module 5; energy transfers in & between organisms Flashcards
describe the structure of chloroplast
outer membrane
inter-membrane space
inner membrane
stroma (aqueous fluid)
granum (stack of thylakoid)
thylakoid
lamella
lumen (inside of thylakoid)
state the structure & function of thylakoid membranes
structure: folded membranes which contain photosynthetic proteins (chlorophyll) & e- carrier proteins are embedded within these membranes
function: involved in light-dependent reactions (LDR)
state the structure & function of the stroma
structure: fluid centre which contains enzymes
function: involved in the light-independent reaction (LIR)
state the function of the inner & outer membranes
they control what can enter & leave the organelle
state the stages of photosynthesis
- light-dependent reaction
- light-independent reaction
where do the stages of photosynthesis occur?
both the LDR & LIR occur in the chloroplast of a plant cell but in different locations - LDR occurs on the thylakoid membranes/grana & LIR occurs in the stroma
what is the LDR?
the LDR is the 1st stage of photosynthesis & it requires light - light energy & water are used to create ATP & reduced NADP which are needed for the light-independent stage
state the stages of the LDR
- photolysis
- photoionisation of chlorophyll
- chemiosmosis
- production of ATP & reduced NADP
name & explain what happens in the 1st stage of LDR
photolysis of water:
light energy is absorbed by chlorophyll & splits water into oxygen, H⁺ & e-
the H⁺ is picked up by NADP to form NADPH & is used in the LIR
the e- are passed along a chain of e- carrier proteins
the oxygen is either used for respiration or diffuses out of the leaf through the stomata
name & explain what happens in the 2nd stage of LDR
photoionisation of chlorophyll:
light energy is absorbed by the chlorophyll & the energy results in e- becoming excited & raising an energy level to leave chlorophyll (chlorophyll has been ionised by light)
some of the energy from the released e- is used to make ATP & reduced NADP in chemiosmosis
name & explain what happens in the 3rd stage of LDR
chemiosmosis:
the e- that gained energy & left the chlorophyll to move along a series of proteins embedded within the thylakoid membrane
as they move along they release energy & some of the energy from electrons is used to pump the protons across chloroplast membranes
an electrochemical gradient is created
the protons pass enzyme ATP synthase - results in production of ATP
the protons combine with the co-enzyme NADP to become reduced NADP
as protons move from a high to low conc gradient this is known as chemiosmosis
what is LIR?
LIR is a cycle (the calvin cycle)
where does the calvin cycle occur?
occurs in the stroma as its fluid contains the enzyme RuBisCo which catalyses the reaction - this stage temp sensitive as it involves enzymes
what does the calvin cycle form?
hexose sugars
how does the calvin cycle form hexose sugars?
it uses CO₂, reduced NADP & ATP
why are the reactants in the calvin cycle important for the LIR?
the ATP is hydrolysed to provide energy for this reaction & the reduced NADP donates the H to reduce molecules GP in the cycle
explain the process of the LIR
- CO₂ reacts with ribulose bisphosphate (RuBP) to form 2 molecules of glycerate 3-phosphate (GP) a 3-carbon compound - RuBisCo catalyses reaction
- GP is reduced to triose phosphate (TP) using energy from ATP & by accepting a H from reduced NADP
- some of the carbon from TP leaves the cycle each turn to be converted into useful organic substances
- the rest of the molecule is used to regenerate RuBP with the energy from ATP
- glucose is the product but it can join to form disaccharides (e.g. sucrose) & polysaccharides (e.g. starch & cellulose) - can also be converted into glycerol & so it can combine with fatty acids to make lipids for the plant
state the limiting factors of photosynthesis
temperature
CO₂ concentration
light intensity
give examples of agricultural techniques that remove limiting factors
heating a greenhouse to increase the temp
burning fuel (e.g. paraffin burners) to release more CO₂
artificial lighting to maximise light intensity
to what extent are agricultural techniques used?
the extent of each technique is used is considered in terms of profit - e.g. if extra growth from photosynthesis is minimal, it will not be cost effective to pay for heating/lighting/fuel
state the 4 key stages of aerobic respiration & where they occur
- glycolysis ~ cytoplasm
- link reaction ~ mitochondrial matrix
- krebs cycle ~ mitochondrial matrix
- oxidative phosphorylation ~ mitochondrial inner membrane cristae
name & explain what occurs during the1st stage of aerobic & anaerobic respiration
glycolysis - occurs in the cytoplasm & its an anaerobic process
- phosphorylating glucose to glucose phosphate, using ATP
- production of triose phosphate
- oxidation of triose phosphate to produce pyruvate with a net gain of ATP & reduced NAD
how & where are pyruvate & NADH transported?
by active transport to the cytoplasm into the mitochondrial matrix
explain what occurs in the link reaction
- the pyruvate in glycolysis is oxidised to acetate
- NAD picks up the H & becomes reduced NAD
- acetate then combines with coenzyme A in to produce acetyl coenzyme A
- the link reaction occurs twice for every glucose molecule
explain what occurs in the kerbs cycle
- acetyl-CoA reacts with a 4 carbon molecule, releasing coenzyme A & producing a 6. carbon molecule that enters the krebs cycle
- in a series of redox reactions, the krebs cycle generates reduced coenzymes & ATP by substrate-level phosphorylation & CO₂
state the products that are formed from the krebs cycle
products per cycle:
3x reduced NAD
1x reduced FAD
1x ATP
2x CO₂
products per glucose molecule:
6x reduced NAD
2x reduced FAD
2x ATP
4x CO₂
