Photosynthesis Flashcards
what are coenzymes
non protein organic molecules that are mostly derivatives of vitamins
what are cofactors
non-organic doesnt contain carbon eg) Cl- Zn-
how do cofactors or coenzymes work
-bound to enzyme active sites to aid with their proper functioning
-coenzymes can be used by a number of different enzymes so not specific eg)NAD is used by over 700 enzymes
EXAMPLE
-apoenzyme becomes active by binding of coenzymes or cofactor to enzyme
-holoenzyme is formed when associated cofactor or coenzyme binds to active site
Vitamins and their coenzymes
Riboflavin and ____
-FAD and FMN
|»_space;>in respiration
Vitamins and their coenzymes
Niacin
NAD and NADP
|»_space;>similar to FAD but in photosynethesis
Vitamins and their coenzymes
Pantothenic acid
CoA
|»_space;>also in respiration
what is a key role of coenzymes
transport groups between enzymes
such as:
-hybride ions (protons and electrons) which are carried by coenzyme such as NAD
-Phosphate groups which are carried by coenzymes such as ATP can act as coenzyme> carrying chemical group
-Acetyl groups by coenzyme A
Coenzymes that gain/lose these chemical groups are often reformed in same metabolic pathway
which processes require energy in body? (anabolism)
- growth eg )mitosis
- sensitivity eg) nerve impulse movement
- protection/reproduction eg) exocytosis of poisons to protect
- obtain food eg) muscle contraction/ cilia movement
How does leaf structure make it well adapted for photosynthesis
large flat surface
absorb max. light energy
How does leaf structure make it well adapted for photosynthesis thin lamina (broad flattened surface)
allows C02 to reach inner cells rapidly due to short diffusion path
sunlight can reach mesophyll cells
How does leaf structure make it well adapted for photosynthesis
chloroplasts contain chlorophyll in all mesophyll cells
absorbs and transduces light energy to chemical energy
How does leaf structure make it well adapted for photosynthesis
more chloroplasts in upper palisade tissue which move by cyclosis
more light energy can be absorbed near surface
How does leaf structure make it well adapted for photosynthesis
interconnecting air spaces in mesophyll layer
allows for rapid diffusion of carbon dioxide to mesophyll cells
How does leaf structure make it well adapted for photosynthesis
stomata present in epidermal layers
allow rapid diffusion when open in sunlight
How does leaf structure make it well adapted for photosynthesis
veins containing xylem and phloem
xylem provide increased availability of water and mineral salts to mesophyll cells
phloem transports sugars away from leaf
How does leaf structure make it well adapted for photosynthesis
petiole (leaf stalk)
holds leaf in position to absorb light energy
during the day plants photosynthesise ____ than they respire
what are the extra sugars used for
more
made into starch or used in cellulose lipids or amino acids
what is the compensation point
when does it occur
when the volume of oxygen produced by photosythesis is equal to that used in aerobic respiration
> > > occurs at low level light intensity
what are the products of photosynthesis
glucose and oxygen (used in respiration)
how are photosynthesis and respiration complementary reactions
most produces aka autotrophs undertake both photosynthesis and cell respiration to survive
consumers aka heterotrophs only undertake cell respiration but will ingest or absorb photosynthetic products
respiration produces inorganic products which are used as reactants in photosynthesis and converted to organic products such as glucose using light energy
photosynthesis is a _____ process
cell respiration is a _____ process
anabolic
catabolic
what is broken down in photosynthesis to release electrons for an electron transport train
what happens to these electrons
water is broken down to oxygen
taken up by hydrogen carriers NADPH (from the transport chain)
what is the calvin cycle involved in and what does it do
where does the hydrogen come from
photosythesis-
synthesise glucose in reduction reaction which reduces CO2 ATP also produced
»>requires hydrogen carriers and carbon dioxide
hydrogen comes from water which is split into protons and electrons and uses energy store for chemeosmosis
which cycle is involved in cell respiration and what does it do
