Energy for Processes Flashcards
describe the structure of a chloroplast
usually disc shaped
double membrane
thylakoids-flattened discs stack to form grana
integral lamellae -tubular extensions attach thylakoids to adjacent grana
stroma- fluid filled matrix with high enzyme and substrate conc
where do the light dependent and light independent stages occur
light dependent-thylakoids
light independent -stroma
what is the role of photosynthetic pigments
absorb wavelengths of light
name the two main groups of photosynthetic pigments
primary pigment-chlorophyll found in photosystems
accessory pigments-carotenoids found in light harvesting systems
name the processes in the light dependent reaction
photoionisation
electron transfer chain
chemiosmosis
explain the role of light in photoionisation
chlorophyll molecules absorb energy from photons in light
this excites electrons raising them to higher energy level
causes them to be released from chlorophyll
what happens in the electron transfer chain
electrons released from chlorophyll move down a series of carrier proteins embedded in thylakoid membrane
undergo redox reactions which release energy
how does chemiosmosis produce ATP in light dependent stage
some energy released from ETC is coupled to active transport of H+ ions from stroma into thylakoid space
H+ ions move down concentration gradient into stroma by transmembrane channel protein ATP synthase
ATP synthase catalyses ADP+Pi–> ATP
describe non-cyclic photophosphorylation
uses photosystems 1 and 2
excited electrons enter ETC to produce ATP
NADP acts as final electron acceptor and is reduced
water is photolysed to release electrons to replace those lost in photosystem 2
purpose is to produce ATP and reduced NADP for Calvin cycle
describe cyclic photophosphorylation
uses only photosystem 1
excited electrons enter ETC to produce ATP then return directly to photosystem
purpose to produce additional ATP
what happens in photolysis of water
light splits water molecules
what happens to the products of the photolysis of water
H+ ions-move out of thylakoid space by ATP synthase and used to reduce NADP
e- -replace electrons lost from chlorophyll
O2-used for respiration
name the 3 main stages in the light independent reaction
carbon fixation
reduction
regeneration
what happens during carbon fixation
reaction between CO2 and RuBP catalysed by RuBisCo
forms unstable 6 carbon compound that breaks down into 2 glycerate 3 phosphate (GP)
what happens during reduction in the light independent stage
2 GP reduced to 2 triose phosphate
requires 2 reduced NADP and 2 ATP
forms 2 NADP and 2 ADP
outline the roles of TP from the light independent reaction
1 carbon leaves to produce monosaccharides, amino acids and other biological nutrients
involved in regeneration of RuBP
after 1 carbon leaves, 5 carbon compound RuP forms
converted into RuBP with 1 ATP
state the number of carbon atoms in RuBP, GP and GALP
RuBP=5
GP=3
GALP=3
define limiting factor
factor that determines maximum rate of a reaction even if other factors change to become more favourable
name 4 environmental factors that can limit the rate of photosynthesis
light intensity (light dependent)
CO2 concentration (light independent)
mineral levels-maintain normal functioning of chlorophyll
temperature-enzyme stages
how does light intensity affect the rate of photosynthesis
low light intensity-slower light dependent reaction
less ATP and NADP produced to convert to GP and TP
describe the implications of water stress
abscisic acid binds to complementary receptors on guard cell membrane-ca2+ channels open
positive feedback triggers other ion channels to open
water potential of guard cells becomes more positive-water diffuses out by osmosis
guard cells become flacid so stomata close
state the purpose and principle of paper chromatography
molecules in a mixture are separated based on relevant attraction to mobile phase vs stationary phase
outline a method for extracting photosynthetic pigments
use a pestle and mortar to grind a leaf with an extraction solvent
outline how TLC can be used to separate photosynthetic pigments
use capillary tube to spot pigment extract onto pencil line
place chromatography paper in solvent
allow solvent to run until it almost touches other end of paper
