Chapter 7 Cellular Respiration and Fermentation

when most people think about cellular respiration they think about leaving that only a
small part and only represent higher organisms.

All organisms do respiration of some sort.

***If you don’t RESPIRE you expire!!***
REMINDERS:
-making and breaking bonds requires energy.
-Phosphorylation always has to do with energy transfer EX: ADP→ ATP
-photo autotrophs convert solar energy to chemical energy for themselves BUT most
other organisms benefit from this as they are our primary producers of sugars.
-Usable energy from consuming organisms lower on the food chain diminishes by about
90% with each increase in level of consumption.
-When molecules receive electric [electron acceptors] they become reduced.
Okay – Lets Break It Down- Glucose that is…

The breakdown of glucose begins in the cytoplasm (for all organisms) in a process known
as glycolysis.
Glycolysis

Glycolysis (literally breaking glucose) is a series of reactions that start with the 6 carbon
glucose molecule and yields 2 3-carbon pyruvate molecules.

After glycolysis. There are 2 paths that can be taken to continue the breakdown and
yield energy for the cell (depending on available oxygen)

Aerobic respiration OR Anaerobic fermentation.
Aerobic Respiration
o Aerobic respiration continues with two set of reactions within the mitochondria.
The 1st set converts pyruvate into acetyl-CoA (which enters the Krebs cycle)
o carbon dioxide generated from this diffuse out of the cell (NOTE: carbon, which
cleaved from high roofies and oxidized yielding the CO2)
o electrons and hydrogen ions were also given off.
o E- and H+ are received by coenzymes NAD+ and FAD+ (they are reduced)
o this yields NADH and FADH2, which are 2 high energy molecules.
o Only the tiny bit of ATP has been created so far.
The Krebs Cycle 2nd stage
o acetylCoA enters the Krebs cycle.
o It is broken down by a series of reactions, which yield 6 CO2 molecules and 2 ATP,
6 NADH, and 2 FADH2
Electron Transfer Phosphorylation 3rd stage
o coenzymes NADH and NADH2 donate hydrogen ions and electrons to the
electronic transfer chains (ETC) embedded in the inner mitochondrial membrane.
o The flow of electrons down the ETC facilitates hydrogen ion pumps to create a
gradient so that ATP synthase may generate ATP

The overall yields of aerobic respiration are 36 ATP molecules of glucose molecule,
however, results may vary.

60% of the energy is lost as metabolic sheet

These are truly exergonic reactions.
Anaerobic Fermentation

We begin with pyruvate from glycolysis and we remain in the cytoplasm of the cell.

2 options Alcoholic Fermentation OR Lactic Acid Fermentation
Lactic Acid Fermentation also called lactate

electrons and hydrogen ions from NADH transport directly to pyruvate converting to
a 3 carbon lactate molecule, this is the oxidized form of lactic acid.

Some lactate fermenters spoil food, others preserve it.

We use bacteria which use this process to create buttermilk cheese and yogurt.

Yeast fermenters produce pickles sauerkraut and kimchee.

Red versus white muscle fibers.

White muscle fibers contain few mitochondria and no myoglobin, so they do not hold
much oxygen and therefore do not carry out a lot of aerobic respiration.

Most ATP in white muscle fiber is produced by lactate fermentation useful for, quick
strenuous activities such as sprinting or weightlifting.

Red fibers have many mitochondria and produce ATP by aerobic respiration. These
fibers sustain prolonged activity and have an abundance of myoglobin, a protein which
stores oxygen.

Luckily, we humans have a mixture of both red and white muscle fibers to make the
best of both worlds
Ethyl Alcohol Fermentation –Alcoholic Fermentation

the pyruvate from glycolysis is split into carbon dioxide and a 2-carbon acetyl aldehyde

electrons and hydrogen ions are transferred from NADH to the acetyl aldehyde forming
NAD+ and ethanol.

Alcoholic fermentation in the fungus yeast helps us produce beer, wine and bread.

Ethanol produced by the fermenting used cells makes beer alcoholic and carbon dioxide
makes it bubbly