what happens to the hydrogen
Krebs cycle
»>breaks down glucose and releases hydrogen carriers and CO2 (energy released so catabolic)
hydrogen carriers release electrons for an electron transport chain NADH and FADH2
what happens to the electrons in the transport chain in Krebs cycle
they are taken up by oxygen to form water
electrons like hydrogen
similarities between respiration and photosynthesis
> both involve the production of chemical energy ATP
Photosynthesis ATP produced by
photophosphorylation by light energy and in
cell respiration is produced by breaking
downorganic molecules through oxidative
phosphorylation
both involve an electron transport chain and chemeosmosis
PhoSyn-electrons from chlorophyll and protons
accumulate w/in lumen of thylakoid
In Cell resp. electrons donated by hydrogen
carriers and protons accumulate in the
intermembrane space
HOWEVER SOURCE OF ELECTRONS DIFFER`
Differences between respiration and photosynthesis
> photosynthesis anabolic cell respiration is catabolic
>PhoSyn is Calvin cycle to synth glucose whereas cell resp uses Krebs cycle to break down glucose and form water
briefly outline and explain why chloroplasts could have once have been prokaryotes (through endosymbiosis)
1) starts with two independent bacteria
2) one engulfs the other
3) one bacterium now lives inside the other
4) both bacterium benefit from arrangement
5) internal bacteria are passed on from generation to generation
thought chloroplasts could have been engulfed and was once own organism as has smaller 70s ribosomes like bacteria and has evolved to become eukarya
(cyanobacteria)
how are chloroplasts similar in structure to bacteria
- DNA circular and naked
- ribosomes 70s
- metabolic processes susceptible to certain antibiotics
- similar in size to antibiotics
what does the stroma contain which aids the calvin cycle
approriate enzymes and suitable pH for the Calvin cycle
which enzymes does the thylakoid have
ETC and ATP synthase for photophosphorylation
what are the Granum
flat membrane stacks increase SA:V ratio and small internal volumes and quickly accumulate ions
whats are lamellae
and how do they aid chloroplast function
connect and separate thylakoid stacks (grana)
maximise photosynthetic efficiency
how do thylakoids help chloroplasts be adapted for their function
flattened disks with small internal volume to maximise hydrogen gradient upon proton accummulation or the gradient that drive ATP production
how do Grana help chloroplasts be adapted for their function
thylakoids arranged into stacks to increase SA:V ratio of the thylakoid membrane
how do Photosystems help chloroplasts be adapted for their function
pigment organised into photosystems in thylakoid membrane to maximise light absorption
how do Stromahelp chloroplasts be adapted for their function
central cavity that contain appropriate enzymes and suitable pH for the Calvin cycle to occur
characteristics of chloroplasts
where are they found
how big
what shape
found in mesophyll cells
4-10um long 2-3um wide
bioconvex disk w/ double membrane
what are thylakoids made from
membrane bound and made from phospholipids and protein membrane
where are the chlorophyll pigments found
what is within these pigments
sandwiched between lipids and proteins of the thylakoid membranes
enzyme and electron carrier molecules involved in the conversion of light to chemical energy
why are there so many pigment molecules
many wavelengths of light
which colours are absorbed by chlorophyll and which are reflected
BLUE END and red end of spectrum absorbed
green reflected
what pigments does chlorophyll contain
chlorophyll a - blue green
chlorophyll b - yellow-green pigment
carotenoids such as
» carotene, xanthophyll, phaeophythin and phaephytin
why do we get autumnal leaf colours
plants dont want to waste energy on chloroplasts when there is little light and colder
what is used in the stationary phase of TLC
silica gel for thin layer chromatography
used to separate pigents
runs faster and has better separation
how do you calculate Rf value
distance travelled by solute/ distance travelled by solvent
What are photosynthetic pigments grouped into
photosystems- which absorb and funnel light energy
maximises absorption by grouping pigments that have individualised absorption spectra together.
