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Cellular Energy
Chemical Energy and ATP
 Most cell processes use ATP for energy
 Do you get energy from eating sugar?
 Yes?
 No?
All cells use ATP
 ATP is a molecule that transfers energy
 How is ATP like money in your wallet?
 ATP is used to:
 Build molecules
 Move materials
Structure of ATP
 Energy is released when a phosphate
group is removed from the molecule
 ATP = Adenosine TRI-phosphate
ATP
 When the third P is removed, energy is
released
 Unstable and easily
removed for energy
 ATP = ADP + P
 ADP = Adenosine
DI-phosphate
ATP and ADP
Questions
 Where are molecules from food
involved in the cycle of ADP to ATP?
 Describe the relationship between
energy stored in food and ATP.
How many ATP?
 Carbohydrates offer easy ATP
 Carbs are not stored in the body
 One glucose = 36 ATP molecules!
 Proteins about the same as Carbs
 Not typically used for energy but to build
more proteins
 Fats (lipids) offer the most ATP
 One triglyceride = 146 ATP molecules
How do plants eat?
 They make their own
food
 Plants absorb energy
from the sun and
make sugars to break
down for ATP
Chemosynthesis
 Some species of bacteria use chemicals
to make food
 They break the food down for ATP
Solar Energy?
 Calculators, homes and cars use
energy from sunlight
 Energy for people comes from ATP
 ATP comes from the breakdown of
sugars
 How are sugars made?
Photosynthetic organisms
 Producers – organisms that produce the
source of chemical energy for
themselves and for other organisms
 Plants
 Bacteria
 Protists
Basic Food Chains
 Animals eat plants = consumers
 Animals that eat other animals, bacteria
and fungi that decompose organisms
 Wolf eats rabbit, rabbits tissues supply
energy to wolf, tissues were built from
plants, which made the sugars and
other carbon-based molecules
Photosynthesis
 Plant cells use sunlight energy to make
organic compounds
 Directly or indirectly, the energy for
almost all organisms begins as sunlight
Sunlight and Radiant Energy
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Ultraviolet
Microwaves
Visible light
or Radio waves?
 Plants absorb visible light
Where does it occur?
 In the leaves!
Photosynthesis occurs in the chloroplast.
 Anatomy of a chloroplast
grana (thylakoids)
chloroplast
stroma
Chloroplasts
 Contain Thylakoids (flattened sacs)
 Have pigments in their membranes
 Grana - Stacks of thylakoids
 Stroma - Fluid inside
chloroplast
grana (thylakoids)
chloroplast
stroma
Pigments
 Chlorophyll
 Green pigment
 Two forms - a and b
 Absorb blue and red light, reflect
green/yellow
 Accessory pigments - absorb and reflect
other colors
 Can only be seen in the fall of the year
Photosynthesis
 General Equation
CO2 + H2O --> C6H12O6 + O2
 Major Steps
1. Absorb light energy
2. Convert light energy into chemical energy
3. Store chemical energy in sugars
CO2 in, O2 out
 Stomates open - gas is exchanged
 H2O is lost, must be replaced by roots
 Transpiration - H2O diffusion out of
plants
Light-dependent Reactions
Step 1: Absorb sunlight, split water and
transfer energy through the H+
2 H2O  4 H+ + O2
“Electron Transport Chain via
Photosystems I and II”
Step 2: Transfer energy to ATP
“ATP Synthase”
Light-independent Reactions
Step 1: CO2 is converted into larger
molecules using ATP from Lightdependent reactions
Step 2: The larger molecules are
converted into Glucose – C6H12O6
“Calvin Cycle”
Why Respiration?
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Movement
Transport in cells
Maintenance
Nervous Signals
Biosynthesis
Respiration
 Release of energy by breaking down
glucose
 1 Glucose = 38 ATPs!!!!!!
 General Equation
C6H12O6 + O2 --> H2O + CO2 + ATP
Life has options…
 Aerobic - Uses Oxygen!
 Animals
 Plants
 Anaerobic - Little or no oxygen!
 Some animals
 Yeast
 Bacteria
Major Steps of Aerobic Respiration
 Glycolysis
 Kreb’s Cycle
 Electron Transport Chain
Glycolysis
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Simple step in the cytoplasm
Makes 2 ATPs!
Glucose is cut in half!
Yields two Pyruvate molecules
(3 carbons each)
Kreb’s Cycle
 Occurs inside the mitochondria
 Pyruvate molecules get broken into CO2
and H+
 Makes 2 more ATPs!
Electron Transport Chain
 Occurs on the cristae (membrane) of
the mitochondria
 H+ transfer excess energy to ATP
synthase
 Excess H+ + O2  H2O
ATP Synthase
 Enzyme responsible for:
 ADP to ATP and O2 to H2O
Cellular Respiration
Chemical energy (high-energy electrons)
CO2
CO2
Glycolysis
Glucose
Cytosol
of cell
Pyruvic
acid
Mitochondrion
Chemical energy
Krebs
cycle
Electron transport
chain and oxidative
phosphorylation
H2O
Mitochondrial
cristae
Via oxidative
phosphorylation
ATP
ATP
ATP
Fermentation
 When you undergo heavy exercise, you
force your muscles to use fermentation!
 Large amounts of Oxygen for Aerobic
Respiration cannot be stored in cells
 Cells need energy, so they choose the
alternate route!
Can you function without O2?
 Glycolysis yields 2 ATP
 Glycolysis does not require Oxygen
 Yes you can!!
 You just get a little bit of energy
Anaerobic Respiration
 Two types
 Lactic Acid Fermentation
 Yeast and bacteria, your muscles
 Alcoholic Fermentation
 Without fermentation, glycolysis would
not continue
 Fermentation recycles the molecules
that allow glycolysis to continue
Fermentation
A build-up of lactic acid?
 That must burn!
 It does until you recovery breath,
this is why your body breathes
hard for several minutes after you
stop exercising
 You are making up for the
oxygen loss
 The replenishment of oxygen
allows the cells to remove the
excess lactic acid
Food Diary
 Write down all of the foods you ate in
the last 24 hours
 Now, cross out…
Lactic Acid Fermentation
 What would life be like without:
 Cheese, bread and yogurt?
 Bacteria and Mold
 Convert milk into cheese
 Make yogurt go sour
Alcoholic Fermentation
 Some yeast and plants
 Begins at the same point of lactic acid
fermentation
 Used to produce
 Bread, beer and wine
Microbes in our Digestive System?
 Bacteria in your digestive tract rely on
fermentation
 Without them we would not fully digest food
 They allow us to absorb more nutrients from
food
All cells need chemical energy.
 Processes that make food include:
 Photosynthesis
 Chemosynthesis
 Processes that make energy include:
 Respiration (two types)
 Fermentation (two types)