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Bioenergetics - Photosynthesis - Coggle Diagram
Bioenergetics - Photosynthesis
Bioenergetics
The study of
energy
in
living systems
(environments) and the
organisms
(plants and animals) that utilise them
Photosynethesis
Process by which plants make their own food
Therefore plants are known as
producers
(they produce their own food)
Plants need
CO
2
, H
2
O , light and chlorophyll
to carry out photosynthesis
CO
2
and H
2
O are the
raw materials
for photosynthesis (used to make the products)
Light energy is needed to provide
energy
to drive the reactions
Chlorophyll is needed to
absorb
the light energy. Found in the chloroplasts of the plant cells
Equations for photosynethesis
Photosynthesis is an
endothermic reaction
More energy
is transferred from the environment
to break the bonds in the CO
2
and the H
2
O
than is transferred to the environment when the bonds in the glucose are formed
Energy is transferred from the environment to the
chloroplasts
by
light
How is CO
2
used in the process of photosynthesis
CO
2
Air
contains 0.04% CO
2
DIFFUSES
into leaf through
stomata
DIFFUSES into the palisade mesophyll and spongy mesophyll
calls to the
chloroplasts
where photosynthesis takes place
How is H
2
O used in the process of photosynthesis
Comes from the
soil
enters the root through
root hair cells
through
OSMOSIS
(large SA to absorb more water)
Water travels up the plant through the root, stem and into the leaves (
xylem
vessels) (called
TRANSPIRATION STREAM
)
How is glucose used in the process of photosynthesis
Moved in the
phloem
vessel as soluble
sucrose
Used for:
respiration
to release
energy
cellulose
for
cell walls
lipide
for
cell membranes
Chlorophyll
Starch, lipids
(fats and oils) for
energy stores
amino acids
to make
proteins
for
growth and repair
. (
proteins = enzymes = photosynthesis and respiration
)
small and soluble
-
can't store it
(needs to be converted into
insoluble molecules
(starch, fats and oils)
REQUIRED PRACTICAL
(The effect of changing light intensity on the rate of photosynthesis)
Independent: light intensity Dependent: rate of photosynthesis
Control: temperature, same pondweed, levels of Co
2
Q: Why is the pondweed placed in sodium hydrogencarbonate solution?
A: So CO
2
doesn't become a
limiting
factor
Q: How is the temperature controlled? A: Thermometer could be used
Q: Why does the pondweed have to be left for a few minutes at each new distance from the lamp before counting the bubbles?
A:The plants has to get used to the new light intensity (allows the plant to equilibrate)
Q: Why is counting the number of bubbles not an accurate way of measuring the rate of photosynthesis?
A: Sometimes bubbles produced very fast - miscount
Bubbles may not be all the same size
Q: How could this experiment be made more accurate? A: Using a gas syringe or upside down measuring cylinder to collect the gas and calculate the volume of O
2
produced instead of counting the bubbles
light intensity ∝ 1 / (D)
*2
WHEN ASKED TO PLOT LIGHT INTENSITY TIMES YOUR INITIAL LIGHT INTENSITY BY A FACTOR OF 10 TO PLOT
Storing Glucose
Glucose is a
small, soluble
molecule
Unsuitable for storage
as it
dissolves easily
and increases the
sugar concentration
of the cell fluid which can
damage
it
Why is starch good for storage?