what were the findings of engalmans experiment
oxygen sensitive bacteria numbers were greater in areas where oxygen produced by agal cells was greater
> > > wavelengths responsible for oxygen production therefore around 650-450nm (red and blue wavelengths)
chlorophyll contain magnesium
this is just in here incase u forget! yellow spots are a deficiency of this as chlorphyll production decreased
extra reading- magnesium activates 2 key enzymes needed for chlrophyll production
what is the role of accessory pigments
form light harvesting system and absorb light energy and release high energy electrons (funnel them to the reaction centre to chlorophyl a where photosynetheis reaction starts)
activity of enzymes involved in production of pigments is dependent on temerature and light intensity as
»3D shape changed
properties needed in a membrane to create a proton gradient
-impermeable to ions/protons
-embedded channel proteins
»>such as ATP synthase
enzyme responsible to synthesise ATP
-concentrations of protons on each side of the membrane
what is the antenna complex made up from
hundreds of accessory pigments which funnel light energy to reaction center
»>this is so chlorophyll a receives all the light energy
define chemioosmosis
movement of ions across a partially permeable mebrane down their electrochemical gradient from a region of higher ion concentration to a region of lower ion concentration
this process forms ATP in the light dependent stage of photosynthesis
what do proton pumps generate
electrochemical gradients
how do protons diffuse out of proton pump ATP synthase
facillitated diffusion with channel protein ATP synthase
H+ ions catalyse reaction to form ATP
what is a bioproduct of the light dependent reaction
O2 (H20 broken down for protons and oxygen given out)
what is a hydrogen carrier and what does it transprot
organic macromolecule which transports hydrogen from one place in the cell to anotherpart of the cell to be used in metabolic processes
can be electron carriers
what is NAD+ reduced to and what is it used in
NADH used in respiration
what is NADP+ reduced to and what is it used for
NADPH acts as hydrogen carrier used in photosynthesis
ITS A COENZYME
the light dependent phase >occurs in daylight >absorbs sunlight energy >hydrogen from water reduces the coenzyme NADP to NADPH for use in light independent stage >occurs in thylakoid membranes
Light Independent phase
>can occur in darkness
>occurs in the stroma
>hydrogen from the reduced NADPH and C02 used to make organic molecules like glucose
>energy is supplied by ATP so sunlight not involved
this reduces CO2 to glucose
what are the names of the photosystems in the light dependent stage and where are they found
Photosystem II and Photosystem I
found in the thylakoid membrane
the two photosystems differ in wavelengths they absorb by the primary pigment in the reactioncentre
what is photolysis
breaking down of molecules with light energy
Two water molecules undergo a series of four electron removals (oxidations) to replenish the reaction center of photosystem II.
what is photophosphorylation
ATP synthase uses the passage of H+ ions to catalyse synthesis of ATP from ADP + Pi
»>photophosphorylation as light provides initial energy source
how are electrons excited to higher energy levels in photosystem 2
absorbtion of light energy to a higher energy level
what is the role of photosynethetic pigments like chlorophyl a
convert light energy to chemical energy like ATP and NADPH
which photosystem is involved in
cyclic photophosphorylation
non- cyclic photophosphorylation
- PS1
-PS2 folllowed by PS1
involves splitting of water by light -photolysis
produces reduced NADPH
what did melvin celvin study
used autoradiography with radioactive isotope C14 in 14CO2 to determine chemical steps causing reduction in of CO2 to a carbohydrate
he found that the 1st carbohydrate stabel compound incorporating CO2 was glycerate 3-phosphate or GP a 3C compound (6C compound is unstable)
what happens to C02 in calvin cycle
reduced to organic molecules like gluocose
intermediates GP and TP
what is the 5C compound called that joins with C02 to make 2 3C carbon compounds
whats the name of the enzyme which catalyses the attachment
RuBP
rubisco
what is the purpose of NADPH and ATP
to reduce GP to TP
what are 5 of the TP molecules used for
what is 1 TP used for
recombined to regenerate RuBP with energy from hydrolysis of ATP
the 1 TP makes half a glucose molecule
how is photosynthesis is affected by stomata
calvin cycle effected as 02 not released so rubisco production inhibited + CO2 cant enter cycle so product not made
if there is a lack of water what can’t happen
no photolysis (splitting water)
flaccid /plasmosysed
transpiration decreased
