photosynthesis 5.6

Question 1

the relationship between respiration and photosynthesis

Answer 1

-photosynthesis uses the products of respiration being water, carbon dioxide to make glucose which is a energy store needed for plants
- animals cant produce their own food so eat plants and absorb glucose from them so their processes can occur

Question 2

structure of the chloroplast

Answer 2

• contains starch = energy storage
• ribosomes= protein synthesis
  -DNA= genes the code for proteins needed in photosynthesis
  -stroma=gel-like substance= site of light independent stage
  -thylakoid membrane= site of the light dependent stage
  -stacked thylakoid as granum joined by a intergranal lamelle
  contains photosystems 1 and 2 which absorb sunlight containing pigments. pigments= primary= chlorophyll and secondary pigments= chlorophyl B and carotine
  -double membrane

Question 3

the light dependent stage of photosynthesis

Answer 3

• PHOTOLYSIS= light energy from the sun breaks down the water molecule in the thylakoid membrane making o2 and 2H+
• Light energy also excites the electrons in photosystem 2 (2e-)
• electron carriers move excited electrons along the electron-transport chain
  -electrons loose energy along electron-transport chain and arrive at photosystem 1
• PHOSPHCHLORONATION= ADP and inorganic phosphate is combined forming ATP need for electrons to be transported
• light energy also excites the electron in photosystem 1
• if plant has enough energy it goes through non cyclic phosphocloranation= electrons are transferred to NADP along with H+ion from the water molecule previously broken down in photolysis to formed reduce NADP ATP is also a product
  -if cyclic phosophoclorantation occurs = electrons are passed back into photosystem 1 via electron carriers produced ATP
  -

Question 4

the light independent stage (calvin cycle)

Answer 4

• FIXATION= co2 combines with 5 carbon molecule Ribulose biphosphate (RuBP) forming 6 carbon molecule glycerate-3-phosphate (Gp) catalysed by the enzyme ribulose biphosphate carboxylase(RuBisco)
  -REDUCTION= Glycerate-3-phosphate forms another carbon molecule triose phosphate (Tp). for this process ATP is needed. ADP + pi= ATP
  -reduced NADP produced in the light dependent stage is used as a H+ is needed. reduced NADP is o=converted back to NADP.
  -Tp is converted to useful compounds
  -REGENERATION= Tp is converted back into RUBP to be used in next cycle using ATP

Question 5

uses of Tp

Answer 5

glycerol from TP combines with the fatty acids made by glycerate-3-phosphate to make lipids
- glucose is a hexose sugar. joining two tp molecules which is a triose sugar forms glucose. combining hexose sugars can also make complex carbohydrates such as starch and sucrose
- Gp can make amino acids= proteins

Question 6

Factors affecting photosynthesis

Answer 6

high light intensity- more energy in light dependent stage= increased rate of photosynthesis until another factor is limiting low light intensity- short supply of reduced NAD and ATP which are
products of photosynthesis. therefore conversion of GP to TP = slow.
levels of Gp rise as they are still being made but levels of TP and RuBp. as used to make GP
low temperature= enzymes involved income inactive high temperatures- enzymes become denatured, stomata closes to avoid loosing too much water. so less co2 can be taken in by the plant slowing down photosynthesis.
- levels of RuBp.GP and TP fall
-increasing CO2 = higher rate of photosynthesis but any higher than
0.4% stomata starts to close
-RuBP to GP conversion =slow
So the level of RuBP will rise (as it’s still being made) and levels of GP and TP will fall (as they’re used up to make RuBP).

Question 7

Photosystems

Answer 7

• within the thylakoid membrane= funnel shaped structures that contain photosynthetic pigments which absorb different wavelengths of light.
• The accesory pigments (carotenoids-ither xanthophyll or B carotene) pass the energy to the primary pigment (chlorophyll a)
• -the primary pigment becomes excited and looses electrons in the electron transport chain
• these excite electrons to a higher energy level to be used in the light dependent reaction

Question 8

TLC of photosynthetic pigmnets

Answer 8

• crush the plant to break down the cell wall and cell membrane to release the photosynythetic pigments
• place the pigmnets on the pencil line on the paper
• handle the TLC with gloves so that the amino acids n your hands do not contaminate the results
• place in solvent below the pencil line
• calculate the RF value and compare to known value