Exam #3 Review
Exam #3 will cover from glycolysis to complex gene regulation. This includes all glucose
degrading pathways (glycolysis (Embden-Meyerhoff), Entner-Doudoroff, pentose
phosphate pathway) as well as fermentation, the TCA and ETC (respiration). It also
includes photosynthesis, the Central Dogma of Gene Transfer in prokaryotes (replication,
transcription and translation), eukaryotic gene expression, and the regulation of gene
expression (the lac operon).
Note: On the exam, you will be allowed to use a poster of your own making that
summarizes all of the metabolic pathways and gene expression. This poster may not
include large blocks / paragraphs of text. It must be a picture. It must be of your
own making and it can only be one sheet (of any size). Questions will be geared more
toward the understanding of these processes rather than memorization. It is not
necessary to memorize most of the enzymes if you remember that the enzymes
catalyzing redox reactions in which either NADH/NADPH or FADH
2
are formed
are named: Reactant name + dehydrogenase. Reactions in which a phosphate group
is added generally have a root name followed by -kinase. Enzymes catalyzing
rearrangements are generally called either isomerases or mutases.
I. Metabolism (the pathways) - *Note these are for aerobic growth in chemoheterotrophs
(remember that these use an organic carbon source for energy and carbon)
A. Glycolysis (The Embden Meyerhoff pathway) (“the splitting of something
sweet”) - glucose, a six-carbon molecule, is converted into two, three carbon
pyruvate molecules. Energy released when the high-energy glucose bonds are
broken is harvested to form ATP (substrate-level phosphorylation). The continual
oxidation of glucose allows for the reduction of NAD+ to form NADH, which
(when the ETC is present and functional) carries its electrons to the electron
transport chain. Some of the intermediates in glycolysis can be used as precursor
metabolites in anabolic pathways.
Practice: Glycolysis occurs in the ___________ of eukaryotic cells.
a. nucleus
b. mitochondria
c. cytoplasm
d. vacuoles
*Important points to remember about glycolysis:
1. ATP is expended in steps 1 and 3. Thus, after step 3, two molecules of ATP
have been used and no ATP has been generated.
2. Step 3: the phosphorylation of fructose 6-phosphate, is the first committed
step of glycolysis. This step is catalyzed by phosphofructokinase, an
enzyme that can be regulated allosterically by many molecules (two of which
are ADP and phosphoenolpyruvate). Why is this regulation important?
3. In step 4, the 6-carbon fructose-1,6-bisphosphate is split into two 3-carbon
molecules. It’s important to note that there is an equilibrium between these
two 3-carbon molecules so essentially both of these molecules are used in step
6. **From here on out, every reaction occurs twice for every one molecule
of glucose**.