Photosynthesis Flashcards
(25 cards)
What are the two stages of photosynthesis?
Light-dependent reaction and light-independent reaction.
What is the equation for photosynthesis?
6COv2 + 6Hv2O = Cv6Hv12Ov6 + 6Ov2
Carbon dioxide + Water = Glucose + Oyxgen
Where does photosynthesis take place?
Both stages of photosynthesis occur in the chloroplast in different places (LDR in thylakoid membranes, LIR in the stroma).
What is the function of the thylakoid membranes in the chloroplast?
Thylakoid membranes provide a large surface area for the absorption of light and for the attachment of chlorophyll, electron carriers, and enzymes which are needed in the LDR.
What is the function of the permeable membrane in the chloroplast?
The permeable membrane allows diffusion of gases as it controls what enters and leaves the organelle.
What is the function of the stroma in the chloroplast?
The fluid in the stroma contains all enzymes required to make carbohydrates in the LIR.
What is the function of the DNA and ribosomes in the chloroplast?
The DNA and ribosomes allow for quick protein synthesis for photosynthesis.
What are the key stages of the light dependent reaction?
1) Photoionisation
2) Photolysis
3) Chemiosmosis
4) Formation of NADPH
What happens during photoionisation?
In photoionisation, chlorophyll absorbs light energy which excites and raises electrons up an energy level allowing them to leave the chlorophyll (ionisation). The electrons are donated to an electron carrier and begin moving down the electron transport chain (ETC).
What happens during photolysis?
In photolysis, water is split into oxygen, electrons (e-), and protons/hydrogen ions (H+) to replace previously lost electrons.
What happens during chemiosmosis?
In chemiosmosis, the excited electrons lose energy as they move down the ETC. This energy is used to pump the H+ ions into the thylakoid space via a proton pump which creates a proton gradient for diffusion of H+ ions into the stroma via ATP synthase which catalyses the reaction between ADP and Pi to form ATP, this production of ATP is known as photophosphorylation.
What happens during the formation of NADPH?
During the formation of NADPH, electrons from the ETC and H+ ions that have diffused through ATP synthase are used to form reduced NADP (NADPH).
Why does NADP become reduced?
NADP becomes reduced as it gains a hydrogen atom.
What is the light independent reaction also known as?
The Calvin cycle.
What are the key stages of the light independent reaction?
1) CO2 fixation
2) Reduction phase
3) Organic molecule production
4) RuBP regeneration
What happens during CO2 fixation?
The enzyme Rubisco catalyses the reaction of RuBP with CO2, producing 2 GP.
What happens during the reduction phase?
GP is reduced to triose phosphate (TP) using NADPH, using energy from ATP hydrolysis.
What happens during the organic molecule production?
Some TP is converted to useful organic compounds.
What happens during RuBP regeneration?
Some (most) of the TP is converted back into RuBP using energy from ATP hydrolysis.
What are the key limiting factors of photosynthesis?
Temperature, CO2 concentration, and light intensity.
What is the importance of temperature as a limiting factor in photosynthesis?
Both the LIR and LDR involve enzymes, and enzyme activity is affected by temperature. Also, stomata close at high temperatures, meaning less CO2 will enter the leaf, slowing the LIR.
What is the importance of CO2 concentration as a limiting factor in photosynthesis?
The LIR requires a source of carbon. In an environment with a low CO2 concentration, carbon fixation will be slowed.
What is the importance of light intensity as a limiting factor in photosynthesis?
Energy from sunlight is required to excite electrons in the chlorophyll during the LDR. A low light intensity would slow the LDR.
What are common agricultural practice techniques used to remove or minimise the limiting factors of photosynthesis?
Growing plants under artificial lighting to maximise the light intensity, heating a greenhouse to increase the temperature, and burning fuel (paraffin burners) to release more carbon dioxide.
