Photosynthesis
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Transcript Photosynthesis
Where does the energy that living
things need come from?
Food!
You’re not you when you’re hungry!
Where does the energy that living
things need come from?
Originally, though the energy in most food come from
the sun
PLANTS AND SOME OTHER TYPES OF
ORGANISMS ARE ABLE TO USE LIGHT ENERGY
FROM THE SUN TO PRODUCE FOOD
Autotrophs
Organisms that make their own food
Heterotrophs
Organisms that cannot use the sun’s energy directly
Animals
Obtain energy from the foods they consume
Grass – autotroph
Impala - heterotroph
Cheetah…
Cheetah and Impala…
AUTOTROPH!!!!
AHHHHHH!!!!!!!!
Heterotrophs
Obtain energy from the foods they consume
Cheetah: obtains energy stored in autotrophs
indirectly by feeding on animals that eat autotrophs
Mushrooms
Heterotroph or Autotroph?
Mushrooms - Heterotroph
Obtain food by decomposing other organisms
Chemical Energy and ATP
What forms of energy can you think about?
Chemical Energy and ATP
What forms of energy can you think about?
Light
Heat
Electricity
Stored in chemical compounds, too
Burn a candle
Energy is released in the form of light and heat
Bonds between carbon and hydrogen are broken
Energy is released from those electrons
When the electrons in those bonds are shifted from
higher energy levels to lower energy levels, the extra
energy is released as heat and light
Living things use chemical fuels as
well
Adenosine triphosphate (ATP)
ATP
Adenine
Ribose: a 5-carbon sugar
Three phosphate groups
X3
ATP ADP and ADP ATP
Releasing stored energy
Adenosine diphosphate
A phosphate bond has broken – RELEASED ENERGY
When a cell has energy available, it can store small
amounts of it by adding a phosphate group to ADP
molecules, producing ATP
ATP has enough energy to power a
variety of cellular activities,
including active transport across
cell membranes, protein synthesis,
and muscle contraction
The characteristics of ATP make it
exceptionally useful as the basic
energy source of all cells
Old Guys Assignment
Jan van Helmont
Joseph Priestley
Jan Ingenhousz
Write a paragraph about each of these guys and his
contribution to the discovery of photosynthesis
Photosynthesis
The key cellular process identified with energy
production
Plants use the energy of the sunlight to convert water
and carbon dioxide into high-energy carbohydrates –
sugars and starches – and oxygen
Oxygen is a waste product
Photosynthesis
¾Light
¾¾
® C6H12O6 + 6O2
Carbon dioxide + water ¾Light
¾¾
® sugars + oxygen
6CO2
+ 6H2O
Photosynthesis uses the energy of
sunlight to convert water and
carbon dioxide into high-energy
sugars and oxygen
How do plants use low-energy, raw
materials to produce high-energy
sugars?
How do plants use low-energy, raw
materials to produce high-energy
sugars?
They capture the energy of sunlight
How do plants use low-energy, raw
materials to produce high-energy
sugars?
They capture the energy of sunlight
So… how do they capture sunlight?
In addition to water and carbon
dioxide, photosynthesis requires
light and chlorophyll, a molecule in
chloroplasts
https://www.youtube.com/watch?v=-XP7yflhOtE
Chemical Energy and ATP
What forms of energy can you think about?
Light
Heat
Electricity
Stored in chemical compounds, too
Energy from the sun travels to
Earth in the form of light.
“White” light: Sunlight that is visible
Mixture of different wavelengths of light
Many are visible and make up the visible spectrum
Different wavelengths = different colors
400Violet
450Blue
500Cyan
550Green
600Yellow
650Orange
700Red
750Infrared
How do plants gather the sun’s
energy?
How do plants gather the sun’s
energy?
Pigments: light-absorbing molecules that gather the
sun’s energy
Chlorophyll: the plant’s principle pigment
Chlorophyll a
Blue-violet
Red
Chlorophyll b
Blue
Red
Carotene: can be red, yellow, or orange
Carotene ≈ Carrot
When chlorophyll absorbs light,
much of the energy is transferred
directly to electrons in the
chlorophyll molecule, raising the
energy levels of these electrons.
These high-energy electrons allow
photosynthesis to work.
