CELL ENERGYPhotosynthesis 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

(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 ATPActivity

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…1. Where in the chloroplast do the light reactions take place?

2. Where in the chloroplast does the Calvin Cycle occur?

3. What is another name for the Calvin Cycle?

4. What are the reactants of photosynthesis?

5. What are the products of photosynthesis?

6. What is the role of energy carriers in photosynthesis?

7. How is energy transformed in photosynthesis?

8. Is photosynthesis energy absorbing or energy releasing?

9. What is the form of energy used by ALL cells called?

10. How are you connected to the process of photosynthesis?

CELL ENERGYCellular 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

C C C C C C

C C C C C C

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

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 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?