Fermentation*and*Cellular*Respiration*
*
1. Define:
Glycolysis – Glycolysis is a metabolic pathway allowing for the partial catabolism of
glucose. During glycolysis, each glucose molecule is split into two pyruvic acid molecules
with the associated production of two molecules of ATP and the reduction of two molecules
of NAD to form NADH + H+ (also known as the Embden-Meyerhof-Parnas pathway).
Fermentation – Fermentation is the anaerobic decomposition of organic compounds
(especially carbohydrates) that involves an organic compound (usually) as the final electron
acceptor. For those examples used in class, pyruvic acid serves as the final electron acceptor,
but some organisms use other compounds.
Heterofermentative – The term heterofermentative applies to organisms that produce a
variety of end products (more than one) as the result of their fermentation activities. For
example, Saccharomyces cerevisiae produces both ethanol and CO2 during its fermentation
activities, so is heterofermentative.
Krebs cycle – The Krebs cycle, also known as the tricarboxylic acid (TCA) cycle or citric
acid cycle, is a cyclic series of chemical reactions that plays a central role in metabolism.
When functioning catabolically, it involves the decarboxylation of organic acids (isocitric
acid and a-ketoglutaric acid). The carboxyl groups removed form carbon dioxide, a waste
gas. Most of the energy released during the cycle is captured in the form of reduced
coenzymes (NADH + H+ and FADH2). A small amount of energy is captured in the form of
GTP or ATP. When functioning anabolically, the TCA cycle provides precursors for various
biosynthetic pathways. In eukaryotic cells, the enzymes involved in this cycle are found in
the matrix of mitochondria, while in prokaryotic cells they are found in the cytoplasm.
Cytochromes – Cytochromes are pigmented enzymes with iron (haem) prosthetic groups.
They are found within or on the surface of membranes (cristae, thylakoids or cell
membranes) and are involved in electron transfers and the transport of hydrogen protons
across membranes to establish the proton motive force. The prosthetic groups of these
enzymes can be alternately oxidized and reduced while passing electrons from one to the
next. During cellular respiration, the last cytochromes in the series (electron transport chain)
pass electrons to a final electron acceptor (e.g., oxygen). During photophosphorylation, the
cytochromes pass electrons to pigment molecules.
2. Glycolysis
3. Pyruvic acid (two per glucose)
4. Kinase/ ATP
5. Glucose/ reduced
6. Phosphate
7. Kinase / isomerases
