Cellular Respiration

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Cellular Respiration

 Photosynthesis – stores energy

 Cell Respiration – releases energy

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General Information:

 CELLULAR RESPIRATION

 A chemical process in which nutrients are broken down to produce usable energy

 You can think of respiration as the

combustion of gasses in a car’s engine.

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Car’s Engine

• MAIN ENGINE = Mitochondrion – The site of the majority of ATP synthesis

• MAIN FUEL = Glucose – fats and proteins may also be used in some instances

• MAIN EXHAUST = CO₂ and H₂O.

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General Information (con’t)

· Notice that the wastes from photosynthesis are used as raw materials in cellular

respiration

· There are

2

types of respiration

· Aerobic – takes place in the presence of oxygen

· Anaerobic – takes place in the absence of oxygen.

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Metabolism

 METABOLISM – The sum total of all chemical reactions that occur in the body

 (ATP MADE vs. ATP USED)

 There are 2 types of metabolism

 Catabolism

 Anabolism

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1) Catabolism

 The breaking down of a large molecule into smaller, simpler molecules

+ +

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2) Anabolism

 the synthesis of complex molecules form simple ones

+ +

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ATP

 WHAT IS ATP?

 Universal Energy Molecule

 Makes energy readily available

 Continuously being remade

 Stands for Adenosine Triphosphate P P + P

Adenosine

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ATP

 WHAT IS ATP?

 Universal Energy Molecule

 Makes energy readily available

 Continuously being remade

 Stands for Adenosine Triphosphate P P + P

P P P

High Energy Bond

Adenosine Adenosine

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ATP

 What is ATP used for?

 Movement -- muscle contraction

 Heat -- Hypothermia

 Synthesis -- hair, blood cells, fingernails

 Active Transport -- nervous system, kidneys

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Mitochondria

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Mitochondria

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The Steps of Cellular Respiration

 Glycolysis

 Occurs in cytoplasm

 Breaks glucose into two molecules called PYRUVATE.

 Takes place in the ABSENCE OF OXYGEN

 A little bit of ATP is made (2)

Glucose

Pyruvate Pyruvate

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Glycolysis (in cytoplasm)

Glucose 2 ATP

2 ADP 2 ADP

2 ATP NAD+

NADH

2 ADP

2 ATP NAD+

NADH Pyruvate Pyruvate

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Glycolysis

 Glycolysis literally means “splitting of sugar”.

Notice that we have not yet used any oxygen.

 Two ATP molecules are used up in the process, but four are produced.

 A net gain of 2 ATP

 Two molecules of NAD⁺ are reduced to NADH therefore

 2 NADH are produced

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Stage 2: Pyruvate Oxidation

 Begins when the two pyruvate

molecules formed in glycolysis are transported through the two

mitochondrial membranes into the matrix.

 A CO²is removed from each pyruvate and released as a waste product.

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Stage 2: Pyruvate Oxidation

 The remaining 2-carbon portions are oxidized by NAD+ which gain two

hydrogen ions from pyruvate forming acetic acid (acetyl) group.

 A compound called coenzyme A (CoA) becomes attached to the acetic acid group, forming acetyl-CoA which then enters Krebs cycle.

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Stage 2: Pyruvate Oxidation

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The Steps of Cellular Respiration

 Krebs Cycle (Step 2)

 Occurs in mitochondrion

 Completely decomposes pyruvate into CO₂

 Needs oxygen to occur.

 A little bit of ATP is made (2)

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Krebs Cycle

Pyruvate

1

2

3

4 5

6 7

8

CO2 Needs Oxygen NAD+

NADH Acetyl Co A

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Krebs Cycle

Pyruvate

1

2

3

4 5

6 7

8

Needs OxygenCO2 NAD+

NADH

Acetyl

Co A Citric Acid

NAD+

NADH CO2

NAD+

CO NADH 2

A D PP

ATP

FAD+

NAD+ NADH

FADH

2

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Krebs Cycle

 8 steps to produce

 NADH

 FADH₂

 ATP

 CO₂

 Pyruvate is torn into 6 CO₂ molecules!

