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Lecture 3

MCDB 310 Lecture Notes - Lecture 3: Dihydroxyacetone Phosphate, Biomolecule, Glyceric Acid


Department
Molecular, Cellular and Developmental Biology
Course Code
MCDB 310
Professor
Kenneth Balazovich
Lecture
3

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You are studying a pathway in the cell that starts with D-Fructose and ends in D-Ribulose 5-
Phosphate.
Q1) Name all the intermediates that are formed when going from D-Fructose to D-Ribulose 5-
Phosphate. Please number each intermediate 1., 2., 3. etc. with 1. being the earliest intermediate,
2. being the next, and so on. (2 points)
1. Starting Material: D-Fructose
2. D-Fructose 6-phosphate
3. Glucose 6-phosphate
4. 6-Phosphogluconolactone
5. 6-phosphogluconate
6. Final product: D-Ribulose 5-phosphate
Q2) Name any one reaction in this pathway (by naming the reactant and product of that step) that
is unlikely to be the committed step of this pathway. Give a reason for your answer. (2 points)
6-Phosphogluconolactone to 6-phosphogluconate. The enzyme in this step is not regulated by
availability of any substrates, as is the case in the previous step. After the concentration of
NADP+ increases such that the PPP is stimulated, the remainder of the PPP can accomplish the
conversion to D-Ribulose 5-phosphate. Another reason is it is not a committed step because it's
reversible and committed steps are irreversible.
Q3) What is the net change in ATP molecules when 1 molecule of fructose is converted by this
pathway to 1 molecule of Ribulose 5-Phosphate (and other products, of course). Based on your
answer, is this a pathway that is useful for generating energy for the cell? (2 points)
1 ATP is required to go from fructose to fructose 6 phosphate, but not required for rest of this
pathway and none are produced. Net change is negative 1. It is primarily anabolic so it requires
energy but does not generate any for cell, so it is not useful for energy production.
Q4) Some products of this pathway are important for generating major kinds of biomolecules in
the cell. Name two different products and two different biomolecules that they facilitate the
synthesis of. (2 points)
#1 Product = NADPH #1 Biomolecule = Fatty Acids
#2 Product = Ribulose 5-phosphate #2 Biomolecule = DNA
Q5) Starting from one molecule of an intermediate or the starting molecule or the final product
of this pathway, write down a new pathway (with arrows indicating the conversion of one
molecule to the next) that will result in a net gain of 3 ATP molecules. You must indicate the
steps that generate or consume ATP and also indicate how many ATP molecules are generated or
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