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CELL ENERGY
Photosynthesis and Respiration
You should be able to…
1. Describe the role of ATP in biochemical reactions.
2. Describe the fundamental roles of chloroplasts and
mitochondria in energy transformations.
3. Compare the basic transformation of energy during
photosynthesis and cellular respiration.
A3 Vocabulary
• adenosine triphosphate
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(ATP)
heterotroph
autotroph
photosynthesis
pigment
chlorophyll
thylakoid
stroma
NADP+
light-dependent reactions
• light independent reactions
• aerobic
• anerobic
• cellular respiration
• glycolysis
• matrix
• Kreb’s cycle
• NAD+
• fermentation
• calorie
Chemical Energy and ATP
• Energy = ability to do work
• Energy comes in different forms (light, heat, electricity)
• Cells need energy to do work
• Cell energy comes from ATP (adenosine triphosphate)
• Consists of adenine, a 5-carbon sugar and THREE phosphates
• Phosphates are the key to ATP’s ability to store and release energy
Examples of ATP in action
• Active transport
• Protein pumps in cell membrane need ATP
• Movement
• Muscle contractions
• Protein synthesis
How do cells release the energy stored in
ATP?
• Cells release energy from ATP when the bond
between the second and third phosphate groups is
broken
• Phosphate released = energy released
• ATP minus a phosphate group = ADP
Regenerating ATP
• ADP (adenosine diphosphate) can be
recharged by adding another
phosphate group to become ATP
again
• Phosphate gained = energy stored
• Cells regenerate ATP from ADP by using
energy in food like glucose
Quick Check
• Where is the energy stored in the molecule of ATP?
• How would you change the figure to show a molecule of ADP?
The connection between the food you eat
and ATP…
• Cells do not keep a lot of ATP
• Food is digested and converted into ATP
• Different foods give different amounts of ATP
• Carbohydrate = 36 ATP
• Lipid = 146 ATP
• Proteins = broken down to make other proteins, not energy!!!!
• Plants use photosynthesis to produce the carbs so their
cells can get ATP
MODELING ATP
Activity
What are the green organelles inside the
leaf cells?.
What is the function (job) of the chloroplast?
LIGHT
• Energy
• Mixture of different wavelengths (color)
• Can be absorbed, transmitted or reflected
• Absorbed energy can be used for photosynthesis
• Reflected light is not used for photosynthesis
• Absorbed by pigments (chlorophyll) in plant cell
chloroplasts
Quick Check…look at the light absorption
spectrum on the previous slide
• What color light is least absorbed?
• What color(s) of light are most absorbed?
• What color of light can be used for photosynthesis?
• How would a plant grow if only given green/yellow light?
What are the green organelles inside the
leaf cells?.
What is the function (job) of the chloroplast?
CHLOROPLASTS
CHLOROPLASTS
• Thylakoids = photosynthetic membranes (contain
chlorophyll)
• Arranged in stacks called grana
• Stroma = space around the thylakoids
Photosynthesis – BIG PICTURE
• Multi-step process
• Energy from the sun is used to convert water and carbon
dioxide (reactants) into high energy sugars and oxygen
(products
• Plants then use the sugars to make ATP (cell respiration…stay tuned)
High-Energy Electron Carriers
1. Chlorophyll absorbs light
2. Absorption of light produces high-
energy electrons
3. Electrons picked up by NADP+ to
become NADPH
4. NADPH carries the high-energy
electrons to chemical reactions
elsewhere in the cell
Photosynthesis - Details
I.
Light dependent reactions
• INPUT= sunlight, water, chlorophyll
• OUTPUT = oxygen (waste), ATP, energy carriers (NADPH)
• LOCATION = thylakoid
Photosynthesis - Details
II.
Light Independent reactions (a.k.a. Calvin Cycle)
• INPUT– carbon dioxide, energy carriers from light reactions
• OUTPUTS – sugar (carbohydrate)
• LOCATION - stroma
QUICK CHECK…
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Where in the chloroplast do the light reactions take place?
Where in the chloroplast does the Calvin Cycle occur?
What is another name for the Calvin Cycle?
What are the reactants of photosynthesis?
What are the products of photosynthesis?
What is the role of energy carriers in photosynthesis?
How is energy transformed in photosynthesis?
Is photosynthesis energy absorbing or energy releasing?
What is the form of energy used by ALL cells called?
How are you connected to the process of photosynthesis?
CELL ENERGY
Cellular Respiration
CHAPTER 9
What role do mitochondria have in
bioenergetics?
