Introduction/Basic Info
Respiration
 Controlled release of energy from organic compounds
in cells to form adenosine triphosphate (ATP)
 Glycolysis is the first step in respiration
 Two types of respiration: Aerobic (uses oxygen) and
anaerobic (without oxygen)
 Two types of anaerobic respiration: Lactic acid
fermentation (humans) and alcoholic fermentation
(yeast)
Respiration
 Organic compounds contained stored (potential)
chemical energy in their bonds
 When that energy is released, cells can use it for
metabolism
 Glucose (from glycogen stores) typically used first as
the source of energy
 No glucose? Lipids next, then amino acids/proteins
(only in extreme cases- i.e. starvation)
ATP- synthesized in mitochondria
 Energy “currency” of life
 High energy molecule that stores energy for just about
every cellular process we need
 Found in the cytoplasm and the nucleoplasm
ATP
ATP
 Phosphate part is most
important
 Because of the negative charge on all the attached
oxygens, there is a lot of potential energy in these
bonds
 Removing the last phosphate group makes the
molecule much “happier” (chemically stable)
 Breaking that bond releases about 7,000 calories per
mole (6.02 x 1023 molecules) similar to a whole peanut!
ATP to ADP
 “renewable” molecule; ATP
ADP, energy to do
this comes from food you eat
 Constantly being used and remade…estimated the
more than 2 x 1026 molecules or >160kg (352lbs) of ATP
is formed in the human body daily!
Glycolysis- in the cytoplasm
 Glucose enters the cell via the cell membrane and stays
in the cytoplasm
 After a few modifications and a handful of reactions (Ch.
8) glucose eventually cleaved into 2 pyruvate (3-C)
 2 ATP molecules needed to start, 4 ATP molecules
produced, net gain of 2 ATPs
Anaerobic Respiration-cytoplasm
 Breakdown of organic molecules for ATP WITHOUT
using oxygen
 Organisms that do this only are called anaerobes
 Fermentation is another word for this
 Two main pathways: Alcoholic Fermentation and
Lactic acid fermentation
 ONLY ATP comes from glycolysis
Anaerobic Respiration
Lactic Acid Fermentation
 Occurs in Humans—why your muscles “burn” when
you workout
 Normally in aerobic organisms that find themselves in
a situation where oxygen is no longer available—why
you breather harder when you work out
 Pyruvate converted to lactate (3-C), no CO2 produced,
no ATP produced
 When O2 becomes available, lactate converted back to
pyruvate and then pushed through the aerobic
pathway
Anaerobic Respiration
Alcoholic Fermentation
 Occurs in yeast cells
 This is a “normal” situation for the yeast
 Pyruvate converted to ethanol (2-C) and CO2 is
released…both waste products for the organism
 Bakers’ and brewers’ yeast allows bread to rise and
beer to be carbonated (most commercial beer is
forcibly carbonated as well)
Aerobic Respiration-mitochondria
 Most efficient pathway to produce ATP
 Begins with glycolysis just like anaerobic…pyruvate
enters a mitochondrion to finish pathway though
 Pyruvate loses a C as CO2, becomes acetyl-CoA
 Acetyl-CoA enters Kreb’s cycle where two more CO2
molecules are produced, as well as some ATP
 Byproducts of Kreb’s cycle move onto electron
transport chain where most ATPs are produced
Aerobic Respiration
Kreb’s Cycle-mitochondrial matrix
Aerobic Respiration-mitochondria
 Folds of the mitochondrial cristae provide huge
surface area = high efficiency/production
Cellular Respiration-Summary
 Can occur with or without oxygen
 Aerobic is more efficient (net gain of 2 ATPs vs
possible gain of 36 ATPs)
 Glycolysis and anaerobic respiration occur in the
cytoplasm
 Aerobic respiration occurs in the mitochondria