Name___________________________________
Notes - Photosynthesis
I.
The Role of Energy
A.
B.
C.
D.
E.
F.
G.
II.
Every cell needs a source of energy in order to perform work.
Plants and some other type of organisms are able to use light energy from the Sun to
produce food.
The solar energy (light energy) is converted to chemical energy in the form of food and passed
down the food chain.
Autotroph - make their own food.
Heterotroph - obtain energy from the food they consume.
ATP (Adenosine Triphosphate is an energy storage molecule)
Using biochemical energy – Active transport (sodium potassium pump), movement of cell
organelle.
Photosynthesis
A.
Photosynthesis is the chemical process used by autotrophic organisms (producers) to make
food.
B.
Photosynthesis is carried out by plants, algae and some prokaryotes (Cyanobacteria).
C.
The process in which energy of Sunlight is used to convert water, carbon dioxide (CO2) into
Oxygen(O2) and high-energy carbohydrates – sugar and starch.
D.
Investigating photosynthesis
Van helmont – Water is involved in increasing mass of a plant.
Priestley – Plant produces a substance required for burning candle.
Ingenhousz – Light is necessary for plants to produce O2
E.
The chemical equation for Photosynthesis:
6CO2 + 6H2O Sunlight C6H12O6 + 6CO2
F.
The products of photosynthesis are used by heterotrophic organisms to supply energy.
G.
Light & Pigment (light absorbing molecules, Chlorophyll a
Chloroplast).
& Chlorophyll b present in
III.
Chloroplasts
A.
B.
C.
D.
E.
IV.
These are the sites of the photosynthesis reaction.
Chloroplasts are plastids that contains photosynthetic membranes called thylakoid, arranged in
stacks known as grana.
Thylakoids contain clusters of chlorophyll & other pigments and proteins known as
photosystem that are able to capture the energy of Sunlight.
Chlorophyll captures light between 450-600 nm. This is violet blue and red light.
Chlorophylls reflect the green light, causing plants to appear green. They are the most
common and important pigments in plants and algae.
Photosynthetic Reactions
A.
Light Dependent Reaction- (require light, takes place within Thylakoid membrane) – produce
O2 gas and convert ADP+P and NADP + (carrier molecule which carry high energy electrons)
into energy carriers ATP and NADPH.
i.
ii.
iii.
iv.
v.
vi.
vii.
viii.
In photosystem II, energy from light is absorbed by Chlorophyll and transferred to
electrons.
These high energy electrons are passed on electron transport chain.
Water is broken down on the inner surface of thylakoid membrane into 2 electrons, 2
H+ ions, 1 oxygen atom (released into air)
High energy electrons move from Photosystem II to Photosystem I. Their energy is
used to transport H+ from stroma to inner thylakoid.
Inside of thylakoid (filled up with H+)becomes positively charged and outside becomes
negatively charged.
H+ pass through protein ATP synthase, ADP is converted into ATP
NADP+ picks up high energy electrons from photosystem I at the outer surface of
thylakoid membrane and becomes NADPH.
The light energy is converted into ATP in the thylakoids.
B.
Light Independent Reaction/Calvin Cycle (does not require light, takes place in stroma, the
region outside thylakoid membrane) – it is a carbon-fixing reaction that uses the products of
light-dependent reactions (ATP and NADPH) to produce high energy sugars (which are used
by the plants to make more complex carbohydrates – starch, cellulose).
Location?
Reactants?
Products?
V.
Factors affecting photosynthesis
A.
B.
C.
Water – Raw material – shortage stops photosynthesis
Temperature (enzymes function best between 0 C to 35 C).
Intensity of light – Increase in the intensity increases photosynthesis upto a certain level.