Module 5.2.1 - Energy for biological processes Flashcards
Energy cannot be…?
Created or destroyed
What is the purpose of photosynthesis?
To trap energy and create glucose
What is the equation for photosynthesis?
6CO2 +6H2O -> 6O2 + C6H12O6
What is the equation for respiration?
6O2 + C6H12O6 -> 6CO2 +6H2O
What is the purpose of respiration?
To release energy
What are carbon-hydrogen bonds?
- energy is used to break bonds
- energy is released when bonds are formed
- exothermic reactions release energy overall
- endothermic reactions take in energy overall
What is the process of chemiosmosis?
- electrons are excited from the sun
- high energy electrons move from 1 carrier in electron transport chain to the next
- this releases energy that’s used to pump protons across membrane
- protons move down their conc gradient through channels linked to ATP synthase
- flow of protons provides energy used to synthesise ATP from ADP + Pi
What is chemiosmosis?
- diffusion of protons from high to low conc through partially permeable membrane
- releases energy to attach an inorganic phosphate to ADP and form ATP
How is ATP synthesised?
Photosynthesis - light provides energy to form chemical bonds in ATP which are then broken to release energy needed to make bonds as glucose is formed
Respiration - organic molecules are broken down and energy released synthesises ATP which is used to supply energy needed to break bonds in metabolic reactions of cell
What is a photosystem?
Reaction center - location of chlorophyll a and site of reactions involved in photosynthesis
Antenna pigment molecules - location of other pigments such as chlorophyll b, xanthophylls and carotenoids
What the first pathway of photosynthesis?
H2O - photolysis - light dependent reactions - O2 removed - reduced NADP and ATP produced - goes into light independent reaction
what is the light dependent stage?
- has 2 photosystems involved in non cyclic phosphorylation , photosystem II and I
- PSI absorbs light at higher wavelength than PSII
- light absorbed excites electrons at reaction centre
What happens in PSII?
- light absorbed excites electrons that’re released from reaction centre of photosystem
- ATP produced by chemiosmosis
What is PSI?
- excited electrons released from reaction centre are passed to another electron transport chain
- producing ATP by chemiosmosis
- electron leaving ETC are accepted by coenzyme NADP along with hydrogen ion form NADPH
How are electrons replaced in the independent light reaction?
- electrons lost from PSI are replaced by electrons from PSII ETC
- electrons from PSII are replaced by splitting water into hydrogen ions, electrons and oxygen molecules by the sun/light, photolysis
What is the light independent stage?
- takes place in stroma
- uses CO2 and products from light dependent stage
- series of reactions called Calvin cycle
- produces organic molecules
What is photorespiration?
When CO2 levels fall and oxygen levels increase so oxygen is used instead, CO2 is lost as result, less efficient
What happens in the Calvin cycle?
- rubisco catalyses the reaction of CO2 and RuBP (5C)
- forms a 6 carbon unstable intermediate molecule
- is split into 2 3Ccarbon molecules called glycerate-3-phosphate (GP)
- ATP is hydrolysed into ADP and NADP is reduced
- NADPH forms triose phosphate (TP)
- 1 TP is used to make glucose, the other 5 TP are recycles
- ATP is hydrolysed again
- x6 RuBP is reformed again to continue cycle
What happens during photosynthesis when light intensity is the limiting factor?
Low - less excited electrons, increase GP, decrease TP and RuBP
High - lots of energy, increase TP and RuBP, decrease GP
What does limiting factor mean?
In short supply and limits the rate of reaction
What are photosynthesis’s limiting factors?
- light intensity
- CO2 levels
- temperature
What happens during photosynthesis when temperature is the limiting factor?
Low - not enough KE, less collisions, decrease GP, TP and RuBP
High - enzymes will denature, decrease GP, TP and RuBP
What happens during photosynthesis when carbon dioxide is the limiting factor?
Low - less GP and TP, increase RuBP
High - increase everything made
