Photosynthesis Flashcards
Define photosynthesis
Plants making food
Briefly outline the process of photosynthesis (the conversion of energy)
light energy -> chemical energy (in the form of glucose to become polysacc)
Outline the two reactions in photosynthesis
Light dependent and light independent
Can non plants do photosynthesis
yes
Define autotrophs
Can make their own food
Outline the two types of autotrophs
1.) Photo autotrophs
2.) Chemo autotrophs
Give the chemical equation of photosynthesis
6CO2 + 6H2O - sunlight/chlorophyll -> C6H12O6 + 6O2
Why isn’t photosynthesis an “inverse” of cell respiration?
Because they take place in diff parts
- only certain things have chloroplasts
But why does photosynthesis and cell respiration have a relationship
Another man’s trash is another one’s treasure (the input and output are dissimilar)
What are the two stages of photosynthesis
1.) Light-dependent reaction
2.) Light-independent reaction [aka dark rxn/Calvin cycle]
What occurs in the first stage, “Lyse”?
Break down the water into hydrogen and oxygen to get ATP for stage 2 [PHOTOLYSIS]
- Gets ATP from Hydrogen ion of water (like ETC hehe)
- End product: hydrogen ion -> 2 ATP and oxygen (“waste product”)
What occurs in the second stage/Carbon Fixation?
Energy from ATP to transform carbon dioxide -> carbs (to make da glucose)
- Catalyzed by Rubisco
-> Rubisco helps the bonding of the single carbon atom to the RuBP
Where does light independent reaction occur?
Stroma, gel like structure
Granum vs thylakoid
Where does the Krebs Cycle and Link Reaction take place (Cell resp.)
in the matrix
In the chemical reaction of photosynth, which is the reduced and which is oxidized?
Reduced: 6 Co2
Why do plants convert glucose into sucrose / into polysaccharides
Anabolic pathway because they need polysacc such as starch and cellulose
How is starch formed?
Condensation
Outline the range of the wavelengths of light
ROYGBV
(Red - longest wavelength,
Violet - shortest wavelength)
which wavelength of light is used by green plants?
Blue and Red are absorbed
Why do plants appear green?
Chlorophyll absorbs the Red and Blue wavelengths but the green light is reflected.
(color shown - reflected) [LIGHT-DEPENDENT REACTION]
Differentiate action vs absorption spectrum
Action spectrum
- after absorbing the wavelenth, what will be the of wavelength used ?
- not green, e.g.: red and blue?
Absorption spectrum
- wavelengths absorbed/got
-ie. all except green (green is reflected) [for chlorophyl — for the green plants]
Do all plants have the same action/absorption spectrum
They all have diff colours.
Which pigment aids plants in winter?
So they could produce food, they’ll use accessory pigments which can do photosynthesis for them
How can CO2 concentration affect photosynthesis?
affects the rubisco — the fixation enzyme (carbon fixation — attaches a carbon atom to the RuBP)
Main idea: ^ CO2 concentration = ^ rate of photosynthesis to a certain point.
- if less carbon concentration, less carbon collide w/ active site -> v rate pf photo synthesis
- if more then, ^ rate of photosynthesis but there’d be a queue
How does light intensity affect the rate of photosynthesis?
If high light, there’s a plateau because chloroplasts are working at full efficiency — chloroplast is occupied || The photosystems can only absorb a certain amount of light, carrier proteins can only carry one proton at a time,
-> There’s no enzyme being affected
if low light, v photosynthesis = v production of sugars
How does temperature affect the rate of photosynthesis?
Affects enzyme Rubisco.
-> denaturation
Define mesophyll layer
Layer that is rich in choloroplasts
Describe Calvin Cycle
CARBON FIXATION
- “Rubisco” = RuBP — 5 carbon with two phosphates @ the end
1.) A CO2 atom bonds to the RuBP [6 carbon muolecule, 2 phos at the ends]
2.) Instability due to phos — bonds break -> 2 3C mols w/ phosphate each
3.) Phosphorylation from 2 ATP; came from light-dep (2 ATP -> 2 ADP) — why?
4.) NADPH -> NADP to remove the added phosphates (to diminish instability)
5.) 1 carbon deposited to form glucosw
6.) [Regeneration of RuBP] The rest (5 carbons — 1 2C with 1 Phos & 1 3C with 1 Phos) to form RuBP
Describe the calvin’s cycle (ADD PHOTO) [actual]
1.) [CARBON FIXATION] Co2 (a carbon atom of it) gets attached to RuBP -> 6 carbons 2 phosphates catalyzed by Rubisco (attaches them tgt)
2.) The molecule splits into two 3 carbon molecule w/ a phosphate atom each (PGA) — due to instability from phosphate group
3.) [PGA REDUCTION] 2 ATP (from light dependent reaction) reduces to 2 ADP -> donates the 2 phosphates to the carb molecules (becomes Biphosphoglycerates)
4.) the 2 NADPH uses energy to remove the two added phosphate atoms to the two groups (phosphoglyceraldehydes — PGAL)
5.) One of the carbon atoms from the 2 generated PGALs will be removed to become of one of the carbon atoms in the glucose.
Explain the relationship between the chloroplast structure and function?
1.) Fold in thylakoid: electron carries can be closer together (?), big SA:V ratio in order to maximize proton accumulation
2.) Chlorophyll: molecules grped together to form the photosystems — embedded in the membrane ?
3.) Grana - stacked thylakoids to increase SA:V ratio
4.) Stroma - central cavity that contains appropriate enzymes and suitable pH for Calvin’s Cycle
5.) Lamellae - maximizes photosynthetic efficiency by connecting and stacking thylakoids (grana)
Differentiate the C3, C4 and CAM plants
Describe non-cyclic phosphorylation [5]
Non-Cyclic Photophosphorylation
- Chlorophyll in photosystems I and II absorbs light, which triggers the release of high energy electrons [photoactivation]
- The electrons from photosystem II *pass along a series of carriers (electron transport chain), producing ATP via chemiosmosis *
- The electrons from photosystem I reduce NADP+ to generate NADPH + H+ using the enzyme NADP reductase
- Electrons lost from photosystem I are replaced by electrons from photsystem II
- Electrons lost from photosystem II are replaced by electrons generated by the photolysis of water (oxygen is produced as a by-product)
Describe cyclic photosphorylation
- Only photosystem I is involved in cyclic photophosphorylation
- The high energy electrons released by photoactivation pass along an electron transport chain (producing ATP) before returning to photosystem I
- does not produce NADPH + H+, which is needed for the light independent reactions
- Thus while cyclic photophosphorylation can make chemical energy (ATP) from light, it cannot be used to make organic molecules
PURPOSE: ATP
Describe this [4]
- light dependent exn;
- a correct description of the four processes: the photolysis, the proton motive force, the chemiosmosis and the reduction of NADP;
- a correct description of non-cyclic photophosphorylation and cyclic photophosphorylation
Identify the parts of the chloroplast