characteristics of Rubisco
8 active sites for C02
its an enzyme which joins RuBP and C02
what is photorespiration
where plants take in some oxygen and light and make CO2
the enzyme rubsico oxygenates RuBP which wastes some of the energy produced by photosynethesis
when does photorespiration occur
occurs in conditions when concentrations of CO2 low and O2 conc. high because Rubsico favours O2 as a substrate than CO2
> > > > hot dry days when plants close their stomata to prevent water loss and oxygen concentration in leaf is higher than CO2
which stage of photosynthesis is effected by photorespiration
the calvin cycle
stage 1 carbon fixation cannot occur as there is no CO2 present which means there is no reduction of glycerate 3-phosphate (GP) to triose phosphate (TP) and therefore no regeneration of ribulose bisphosphate or RuBP. The CO2 must bind to the RuBP to make a 6C molecule whih is catalysed by rubisco in stroma
what is the first stable product of carbon dioxide fixation
GP
name 2 polysaccahrides synthesised in light indpendent stage
starch and cellulose
what are the limitting factors of photosynthesis
light intensity
carbon dioxide
temperature
how does light intensity affect the rate of photosynthesis
-needed to split the waterr in photolysis for electrons for ETC which makes ATP and NADPH for the dark phase
what will be effected if the light intensity is low
less light dependent reaction occurs
so:
less ATP and less NADPH
GP will increase as it can’t be converted to TP by ATP and NADPH
TP will decrease
less regeneration of RuBP so this decreases
how does CO2 affect the rate of photosynthesis
source of carbon for carbon fixation in the first part of the calvin cycle to produce GP and TP which creates glucose molecules after 2 cycles
increase yield of glucose
what will be effected if co2 concentration low
- no glucose created as oxygen will bind to Rubisco instead in photorespiration
- reduced conc. of TP and GP
- more RuBP as not used in a reaction of carbon fixation but still made by left over TP
how does temperature affect the rate of photosynthesis
effects the enzzyme rate of reaction
can cause photorespiration if too hot
-decrease activation energy
-increase rate of collisions and catalysing reactions
what will be effected if temperature too high/ low
-cold all decrease as less KE so reduced rate
how can the rate of photosynethesis be measured
gas syringe or CO2 probe more accurate than agal balls
-the glucose productions can be indirectly measured with change in plant biomass too/ oxygen produced
how is rubisco competitively inhibited
rubisco can bind either O2 or CO2 which joins RuBP in carbon fixation. factors effecting which is used is the relative concentrations of both O2 and CO2 and the temperature.
when stomata close when warm to reduce water loss, there is a build up of O2 so photorespiration increases. At higher temps Rubisco has higher affinity for O2 but room temp is CO2
why should commercial growers avoid photo respiration
means they don’t produce much glucose and so therefore don’t carry out much growth. If no glucose made there aren’t enough Carbon atoms to regenerate RuBP which joins CO2 in step 1 of the carbon cycle.
how is C4 photosynthesis different to C3
C4 from evolved plants to avoid photorespiration
C3 plants produce GP (3 phosphoglycerate)
C4 CO2 is fixed to a 4 carbon chain hence C4 and the CO2 goes into mesophyll and reacts with PEP instead of RuBP to make the 4C molecule
goes through mesophyll as bundle sheath cells don’t have access to air from stomata.
what is different to PEP than RuBP
PEP can only fix CO2 not oxygen so is a more specific enzyme.
how is PEP reformed
as there is no access to O2 the malate produced from oxaloacetate makes malate which reacts to make CO2 and pyruvate which makes PEP again.
what is non- cyclic photophosphorylation
light energy excites electron at reactor centres PS1 and 2 which get passed to ETC
ATP produced by chemiosmosis.
-electrons lost by PS1 are replaced by PS2 and those are replaced by water electrons
-electron acceptor accepts electrons from PS1 and so H+ and NADP make reduced NADPH
this provides Hydrogen for making organic molecules like glucose in light independent phase.
THIS IS THE NORMAL ONE
what is cyclic photophosphorylation
electrons leaving PSI can be returned to PSI (cyclic) instead of forming NADPH
PSI can still lead to ATP production withought electrons from PSII but NADPH not produced
when does cyclic photophosphorylation occur
when there is no water or sugar
is oxygen involved in cyclic or non cyclic
non-cyclic as in cyclic there is no water involved so oxygen not there
Cyclic makes additional ATP for cellular demand RATHER THAN products for calvin cycle as Non-cyclic does
