photosynthesis Flashcards
how does photosynthesis work?
Absorption of light by chlorophyll
Energy synthesises glucose from CO2 and H2O
what is the equation?
Light energy
6CO2 + 12H2O —————> C6H12O6 + 6H2O + 6O2
Chlorophyll
what may glucose be used for?
As an immediate source of energy
Stored as starch
Used to form cellulose and proteins
what may oxygen be used for?
Oxygen may be used:
For aerobic cellular respiration
Released
structure of chloroplasts
Outer and inner membrane that regulate movement of substances
Fluid matrix called stroma
Thylakoid membrane system
Thylakoid stacked together form grant
Between each granum there are thylakoid lamellae
origin of chloroplasts
Cyanobacteria photosynthetic prokaryotes
Highly folded inside membranes like thylakoid
Contain chlorophyll and enzymes like chloroplasts
Endosymbiosis
Cyanobacteria engulfed by eukaryotic cells 2 billion years ago
Lived in a symbiotic relationship
Overtime became chloroplasts
Evidence:
Chloroplasts have plastidial DNA or circular DNA and can replicate by binary fission
Have ribosomes similar to bacterial similarities
The cell in unable to generate new chloroplasts if removed
Studies of DNA suggest common ancestor
Have porins (transport proteins) that are found in mitochondria and prokaryotes
when do photosynthetic pigments have most and least absorbance? autumn leaves?
Highest rate of photosynthesis with red and blue light
Lowest rate of photosynthesis with green light
Autumn leaves change colour because chlorophyll is removed so that when leaf falls off it isn’t wasted
what happens in the light-dependent reaction? what are the inputs and outputs?
Occurs in thylakoid membranes where chlorophyll and enzymes are
Only takes place in light
Light in absorbed by chlorophyll to:
Split water into hydrogen and oxygen
Form ATP from ADP and NADPH from NADP+ (nicotinamide adenine dinucleotide phosphate)
Inputs:
NADP+
ADP + Pi
Water
Outputs:
NADPH
ATP
Oxygen gas
what happens in the light-independent reaction? inputs and outputs?
NADPH and ATP released into stroma
These coenzymes provide energy needed to drive these biochemical pathways
Inputs:
NADPH
Carbon dioxide
ATP
Outputs:
NADP+
Glucose
ADP + Pi
Does not need light
The main stage is the Calvin cycle
what is the Calvin cycle?
Carbon dioxide is reduced to a GAP molecule (3 carbon carbohydrate)
In the cytoplasm 2 GAP join to form glucose
The GAP left over can be recycled into ribulose 1,5 bisphosphate, the starting molecule of the light independent reaction
what plants are we talking about?
C3
how does carbon dioxide affect rate?
Stomata can open and close to monster levels
The rate of photosynthesis increases to a certain point as concentration of carbon dioxide increases
how does light affect rate?
Light saturation curve
Increase of photosynthesis as light intensity increases until a point where it plateaus
Plateau is max level of photosynthesis when enzymes are working at optimum rate
how does temperature affect rate?
Enzymes increase in rate as temp increases
Too hot they denature
Too cold, rate slows down
