photosynthesis Flashcards
where does photosynthesis take place
in the chloroplasts
what is the first and second stage of photosynthesis
light dependent reaction and light independent reaction
where does the light dependent reaction take place
in the thylakoid membrane
which enzyme in the light dependent reaction produces ATP and where does the energy come from
ATP synthase, to catalyse this energy is supplied by the diffusion of protons down a concentration gradient from the thylakoid space to the stroma
what is chemiosmosis
The movement of ions across a partially permeable membrane, from an area of a high concentration to an area of low concentration
what is photoionisation
when chlorphyll in the thylakoid membrane absorbs light energy, this means that its electrons become excited and leave it, this means that chlorophyll is oxidised and positively charged
what do the electrons from photoionisation do
they give energy to transport proteins in the thylakoid membrane for the active transport of protons into the thylakoid space through passing through an electron transfer chain
what are the two important products of the light dependent reaction
ATP and NADPH
what do the electrons in the electron transfer chain do at the end of the chain
they react with protons and NADP to form reduced NADP (NADPH)
what is photolysis
the breakdown of water using light energy into protons which maintain the proton gradient, electrons which replace those lost in photoionisation, and oxygen which is diffused out
what is non-cyclic photophosphorylation
initiated by photosystem 2, it is where the electron carries on to make reduced NADP instead of going back into the electron transfer chain
what is cyclic photophosphorylation
initiated by photosystem 1, the electrons absorbs light energy and is excited but instead of going on to make reduced NADP it goes back into the electron transfer chain to keep allowing protons to actively transport protons into the thylakoid space, this means that photolysis doesnt need to take place
why does cyclic photophosphorylation take place
due to different wave lengths of light being absorbed, photosystem 1 and 2 absorb different wavelengths, helps when there is a sufficient amount of reduced NADP present but not enough ATP
how are chloroplasts adapted for photosynthesis
thylakoid has a large surface area for molecules involved in light dependent reaction, lamella hold the chlorophyll in such a way that the maximum amount of light can be absorbed at one time, contain ATP synthase in thylakoid membranes which are selectively permeable, chloroplasts contain both DNA and ribosomes which means that proteins involved can be quickly made
where does the light independent reaction take place
the stroma of the chloroplast
when CO2 enters the stroma what molecule does it react with
ribulose bisphosphate
in the reaction between CO2 and ribulose bisphosphate what molecule is produced
2 molecules of glycerate 3-phosphate
what enzyme catalyses the fixation of CO2 in the light independent reaction
rubisco
what is glycerate 3-phosphate converted to
triose phosphate by a reduction reaction that forms NADP and ADP
what percent of triose phosphate molecules are converted back into ribulose bisphosphate
80%, requires ATP
what are the three organic molecules produced by triose phosphate
glucose which is used in respiration, amino acids which are used to make proteins, and lipids which are made into triglycerides which are good energy and water storage
what are the three main factors that limit the rate of photosynthesis
light, temperature and carbon dioxide
