Cellular Respiration

How cells use food and oxygen to make energy in the form of

ATP and do work.

Types of Cellular Respiration

• Aerobic Cellular Respiration- Cells make ATP using Oxygen in mitochondria

• Anaerobic Cellular Respiration- Cells make ATP without using Oxygen in the cytoplasm of the cell. Also referred to as fermentation.

Both are catabolic reactions that produce energy in the form of ATP.

Big Picture

Aerobic cellular respiration is the

chemical (metabolic) reaction that uses

O2 and produces CO2 so it is the reason

why we need to breathe.

Equation for Aerobic Cellular Respiration

Glucose + O2 CO2 + H2O + ATP

3 main chemical reactions in aerobic cellular respiration

Glycolysis

Krebs Cycle

Electron Transport System

1. Glycolysis

• Catabolic reaction that breaks glucose into 2 molecules of pyruvic acid or pyruvate.

• Occurs in the cytoplasm of the cell

• Does not use O2 (it is part of cellular respiration but it is also the first step in the fermentation process as well)

Glucose----------> 2 molecules pyruvate

+ 2 ATP

+ 2 NADH (Electron Carrier)

Glycolysis produces a little bit of energy in

the form of ATP and NADH.

What are Electron Carriers?

They pick electrons up and transport them to The Grand Central Station for Electrons- the ets

NADH and FADH2 are Electron Taxi Cabs

Oxidation- removes electrons

Reduction adds electrons

2. Krebs Cycle

• Complex sequence of reactions that occur

in the mitochondrial matrix.

• Reactions complete the breakdown of the original glucose molecule by acting on pyruvic acid

We call it a cycle because it is continuously running and it is always recycling the starting molecule.

•Completes the break down of glucose

•Makes a lot of electron carriers (NADH, FADH2)

•Produces the majority of CO2 that must be eliminated from the system

Major Impact of the Krebs Cycle

Sometimes called the matrix reactions because of where they occur in the mitochondria

Matrix

Cristae

How?

Pyruvic acid enters the mitochondria from

the cell cytoplasm and then is converted into

another molecule called Acetyl Co-A.

How much energy is made during the Krebs Cycle ?

1. 2- ATP

2. 8 NADH

3. 2 FADH2

4. 6 CO2 (We get rid of it by exhaling)

3. Electron Transport System

The electron transport system is a series

of molecules embedded in the cristae of

the mitochondria that accept and

transfer electrons. (Oxidation-Reduction)

The ETS uses the shuttling of electrons donated by NADH and FADH2 to make a lot of ATP.

Oxidation- molecule loses an electron

Reduction- molecule gains an electron

The ETS proteins take the electrons from NADH and FADH2 and move them down to oxygen.

NADH NAD+

FADH2 FADH

At each transfer (oxidation-reduction)

some energy is lost.

This creates energy that is used to take Pi

(inorganic PO4) and add it to ADP to

make ATP in a process called oxidative

phosphorylation.

Phosphorylation

Adding phosphate to another molecule

Oxidative Phosphorylation

Adding phosphate to another molecule in the electron transport system in the presence of Oxygen

Substrate level phosphorylation

Any other phosphorylation in the cell

Oxidative phosphorylation of ADP to make ATPoccurs through Chemiosmosis.

Chemiosmosis

As electrons are being transferred through the etsthe energy is used to pump Hydrogen ions across one side of the membrane.

This builds up a higher concentration on one side than the other. Like a Hydrogen ion dam.

Because substances have a tendency to movefrom a higher concentration to a lower concentration, the hydrogen ion dam can be used to do work.

The only way for the Hydrogen ions to move down their concentration gradient is back through the membrane through the enzyme ATP Synthase.

The Hydrogen ion turns on the enzyme allowing it to phosphorylate ADP and make an ATP molecule

The electron transport system uses all of the electron carriers to produce about 34 molecules of ATP.

This system uses oxygen as its final electron acceptor.

Anaerobic Cellular Respiration (Fermentation)

There are lots of different kinds of fermenations

They are usually named after their end-product

1. Ethanol and CO2- alcohol

2. Lactic acid- yogurt- also occurs in muscles

Glycolysis always occurs first with glucose being converted into 2 molecules of pyruvate.

Ethanol Fermentation

Pyruvate Ethanol + CO2

Lactic Acid Fermentation

Pyruvate Lactic Acid

This can occur by adding microbes to milk to make cheese or yogurt but also occurs in the muscles when O2 is not being delivered fast enough to run aerobic cellular respiration.

Glycolysis and fermentation onlyproduces 2 ATP per glucose moleculeso it is a very inefficient way to make ATPfor cells.

Once we add the mitochondria in and useO2 to make ATP we can get as many as36-38 ATP’s being formed per glucose molecule