Inside a Chloroplast
Inside a Chloroplast
Thylakoids: saclike photosynthetic membranes
Arranged in stacks called grana
Proteins in the thylakoid membrane organize
chlorophyll and other pigments into clusters known as
photosystems
Photosystems: light collecting units
Stroma: the region outside of the thylakoid
membranes
2 parts of Photosynthesis
Light-dependent reactions
Take place in the thylakoid membranes
Light-independent reactions (Calvin Cycle)
Take place in the stroma
Electron Carriers
Carrier molecule: compound that can accept a pair of
high-energy electrons and transfer them along with
most of their energy to another molecule
ELECTRON TRANSPORT
NADP+: accepts and holds 2 high-energy electrons
along with a hydrogen ion
NADP+ NADPH
Light Dependent Reactions
Require light
Use energy from the light to produce ATP and NADPH
The light dependent reactions produce oxygen gas and
convert ADP and NADP+ into the energy carriers ATP
and NADPH
Light Dependent Reactions
1.
2.
3.
4.
5.
Photosystem II
Electron Transport Chain
Photosystem I
Hydrogen Ion Movement
ATP Formation
Photosystem II
Light absorbed by photosystem II is used to break up
water molecules into energized electrons, hydrogen
ions (H+), and oxygen
Electron Transport Chain
High-energy electrons from photosystem II move
through the electron transport chain to photosystem I
Photosystem I
Electrons released by photosystem II are energized
again in photosystem I. Enzymes in the membrane
use the electrons to form NADPH. NADPH is used to
make sugar in the Calvin Cycle
Hydrogen Ion Movement
The inside of the thylakoid membrane fills up with
positively charged hydrogen ions. This action makes
the outside of the thylakoid membrane negatively
charged and the inside positively charged.
ATP Formation
As hydrogen ions pass through ATP synthesis, their
energy is used to covert ADP into ATP
ATP Synthase
ATP synthase: protein in the cell membrane
This protein spans the membrane and allows H+ ions
to pass through it.
As H+ ions pass through ATP synthase, the protein
rotates like a turbine being spun by water in a
hydroelectric power plant
As it rotates, ATP synthase binds ADP and a phosphate
group together to produce ATP
Light Dependent electron transport produces not
only high energy electrons, but ATP as well
Calvin Cycle
The ATP and NADPH formed from the light
dependent reactions contain an abundance of
chemical energy, but they are not stable enough to
store that energy for more than a few minutes
The Calvin cycle uses ATP and NADPH from the
light-dependent reactions to produce high-energy
sugars
Calvin Cycle
CO2 Enters the Cycle
2. Energy Input
3. 6-Carbon Sugar Produced
4. 5-Carbon Molecules Generated
1.
CO2 Enters the Cycle
6 carbon dioxide
molecules are
combined with six 5carbon molecules to
produce twelve 3carbon molecules
Energy Input
Energy from ATP and
high-energy electrons
from NADPH are used to
convert the twelve 3carbon molecules into
higher-energy forms
6-Carbon Sugar Produced
Two 3-Carbon molecules
are removed from the
cycle to produce sugars,
lipids, amino acids, and
other compounds
5-Carbon Molecules Regenerated
The 10 remaining 3-
carbon molecules are
converted back into six 5carbon molecules, which
are used in the next cycle
This step uses energy
6ATP 6 ADP
Factors that affect Photosynthesis
Water
Temperature
Light Intensity
Factors that affect Photosynthesis
Water – shortage can stop or slow photosynthesis
Plants that live in dry conditions, such as desert plants
and conifers, have a waxy coating on their leaves that
reduces water loss
Temperature
Light Intensity
Factors that affect Photosynthesis
Water – shortage can stop or slow photosynthesis
Plants that live in dry conditions, such as desert plants
and conifers, have a waxy coating on their leaves that
reduces water loss
Temperature
Photosynthesis depends on enzymes that function best
between 0℃ and 35℃
Temperatures above or below this range may damage the
enzymes, slowing down the rate of photosynthesis
Very low temps – possibly stop
Light Intensity
Factors that affect Photosynthesis
Water – shortage can stop or slow photosynthesis
Plants that live in dry conditions, such as desert plants and conifers,
have a waxy coating on their leaves that reduces water loss
Temperature
Photosynthesis depends on enzymes that function best between
0℃ and 35℃
Temperatures above or below this range may damage the enzymes,
slowing down the rate of photosynthesis
Very low temps – possibly stop
Light Intensity
Increasing light intensity increases the rate of photosynthesis
At a certain level, the plant reaches its maximum rate of
photosynthesis