Transcript Where Do We Get Our Energy?

Warm-up
What is the equation below?
6CO2 + 6H2O + light energy → C6H12O6 + 6O2
Where Do We Get Our Energy?
•From the air we breathe?
•From the water we drink?
•From the food we eat?
Where does our food get its energy?
• Steak = cows get their energy
by grazing on grass
• But how does grass get its
energy????
Where Does Our Food Get Its Energy?
• Chicken = chickens get their
energy by eating grain
• Grain usually comes from corn
or wheat
• Where do corn and wheat get
their energy???
Where Does Our Food Get Its Energy?
• Many vegetarians eat TOFU
which comes from soybeans
• Soybeans are produced by a
plant
• Where do soybeans get their
energy???
So almost all living things get
their energy from:
THE SUN!!!
Autotrophic vs. Heterotrophic
• Autotrophs are
• Heterotrophs are
“self-feeders”
“other feeders”
• They can make
• These organisms
their own food!
cannot make their
own food
• Usually they use
photosynthesis to • They must eat food
make food
made by others
Plants are
autotrophs!!
• They undergo photosynthesis
to make food for
themselves…and for us!! Thank
you plants! 
Extra Credit Opportunity
• Someone explain why leaves change
color? What happens to the
chloroplasts?
Tell me about it tomorrow before class
and be willing to share your findings
with the class!
AUTOTROPHS
You will now see some pictures of
autotrophic organisms...
Algae
Some
bacteria
The tree, not the person…
So what do Autotrophic
organisms have in
common?
They can make their
own food!!
Autotrophic = “self-feeder”
HETEROTROPHS
Can’t make their own food,
so they eat food made by other organisms!
You will now see some pictures of
heterotrophic organisms...
Animals are
heterotrophs
Sleepy baby sloths are
heterotrophs
Where is this fungus getting its
nutrition?
Sharks are very hungry heterotrophs
Mold in Blue Cheese
Gangrene –
decay of
tissue from
a bacterial
infection
(the bacteria is
the heterotroph)
Ewwww…
So what do Heterotrophic
organisms have in
common?
They get their food from
some other source!
Heterotrophic = “other-feeder”
Now that the review is over, let’s get down to the
nitty gritty of photosynthesis!
Photosynthesis
Carbon dioxide + water + light
Glucose + oxygen
Where does photosynthesis
occur in plants?
• You should already know the
answer to this question!
• It occurs in the chloroplasts of
plant cells
The structure of a chloroplast
Outer membrane
Inner membrane
Thylakoid
membrane
Stroma
(fluid)
Key Molecules in photosynthesis:
1) ATP (adenosine tri-phosphate) =
energy that the cell can use
• ADP is the low energy form (only has two
phosphates)
• ATP is high energy (it has three phosphates)
2) NADPH = temporarily stores
electrons for the cell
• NADP+ stores no electrons, NADPH stores
two electrons
Once sunlight is captured, its
energy is trapped in the
chemical bonds of sugars such
as Glucose
That is photosynthesis in a
nutshell
Photosynthesis occurs in two steps:
Step 1: The light reactions: light is
required for this step!!
Step 2: The Calvin cycle (also known
as the light-independent
reactions)
The Light Reactions
• Location: the thylakoid membrane of
the chloroplast
• Purpose: to generate ATP and NADPH
(energy storing compounds) that will be
used in the Calvin cycle
Key Molecules in photosynthesis:
1) ATP (adenosine tri-phosphate) =
energy that the cell can use
• ADP is the low energy form (only has two
phosphates)
• ATP is high energy (it has three phosphates)
2) NADPH = temporarily stores
electrons for the cell
• NADP+ stores no electrons, NADPH stores
two electrons
Here’s what happens in the
light reactions:
1) Light is absorbed by chlorophyll
***chlorophyll is a green pigment that
absorbs light
Here’s what happens in the
light reactions:
2) Chlorophyll then releases electrons to a
series of proteins in the thylakoid
membranes
***these proteins are called electron carriers
****these electron carriers pass the
electrons from one to another along an
electron transport chain
****at the end of the chain, the electrons are
passed to NADP+ making it into NADPH
The electron transport chain
Electron carrier
Electrons (from
Chlorophyll)
H+
H+
H+ H+
H+ H+
H+ H+
H+
H+
Phospholipids
NADP+ + e- = NADPH
OUTSIDE THE MEMBRANE
Here’s what happens in the
light reactions:
3) As the electron carriers pass the electrons down
the electron transport chain, they also pump H+
ions inside the thylakoid membrane
***the inside of the membrane becomes +
charged
***the outside of the membrane becomes –
charged
***this difference in charge is a source of energy
ATP synthase uses this energy to make ATP!!!!!
Here’s what happens in the
light reactions:
4) Oxygen is produced when water splits to
donate its electrons to chlorophyll
• this replaces the electrons donated by
chlorophyll to the electron transport chain
• This is the reaction when water splits:
2H2O  4 H+ + O2
• We benefit from this oxygen
production…take a deep breath!!!
Summary of the Light Reactions
Reactants
Products
*Water
*ATP
*Sunlight
*NADPH
*NADP+
*ADP
*Oxygen
The second step of
photosynthesis is
called the….
•Step 1 = the Light Reactions
•Step 2 = the Calvin Cycle
Here’s what happens in the
Calvin Cycle
CO2
2 ATP
*Rubisco
2 ADP
2 NADPH
2 NADP+
Glucose (+ Lipids & Amino Acids)
The Calvin Cycle
• Location = the stroma of the
chloroplast
• Does not require light to work!
(unlike the light reactions)
• Does require ATP, NADPH and CO2
• Does require Rubisco to bring in
CO2
A Summary of Photosynthesis
Light + H2O + CO2
Light Reactions
Calvin Cycle
Oxygen + Glucose