Cellular Respiration

Respiration: An Overview• The process by which cells

break down food sources such as glucose, fats, and protein and release their stored energy.

• Two main types– Anaerobic – no oxygen

required– Aerobic – requiring oxygen

• Both forms produce energy storage molecules called ATP – adenosine triphosphate.

http://www.chemistry.wustl.edu/~courses/genchem/LabTutorials/Cytochromes/images/flowchart1.jpg

Anaerobic Processes• No oxygen is

required for these processes.

• Includes glycolysis, the breakdown of glucose, and fermentation.

• Some bacteria and yeast are examples of anaerobes.

http://www.biol.vt.edu/research/images/C._perfringens_in_mac._jpg.jpg

http://www.utoronto.ca/greenblattlab/images/a/yeast%201.jpg

Glycolysis• Occurs in the

cytoplasm.• Breaks down glucose

into 2 molecules of pyruvate (3-carbon structures)

• 2 ATP molecules are formed.

• 2NADH energy shuttles are also formed.

• This pyruvate is further metabolized during fermentation

http://www.emc.maricopa.edu/faculty/farabee/BIOBK/enyld1.gif

Fermentation• Pyruvate can be metabolized by:

– Alcoholic fermentation– Lactic acid fermentation

• AF produces ethyl alcohol and CO2 – yeast can ferment apple juice to fill a balloon.

• LAF produces lactic acid. It can build up in muscles during strenuous exercise and cause burning and soreness.

Aerobic Processes• Requires oxygen.• Most organisms are aerobes.• Equation for Aerobic respiration:

C6H12O6 + 6O2 6CO2 + 6H2O + Energy

• Based on this equation – Why do we breathe?

http://www.oum.ox.ac.uk/thezone/animals/life/images/excrete.gif

The Mitochondria• If O2 is present following

glycolysis, pyruvate is modified and enters the mitochondria.

• Here food is broken down completely into CO2.

• Energy storage molecules like NADH and ATP are produced. This is why the mitochondria is called the power house of the cell.

The Role of Oxygen• Energy carriers like

NADH drop off electrons and as

they “fall” to oxygen during metabolism energy is stored in a payload of ATP.

• Oxygen picks up electrons and

hydrogen ions to form water.

ATP

ATP

ATP

Energy from

electrons

O2

H2O

ATP: Adenosine Triphosphate• ATP is the cells

energy currency.• Cellular work such as

metabolism, transport, and movement is powered by the breakdown of ATP.

ATP Structure– Ribose – a 5-carbon

sugar– Adenine – a N-base– 3 phosphate groups

ATP / ADP Cycle• ATP is constantly being used and remade in

the cell.• Energy is released or stored by breaking or

making a phosphate bond.

http://www.columbia.edu/cu/biology/courses/c2005/purves6/figure06-09.jpg

Summary of Cellular Respiration

Respiration

Process

Where Process Occurs

Net Gain of ATP

Per Glucose

Anaerobic Glycolysis & Fermentation

Cytoplasm 2 ATP

Aerobic Krebs Cycle and Electron

Transport

Mitochondrion 36 ATP