photosynthesis

Question 1

ATP

Answer 1

-Adenosine triphosphate
-nitrogenous organic base
-ribose sugar
-3 phosphate groups
-used as an energy source

Question 2

Use of ATP

Answer 2

-provides energy ( active transport)
-phosphorylation ( binds to enzymes/substrates and lowers the Ea or alters the 3 structure

Question 3

why is ATP useful

Answer 3

-releases energy in small manageable amounts
-broken down in one step
-immediate energy compound
-phosphorylates
-lowers activation energy
-reformed

Question 4

forming ATP

Answer 4

-ADP and inorganic phosphate
-requires energy to add a phosphate to ADP-forms ATP with a high energy bond
-condensation reaction

Question 5

breaking ATP

Answer 5

-into ADP and inorganic phosphate
-bond between 2nd and 3rd phosphate breaks
-releasing small manageable amounts of usable energy
-hydrolysis reaction which requires 1 molecule of water

Question 6

Give two ways the hydrolysis of ATP is used in cells

Answer 6

-muscle contraction
-active transport

Question 7

NADP

Answer 7

• Nicotinamide Adenine Dinucleotide Phosphate
  -acts as a hydrogen acceptor
  -reduced to form NADPH

-NADPH is a reducing agent
-it can donate H+ to other molecules in REDOX reaction
-NADPH becomes oxidised (to NADP) and the other molecule that accepts the H+ is reduced

Question 8

Photosynthesis equation

Answer 8

6CO2 + 6H20 —> C6H12O6 + 6O2

Question 9

chloroplasts

Answer 9

site of photosynthesis

Question 10

thylakoids

Answer 10

-contains chlorophyll in the membrane
-Large SA
-Has light dependent reactions

Question 11

Granum

Answer 11

a stack of thylakoids

Question 12

stroma

Answer 12

-enzyme controlled reactions take place
-light independent reactions

Question 13

starch grain

Answer 13

• alpha glucose monomers
  -linked by glycosidic bonds

Question 14

70s ribosomes

Answer 14

-site of protein synthesis

Question 15

circular DNA characteristic

Answer 15

-shorter DNA
-not associated with histones
-has genes that code for proteins involved with photosynthesis

Question 16

membranes

Answer 16

-inner membrane
-outer membrane

Question 17

Light dependent reactions

Answer 17

-in the Granum
-light + H2O —> O2 + NADPH +ATP

Question 18

Light independent reactions

Answer 18

-in the Stroma
-CO2 + NADPH + ATP —-> Glucose

Question 19

Light dependent reactions ( 6 marks)

Answer 19

-chlorophyll absorbs light energy via (photoionisation)
-electrons become excited so chlorophyll is oxidised
-electrons then move across the electron transport chain
-energy released by electrons produces a proton gradient
-H+ ions then diffuse through the ATP synthase via (photophosphorylation)
-provides energy to join ADP + Pi to form ATP
-electrons that left chlorophyll are replaced by electrons from water molecules via (photolysis) so chlorophyll is reduced
- H+ and an associated electron are used to reduce a Hydrogen carrier NADP to form NADPH

Question 20

site of photolysis

Answer 20

thylakoid space

Question 21

proton electrochemical gradient

Answer 21

• high conc. of H+ ions in thylakoid space than on the other side of the membrane
  -H+ ions diffuse from high to low conc. to try to reach equilibrium
  -can only move through ATP synthase

Question 22

herbicide

Answer 22

-Reduced transfer of protons across thylakoid membrane
-Reduced proton gradient across thylakoid membrane
-less ATP produced
-less NADPH produced
-light-independent reaction slows/stops

Question 23

Fluorescence

Answer 23

• ETC not available for excited electron
  -releases energy as light

Question 24

suggest why LID reaction is not the only source of ATP

Answer 24

• plants don’t photosynthesise in the dark
  -not all parts can photosynthesise (roots)
  -plants require more ATP then what is produced in the LDR
  -ATP used in active transport

Question 25

Light Independent reaction 3 phases:

Answer 25

• Carbon fixation
• Reduction
• Regeneration

Question 26

Light independent reaction ( 5 marks )

Answer 26

• CO2 fixes with RuBP
  produces 2x glycerate-3-phosphate
  -GP reduced to triose phosphate
  -using NADPH
  -using energy from ATP hydrolysis
  -TP converted to glucose/amino acid
  -most TP used to regenerate RuBP

Question 27

RP7: Chromatography method

Answer 27

-draw a straight line in pencil 1cm above bottom of filter paper
-place leaf in mortar, add acetone + use pestle to grind up leaf + release the pigments
-use capillary tube to extract some of pigment + blot it on centre of pencil line
-suspend paper in solvent and ENSURE the liquid isn’t above the pencil line
-leave paper until the solvent has run up paper to near the top
-remove paper from solvent + draw a pencil line marking solvent front
-calculate Rf value for each spot

Question 28

RP7: why use a pencil to mark the line?

Answer 28

• ink and pigments would mix

Question 29

RP7: Rf value equation

Answer 29

Rf= distance moved by pigment/ distance moved by solvent front

Question 30

factors affecting photosynthesis

Answer 30

• temp
• light intensity
• co2 conc.

Question 31

The concentrations of carbon dioxide in the air at different heights above ground in a forest changes over a period of 24 hours.

Use your knowledge of photosynthesis to describe these changes and explain why they occur. [5]

Answer 31

-High concentration of carbon dioxide linked with night
-No photosynthesis in dark as light is required for photosynthesis
-In dark plants respire instead
-Plants use more carbon dioxide than they produce
-Decrease in carbon dioxide concentration with height
-At ground level less light
(e.g. roots do not photosynthesise)