Plants and Photosynthesis
How do plants make their
own food?
Plants are autotrophic – This
means they make their own food.
The way plants make their own
food is through a process called
Photosynthesis
One of the raw materials that plants need to make food does
come from the soil, the other comes from the air.
What are these two raw materials called?
carbon dioxide
(from the air)
water
(from the soil)
Plants use carbon dioxide and water to make their own food
in a chemical reaction. What is the name of this reaction?
Photosynthesis
Plants need energy for photosynthesis to take place.
Where does this energy come from?
light energy
carbon dioxide
(from the air)
water
(from the soil)
The energy for photosynthesis comes from the Sun.
Where in a plant does photosynthesis take place?
Photosynthesis takes place in the
chloroplast found in plant cells.
Notice that plant cells have many chloroplast in them.
What are the products of photosynthesis?
light energy (radiant )
carbon dioxide
(from the air)
Glucose
(chemical energy)
oxygen
water
(from the soil)
What type of energy transformation occurs during
photosynthesis?
Radiant / light energy to chemical energy
Plant cells in the upper surface of leaves have chloroplasts
which contain the green pigment called chlorophyll.
light energy
carbon dioxide
(from the air)
chlorophyll
glucose
oxygen
water
(from the soil)
It is chlorophyll that absorbs light/radiant energy
from the Sun to make photosynthesis happen.
Plants make their own food by the process of photosynthesis.
In this chemical reaction, chlorophyll in plant cells absorbs light
energy to change carbon dioxide and water into glucose and
the by-product oxygen.
What is the word equation for photosynthesis?
light energy
carbon
dioxide
water
glucose
oxygen
chlorophyll
This equation can be read as:
“carbon dioxide and water, in the presence of light energy
and chlorophyll, produces glucose and oxygen”.
Cellular Respiration
• Mitochondria give animal and plant cells
energy by breaking down glucose to
release energy.
• Cellular respiration is a process that
uses the products of photosynthesis to
produce energy.
• What part of the cell helps produce
energy?
• What process produces energy?
Cycle of Carbon Dioxide and
Glucose
Cellular Respiration:
C6H12O6 + 6O2 → 6CO2 + 6H2O
Photosynthesis:
6CO2 + 6H2O + energy from the sun→C6H12O6 + 6O2
Leaves are small ‘factories’
that produce food for plants
by photosynthesis.
Leaves are adapted so that
photosynthesis can take place.
Plants need carbon dioxide,
water, sunlight and chlorophyll
to carry out this important
process.
What features of leaves
make them suitable for
photosynthesis?
The features of leaf that make it
suitable for photosynthesis are:
 A leaf is broad and flat to
capture lots of sunlight.
 Veins carry water to the leaf
and take food from the leaf
to the rest of the plant. Veins
also help to support the leaf.
 Certain plant cells contain
chloroplasts with chlorophyll.
 Small holes called stomata in
the underside of a leaf allow
gases in and out.
How does water enter a
plant?
Water is one of the raw materials
needed for plants to carry out
photosynthesis.
How does water enter a plant?
Water from the soil enters a plant
through the roots.
You can’t normally see them but
roots are a very important part of a plant.
Why are roots branched and spread out through the soil?
How are roots adapted?
Roots are branched and spread out
for two reasons:
 to absorb water (and mineral salts)
from a large amount of soil.
 to anchor the plant in the soil.
Taking a closer look, roots are
covered in root hair cells.
Root hair cells have thin walls
and a large surface area to help
them absorb lots of water.
How are roots adapted to their job?
water
Why do plants need water?
Water is needed by plants for photosynthesis
but this important liquid is also used in many
other ways:
 to provide dissolved minerals that keep the plants healthy;
 to transport substances around the plant;
 to keep the plant rigid and upright;
 to keep the plant cool;
 to allow other chemical reactions to occur in plant cells.
What happens to a plant if it does not get enough water?
Glossary
 chlorophyll – The green pigment inside chloroplasts
that plants need for photosynthesis to take place.
 chloroplast – The part of a plant cell where
photosynthesis occurs.
 glucose – The sugar plants make during photosynthesis.
 palisade cell – A type leaf cell with lots of chloroplasts.
 photosynthesis – The process by which plants use
carbon dioxide and water to produce glucose and oxygen
in the presence of light and chlorophyll.
 starch – Extra glucose from photosynthesis is stored as
this substance which can be tested for with iodine.
 stomata – Small holes in the lower surface of a leaf
that allow gases in and out.
 xylem – Tubes in veins that carry water around a plant.