Photosynthesis Flashcards
What do all living organisms require to survive?
Energy
Radiant
Why are plants green?
Chloroplasts and chlorophyll
How are leaves well suited to absorb light?
Held in a position which is exposed to light
Transparent cuticle and epidermis which allows light to pass through
It’s flat with a larger SFA
Thin so the son can penetrate lowest tissues easily
What is photosynthesis?
The process by which autotrophic organisms use light energy to make sugar and oxygen from carbon dioxide and water.
Where does photosynthesis occur?
In chloroplasts:
Thylakoids= sac like photosynthetic membranes inside chloroplasts.
Granum (grana)= stack of thylakoids
What is the stroma?
Gel filled space inside chloroplast outside the thylakoid.
What are the two phases of photosynthesis?
Light Dependent Phase
Light Independent Phase
Explain the light dependent phase.
Takes place in the the grana of the chloroplast
Requires light
Chlorophyll molecules trap light energy which activates chlorophyll
Electrons become energised
Light E turns into Chemical E
What are the energised electrons used to do?
1.) Split water molecules => Photolysis
Oxygen leaves chloroplast
Energy rich HYDROGEN moves to LDP carried by NADP
2.) Form high energy ATP => PHOSPHORYLATION
(ADP + P => ATP)
Energy rich HYDROGEN and ATP are used in the next phase.
Explain the LIP.
Takes place in the STROMA of chloroplast
Also called the CALVIN CYCLE
Does NOT require light
Uses energised H2 and ATP from light phase as well as CO2
Energised H atoms to bond with CO2 to make GLUCOSE
This reaction requires energy => ATP
Glucose can now be used to make other organic compounds eg. Starch
Glucose can be used during respiration.
What is the importance of pss?
Suns energy stored as chemical energy in glucose
Releases OXYGEN as a waste product => used in respiration (to release E for living organisms)
Keeps CARBON DIOXIDE concentration fairly constant
Fossil fuels store products of pss
What are the factors that affect the rate of pss?
Light intensity
Carbon Dioxide
Temperature
How does light intensity affect the rate of pss?
When light increases the rate of pss also increases
It levels off as it reaches maximum rate
Any further increase in might intensity will not result in an increase in pss. This is bc enzymes are all busy photosynthesising as fast as they can.
How does Carbon Dioxide affect the rate of pss?
When co2 concentration increases so does the rate of pss. But it levels off at a point.
Biochemical reactions can’t go any faster
Any further increase in co2 will not result in an increase in photosynthesis.
How does temperature affect the rate of pss?
Temp low = rate of pss low
Temp increases = rate of pss increases until optimum temp is reached
Enzymes will denature if the temp is too hot and the rate of pss drops.
