By: Riley Thomasand Katie Tibus

Food provides living things with chemical building blocks they need to grow and reproduce. › Serves as source of raw materials from

which the cells of the body can synthesize new molecules.

* Food serves as a source of energy

Calorie- the amount of energy needed to raise the temperature of one gram of water, one Celsius degree

› One gram of the sugar glucose (C6 H12

O6) when burned in the presence of oxygen releases 3,811 calories of heat energy

› Cells do not burn calories they gradually release the energy from glucose and other food compounds

› The calorie used on food labels is the kilocalorie (1,000 calories)

Cells do not release all of the energy from glucose all at once, instead it gradually releases the energy in the first process glycolysis.

Glycolysis only releases a small amount of energy, if not most of the energy would be lost in the form of heat and light.

If O2 is present glycolysis is followed by the Krebs Cycle, Electron Transport Chain(ETC).

If O2 is not present glycolysis is followed by fermentation.

Glycolysis, the Krebs cycle(citric acid cycle), and the electron transport chain make up a process called cellular respiration.

Cellular respiration is the process that releases energy by breaking down food molecules in the presence of oxygen

Equation for Cellular Respiration

Cellular respiration requires a food molecule such as glucose and oxygen and gives off carbon, water, and energy.

There are 3 stages in cellular respiration› Each of the stages captures some of the

chemical energy available in food molecules and uses it to produce ATP

Glycolysis is the process in which one molecule of glucose is broken in half, producing two molecules of pyruvic acid, a 3 carbon compound.

ATP Production.› 2 molecules of ATP are needed to begin

glycolysis. › When glycolysis is complete 4 ATP is

produced. That is a net gain of 2 ATP.

One of the reactions of glycolsis removes four high energy electrons and passes them to an electron carries called NAD+

Like NADP+ in photosynthesis, each NAD+ accepts a pair of high energy electrons. This molecule known as NADH hold the electrons until they can be transferred to other molecules.

By doing this NAD+ helps pass energy from glucose to other pathways in the cell

Glycolysis yields a small amount of energy, however the process is so fast that the cells can produce thousands of ATP molecules in milliseconds

Another advantage is that glycolysis does not require oxygen. This means glycolysis can supply chemical energy to cells when oxygen is not available

When a cell generates large amounts of ATP from glycolysis it runs into a problem.

All of the cells available NAD+ molecules are filled up with electrons.

Without NAD+ the cell cannot keep glycolysis going, and ATP production stops.

When oxygen is not present glycolysis is followed by a different pathway. (anaerobic conditions)

Cells convert NADH into NAD+ by passing the electrons back to pyruvic acid.

The process of this pathway and glycolysis is called fermentation

Fermentation releases energy from food molecules in the absence of oxygen

The two main types of fermentation are alcoholic fermentation and lactic acid fermentation.

Alcoholic Fermentation causes bread to rise. The alcohol bakes out of the

bread.

Pyruvic Acid that accumulates is converted into lactic acid.

This process regenerated NAD+ so that glycolosis can continue.

Equation for lactic fermentation is… pyruvic acid + NADH lactic acid+

NAD+

Lactic acid is produced when your body can not supply enough oxygen to the tissues(muscles) to produce all of the ATP that is required.

Without oxygen ATP cannot be produced without oxygen.

The muscle cells then begin to produce ATP via lactic acid fermentation.

Build up of lactic acid is what causes muscles to burn after vigorous activity.

If pathways require oxygen for cellular respiration they are said the be aerobic

Example: Richard Simmons’ pathways require oxygenFor cellular respiration.

During the Krebs cycle or the citric acid cycle pyruvic acid is broken down into CO2 in a series of energy extracting reactions.

It takes place in the mitochondrion. The Krebs Cycle begins when pyruvic

acid ( from glycolysis) enters the mitochondrion. › One carbon atom from pyruvic acid

becomes part of a molecule of CO2

The other two atoms of carbon from pyruvic acid are joined to a compound called coenzyme A to form acetyl- CoA.

Acetyl-CoA then adds the two 2 carbon acetyl group to a 4 carbon molecule , producing a 6- carbon molecule called citric acid.

As the cycle continues . Citric acid is broken down inot a 4 carbon molecule, more CO2 is released and electrons are transferred to energy carriers.

For every turn of the cycle one ATP is produced. › 5 pairs of electrons are captured by 5

carrier molecules, 4 NADH , and 1 FADH2 .

During the Krebs Cycle, pyruvic acid from glycolysis is used to make:› carbon dioxide› NADH› ATP

› FADH2

1. CO2 is released into the ATP

2. ATP produced is used for cellular activities.

3. NADH and FADH can be used to generate huge amounts of ATP.

2 turns of the Krebs cycle is needed

for one molecule or C6 H12 O6

The Krebs Cycle spins around and around generation high energy electrons that are passed to NADH, and FADH2

The electron transport train uses the high energy electrons from the Krebs Cycle to convert ADP into ATP

High energy electrons from NADH and FADH2 are passed into and along the electron transport chain.

In eukaryotes the electron transport chain is composed of a series of carrier proteins that is located in the inner membrane of the mitochondrion› In prokaryotes the same chain is in the cell

membrane

NADH and FADH2 are passed along the ETC. › The ETC is composed of a series of carrier

proteins that’s is located in the inner membrane of the mitochondrion.

› High energy electrons are passed from one carrier protein to the next At the end of the ETC is an enzyme that combines electrons from the ETC w/ Hydrogen and oxygen to form H2O.

› Everytime 2 high energy electrons transport down the ETC their energy is used to transport H+ across the membrane.

During the ETC H+ ions build up in the inner-membrane space, making it positively charged. The other side from which those H+ ions have been taken is now negatively charged.

The inner membrane contains protein spheres called ATP synthases. › As the H+ ions escape through the

channels into these proteins, the ATP synthase spin.

› Eaxh time it rotates the enzyme grabs a low energy ADP and attaches a phosphate to make ATP.

› On average each pair of high energy electron that moves down the ETC provides enough energy to convert 3 ADP into 3 ATP.

High energy electrons are passed from one carrier protein to the next

At the end of the electron transport chain is an enzyme that combines electrons from the electron chain with hydrogen ions and oxygen to form water

Oxygen serves as the final electron acceptor of the electron transport chain

The Krebs Cycle and the electron transport enabled the cell to produce 34 more ATP molecules per glucose molecule in addition to the 2 ATP molecules obtained from glycolysis› 18 times as much ATP can be generated from

glucose in the presence of oxygen. › For 1 glucose molecule › 2 ATP from Glycolysis and 34 from the Krebs

Cycle and ETC.› Total of 36 ATP.

Photosynthesis is the opposite of cellular respiration

Photosynthesis deposits energy, cellular respiration withdraws energy

Boraphyll allows this tree to take in light, go through photosynthesis and “deposit” energy.

Comparing Photosynthesis

and Cellular Respiration

Photosynthesis Cellular Respiration

Function Energy Storage Energy Release

Location Chloroplasts Mitochondria

Reactants CO2 and H2O C6H12O6 and O2

Products C6H12O6 and O2 CO2 ,H2O and energy(36 ATP molecules)

Equation 6CO2 + 6H2O + Energy C6H12O6 + 6O2

C6H12O6  +  6O2  6CO2  +  6 H2O  +  36 or 38 ATP