photosynthesis Flashcards
what do both chloroplasts and mitochondria have in common?
- 70s ribosomes
- small DNA molecule
- ATP synthase
- liquid component where where chemical reactions occur
- double membrane
what are the differences between chloroplasts and mitochondria?
- m: matrix, c: stroma
- m: cristae, c: no folds
- m: none, c: starch granules and oil droplet
m: none, c: thylakoids/granum
what are the adaptions of a leaf for photosynthesis?
- large SA
- thin
permeable, with stomatal pores - large air spaces in spongy mesophyll
- transparent cuticle/upper epidermis
- palisade mesophyll cells are elongated and packed with chloroplasts
name 4 pigments in the chloroplasts
- chlorophyll a
- chlorophyll b
- xanthophyll
- B-carotene
define ‘action spectrum’
the amount of photosynthesis occurring at different wavelengths
define ‘absorption spectrum’
a graph showing the degree of the amount of light absorbed at different wavelengths
what happens in a photosystem?
light photons are transferred through the antenna complex via pigment molecules toward the reaction center, where they are then absorbed by chlorophyll a
describe Engelmann’s experiment
- shined a light through a prism (to separate the different wavelengths) and onto a leaf cell
- exposed it to a suspension of motile, aerobic algae
- RESULT: algae congregated toward parts of chloroplast exposed to blue and red ends of spectrum
- chloroplast absorbed those wavelengths best, photosynthesized more and produce more oxygen- algae more attracted
describe steps of non-cyclic photophosphorylation
- light dependent
- chlorophyll a molecules in reaction center of photosystem II absorb light energy
- light energy removes 2 electrons from chlorophyll a and e’s are passed onto electron acceptor
- these electrons are replaced by photolysis: H20 -> 2H+ + 2e + 1/2O2
- high energy e’s then passed onto chain of electron carriers
- energy from high energy e’s is used to pump H+ across membrane (chemiosmosis)
- Allowing generation of ATP from ADP + Pi
- e’s then passed to photosystem I, absorbs more photons and releases more e’s
- electron acceptor
- e’s then used to reduce NADP to NADPH2
describe the steps of cyclic photophosphorylation
- light absorbed by chlo. a in photosystem I
- light energy removes 2 electrons
- e’s passed onto electron acceptor
- passed onto chain of electron carriers
- carried along chain, generating ATP via chemiosmosis
what are the differences between non-cyclic and cyclic?
- n: NADPH2 produced, c: no NADPH2
- n: photolysis, c: no photolysis
- n: both photosystems I and II involved, c: only I
describe the steps of the calvin cycle
- RuBP reacts with CO2, catalysed by RuBiSCO enzyme
- produces unstable 6C intermediate
- Broken down into 2x GP
- reduced to TP, NADPH2 gets converted to NADP using energy from ATP (-> ADP + Pi)
- TP used to regenerate (-> RuP, ATP-> ADP) RuBP (6C -> 5C so 1C produced- 6 turns of cycle= 1 glucose)
described the experiment carried out that used to investigate the calvin cycle
- light shined through glass onto single-celled chlorella algae supplied with 14CO2 (done by injecting 14C NaHCO3 into a lollipop flask containing the algae)
- removed samples into flask of boiling methanol (to kill algae and stop enzyme reactions) at regular time intervals
- performed chromatography and auto-radiography (to detect products containing the 14C in order)
- RESULTS (in order): HCO3-, GP, TP, RuBP, glucose
what are the factors affecting photosynthesis?
- light intensity (more light absorbed, more ATP and NADPH2 produced, plateaus as other factors become limiting)
- temperature (photosynthesis is controlled by enzymes, temp increases KE of the molecules, causing more frequent collisions between substrate and active site- drops as too high a temp causes denaturing)
- CO2 concentration (plateaus as other factors become limiting)
