Transcript What is photosynthesis? - missdannocksyear11biologyclass

What is photosynthesis?
Plants make their own food by photosynthesis.
This process is a chemical reaction that uses light energy.
light energy
The word photosynthesis comes
from the Greek language:
“photo” means “light”
“synthesis” means “putting together”
Photosynthesis just means “putting together with light”.
What do green plants “put together” to make their food?
Photosynthesis: raw materials
The raw materials
for photosynthesis
come from the air
and the soil.
What are these raw
materials called?
What else do plants
need to turn
carbon dioxide
and water into food?
carbon
dioxide
water
Photosynthesis: energy for the reaction
Photosynthesis is a
chemical reaction
between carbon
dioxide and water.
Energy is needed
for this reaction to
take place.
Where do plants
get this energy
from?
light
energy
carbon
dioxide
water
Photosynthesis: where it happens
Plants use light
energy from the
Sun to power
photosynthesis.
light
energy
Where in the leaf
does this reaction
take place?
Photosynthesis
takes place in what
part of plant cells?
carbon
dioxide
water
Photosynthesis: where it happens
Photosynthesis takes
place in plant cells
with chloroplasts.
light
energy
Chloroplasts contain
the green chemical
called chlorophyll.
Chlorophyll absorbs
the energy from
sunlight that allows
carbon dioxide and
water to react.
What are the products
of this reaction?
chlorophyll
carbon
dioxide
water
Photosynthesis: products of the reaction
The products of the
reaction between
carbon dioxide and
water are glucose
and oxygen.
light
energy
chlorophyll
Which of these
products is used
by plants?
What happens to the
‘waste’ product?
carbon
dioxide
oxygen
glucose
water
Photosynthesis: products of the reaction
Glucose is the useful
product for plants.
Some glucose is used
straightaway by plant
cells, some is
converted to starch
for storage and later
used for food.
light
energy
chlorophyll
carbon
Oxygen is the ‘waste’
dioxide
product. This gas is
transported out of the
leaf into the air.
Why is this important
for humans and other
living things?
oxygen
glucose
water
Photosynthesis: summary
Summarize the process of photosynthesis in one sentence.
Photosynthesis is a chemical reaction
that takes place in the chloroplasts
in green plant cells, where light energy
is used to convert carbon dioxide and water
into glucose and oxygen.
Photosynthesis is a chemical reaction which means it can
also be summarized in a word equation.
What is the word equation for this vital chemical reaction?
Photosynthesis: word equation
light energy
carbon
dioxide
water
glucose
chlorophyll
light
energy
chlorophyll
carbon
dioxide
water
oxygen
glucose
oxygen
Photosynthesis: chemical formulae?
Photosynthesis is a chemical reaction involving molecules.
light energy
carbon
dioxide
water
glucose
oxygen
C6H12O6
O2
chlorophyll
CO2
H2O
The chemical formula of a glucose molecule is C6H12O6.
What are the chemical formulae of the simple molecules
that make up carbon dioxide, water and oxygen?
!!!YOU MUST LEARN THIS EQUATION!!!!
PHOTOSYNTHESIS
Using Sunlight
Energy
Carbon
Dioxide
6CO2
+
Water
6H2O
Glucose
Absorbed by
Chlorophyll
These four things must all be present in
order to make food by Photosynthesis
C6H12O6
+
Oxygen
6O2
Glucose sugar is
made and stored
as starch. Oxygen
is given off as a
waste product
Leaves: maximizing photosynthesis
Leaves are the most efficient
solar panels on Earth!
Why can they be called this?
Light energy is absorbed
by the chlorophyll in leaves
and used to carry out
photosynthesis.
Leaves come in all shapes
and sizes but what features
do they have in common
to maximize photosynthesis?
Structure of a leaf
How are leaves designed to maximize photosynthesis?
Leaves are wide and flat
Leaves are thin so gases
to create a large surface
can reach cells easily.
area and absorb as much
light as possible.
