(has two meanings...)

* the life function which involves the transfer of potential (stored) chemical energy into a form that an organism can use--CELLULAR RESPIRATION
* the exchange of gases (namely CO2 and O2) between the organism and the environment--ORGANISMAL RESPIRATION

I. Cellular Respiration
* energy is released from glucose (a carbohydrate...a monosaccharide)
* this energy is converted by enzymes (a protein...a polypeptide) to a more usable form called ATP

ATP = adenosine triphosphate

* all cells carry out cellular respiration
* all cells use ATP

triphospate= 3 phosphates

* ATP = ENERGY!!! the bonds between the phosphates are high energy bonds

* when these bonds are broken (that is, when ATP is hydrolyzed) lots of energy is released that can be used by the organism

THE REACTION... ATP + H2O <====> ADP + P +

* ATP (adenosine triphosphate) is hydrolyzed (split with water) to form ADP (adenosine diphosphate) and energy

diphosphate--2 phosphates


* ATP and ADP are constantly converting back and forth with the help of the enzyme ATP-ase

ATP ---> ADP releases energy

ADP ---> ATP needs energy


what is this cowboy trying to sell me? oh yeah, that would be respiration
make an ATP molcule here
what is ATP?
the ATP/ADP cycle is described here

okay...back to cellular respiration

* cellular respiration (releasing the chemical energy of glucose to form ATP which is used for energy) can happen with or without oxygen (O2)


AEROBIC RESPIRATION--uses O2; most organisms carry out aerobic respiration

A) Anaerobic Respiration (Fermentation)

* the breakdown of glucose without oxygen
* some organisms like bacteria (KINGDOM--Monera) and yeast (KINGDOM--Fungi) do not have the necessary enzymes to use oxygen
* other cells use anaerobic respiration (fermentation) when no O2 is present
* the enzymes for anaerobic respiration (fermentation) are found in the cytoplasm

* during anaerobic respiration (fermentation) glucose is broken down to either lactic acid or alcohol/CO2 depending on the organism

LACTIC ACID--muscle fatigue in animals; also produced by bacteria; used to make cheese, buttermilk and yogurt
ALCOHOL and CO2--produced by yeast; used in baking and brewing

The reaction of anaerobic respiration (fermentation)...
* it takes 2 ATP molecules of energy to break down glucose, which gives off 4 ATP...this means there is a NET GAIN of 2 ATP for anaerobic respiration (fermentation)

glucose ------> 2 lactic acid
both sets of end products
can be used to get more energy)
glucose ------> 2 alcohol + 2 CO2

The process of breaking down glucose to start cellular respirstion is called...


So, glycolysis (the breakdown of glucose) results in the formation of 2 pyruvic acid and a net gain of 2 ATP. The pyruvic acid is then converted to either lactic acid or alcohol and carbon dioxide without the production of any more ATP.


watch the basics of glycolysis

B) Aerobic Respiration

* the breakdown of glucose with oxygen
* the energy from glucose is released gradually in a series of enzyme controlled steps (the electron transport chain)
* the enzymes for aerobic respiration are found in the mitochondria


glucose + oxygen -----> water + carbon dioxide + ATP

C6H12O6 + O2 ------> H2O + CO2 + 36 ATP

...this reaction is essentially the reverse of photosynthesis!

* organisms that can perform aerobic respiration only do so when there is oxygen present...otherwise, they carry out anaerobic respiration (fermentation)


1) The anaerobic phase:
* the first step of aerobic respiration is GLYCOLYSIS (the breakdown of glucose)(REMEMBER: this step does not require OXYGEN!!!)

*this step yields (gives) a net gain of 2 ATP

2) The aerobic phase:
* here, pyruvic acid (now with oxygen available) is broken down slowly in a complex chain of events called the Krebs Cycle where hydrogen ions are kicked out
* during this cycle, 34 more ATP are produced...for a net gain of 36 ATP that is from both steps combined" oxygen picks up the hydrogen and forms water...
O2 + 4H ----> 2H2O

* the carbon from the pyruvic acid is kicked out as carbon dioxide


a brief review of aerobic respiration
see the basic reactants and products of aerobic respiration

II. Organismal Respiration

* involves the diffusion of gases (carbon dioxide and oxygen) between the organism and its environment

* for this to occur, you need:

1) a thin surface
2) a moist surface--so the gases can be dissolved
3) to be near oxygen

A) Monera, Protists, and Fungi
* exchange of gases is done by simple diffusion (passive transport) of gases through the outer membrane

B) Plants

1) Leaves

* outer covering (cuticle and epidermis) does not allow gases to enter
* gases only leave the leaf through the stomate
* only after the gases enter a leaf does the intercellular gas exchange take place-- occurs in the air spaces in the spongy mesophyll (layer)

2) Stems

* some stems of woody plants contain lenticels which are loosely packed cells that permit the exchange of gases

3) Roots

* some gas exchange occurs across the moist membranes of the root hairs and other epidermal cells



organismal respiration--the exchange of gases; boy, he looks tired on the treadmill