photosynthesis Flashcards
What is the equation for photosynthesis?
Carbon dioxide + water + energy –> glucose + oxygen
6CO2 + 6H2O + energy –> C6H12O6 +6O2
CO2 becomes ___ to sugar as they __ electrons along with hydrogen ions from water.
CO2 becomes reduced to sugar as they gain electrons along with hydrogen ions from water.
Water molecules are ___ when they __ electrons along with hydrogen ions.
Water molecules are oxidised when they lose electrons along with hydrogen ions.
Chlorophyll is…
Chlorophyll is an important light-absorbing pigment in chloroplasts. It plays a central role in converting solar energy to chemical energy.
Where does the light-dependent stage occur?
It occurs at the photosystems in the chloroplast grana in the presence of light.
What happens in the photochemical step of the light-dependent stage?
- Light energy is harnessed to split water molecules into oxygen and hydrogen atoms (photolysis OF WATER)
- Hydrogen is removed by NADP (hydrogen acceptor) to form NADPH (reduced NADP).
- Oxygen is released as a by-product.
- ATP is generated from ADP and phosphate.
Where does the light-independent stage (Calvin cycle) occur?
It can take place in the absence of light / under low light, in the stroma of chloroplasts.
What are the 3 main steps of the light-independent stage?
- Carbon fixation
- Reduction
- Regeneration of RuBP
What happens during carbon fixation (light-independent stage 1)?
Co2 diffuses into the stroma and combines with RuBP, in the presence of RuBisCO
- Product: 2 molecules of 3C glycerate-3-phosphate (GP)
What happens during reduction (light-independent stage 2)?
GP is reduced to triose phosphate (3-carbon sugar) by hydrogen from NADPH and energy from ATP (from light-dependent stage)
From triose phosphate, carbohydrates, lipids and amino acids can be synthesised.
What happens during the regeneration of RuBP (light-independent stage 3)?
RuBP is regenerated using energy from ATP, so that more CO2 can be fixed.
Why is light needed for photosynthesis (light intensity - limiting factor)?
Light is needed for light-dependent reactions to occur on the thylakoids of chloroplasts.
Why is CO2 needed for photosynthesis (CO2 concentration - limiting factor)?
Carbon dioxide is needed for carbon fixation to occur during the light-independent reactions of photosynthesis.
Why is a suitable temperature needed for photosynthesis (temperature - limiting factor)?
A suitable temperature is needed for photosynthetic enzymes such as Rubisco to function.
Low light conditions ___ rate of photosynthesis, ___ the light intensity past the optimum light intensity has __ ___ on the rate of photosynthesis.
Low light conditions decreases rate of photosynthesis, increasing the light intensity past the optimum light intensity has no effect on the rate of photosynthesis.
