Cellular Respiration 9-1 – 9-2. Chemical Energy and Food All living things consume and use energy...

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Cellular RespirationCellular Respiration

9-1 – 9-29-1 – 9-2

Chemical Energy and FoodChemical Energy and Food

• All living things consume and use energy– Heterotrophs take in food which is digested

and broken down into C6H12O6

– Autotrophs can’t “eat” so they make C6H12O6 through photosynthesis

– Mitochondria then transform the “food energy” into chemical energy ( )ATP

• Calories– Unit of measurement for energy– Amount of energy needed to raise the

temperature of 1 gram of water 1 degree Celsius

– Nutrition information on food is Calories (1000 calories)

• Calories– 1 gram of glucose (sugar) produces 3811

calories when burned– A lot of energy for a cell– Our bodies use glycolysis and cellular

respiration to gradually release energy in food

Overview of Cellular RespirationOverview of Cellular Respiration

• Mitochondria “make change” energetically

• Take the energy in a sugar and convert it into more conveniently-sized packages

• Definition: process that releases energy by breaking down glucose and other food molecules

• Requires oxygen

C6H12O6 + 6O2 → 6CO2 + 6H2O + energyCarbondioxide

WaterCarbohydrate Oxygen ATP

• Step 1: Glycolysis

• Step 2: Krebs cycle

• Step 3: Electron transport chain

MATRIX:Breakdown ofpyruvic acid, Krebs cycle

Outer membrane

INNER MEMBRANE:Electron transportchain

CYTOPLASM:Glycolysis

MITOCHONDRION

Step 1: GlycolysisStep 1: Glycolysis

• Occurs in cytoplasm of ALL cells

• Does not require oxygen

• Process of splitting a glucose (C6H12O6) molecule in half

• Products:– 2 pyruvic acid molecules

• What you get when you split glucose in half• Used in Krebs cycle

– Energized electrons• Carried to the electron transport chain (ETC) by

• Used to generate

• Products:– 2

• Uses up 2 ATP• Produces 4 ATP

– Net yield = 2

1 GlucoseC6H12O6

2 ADPATP2

1 GlucoseC6H12O6

2 PGAL

1 GlucoseC6H12O6

2 PGAL

4ADP + 4 Pi

2 NAD+ 2 NADH

4ATPATP2

To ETC

1 GlucoseC6H12O6

2 PGAL

4ADP + 4 Pi

2 NAD+

2 Pyruvicacid

2 NADH

To ETC

• If oxygen is present pyruvic acid molecules enter the mitochondria for the Krebs cycle– Leads to production of lots of

• If oxygen is absent pyruvic acid molecules stay in the cytoplasm for fermentation– No more ATP is produced

Step 1: Glycolysis

• Step 2: Krebs cycle

Step 2: Krebs CycleStep 2: Krebs Cycle

• Requires oxygen– If there is no oxygen present pyruvic acid

stays in the cytoplasm and does fermentation

• Involves first breaking down pyruvic acid formed during glycolysis

• Occurs as pyruvic acid crosses the mitochondrial membrane

• Rest of the cycle occurs in the mitochondrial matrix

• Products:– 3 CO2

• Exhaled

– 2– Lots more energized electrons

• Carried to ETC by and• Used to generate more

NADH FADH2

Step 2: Krebs Cycle – Break Step 2: Krebs Cycle – Break Down of Pyruvic AcidDown of Pyruvic Acid

CYTOPLASM Mitochondrialmembrane

MITOCHONDRION

Pyruvicacid

(from glycolysis)CO2

NAD+ NADH

Acetyl Co-A

TOKREBSCYCLE

3 carbons

Exhaled

To ETC

4 carboncompound

Co-ACo-A

CitricAcid

5-carboncompound

CO2NAD+

KREBSCYCLE

Step 1: GlycolysisStep 2: Krebs cycle

Mitochondrialmatrix

Outer membrane

Inner membrane

CYTOPLASM

MITOCHONDRION

Intermembranespace

Step 3: Electron Transport ChainStep 3: Electron Transport Chain

• Happens on inner membrane of mitochondria

• Major production of

• Uses energized electrons delivered by and created during glycolysis and the Krebs cycle

• Energized electrons are passed along a series of molecules embedded in the inner mitochondrial membrane

• ETC molecules take the electrons’ energy

• Uses energy to make ATP

Step 3: Electron Transport ChainStep 3: Electron Transport ChainCYTOPLASM

OUTERMEMBRANE

INNERMEMBRANE

ELECTRON TRANSPORT CHAIN

MITOCHONDRIALMATRIX

INTERMEMBRANE

• Oxygen is the final electron acceptor– If oxygen is not present electrons stop flowing

through ETC– ATP production stops – Combines with H+ ions to form water

Step 3: Electron Transport ChainStep 3: Electron Transport ChainCYTOPLASM

OUTERMEMBRANE

INNERMEMBRANE

ELECTRON TRANSPORT CHAIN

MITOCHONDRIALMATRIX

INTERMEMBRANE

Overall ATP ProductionOverall ATP Production

Glycolysis produces 2 ATP

Krebs cycle produces 2

Electron transport chainproduces **32

**Makes ATP from electrons carried to it from the first 3 steps

FOR EVERY GLUCOSE MOLECULE:

Overall ATP ProductionOverall ATP Production

Overall,cellularrespirationmakes

FermentationFermentation

• Occurs when there is no oxygen available

• Pyruvic acid molecules are still formed through glycolysis

• Occurs in the cytoplasm– Mitochondria are not involved

• Pyruvic acid is broken down differently:– No ATP is produced after glycolysis

• 2 types:– Alcoholic fermentation– Lactic acid fermentation

Alcoholic FermentationAlcoholic Fermentation

• Ethyl alcohol and CO2 are byproducts

• Occurs in organisms that live in environments lacking oxygen

Glycolysis

2 Ethanol

• Example: yeast– When spores are placed in a food-rich,

oxygen-free environment the organisms come to life

– Begin doing alcoholic fermentation

– CO2 produced makes bread rise

– Tiny amounts of alcohol produced evaporate as bread bakes

Lactic Acid FermentationLactic Acid Fermentation

• Performed by cells when they run out of oxygen

• After glycolysis pyruvic acid is transformed into lactic acid

• Causes burning sensation in muscles

Lactic Acid FermentationLactic Acid Fermentation

Glycolysis

Glucose

Pyruvic acid

Lactic acid

Energy and ExerciseEnergy and Exercise

• Muscle cells use tremendous amounts of ATP to contract and create movement

• Cells keep a small amount of ATP on hand– Enough for only a few seconds of intense

exercise

• After that ATP is produced by lactic acid fermentation

• Lactic acid fermentation can provide ATP for about 90 seconds of intense exercise

• Lactic acid is produced by a series of reactions that require extra oxygen– Reason for breathing heavily at the end of a

longer race

• Cellular respiration is the only way to generate ATP after 90 seconds– Slow process– Why a marathon and a sprint look differently

• Cellular respiration is the only way to generate ATP after 90 seconds– Slow process– Why a marathon and a sprint look differently– Training allows a person to exercise more

vigorously beyond the 90 second barrier

• Fuel for making ATP is stored as glycogen– Carbohydrate– Body contains enough glycogen to fuel

cellular respiration for 15-20 minutes– Body burns fat after that

Cellular Respiration 9-1 – 9-2. Chemical Energy and Food All living things consume and use energy...

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