Cellular RespirationIntroduction/Basic Info

RespirationControlled 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)

RespirationOrganic 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

ATPPhosphate 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 cytoplasmGlucose 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-cytoplasmBreakdown 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 RespirationLactic Acid FermentationOccurs 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

When O2 becomes available, lactate converted back to pyruvate and then pushed through the aerobic pathway

Pyruvate converted to lactate (3-C), no CO2 produced, no ATP produced

Anaerobic RespirationAlcoholic 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-mitochondriaMost 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 RespirationKreb’s Cycle-mitochondrial matrix

Aerobic Respiration-mitochondria

Folds of the mitochondrial cristae provide huge surface area = high efficiency/production

Cellular Respiration-SummaryCan 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