Cellular Respiration

• Cellular respiration is the process by which the chemical energy of "food" is converted into ATP.

• Carbohydrates, fats, and proteins can all be used as fuel for cellular respiration, but for our purposes we will look at how glucose is used.

Cellular Respiration• In the presence of oxygen, one gram of

glucose releases 3811 calories of heat energy.– However, if you were to read a nutrition label it

would claim that one gram of glucose only releases 3.8 Calories.

• What is the difference between a calorie and Calorie?

• A food calorie, or Calorie, is actually equal to 1000 calories, or 1 kcal. One calorie is the energy it takes to heat 1 g of water by 1 °C. Therefore one Calorie, or food calorie, is just 1000 times that, or the energy to heat 1 kg of water by 1 °C.

Overview of Respiration

• Respiration, like photosynthesis, is a multi-step process.– The first step is a process called glycolysis.

Glycolysis

• In glycolysis glucose is broken down into two molecules of pyruvate.

• This change is accompanied by a net gain of 2 ATP molecules and 2 NADH molecules.

Glycolysis• Notice from the

picture that glycolysis requires some energy input.

2 ATP go in and 4 ATP come out for a net gain of 2 ATP.

Glycolysis

• Also notice that glycolysis produces a molecule called NADHNADH.– NAD+ NADH

• This is very similar to the electron carrier we saw in photosynthesis. – NADP+ NADPH• If you are worried about getting the two confused just

think NADPH has a P and is in Photosynthesis.

Glycolysis

• Glycolysis occurs in ALL organisms.• Glycolysis occurs in the cytoplasm of cells.• It is always the FIRST step in converting the

energy in food into ATP.• Let’s check it out!

Following GlycolysisGlucoseGlucose

GlycolysisGlycolysis

2 Pyruvate, 2 ATP & 2 NADH2 Pyruvate, 2 ATP & 2 NADH

In the presence of Oxygen

FermentationFermentationKreb Cycle & Electron Transport ChainKreb Cycle & Electron Transport Chain

In the absence of Oxygen

Anaerobic RespirationAerobic Respiration

Anaerobic Respiration

• Following glycolysis if oxygen is not present, pyruvate is metabolized in a process called fermentation.– Fermentation complements glycolysis by recycling

NADH back into NAD+– This allows glycolysis to continue and ATP to be

produced.

Fermentation

Notice the recycling of NAD+ for glycolysis

Fermentation

• There are two types of fermentation– Lactic Acid Fermentation• Lactic Acid is formed during fermentation.• This occurs in our muscles.

– Alcoholic Fermentation• Alcohol (and CO2) is formed during fermentation.

• This occurs in bacteria.

Fermentation

• Fermentation can be performed by all organisms.

• It occurs following glycolysis in the absence of Oxygen.

• Fermentation occurs in the cytoplasm of cells.

Summary of Anaerobic Respiration

The purpose of respiration is to convert the energy in food into ATP. How much ATP does anaerobic respiration create?

The purpose of respiration is to convert the energy in food into ATP. How much ATP does anaerobic respiration create?

Following GlycolysisGlucoseGlucose

GlycolysisGlycolysis

2 Pyruvate, 2 ATP & 2 NADH2 Pyruvate, 2 ATP & 2 NADH

In the presence of Oxygen

FermentationFermentationKreb Cycle & Electron Transport ChainKreb Cycle & Electron Transport Chain

In the absence of Oxygen

Anaerobic RespirationAerobic Respiration

Aerobic Respiration

• Following glycolysis if oxygen is present, pyruvate is metabolized in two processes called:– The Kreb Cycle – Electron Transport Chain

• The equation for aerobic respiration is:

From Glycolysis to the Kreb Cycle…

• Following glycolysis, pyruvate is transported into the mitochondria.

• As it moves it loses carbon dioxide to form acetyl-CoA, a 2-carbon molecule.

• This process creates NADH.

Kreb Cycle• The Krebs cycle occurs in the mitochondrial matrix. It

turns Acetyl-CoA into CO2. In doing so it generates a pool of chemical energy (ATP, NADH, and FADH2).

• Click picture to follow the link…

Electron Transport Chain

Click on the picture to see it in action…

Electron Transport Chain (ETC)• The electron transport chain (ETC) consists of a series of molecules,

mostly proteins, embedded in the inner mitochondrial membrane. • The electron transport chain captures the electrons stored in

NADH and FADH2 and passes them along the membrane. – As the electrons move along the membrane H+ build up in the intermembrane space.

• The electrons are eventually passed to Oxygen. This makes Oxygen very negative. It quickly bonds with H+ to form water.– The H+ that has built up in the intermembrane space wants out! It flows through a

molecule called ATP synthase. As it does ATP is formed. • Each NADH that donates electrons to the chain will fuel the creation of 3 ATP. • Each FADH2 that donates elections to the chain will fuel the creation of 2 ATP.

Aerobic Respiration

Glucose Carbon DioxideDuring glycolysis, the formation of Acetyl- CoA & the Kreb Cycle

Oxygen WaterDuring the electron transport chain

Glucose Carbon DioxideDuring glycolysis, the formation of Acetyl- CoA & the Kreb Cycle

Oxygen WaterDuring the electron transport chain

Aerobic Respiration

• Aerobic Respiration has three distinct parts:– Glycolysis occurs in the cytoplasm (yields 2 ATP)– Krebs cycle takes place in the matrix of the mitochondria

(yields 2 ATP)– Electron transport chain is carried out on the inner

mitochondrial membrane (yields 34 ATP)

• Total ATP = 38!!!!

SUMMARY

GlycolysisGlycolysis

Anaerobic RespirationAerobic Respiration

38 ATP 2 ATP