9C Plants and photosynthesis
© Tony P. Thould
September 2000
HOW DO PLANTS GET THEIR FOOD THEY DO NOT HAVE MOUTHS!?!
This was a problem the scientist
Van Helmont investigated
2Kg small tree
Five years later with only
Rain water given to it
75Kg
dry soil
After 5 years grew into a 75Kg tree and the
soil in the pot weighed 74.94Kg when dried
RESULTS ANALYSIS
Gain in weight of the tree compared with
the loss in weight of the soil :-
75kG
-
2kG
=
-
75Kg dry soil
The plant gained 73
Kg after 5 years
=
74.94Kg dry soil
Soil only
lost 0.06Kg
after
5
years
CONCLUSION
From the results it is obvious that the plant
could not have gained all of its weight from
the soil. It must get its food from somewhere
else.
The plant cannot go and find food therefore
the food must be near at hand.
What is there near the plant which it can use to
make food?
AIR :78% Nitrogen
Heat & Light
Energy SUN
21% Oxygen
0.03% Carbon
Dioxide
SOIL
CHLOROPHYLL
in the leaves
WATER (Hydrogen &
Water)
Plants make their own food - Glucose - which is a Carbohydrate (
made up from Carbon, hydrogen and Oxygen ) and stores it as
Starch. Which of the above would provide the plant with the raw
materials to make Glucose?
!!!YOU MUST LEARN THIS EQUATION!!!!
PHOTOSYNTHESIS
Using Sunlight
Energy
Carbon
Dioxide
+
Water
Glucose
+
Oxygen
Absorbed by
Chlorophyll
These four things must all be present in
order to make food by Photosynthesis
Glucose sugar is
made and stored
as starch. Oxygen
is given off as a
waste product
PHOTOSYNTHESIS
Using Sunlight
Energy
Carbon
Dioxide
6CO2
+
Water
6H2O
Glucose
Absorbed by
Chlorophyll
C6H12O6
+
Oxygen
6O2
!!!YOU MUST LEARN THIS WORD EQUATION!!!!
PHOTOSYNTHESIS
+
+
!!!YOU MUST LEARN THIS EQUATION!!!!
PHOTOSYNTHESIS
This is the way by which green plants
make their own food.
They use Carbon Dioxide and Water as these
two raw materials contain the elements
Carbon, Hydrogen and Oxygen which are all
needed to make Glucose sugar - their food,
Energy from the sun is absorbed by Chlorophyll
and used to make the Glucose. This stores the
sun’s energy as chemical energy
AIR :Carbon
Dioxide
WATER
(
Hydrogen and
Oxygen )
SUN’S
ENERGY
CHLOROPHYLL
absorbs the light
energy
These are the four essential raw materials that
every green plant needs to make glucose by
photosynthesis . the excess glucose is stored
starch.
Iodine is a chemical test for starch
If a drop of Iodine, which is normally
red brown in colour, is placed upon a
substance that contains starch, the
iodine will turn black.
If the substance contains no starch the
iodine stays the same colour I.e. red
/brown.
A CHEMICAL TEST
FOR STARCH
IODINE is a red /
brown liquid
Starch
BY NOW YOU
SHOULD KNOW…..
•The word equation for Photosynthesis
•The four things needed for Photosynthesis
•What is made by Photosynthesis
•The storage form of Glucose in Plants
•The chemical test for Starch
WATER
As water is one of the four essential raw
materials for photosynthesis, a plant must easily
be able to take this in.
A plant’s roots are covered in specialised root
hair cells. These are thin walled and have a
large surface area.
This enables the planned to absorb plenty of
water from the surrounding soil particles.
The water travels up the stem in veins to the
leaves are a where it is absorbed into the
palisade cells.
A ROOT HAIR CELL
Absorbs water from the surrounding soil particles.
SOIL
Root Hair gives
the cell a larger
surface area
through which
it can take in
more water.
Plants take in Carbon
Dioxide and give off
Oxygen when they are
making food by
Photosynthesis
Many people believe that plants breathe in
carbon-dioxide and to breathe out oxygen.
This is not the case.
Plants absorb carbon dioxide when they
make food by photosynthesis. Oxygen is
given off as a waste product of
Photosynthesis.
They briefed in oxygen and breathe out
carbon dioxide just like we do when we
were Respire
RESPIRATION IN PLANTS
Plants breathe in Oxygen
and breathe out Carbon
Dioxide during Respiration just like we do!
Plants and animals need to
Respire in order to gain ENERGY
for movement, growth etc.
USEFUL CHEMICALS
Potassium Hydroxide - This absorbs
Carbon Dioxide and holds on to it
Lime Water - Is an indicator for
Carbon Dioxide. It turns from a clear
liquid to a cloudy white liquid if
Carbon Dioxide passes through it.
AN EXPERIMENT TO SHOW THAT PLANTS BREATHE
OUT CARBON DIOXIDE
AIR
OUT
AIR
IN
Potassium Hydroxide
removes Carbon
Dioxide from the Air
Lime Water goes cloudy
white if Carbon Dioxide
bubbles through it.
AIR
OUT
AIR
IN
No Carbon
Dioxide
Lime Water
stays clear
No Carbon
Dioxide going
into the Bell
Jar
Goes cloudy
showing
Carbon
Dioxide is
present
BY NOW YOU SHOULD KNOW….
•The word equation for Respiration
•The two things needed for Respiration
•Why living things need to respire
•The waste products of Respiration
•The chemical test for Carbon Dioxide
•The effect of Potassium Hydroxide on Air
AEROBIC
RESPIRATION
Energy is released in the cells for the body to
use. The energy is in the Glucose sugar we eat
and can be released by chemically reacting with
Oxygen in our cells - Aerobic Respiration
Summary Equation
Glucose + Oxygen = ENERGY + Carbon Dioxide + Water
C6H12O6 + 6O2 = ENERGY +
Raw Materials
6CO2
+ 6H2O
Waste Products
We also breathed in oxygen and
breathe out carbon dioxide when we
respire.
The oxygen is taken into our blood to
a lungs and is delivered to all of our
cells. Our blood also delivers sugar to
our cells.
Waste carbon dioxide and water is
taken from ourselves by the blood
back to the lungs to be breathed out.
THE LUNGS
Cartilage Rings
Trachea
Left Bronchus
Bronchioles
Ribs
Intercostal
Muscles
Left Lung
Alveoli
Diaphragm
THE
GASEOUS EXCHANGE IN THE ALVEOLI
Exhale the waste
Carbon Dioxide
Deoxygenated Blood
from Pulmonary Artery
CO
2
This has a lot of
Carbon Dioxide in
it which passes
from the blood into
the lungs to be
breathed out.
CO2
Inhale air which
contains 21% Oxygen
Oxygenated Blood out
via the Pulmonary Vein
O2
O
2
Oxygen is
taken from
the lungs in
the blood to
our cells.
Glucose + Oxygen = Energy + Carbon Dioxide + Water