Leaves have lots of veins
to carry water to the cells
and carry glucose away.
Leaves have holes, called
stomata, on their
underside through which
gases move in and out.
Structure of a leaf activity
Take a look inside a leaf
What happens to the glucose?
Photosynthesis and respiration
Only green plants photosynthesize, but respiration occurs
in the cells of all living things to release energy.
Photosynthesis (energy needed)
light energy
carbon
dioxide
water
glucose
oxygen
chlorophyll
Respiration (energy released)
carbon
glucose
oxygen
dioxide
water
Compare the reactants, products and energy results of
these two chemical reactions. How are they connected?
Photosynthesis and respiration
How will the amounts of oxygen and carbon dioxide
in the air vary over 24 hours?
amount of
oxygen
amount
of gas
in the air
amount of
carbon dioxide
12 a.m.
12 p.m.
12 a.m.
What overall effect do photosynthesis and respiration have
on the levels of oxygen and carbon dioxide in the air?
The rate of photosynthesis
Photosynthesis is a chemical reaction and so has a rate.
light energy
carbon
dioxide
water
glucose
oxygen
chlorophyll
Is the rate of photosynthesis always the same?
The rate of photosynthesis varies depending on three
main factors:
light
carbon dioxide
temperature
How do these factors affect the rate of photosynthesis?
Light and the rate of photosynthesis
Light energy has to be absorbed by chlorophyll
for photosynthesis to take place.
light energy
carbon
dioxide
water
glucose
oxygen
chlorophyll
The brighter the light, the more light energy there is,
so will photosynthesis be faster or slower?
More light energy means that photosynthesis will be faster.
If light intensity is too high plant cells can be damaged.
How is photosynthesis affected if this happens?
Carbon dioxide and the rate of photosynthesis
Carbon dioxide is one of the raw materials
used by plants to make their food.
light energy
carbon
dioxide
water
glucose
oxygen
chlorophyll
The concentration of carbon dioxide in the air (0.03%)
is actually quite low.
Why is the concentration of carbon dioxide in
commercial greenhouses often raised to about 0.1%?
More carbon dioxide means more photosynthesis,
so plants make more food and grow quicker.
Temperature and the rate of photosynthesis
Photosynthesis is controlled by enzymes.
Enzymes usually work best at warmer temperatures.
light energy
carbon
dioxide
water
glucose
oxygen
chlorophyll
Why is the rate of photosynthesis slower on a sunny day
in winter?
If the temperature gets too hot (above 40 °C), plant enzymes
begin to break down and are destroyed or denatured.
Why does photosynthesis stop under such conditions?
What is a limiting factor?
What is the ideal combination of factors
for the maximum rate of photosynthesis?
enough light
enough carbon dioxide
ideal temperature (not too hot or cold)
How is the rate affected if one of these factors is restricted?
If one of the factors is restricted, the rate of photosynthesis
will be below the maximum possible rate.
The restricted factor controls how quickly photosynthesis
occurs and so limits the rate. It is called the limiting factor.
Photosynthesis and light – limiting factors
rate of photosynthesis
How does the amount of light affect the rate
of photosynthesis on this labelled graph?
1
As the amount of light
increases, so does the rate.
The limiting factor is light.
2
Here, increasing the amount
of light has no affect on the
rate. The limiting factor is
now carbon dioxide or
temperature.
2
1
light intensity
What must be increased for
the rate to increase?
Photosynthesis and carbon dioxide – limiting factors
rate of photosynthesis
How does the amount of carbon dioxide affect
the rate of photosynthesis on this labelled graph?
1
As the amount of carbon
dioxide goes up, so does
the rate. The limiting
factor is carbon dioxide.
2
Here, increasing the
amount of carbon dioxide
has no affect on the rate.
Light or warmth is now
the limiting factor.
2
1
concentration of
carbon dioxide
What must be increased
for the rate to increase?