5.2- photosynthesis Flashcards
word equation for photosynthesis
carbon dioxide+water=glucose+oxygen
-light and chlorophyll over arrow
symbol equation for photosynthesis
6CO2+6H2O=C6H12O6+6O2
-light and chlorophyll over arrow
what is an autotroph
-an organism which makes complex organic compounds
-e.g. glucose from simple inorganic compounds such as Co2 and H2O
what is a Heterotroph
-organism that obtains complex organic compounds
-e.g. glucose by feeding on other organisms or their dead remains
what are the two stages of photosynthesis
-light dependent stage
-light independent stage
what does photosynthesis do
-series of chemical reactions that occur in autotrophs
-converts light energy into chemical energy which is then stored in biomass of autotrophs
what does the light energy do
-splits strong bonds in water molecules, releasing hydrogen and oxygen
-oxygen released in to atmosphere as a waste product
-hydrogen is combined with CO2 to produce glucose
what is OILRIG
-oxidation is loss
-reduction is gain
light dependent stage similarities to ETC
-as electrons are passed down the carriers, there is a release of energy which is used to synthesise ATP
summary of LD reaction
-occurs within thylakoids which contain chlorophyll
-photon of light hits chlorophyll molecules, pigment raises to higher energy level and emits two high energy electrons
-these electrons pass down an electron transfer chain on thylakoid membrane
-Chemiosmosis results in phosphorylation of ADP in to ATP
Ld reaction- cyclic photophosphorylation
-light hits photosystem I
-electrons excited and leave
-electrons pass along ETC, releasing energy
-H+ ions pumped from low conc in stroma to high conc in thylakoid space, creating a gradient across membrane
-H+ ions diffuse back across the thylakoid membrane into the stroma via ATP synthase enzymes embedded in the membrane
-The movement of H+ ions cause the ATP synthase enzyme to catalyse the production of ATP
-At the end of the electron transport chain the electrons rejoin photosystem I in a complete cycle
-The ATP produced enters the light-independent reaction
LD reaction- non cyclic photophosphorylation pt1
-Light energy hits photosystem II in the thylakoid membrane
-Two electrons gain energy and are excited to a higher energy level
-The electrons leave the photosystem and pass to the first protein in the electron transport chain
-As the electrons leave photosystem II they are replaced by electrons from the photolysis of water
-The electrons pass down the ETC
-Energy is released as the electrons pass down the electron transport chain which enables chemiosmosis to occur
-H+ ions are pumped from a low conc in the stroma to a high conc in the thylakoid space, conc gradient across the thylakoid membrane
-H+ ions diffuse back across the thylakoid membrane into the stroma via ATP synthase enzymes embedded in the membrane
-The movement of H+ ions causes the ATP synthase enzyme to catalyse the production of ATP
Ld reaction- non clyclic photophosphorylation pt2
-At the end of ETC the electrons from photosystem II are passed to photosystem I
-Light energy also hits photosystem I, exciting another pair of electrons which leave the photosystem
-The excited electrons from photosystem I also pass along an electron transport chain
-These electrons combine with hydrogen ions from the photolysis of water and the coenzyme NADP to form reduced NADP
-H+ + 2e- + NADP+ → NADPH
-The reduced NADP and the ATP pass to the light-independent reactions
Summary of light independent reactions
-Occurs in the stroma of the chloroplasts
-The ATP and reduced NADP produced in the light reactions are used in the Light Independent Reactions which result in Carbon Dioxide being ‘fixed’.
-Carbon Dioxide is converted to Glucose in a series of reactions discovered by Melvin Calvin using his ‘lollipop’ apparatus.
4 main steps of LIR
1.Carbon dioxide (5C) combines with Ribulose Bisphosphate, RuBP, (5C) catalysed by the enzyme Rubisco (Ribulose bisphosphate carboxylase)
2.A highly unstable 6C compound is formed which immediately splits into two molecules of of a 3C molecule, Glycerate 3-phosphate (GP)
3.ATP and NADPH are used to reduce GP into Glyceraldehyde Phosphate (GALP) also known as Triose Phosphate (TP)
4.Some of this GALP is used to make carbohydrate, but most is used to make more RuBP so the cycle can continue. For every glucose produced five molecules of RuBP are resynthesized.