Chemical Energy and “Food”
• Autotrophs (plants) make their own food
• Heterotrophs (animals) need to consume other
organisms as food
• Food represents chemical energy
• Fats and carbohydrates are primary sources of energy
• Energy stored in food is measured by the calorie
• Amount of energy needed to raise the temperature of 1 gram of
water 1 degree Celsius
• The Calorie on food labels is actually a kilocolarie or 1000
calories
Mitochondria
• Site of Cellular Respiration
• Similar structure to chloroplast
• Double membrane
• Inside of mitochondria = matrix
• Folds of mitochondria = cristae
• Increase surface area
Cellular Respiration
• The process that converts food energy into cellular
energy in the presence of oxygen
• Consists of many chemical reactions and many enzymes
Stages of Cell Respiration
1. Glycolysis
2. Kreb’s cycle
3. Electron transport chain
Stages of Cell Respiration
Energy transformations begin with
glycolysis
• GLYCOLYSIS
• Anaerobic (doesn’t need oxygen)
• Occurs in the cell cytoplasm
• Glucose is “cut” in two
• Small amount of ATP is made
• Necessary for cellular respiration
• Products of glycolysis are broken down further in the mitochondria
Kreb’s cycle
• Takes place in the mitochondrial matrix
• Occurs twice for each glucose molecule that enters
glycolysis
• Cycle of chemical reactions, each catalzyed by a specific
enzyme
• Carbon dioxide released as waste
• Electron carriers (NADH and FADH2) produced here are
used in the next step
Electron Transport Chain (ETC)
• Occurs across the inner mitochondrial membrane
• Proteins hand off high energy electrons to pump
hydrogen ions across the inner membrane against the
concentration gradient
• Hydrogen ions, at the end of the chain flow through
ATP synthase, a protein channel equipped with an
enzyme to make ATP
• Oxygen is the final electron acceptor in the ETC
• Without oxygen, the ETC does not run, ATP will not be produced
ATP Production totals
• Glycolysis
• 2 ATP
• Kreb’s Cycle
• 2 ATP
• ETC
• 32 ATP
1 glucose =
36 ATP
As long as oxygen is present, cellular
respiration will occur in the mitochondria
and much ATP will be made.
• What happens if oxygen is not around?
• How will a cell get ATP for its processes to continue working?
Fermentation
• Recall that glycolysis, an anearobic process produced 2
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ATP per molecule of glucose
If oxygen is present, cellular respiration will come next to
produce much more ATP
If oxygen is not present, fermentation will begin to allow
glycolysis to continue
Fermentation DOES NOT produce ANY ATP
Fermentation is anaerobic (oxygen not needed)
Two types of fermentation
1. Lactic Acid Fermentation
• Occurs in your muscle cells and some bacteria
• Produces lactic acid (which makes your muscles “burn”
during intense exercise)
• Yogurt contains bacteria that undergo lactic acid
fermentation – lactic acid gives yogurt its flavor
2. ALCOHOLIC FERMENTATION
• Occurs in yeast, some bacteria and certain types of
plants
• Produces alcohol and carbon dioxide as waste
• Cheese, bread, beer and wine are examples of food
made by fermentation
• Bacteria which go through fermentation help animals
digest food
Three main sources of ATP for use during
exercise…
• Stored ATP (only enough for short bursts)
• ATP made by lactic acid fermentation (about 90 seconds
worth)
• ATP produced by cellular respiration (aerobic; requires
oxygen)
Where does the ATP come from?
QUICK BURSTS of ACTIIVTY…
• Stored ATP (a few seconds worth)
• Lactic acid fermentation can supply cells with an additional 90
seconds worth of ATP
• Builds up an “oxygen debt” that gets repaid by rapid breathing
EXTENDED EXERCISE (more than 90 seconds)
• Cellular respiration (aerobic)
• Stored carbohydrates (glycogen) used first - 15 to 20 minutes
• Stored lipids next
Quick Check…
• Where does glycolyis occur?
• What does glycolysis produce?
• Is glycolysis aerobic or anearobic?
• Where do the products of glycolysis go if oxygen is
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present?
What happens after glycolysis if oxygen is not present?
Is Kreb’s cycle aerobic or anearobic?
Is the ETC aerobic or anaerobic?
What are the two forms of fermentation?
Give an example of lactic acid fermentation.
Give an example of alcoholic fermentation.
Does fermentation produce any ATP?
Another Quick Check…
• What is the role of the mitochondria?
• Do plants have mitochondria?
• Do plants do cell respiration?
• How much ATP can be produced from one molecule of
glucose?
• Describe the energy transformations that are occuring in
respiration.
• What is the connection between breathing and cell
respiration?
• What does ATP synthase do?