Photosynthesis Flashcards
What 3 things is light energy absorbed by photosystems used for?
1) photophosphorylation
2) making reduced NADP from NADP
3) photolysis
What does non-cyclic photophosphorylation produce?
- ATP
- reduced NADP
- oxygen
Where and in what form is energy stored as in ATP?
Chemical energy in the phosphate bond
Name 5 ATP properties
1) stores or releases a small amount of energy at a time so none is wasted
2) it’s small and soluble so is easily transported around the cell
3) easily broken down so energy is easily released
4) it can transfer energy to another molecule by transferring one of its phosphate groups
5) can’t pass out the cell so the cell always has an immediate supply of energy
Name 4 chloroplast adaptation
1) chloroplast envelope keeps the reactants for photosynthesis close to their reactant sites
2) thylakoids have a large surface area for maximum light absorption
3) lots of ATP synthase molecules are present in the thylakoids membranes to produce ATP
4) stroma contains all the enzymes, sugars and organic acids for the light-independent reaction
Describe the process of non-cyclic photophosphorylation
- light energy is absorbed by PS2, exciting the electrons in chlorophyll to a higher energy level, high energy electrons move along the electron transport chain PS1
- electrons lost must be replaced, so water splits into protons, electrons and oxygen
- electrons lose energy as they move along the electron transport chain, this energy is used to transport protons from the stroma into the thylakoid, forming a proton gradient across the membrane (higher conc. in thylakoid)
- protons move down their concentration gradient back into the stroma via the enzyme ATP synthase, the energy from this movement combines ADP and inorganic phosphate to form ATP
- light energy is absorbed by PS1, exciting electrons to a higher energy level, they’re then transferred to NADP, along with a proton from the stroma, to form reduced NADP
What’s the difference between cyclic and non-cyclic photophosphorylation?
In cyclic photophosphorylation, electrons aren’t passed on to NADP, but instead recycled back to PS1
Cyclic photophosphorylation dosent produce any reduced NADP or oxygen, just small amounts of ATP
What catalyses RuBP + CO2?
Rubisco (RuBP carboxylase)
Describe the process of the Calvin cycle
- CO2 enters the leaf through the stomata and diffuses into the stroma of the chloroplast where it combines with RuBP (catalyzed by rubisco)
- this gives an unstable 6C compound which quickly breaks down into two molecules of a 3C compound, GP (glycerate 3-phosphate)
- GP is reduced to TP (triose phosphate), another 3C molecule, using H+ ions from reduced NADP from the light dependent reaction. ATP from the light dependent reaction provides the energy for this, reduced NADP is recycled back to NADP
- 5/6 TP molecules and the rest of the ATP molecules from the light dependent reaction are used to regenerate RuBP, the other molecule is used to make useful organic substances such as glycerol and fatty acids
How many Calvin cycle rotations produce one hexose sugar?
6
What is a hexose sugar (carbohydrate) made from?
Two molecules of TP
What does joining hexose sugars together in different ways give you?
Larger carbohydrates
What are lipids made from?
Glycerol- synthesized from TP
Fatty acids- synthesized from GP
What are some amino acids made from?
GP
What are the photosynthetic pigments? What color light wavelengths do they absorb?
Chlorophyll a, chlorophyll b, carotene
Absorb red and blue light in sunlight
