Energy transfers Flashcards
(33 cards)
where does the light dependent reaction occur
in the thylakoid membranes
where does the light independent reaction occur
in the stroma of the chloroplast
chlorophyll
located in the photosystems on the thylakoid membrane
it is a mix of coloured proteins that can absorb light
each pigment absorbs a different wavelength of visible light, this maximises the spectrum of visible light absorbed
purpose of the light dependent reaction
uses light energy and water to create ATP and reduced NADP which can be used in the light independent stage
light dependent reaction
photolysislight energy is absorbed by chlorophyll and split water into O2, H+, and e-photoionisation of chlorophyll light energy is absorbed by chlorophyll which results in electrons being excitedthey move up an energy level to leave the chlorophyllchemiosmosiselectrons that gained energy move along a series of electron carrier proteins embedded in the thylakoid membrane in a series of redox reactionsas they move along they release energy some of the energy is used to pump the protons from photolysis across the chloroplast membranes this creates an electrochemical gradient protons therefore pass back across the membranes through the enzyme ATP synthase down a conc gradient, resulting in the production of ATP the protons combine with coenzyme NADP to become NADPH (reduced NADP)
the light independent reaction
carbon dioxide reacts with ribulose bisphosphate (RuBP), a 5C molecule, to form two molecules of glycerine-3-phosphate (GP) which is a 3C compound - this is catalysed by the enzyme rubisco
GP is reduced to triode phosphate using energy from ATP and by accepting H from reduced NADP
one molecule of carbon from TP leaves the cycle each turn to be converted into organic substances
the rest of the molecule is used to regenerate RuBP - energy is released from the hydrolysis of ATP
six turns of the cycle is required to produce glucose
how can limiting factors of photosynthesis be overcome
growing plants under artificial lighting to maximise light intensity
heating a greenhouse to increase temperature
burning fuel like paraffin burners to release more CO2
stages of aerobic respiration
glycolysislink reaction Krebs cycle oxidative phosphorylation
where does glycolysis take place
the cytoplasm
where does the link reaction take place
the mitochondrial matrix
where does the Krebs cycle take place
mitochondrial matrix
where does oxidative phosphorylation take place
cristae
glycolysis
substrate level phosphorylation - the glucose has 2 phosphate groups added to it from 2 ATP molecules phosphorylation makes the glucose-2-phosphate unstable and it splits into two 3 carbon compounds, triode phosphate the 2 triode phosphate molecules are oxidised by the removal of H from each to form 2 pyruvate molecules the H is picked up by 2NAD molecules to become NADH (reduced NAD)this process releases 4 ATPthe net amount of ATP produced from glycolysis is 2ATP
link reaction
the NADH and pyruvate made in glycolysis are actively transported into the mitochondrial matrix the pyruvate is oxidised to acetateNAD picks up the H and becomes NADH acetate combines with coenzyme A to produce acetyl coenzyme Athis occurs for each pyruvate molecule (remember there are 2)
this results in 2 Acetyl CoA, 2CO2, and 2 reduced NAD
Krebs cycle
acetyl coA reacts with a 4C molecule which releases coenzyme A and produces a 6C molecule that enters the Krebs cycle the 6C molecule loses 2CO2ADP + Pi –> ATPFAD –> FADH3NAD –> 3NADHthe cycle turns twice per molecule of glucose
in a series of oxidation-reduction reactions, the Krebs cycle generates 6NADH, 2FADH, 2ATP and 4CO2 are lost
oxidative phosphoryaltion
NADH and FADH release H+ and e-the electrons are passed down a series of electron carrier proteins embedded in the inner mitochondrial membrane, losing energy as they movethe energy released by the electrons pumps protons from the mitochondrial matrix into the intermembrane spacethis creates an electrochemical gradient across the membrane so protons move down the electrochemical gradient back into the matrix via ATP synthase, making ATP - the movement of protons is called chemiosmosisoxygen is the final electron acceptor in the electron transport chain - the oxygen combines with electrons and protons to form water
anaerobic respiration
is the absence of oxygen, respiration occurs anaerobically in the cytoplasm of the cell
the pyruvate produced in glycolysis is reduced to formethanol and carbon dioxide in plants and microbeslactate in animals by gaining the hydrogen from reduced NAD
this oxidises NAD so that it can be reused in glycolysis and ensures ATP is still produced
yield of ATP in aerobic respiration
total yield of ATP from one glucose molecule is 38ATP
yield of ATP in anaerobic respiration
2 ATP per glucose molecule
autotrophs
producers that produce their own carbohydrates from carbon dioxide
why is energy lost between trophic levels
lost to respiration and excretion
GPP
gross primary production - the chemical energy stored in plant biomass in a given area or volume, it is the total energy resulting from photosynthesis
NPP
net primary production - the chemical energy stored in plant biomass taking into account the energy lost to respiration
equation for NPP
NPP = GPP - R