made up of
many glucose molecules joined together
STARCH NEEDS TO BE STORED AT NIGHT AS GLUCOSE CAN NOT BE PRODUCED AS THE PLANT IS NOT PHOTOSYNTHESISING, BUT THE PLANT STILL NEEDS GLUCOSE FOR EXAMPLE IN RESPIRATION
insoluble
and
not easily lost
from storage ares in the cells
does NOT affect the
water concentration
inside cells
not very reactive
so is good for storage
The Starch Test
We can test if a leaf has photosynthesised by testing for starch because
stored glucose is converted to starch
We can use the starch test to show that CO
2
, light and chlorophyll are needed for photosynthesis
CO
2
: Put 1 leaf from the same plant in pure O
2
and another leaf from the same plant in pure CO
2
. Leave for a few days and after doing the starch test, the leaf in pure CO
2
will turn blue-black, the leaf in pure O
2
all remain orange (iodine stain)
Light
: Cut a shape in a card and cover a leaf with it. Leave for a few days and after the starch test, the part of the part that was not covered by the card will turn blue-black, the part of the leaf that was covered will remain orange (iodine stain)
Chlorophyll
: Put a leaf in ethanol and heat in a hot water bath. The ethanol will turn green and the leaf pale. Prepare another leaf without ethanol. After the starch test, the leaf with ethanol will be orange (iodine stain) and the one without ethanol will be blue-black
PLANTS SHOULD BE DESTARCHED BEFORE THESE EXPERIMENTS BY PUTING THEM IN A DARK CUPBOARD FOR 1-2 DAYS TO
USE UP ANY EXISTING STORES OF GLUCOSE
Starch Test
1.Put a leaf in hot water (hot water bath) to allow it to soften up.
Heat it in ethanol to take away the green colour (
REMEMBER ETHANOL IS FLAMMABLE
)
Soften it back in hot water
Add iodine to it
**If the leaf has starch in it, it turns blue-black when iodine is dropped on it
How is O
2
used in the process of photosynthesis
Used by the plant for respiration
O
2
is released into the air
The Limiting Factor
The limiting factor is the factor which is
closest to its minimum value
Plants grow faster when they photosynthesis faster
Plants photosynthesise
faster on hot, sunny days
Any factor that
limits or slows down the rate of photosynthesis if it is not present in sufficient amount is known as a
limiting factor
In photosynthesis:
CO
2
, light intensity, temperature and chlorophyll are all limiting factors
glucose ---> amino acids ---> proteins ---> lipids ---> cellulose ---> new cells
Graphs
Effect of Light Intensity
Description and explanation of slope
Description
: As the light intensity increases, the rate of photosynthesis increases
Explanation
: This is because light is provides energy for the reactions of photosynthesis. The light intensity is the limiting factor
Effect of CO
2
concentration
Description and explanation of slope
Description
: As the concentration of CO
2
increases, the rate of photosynthesis also increases
Explanation
: This is because CO
2
provides energy for the reactions of photosynthesis. The concentration of CO
2
is the limiting factor
1 more item...
Description and explanation of straight line
Description
: As the concentration of CO
2
increases further, there is no further increase in the rate of photosynthesis
Explanation
:This is because some other factor is limiting the rate of reaction, such as light intensity, temperature or chlorophyll
Description and explanation of straight line
Description
: As the light intensity increases, there is no further increase in the rate of photosynthesis
Explanation
: This is because some other factor is limiting the rate of the reaction, such as CO
2
concentration, temperature or chlorophyll
Photosynthesis in a greenhouse
Commercial plant growers can
maximise the growth of plants in a greenhouse as they can control the factors which limit the rate photosynthesis
Temperature
: maintained at the
optimum temperature for enzymes
, by opening or closing vents of using heaters
Concentration of CO
2
can be increased by
burning fossil fuels of adding manure** (microbes in manure release energy when they respire)
Sunlight
: passes through transparent glass.
Artificial light
can be used so that the plants have enough like for photosynthesis 24/7
There are less likely to be
pests
in the greenhouse and they can easily be
removed
Hydroponics
Growing a plant without soil
Roots are suspended in water, contains all the mineral ions that they need for efficient growth
Minerals
such as
nitrates
--->
amino acids
--->
proteins for growth
Magnesium is needed to make chlorophyll
Phosphates
needed to make
ATP and DNA
and for
cell membranes
Polytunnels
made of
transparent plastic
and are **cheaper than greenhouses
They
protect plants from frost and trap energy
from the sun to warm the air around the plants. They let
sunlight
thorough to the plant for
photosynthesis
They make the
atmosphere humid
around the plants too, so that they do not
lose as much water by transpiration
