Photosynthesis Module 5 Flashcards
Biological processes which require energy in plants?
Photosynthesis active transport DNA replication Cell division Protein synthesis
Biological processes which require energy in animals?
Everyone in plants except photosynthesis+ maintenance of body temp
Respiration definition?
Living cells release energy from glucose, and used to power all biological processes in the cell
Metabolic pathway?
A series of small reactions controlled by enzymes ( respiration or photosynthesis)
Phosphorylation?
Adding Phosphate to a molecule using light
Photolysis?
Splitting of a molecule using light energy
Hydrolysis?
Splitting of a molecule using water
Decarboxylation?
Removal of CO2 from a molecule
Dehydrogenation?
Removal of hydrogen from a molecule
Coenzyme?
Molecules which aids the function of an enzyme, by moving chemical groups from one molecule to another
In photosynthesis it’s NADP, transfer hydrogen from one molecule to another
Features of chloroplasts?
Small flattened organelles, location of photosynthesis
Have double membrane called chloroplast envelope
Thylakoids are stacked up to from Grana in the chloroplast, and are linked together by lamellae
Contain photosynthetic pigments
What are photosynthetic pigments?
Examples are chlorophyll a, b and carotene
Absorb light energy and found in thylakoid membrane, and are attached to proteins = photosystem
Where are primary pigments found?
Reaction centre, where electrons are excited during LDR
Chlorophyll a
Where are accessory pigments found?
Make up harvesting system, surround each reaction centre and transfer light energy
Chlorophyll b and carotene
PS1 wavelength absorbed?
700nm
PS11 wavelength absorbed?
680nm
Stroma?
Gel like substance surrounding thylakoid membranes, contains enzymes and organic sugars
Chlorplasts have their own circular DNA found in it
Carbohydrates can be stored as starch granules in it
What’s the mobile phase?
Liquid solvent
What’s the stationary phase?
Gel it’s transferring through
How do you find Rr value?
Distance travelled by spot / distance travelled by solvent
Non cyclic photophosphorylation ( LDR)?
Light energy absorbed by PS11 (680nm), exciting electrons in chlorophyll
Electrons move to a higher energy level to an electron carrier, and then move down a transport chain to PS1
As excited electrons leave PS11, they need to be replaced so light energy splits water into H+ ions, electrons and oxygen (goes into atmosphere)
(chemiosmosis)
The excited electrons lose energy as they move down the electron transport chain
This energy is used to transport protons into the thylakoid, via protein pumps, so thylakoid has higher conc of protons than stroma, forming a gradient across the membrane
Protons move down conc gradient into stroma via enzyme ATP synthase, the energy from this movement combines ADP and inorganic phosphate, forming ATP
Light energy absorbed by PS1 (700nm), which excites the electrons to an even higher energy level
Finally electrons are transferred to NADP, along with a H+ ion to form reduced NADP
Cyclic photophosphorylation?
Only uses PS1
Cyclic as electrons aren’t passed onto NADP, but passed back to PS1 via electron carriers
Therefore electrons recycled and repeatedly flow through
No Reduced NADP or O2 formed, little bit of ATP made
Calvin cycle explained (LIR)?
CO2 enters leaf through stomata, diffuses into stroma of chloroplast
Combines with RuBp, making an unstable 6C compound which splits into 2 3C compounds called GP
Rubsico enzyme catalyses reaction between CO2 and RuBp
ATP from LDR turns GP into TP, this reaction also requires H+ ions from reduced NADP in the LDR, reduced NADP is recycled back to form NADP
TP converted into many useful compounds
5 out of every 6 TP molecules aren’t used to make Hexose sugars, but are regenerated to form RuBp
Regenerating RuBP uses rest of ATP produced in LDR
What are the useful substances made by the Calvin Cycle?
Carbs- 2 TP molecules
Lipids, using glycerol synthesised from TP and fatty acids from GP
Amino acids from GP
How many turns of Calvin cycle to produce 1 hexose sugar?
6
Ideal conditions for photosynthesis?
High light intensity of a certain wavelength
Temperature around 25 degrees
If temps too low enzymes become inactive
If temp too high:
enzymes denatured
Stomata close to reduce water loss, so less CO2 enters reducing photosynthesis
Thylakoid membranes damaged, LDR stage slowed as reduced sites for e- transfer
Carbon dioxide levels at 0.4%, any higher stomata start to close
Saturation point?
Where increasing factor anymore doesn’t make a difference
Why does when a plant have low water levels photosynthesis decreases?
Stomata close to reduce water loss, less CO2 enters
How does low light energy affect concentration of different compounds?
Reduced NADP and ATP concs will be low, as slow LDR
Conversion of Gp to Tp and RuBp slow
So Gp levels rise, but Tp and RuBp fall
How does low temperature affect concentrations of compounds?
Enzymes rate will be slower, levels of RuBp Tp and Gp slower
How does low CO2 conc affect concentrations of compounds?
Conversion of RuBp to GP is slow, so RuBp increases and Gp and Tp fall
