Photosynthesis
Biology
Chapter 8
8.1 Energy and Life
• Energy is the ability to do work
• What is work for cells?
• Plants, algae, and some bacteria use
light energy from the sun to produce
food
•
a. Autotrophs
b. Heterotrophs
Chemical Energy and ATP
• Adenosine diphosphate, ADP
• Adenosine triphosphate, ATP
*ATP is used by all types of cells
as their basic energy source
*When a cell has energy available,
it can store small amounts of it by
adding a phosphate group to ADP
molecules, producing ATP
*ATP is like a rechargeable
battery
• Because a cell can subtract the third
phosphate group, it can release
energy as needed
*bond breaks  energy is released
• ATP has enough energy to power
cellular activities like active transport
across cell membranes, protein
synthesis, and muscle contraction
• Most cells have only a
small amount of ATP…
• One molecule of glucose
stores more than 90x
the chemical energy of
1 ATP
• Cells regenerate ATP
from ADP by using the
energy in foods like
glucose
• How do plant cells make
ATP and other molecules
for long-term energy?
Quick Check
1. Organisms that make their own food are called
A. autotrophs B. heterotrophs C. decomposers
2. How is energy released from ATP?
A. A phosphate is added B. An adenine is added
C. A phosphate is removed
3. Why do most cells contain only a small amount of ATP?
…Cells do not need ATP for energy
…ATP isn’t very good for long-term energy storage
8.2 An Overview of Photosynthesis
• Plants use the energy in sunlight to turn water
and carbon dioxide into high-energy
carbohydrates and oxygen.
Some experiments to consider…
• Jan van Helmont devised an experiment
to find out if plants grew by taking
material out of the soil
• Joseph Priestley placed a glass jar over
a burning candle and watched as the
flame went out. He put a live plant in
the jar, and guess what happened?
• Jan Ingenhousz showed that the effect
observed by Priestley occurred only
when the plant was exposed to light
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.
The Structure of a Chloroplast
• Light-dependent rxns. take place on the
thylakoid membrane.
• Thylakoids are “pancake-like” structures.
• The 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 which is a waste
product.
Light Reactions (cont.)
• The NADPH carries the eand the H+ ions to the
membrane where the H+
ions are pumped inside the
thylakoid. (see page 211)
•The pressure of the H+
ions builds up, and the
H+ ions are forced back
out of the membrane
through a structure
called ATP synthase.
Making ATP
• As the H+ ions and
their energy move
through the ATP
synthase, the
protein rotates
and creates 3 ATPs
for every turn.
Light Dependent Reactions