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Photosynthesis
Chapter 8
Energy in Living Systems….
Energy is the ability to do work.
Autotrophs – Living things that can
use energy from the sun or chemicals
to make their own food. Green plants
and some bacteria and algae.
Heterotrophs – living things that
must eat other living things for
energy.
Energy in Cells…
ATP, or adenosine triphosphate is
the form of energy cells make to do
everyday functions.
ADP, or adenosine diphosphate is
ATP without the final phosphate
group. Therefore it has less energy
than ATP.
ADP is used over and over again to
be turned into ATP.
What does ATP look like?
*Only a small amount of ATP is on hand at a time,
It is just regenerated over and over again!
How do plants make ATP and other
molecules for long term energy?
Photosynthesis –
Plants use the
energy in sunlight to
turn water and
carbon dioxide into
carbohydrates and
oxygen.
6H2O + 6CO2 ----------> C6H12O6+ 6O2
Scientists who contributed to our
knowledge of photosynthesis:
Jan van Helmont – concluded most of
the mass of a tree comes from water
(*partially true)
Joseph Priestley – used a bell jar,
candle, and mint plant to conclude
plants release oxygen
Jan Ingenhousz – concluded aquatic
plants only produce oxygen bubbles
in the presence of sunlight
Jan van Helmont’s experiment
Jan Ingenhousz’s experiment
Pigments of Photosynthesis…
Chlorophyll –
green pigment in
plants that absorbs
blue-violet and red,
and reflects green.
Chlorophyll is
present in the
chloroplasts of a
plant cell.
Structure of a Chloroplast…
Structure of a chloroplast…
The light-dependent reactions take
place on the thylakoid membrane.
Thylakoids are the “pancake”
structures. Stacks are called grana.
The Calvin cycle takes place in the
stroma (the fluid the thylakoids float
in).
Making ATP using light energy..
The energy from the sun is absorbed
by the chlorophyll in the thylakoid
membrane.
NADP+ is an electron carrier that
carries high energy electrons and two
hydrogen ions. Turns into NADPH.
The H+ ions are created when
sunlight hits the thylakoid and water is
split, creating free oxygen, a waste
product.
Light reactions, continued…
The NADPH carries the electrons and
the H+ ions to the membrane where
the H+ ions are pumped into the
inside of the thylakoid.
The pressure of the H+ ions builds
up, and the H+ ions are forced back
out of the membrane through a
structure called ATP synthetase.
Making ATP…
As the H+ ions and their energy
move through the ATP synthetase,
the protein rotates and creates 3
ATPs for every turn.
1948 – Melvin Calvin traces the
path of carbon: the Calvin Cycle…
The ATP and the NADPH created in
the light-independent reactions
combined with carbon dioxide to
assemble carbohydrates in the
Calvin Cycle.
The Calvin cycle can also produce
other sugars, amino acids, and lipids.
The Calvin cycle…
Factors affecting photosynthesis:
Water – a shortage of water will slow
or stop photosynthesis.
Temperature – Plant enzymes
function in specific temperature
ranges.
Light intensity – The brighter the
light is, the more photosynthesis can
occur. But only to a certain extent.