What is . . . Cellular Respiration

Chemical Energy and FoodWe eat because food provides our bodies

with energy.Calorie = amount of energy needed to raise 1

gram of water 1 degree Celsius. Cells don’t actually “burn” calories from

molecules like glucose.Instead, they gradually release the energy.

Overview of Cellular Respiration

Process that releases energy by breaking down glucose and other food molecules in the presence of oxygen.

6O2 + C6H12O6 6CO2+ 6H2O + Energy

How does this compare to Photosynthesis??

Overview of Cellular Respiration

There are 3 main stages:◦ Glycolysis◦ Krebs Cycle◦ Electron Transport Chain

Each stage captures some chemical energy in the cell, and uses it to produce ATP.

GlycolysisProcess in which one molecule of glucose is

broken in half, producing two molecules of pyruvic acid.

Occurs in the cytoplasm.Uses the energy from 2 ATP molecules to

produce 4 ATP molecules.What is the net gain of ATP?

GlycolysisUses the electron carrier NAD+ ,

which becomes NADH. Can produce thousands of ATP a

seconds.Does NOT require oxygen.

(Anaerobic)

FermentationReleases energy from food molecules in

the absence of oxygen.

Alcoholic Fermentation – used by yeasts◦ Pyruvic Acid + NADH alcohol + CO2 + NAD+

Lactic Acid Fermentation – muscle cells, bacteria used in dairy products.◦ Pyruvic Acid + NADH lactic acid + NAD+

Both types of fermentation regenerate NAD+ that can be used in Glycolysis.

Instead of Fermentation…At the end of Glycolysis, about

90% of the energy in glucose is still unused, locked away in the bonds of pyruvic acid.

To release the remaining energy, cells must use oxygen.

The next 2 steps of cellular respiration are said to be aerobic.

The Krebs CyclePyruvic acid is broken down

into carbon dioxide in a series of energy-extracting reactions.

Begins when a molecule of pyruvic acid enters the mitochondria.

After many reactions, the pyruvic acid becomes CO2, NADH is formed, ATP is formed, and another electron carrier, FADH2 is formed.

The Krebs CycleCO2 is released when

we exhale.ATP is used to power

the cell’s activities.In the presence of

oxygen, the electron carriers NADH and FADH2 are used to create even greater amounts of ATP.

Electron Transport ChainUses high-energy electrons

from the Krebs cycle to convert ADP to ATP.

The chain is composed of a series of proteins throughout the membranes of the mitrochondria.

These proteins pump H+ ions through the membrane, which powers ATP Synthase to convert ADP to ATP.

Electron Transport Chain

The TotalsGlycolysis alone can only produce 2 net ATP.In the presence of oxygen, Cellular Respiration

can produce 36 molecules of ATP.

Energy and ExerciseQuick Energy

◦When athletes only need energy for a quick burst (~90 seconds), they resort to the energy from Glycolysis and Lactic Acid Fermentation.

Long-Term Energy◦When athletes need energy for an

extended period of time, cellular respiration is the only way to provide continuous energy.

Comparing Photosynthesis and Cellular Respiration

Photosynthesis Cellular Respiration

Function Energy capture Energy release

Location Chloroplasts Mitochondria

Reactants CO2 and H2O C6H12O6 and O2

Products C6H12O6 and O2 CO2 and H2O

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

Make your own concept map: Using the following terms, create a concept map that

describes the process of cellular respiration.

2 ATP2 ATP36 ATP6 NADH2 FADHElectron transport chainMitochondrionCytoplasmFermentationGlycolysisGlucosePyruvateLactic acidKreb's Cycle