RESPIRATION
(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

THE ATP-ADP CYCLE

* 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

Respiration

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)

ANAEROBIC RESPIRATION--does not use 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...

GLYCOLYSIS

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.

Respiration

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

THE OVERALL PICTURE...

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)

THE 2 PHASES OF AEROBIC RESPIRATION

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

Respiration

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

 

Respiration

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