Cellular Respiration

What is link from the energy in food to ATP?

What is link from the energy in food to ATP?

• Much of the energy in a breakfast is stored in organic compounds (proteins, carbohydrates, and fats).

• Before you can use this energy it has to be transferred to ATP.

• Cellular respiration allows organisms to transfer energy from organic compounds to ATP.

The Basics of Cellular Respiration

• Cell Respiration – Breaks down glucose– Requires oxygen– Makes energy (ATP)

• The equation for cellular respiration:

C6H12O6 + 6O2 6CO2 + 6H2O + energy

glucoseglucose ATP

What kind of organisms carry out cellular respiration?

PlantsPlants and and AnimalsAnimals

• Plants are Plants are AutotrophsAutotrophs: they are producers.

• Animals are Heterotrophs: they are consumers.

•BOTH PLANTS and ANIMALS carry out cellular respiration

• All organisms need energy!

Where does cellular respiration take place?

• Remember: cellular respiration takes place in the mitochondria inside of cells.

Innermembrane

Outermembrane

Innermembrane space

MatrixCristae

What are the stages of cellular respiration?

The Stages of Cell Respiration

• Stage 1: – Glycolysis

• Stage 2:– The Krebs Cycle– The Electron Transport Chain

Stage 1: Glycolysis

• Glycolysis occurs in the cytoplasm of the cell outside the mitochondria.

• Glycolysis involves breaking down glucose.• Glucose is a six-carbon sugar.• Glucose is broken down to a three-carbon

sugar called pyruvate during glycolysis– Think ‘glyco’= sugar ‘lysis’= splitting– ‘sugar splitting’

Diagram of Glycolysis

What does glycolosis look like?

Animation of Glycolysis

• http://www.science.smith.edu/departments/Biology/Bio231/glycolysis.html

What do you get at the end of glycolysis?

• 2 three-carbon sugars (pyruvate)

• 2 electron carriers (NADH)

• 2 molecules that store energy (ATP)

More ATP is Made by Aerobic Respiration

Stage 2: Krebs Cycle

• The next part of cellular respiration is the Krebs cycle.

• The Krebs cycle takes place in the mitochondrial matrix

• The pyruvates must go from the cytoplasm into the mitochondrial matrix

• In the process, a the three-carbon pyruvate loses a carbon (as CO2) and becomes a two carbon Acetyl-CoA

The Krebs Cycle

• Two-carbon Acetyl CoA bonds to a four-carbon sugar to make a six-carbon compound

• CO2 is released from the six-carbon compound forming a five-carbon compound

• CO2 is released from the five-carbon compound forming a four-carbon compound

• As the six-carbon compound is ‘recycled’ back to a four-carbon compound NADH, FADH2 and ATP are formed along the way

See Diagram Handout

Diagram of the Krebs Cycle

What does the Krebs cycle look like?

Animation of the Krebs Cycle

• http://www.science.smith.edu/departments/Biology/Bio231/krebs.html

What do you get at the end of the Krebs cycle?

• 2 molecules that store energy (ATP)

• 6 electron carriers (NADH)

• 2 other electron carriers (FADH2)

• NADH and FADH2 now contain much of the energy that was previously in glucose.

• 4 carbon dioxides (CO2)

Stage 2: Electron Transport Chain

Electron Transport Chain

• Remember: NADH and FADH2 are electron carriers.

• The purpose of the electron transport chain is to generate ATP from NADH and FADH2

Electron Transport Chain

• While the electrons from NADH and FADH2 are passed along the chain, H+ are pumped into the inner membrane space.

• H+ wants to diffuse back into the matrix but it can only do so through a specific membrane protein. (This is facilitated diffusion!)

• When H+ diffuses through the membrane back into the matrix ATP is made from ADP and a phosphate group.

Electron Transport Chain

• The electrons are passed along until they are accepted by oxygen forming H2O.

• The final electron acceptor in the electron transport chain is oxygen!

What does the electron transport chain look like?

Electron Transport ChainElectron Transport Chain

NADH+ H+

ATPSynthase

1H+ 2H+ 3H+

higher Hhigher H++

concentrationconcentration

H+

ADP + ATP

lower Hlower H++

concentrationconcentration

H+

(Proton Pumping)

P

E T C

NAD+2H+ + 1/2O2 H2O

Inner membrane SpaceInner membrane Space

MatrixMatrix

InnerMitochondrialMembrane

Animation of the Electron Transport Chain

• http://www.science.smith.edu/departments/Biology/Bio231/etc.html

What do you end up with after the electron transport chain?

• 34 molecules that store energy (ATP)

• You get 3 ATPs from every NADH and 2 ATPs from every FADH2

• The electron transport chain is where you get all the energy ‘payoff’ from the ‘investment’ in electron carriers

Summary of Cell Respiration

• Glycolysis breaks glucose down

• The Krebs cycle makes ATP and the electron carriers (FADH and NADH2)

• The electron transport chain converts all of the electron carriers made from glycolysis and the Krebs cycle to ATP

2 Main Types of Respiration

• There are two main types of cellular respiration:1. Aerobic Respiration - this occurs with

O2

2. Anaerobic Respiration (Fermentation) - this occurs with out O2

* Both begin with Glycolysis.

Can cells produce energy without oxygen?

• Remember: oxygen is the final electron acceptor in the electron transport chain.

• Cells can not carry out the electron transport chain without oxygen.

• Energy (ATP) is a product of glycolysis and this can occur without oxygen.

• Fermentation is when glycolysis occurs without oxygen.

Where does fermentation occur?

• Fermentation occurs in the cytoplasm

What are the two types of fermentation?

• Alcoholic fermentation

• Lactic acid fermentation

What is the main point of fermentation?

• Fermentation allows cells to produce more of the electron carrier NADH.

• This is necessary to make ATP!

Alcohol FermentationAlcohol Fermentation

• This process occurs in some plants & This process occurs in some plants & some unicellular organisms (Yeasts)some unicellular organisms (Yeasts) AlcoholAlcohol

glucose

Glycolysis

CCCCCC

CCC

2 Pyruvic acid

2ATP2ATP2ADP+ 2

2NADH

P

2 NAD+

CC

2 Ethanol2 Ethanol2CO2CO22

releasedreleased

2NADH 2 NAD+

Alcohol Fermentation

• The end products:• 2 ATP• 2 CO2

• 2 ethanol

• The alcohol accumulates and can be commercially harvested. • (Examples: beer, wine, sauerkraut)

Lactic Acid FermentationLactic Acid Fermentation• This process occurs in animals & This process occurs in animals &

some unicellular organisms some unicellular organisms Lactic Lactic AcidAcid

2 Lactic2 Lactic acidacid

2NADH 2 NAD+

CCC

Glucose

GlycolysisCCC

2 Pyruvic acid

2ATP2ATP2ADP+ 2

2NADH

P

2 NAD+

CCCCCC

Lactic Acid FermentationLactic Acid Fermentation• End Products: Lactic Acid FermentationEnd Products: Lactic Acid Fermentation

* 2 - ATP

* 2 - Lactic Acids

• Lactic acid will make muscles tired and sore muscle fatigue after strenuous exercise

• Lactic acid is transported to liver where converted to glucose

ALCOHOLIC

Glucose

Glycolysis

Carbon Dioxide

+Alcohol

+2 ATP

CELLULAR RESPIRATION

Glucose

Glycolysis

[Krebs Cycle][ETC]

Carbon Dioxide

+Water

+38 ATP

LACTIC ACID

Glucose

Glycolysis

Lactic Acid+

2 ATP