaches its max rate at lowlight intensity
one that has a greater ROPS

Question 21

how would a structure of leaf adapted to shade differ from one thats living in sunlight

Answer 21

shade leaf will have more chloroplasts ; more thylakoids in choloplast, larger SA of leaves

Question 22

describe how light is harvested in the choroplast membranes

Answer 22

primary accessory pigments are in the photsystems
light energy absorbed by pigment molecules
electron moves to higher energy level + returned to pigment
energy passed from one pigment to another
energy passed from to reaction centre
accessory pigments allow range of WL to be absorbed

Question 23

suggest the role of DNA+ ribosomes in this organelle

Answer 23

DNA coding for enzymes
ribosome : proteins synthesis
proteins for pigments synthesis
protiens for electron carriers
enzyme for photolysis
enzymes for calvin cycle