, Topic 1: Photosynthesis
Photosynthesis: refers to the chemical process by which carbohydrates (glucose) are produced
using radiant energy (energy from the sun, needed by plants for photosynthesis)
Requirements & Products of Photosynthesis
Plants are adapted to obtain what is required for photosynthesis &
release it’s products
Requirements & Absorption method Products
● CO2: Diffuses into the leaves ● Glucose: A form of
● Water: Inorganic substance carbohydrates which is stored
absorbed by the roots as starch in plants & glycogen in
● Radiant Energy: Absorbed by animals
the leaves from the sun ● Oxygen: Gas released into the
● Chlorophyll: Found inside atmosphere which we breathe in
chloroplasts
● Enzymes: Found inside
chloroplast
● Photosynthesis Equations:
The Structure of a Chloroplast
Chloroplasts are the site of photosynthesis. They are found only in plant cells and give plants their
green pigmentation.
● Thylakoids: Disc shaped membranes containing
chlorophyll
● Granum: A stack of thylakoids
● Lamella: Membranes that make up the thylakoid
● Stroma: Liquid membrane of the organelle
● Starch granule: Structure which stores the
produced glucose in the form of starch
● Chloroplast DNA: contains genetic material
● Double Membrane: Protects the chloroplast
1
, The Process of Photosynthesis
Photosynthesis has 2 phases
● Light Phase- Takes place in the presence of light
● Dark Phase- Can take place in light or darkness
Light Phase (Light Dependant)
● Takes place in the grana/ granum.
● Water is absorbed by the grana & radiant energy is absorbed by chlorophyll in the grana.
● Energy transformation takes place, transforming radiant energy into chemical energy. This
energy is used for 2 processes
○ Water molecules are split up into energy rich hydrogen ions (H+) which will be used
in dark phase & oxygen atoms which are released into the atmosphere
○ This is called photolysis: Splitting of water molecules into hydrogen & oxygen atoms
● ATP (Adenosine triphosphate, energy carrier in cells) is also formed through
phosphorylation: formation of energy transporting molecules called ATP. This will also be
used in the dark phase
Dark Phase (Light independent)
● Takes place in the stroma of the cell
● CO2 is absorbed from the atmosphere & combined with H+ using energy from the ATP
● Energy rich carbohydrates (glucose) are formed
○ Excess glucose (Carbohydrate formed during photosynthesis) is stored as starch
● This process is known as the Calvin cycle (Cyclical process during dark phase of
photosynthesis)
2
Photosynthesis: refers to the chemical process by which carbohydrates (glucose) are produced
using radiant energy (energy from the sun, needed by plants for photosynthesis)
Requirements & Products of Photosynthesis
Plants are adapted to obtain what is required for photosynthesis &
release it’s products
Requirements & Absorption method Products
● CO2: Diffuses into the leaves ● Glucose: A form of
● Water: Inorganic substance carbohydrates which is stored
absorbed by the roots as starch in plants & glycogen in
● Radiant Energy: Absorbed by animals
the leaves from the sun ● Oxygen: Gas released into the
● Chlorophyll: Found inside atmosphere which we breathe in
chloroplasts
● Enzymes: Found inside
chloroplast
● Photosynthesis Equations:
The Structure of a Chloroplast
Chloroplasts are the site of photosynthesis. They are found only in plant cells and give plants their
green pigmentation.
● Thylakoids: Disc shaped membranes containing
chlorophyll
● Granum: A stack of thylakoids
● Lamella: Membranes that make up the thylakoid
● Stroma: Liquid membrane of the organelle
● Starch granule: Structure which stores the
produced glucose in the form of starch
● Chloroplast DNA: contains genetic material
● Double Membrane: Protects the chloroplast
1
, The Process of Photosynthesis
Photosynthesis has 2 phases
● Light Phase- Takes place in the presence of light
● Dark Phase- Can take place in light or darkness
Light Phase (Light Dependant)
● Takes place in the grana/ granum.
● Water is absorbed by the grana & radiant energy is absorbed by chlorophyll in the grana.
● Energy transformation takes place, transforming radiant energy into chemical energy. This
energy is used for 2 processes
○ Water molecules are split up into energy rich hydrogen ions (H+) which will be used
in dark phase & oxygen atoms which are released into the atmosphere
○ This is called photolysis: Splitting of water molecules into hydrogen & oxygen atoms
● ATP (Adenosine triphosphate, energy carrier in cells) is also formed through
phosphorylation: formation of energy transporting molecules called ATP. This will also be
used in the dark phase
Dark Phase (Light independent)
● Takes place in the stroma of the cell
● CO2 is absorbed from the atmosphere & combined with H+ using energy from the ATP
● Energy rich carbohydrates (glucose) are formed
○ Excess glucose (Carbohydrate formed during photosynthesis) is stored as starch
● This process is known as the Calvin cycle (Cyclical process during dark phase of
photosynthesis)
2
