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.
Conditions ___ or ___ the optimum temperature results in ___ rates of photosynthesis. (link to enzymes)
Conditions below or above the optimum temperature results in lower rates of photosynthesis.
__ carbon dioxide conditions decrease the rate of photosynthesis, increasing the concentration above the optimum has __ ___ on the rate of photosynthesis. (substrate of Rubisco)
Low carbon dioxide conditions decrease the rate of photosynthesis, increasing the concentration above the optimum has no effect on the rate of photosynthesis.
