photosynthesis Flashcards
what are the adaptions of leaves for photosynthesis?
large surface area
thin
permeable
cuticle and epidermis are transparent
what are the adaptions of palisade cells?
large vacuole
cylindrical elongated cells
large number of chloroplasts
why are plants green?
photosynthetic pigments in thylakoid membranes of chloroplasts
what do chloroplasts do?
absorb light energy and convert it into chemical energy
how are chloroplasts adapted to photosynthesis?
stacking of thylakoids allows maximum light catchment
outer membrane keeps enzymes in chloroplasts
thylakoid membrane contains photosynthetic pigments
stroma fluid contains enzymes for photosynthesis
what is the role of the stroma?
site of light independent reactions
what is the role of the thylakoid?
site of light dependent reactions
what are the different types of pigments?
chlorophyll a and b
carotenoids
what is chromotography?
separation technique used to separate pigments in plant leaves
what is Rf value?
shows how far a component has travelled compared to solvent font
distance moved by component / distance moved by solvent
what does absorbance spectra show?
degree of absorption of different wavelengths by light by an individual pigment
what lights do chlorophylls absorb strongly in?
violet, blue and red
what lights do carotenoids absorb strongly in?
blue and green
what does action spectra show?
degree to which different wavelengths of light affect rate of photosynthesis
what is photosynthesis?
process by which autotrophic organisms use light energy to make sugar and oxygen from carbon dioxide and water
what happens in light dependent stage (basic)?
converts solar energy to chemical energy
produces ATP, oxygen and reduced NADP
what happens in light independent stage (basic)?
makes glucose from oxygen
ATP provides energy for sugar synthesis
NADPH provides energy for reduction of CO2 to glucose
what happens in the first stage of photosynthseis?
photoexcitation
energy from sunlight causes electrons from chlorophyll to become excited
where are photosystems and what do they do?
in plane of thylakoid membrane
collect accessory pigments which absorb light and transmits energy to reaction centre
what is in the antenna complex?
array of pigment molecules in phospholipids of thylakoid membrane
what is in the reaction centre?
contains 2 molecules of primary pigment chlorophyll a
absorbs light, excites electrons, emits electrons
what is in PSI?
absorption peak of 700nm
what is in PSII?
absorption peak of 680nm
what is the second stage of photosynthesis?
photophosphorylation
what happens in cyclic photophosphorylation?
only PSI
photons of light absorbed by pigments in antenna complex
2 electrons in reaction centre are excited (photoactivation)
electrons emitted and received by electron acceptor
2 electrons pass down electron transport chain
generates sufficient energy to synthesis ATP by chemiosmosis
H+ is pumped into lumen by proton pump then diffuse out through ATP synthase to produce ATP
electrons return to reaction centre of PSI
NO reduced NADP produced
what happens in non-cyclic photophosphorylation?
photons of light absorbed by PSII
2 electrons excited and picked up by electron acceptors
2 electrons passed down electron transport chain then passed onto PSI
energy produced to pump H+ ions into lumen to create gradient
protons then flow through ATP synthase to form ATP
PSII left with positive charge receives electrons from photolysis of water
PSI gets photoactivated at same time as PSII
excited electrons passed down electron transport chain generating ATP
electron acceptors pass the 2 electrons to hydrogen ions where they reduce NADP
what is the passage of protons during photophosphorylation?
energy from 2 electrons along transport chain is used to pump H+ from stroma into thylakoid membrane
protons accumulate in thylakoid membrane
creates electrochemical gradient (also due to photolysis)
H+ flow back into stroma through ATP synthase to synthesis ATP
in stroma, H+ ions combine with NADP to produce NADPH
what happens during the light independent stage?
CO2 in stroma combines with 5C compound to produce RuBP catalysed by RuBISCO
product is unstable 6C
breaks down into 2 molecules of 3C compound GP
ATP and NADPH provide reducing power to convert GP into TP
TP either converted to glucose phosphate then starch or regenerated back to RuBP
how are carbohydrates produced from light independent reaction?
produce fructose phosphate then converted into glucose then sucrose
alpha glucose converted into starch
beta glucose converted into cellulose
how are fats produced from light independent reaction?
GP used for synthesis of acetyl coA
TP converted to glycerol
glycerol and fatty acids condensed into triglycerides
how are proteins produced from light independent reaction?
GP converted to amino acids for protein synthesis
what happens during engelmann’s experiment?
determines which wavelengths of light are most effective
spiral chloroplasts of algae photosynthesise
oxygen gas produced
motile aerobic bacteria exposed to various wavelengths of light
bacteria move towards parts of chloroplasts exposed to red and blue parts of spectrum
what is a transducer?
changes energy from one form into another e.g. chloroplasts
factors affecting photosynthesis?
magnesium concentration
nitrogen concentration
CO2 concentration
light intensity
humidity
temperature