 Can you find them?

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Krebs Cycle

Pyruvate

1

2

3

4 5

6 7

8

Needs OxygenCO2 NAD+

NADH

Acetyl

Co ACitric Acid

NAD+

NADH CO2

NAD+

CO NADH 2

A D PP

ATP

FAD+

NADH

NAD+ NADH

X2 X2 X2 X2

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Krebs Cycle

2

Pyruvic Acid

6

Carbon Dioxide 2 ADP 2P 2 ATP

8 NAD

2 FAD

8 NADH 2 FADH ₂

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We've don't have anything left over from the glucose, and we haven't made enough

ATP yet!!!

How will we EVER get more ATP?

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The 3 Steps of Cellular Respiration

 Electron Transport Chain in the inner membrane of the mitochondrion

 Involves a group of molecules built into the inner membrane of the mitochondrion

 Electrons pulled off of food by Glycolysis and Krebs are passed between these molecules.

 Each time an electron is transferred ATP is made

 Oxygen is required for this step.

 Lots of ATP is made (32)

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Electron Transport Chain

Inner

Membrane

Matrix

Intermembrane Space

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Inner MembraneMatrixIntermembrane Space

NADH

H H H H H+

H+

Electron Cytochro

mes

High EneElectronrgy

Low Energy Electron

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H+

H+H+ H+

H+ H+H+

H+

H+H+H+H+H+

A D P

P ATP

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H+

H+H+ H+

H+ H+H+

H+

H+H+H+H+H+

A D P

P ATP

Oxygen H 2O

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For each NADH that enters

the Electron Transport Chain,

how many ATP are produced?

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H+

H+ A D P

P ATP

H+

NADH

H H H H H+

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H+

H+ A D P

P ATP

H+

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H+

H+ A D P

P ATP

H+

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For Each NADH Entering the ETC, 3 ATP Are Produced!

But What About FADH?

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FADH

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H+

H+ A D P

P ATP

H+

FADH

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H+

H+ A D P

P ATP

H+

FADH

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Each FADH is only able to produce

2 ATP in the ETC

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Accounting

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Electron Transport System

 OBJECT - turn High Energy Electrons into Low Energy Electrons.

 Electrons are passed down a Cytochrome chain

 an iron-containing molecule

 ONE STEP, electron energy would be lost as Heat.

 MANY STEPS – Energy converted to ATP by chemiosmosis!

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What’s Up With Oxygen?

 Oxygen is the final electron acceptor.

 If there is no oxygen, the electron transport chain gets “backed up” as there is no

where for the electrons to go.

NADH NAD⁺

 As a result, Krebs stops due to lack of NAD⁺

 Lack of NAD⁺ also causes [H⁺] to increase

 The body’s pH begins to fall inhibiting normal enzyme activity.

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Anaerobic Respiration

 The production of energy without oxygen.

 Takes place in the cytoplasm.

 Very inefficient -- only 6% of glucose energy is made available.

 Only 2 ATP are produced per glucose molecule (vs. 36 in aerobic respiration)

 Oxygen is required for pyruvic acid to

enter Krebs where it can be broken down.

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Anaerobic Respiration

Since pyruvate is poisonous, it must be converted into a safer form.

 In animals -- LACTIC ACID

 causes muscle cramps

 process is called Lactic Acid Fermentation

 In bacteria and yeast -- ETHANOL & CO₂

 process is called Alcohol Fermentation

 (YOU CANNOT PRODUCE ETHANOL NO MATTER HOW MUCH YOU WORK OUT…)

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Glycolysis

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Krebs Cycle

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H+

H+H+ H+

H+ H+H+

H+

H+H+H+H+H+

A D P

P ATP

Oxygen H 2O