BIOL 2112 Chapter Notes - Chapter 9: Nicotinamide Adenine Dinucleotide, Electron Acceptor, Energy Returned On Energy Invested
3 May 2018
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Lecture 16– Glycolysis
1) A. What is an oxidation-reduction reaction? (Pg. 166, 1st column, 1st paragraph) In a
redox reaction, the loss of electrons from one substance is called oxidation, and the
addition of electrons to another substance is known as reduction.
B. In the oxidation-reduction reaction shown below, which reaction component is the
reducing agent and which is the oxidizing agent?
Reducing agent
C6H12O6 + 6 O2 6 CO2 + 6 H2O + Energy (ATP + heat)
Oxidizing agent
2) A. How is the formation of a polar covalent bond an example of an oxidation-
reduction reaction? (Pg. 166, paragraph 3, sentence 1 and Figure 9.3) Not all redox
reactions involve the complete transfer of electrons from one substance to another;
some change the degree of electron sharing in covalent bonds.
B. How does the potential energy in an electron relate to its association with an
electronegative atom? (Pg. 166, paragraph 5) An electron loses potential energy when
it shifts from a less electronegative atom towards a more electronegative one.
3) What are the roles of dehydrogenase and the coenzyme nicotinamide adenine
dinucleotide (NAD+) in catabolic pathways? (Pg. 167, paragraphs 2-3)
Enzymes called dehydrogenases remove a pair of hydrogen atoms from glucose and
other organic molecules in food, thereby oxidizing it. The dehydrogenase delivers the
2 electrons along with one proton to its coenzyme, NAD+, forming NADH. The other
proton is released into the surrounding solution.
4) A. Energy from electrons carried by NADH (and FADH2) is harvested through a
controlled release as they travel toward an electronegative oxygen atom. How does the
controlled release of energy occur? (Pg. 168, paragraph 2 sentences 1-4 and Fig. 9.5b)
Electron transfer from NADH to oxygen is an exergonic reaction with a free energy
change of -53 kcal/mol (-222 kJ/mol). Instead of this energy being released and
wasted in one explosive step, electrons cascade down the chain from one carrier
molecule to the next in a series of redox reactions, losing a small amount of energy
with each step until they finally reach oxygen, the terminal electron acceptor, which
has a great affiit for eletros. Eah dohill arrier is ore eletroegatie tha,
and thus capable of oxidizing its uphill eighor, ith oge at the otto of the
chain. Therefore, the electrons transferred from glucose to NAD+ which is thus
reduced to NADH, fall down an energy gradient in the electron transport chain to a far
more stable location in the electronegative oxygen atom.
5) Define substrate-level phosphorylation. (One sentence, Pg. 169, Fig. 9.7)
When an enzyme transfers a phosphate group from a substrate molecule to ADP
rather than adding an inorganic phosphate to ADP as in oxidative phosphorylation.
6) A. How does the energy investment phase of glycolysis differ from the energy pay-off
phase? (Describe the products of glycolysis in your answer.) (Pg. 170, Fig. 9.8) During
the investment phase, the cell actually spends ATP. During the payoff phase, ATP is
produced and NAD+ is reduced to NADH. The net energy yield from glycolysis per
glucose molecule is 2 ATP plus 2 NADH
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Document Summary
166, 1st column, 1st paragraph) in a redox reaction, the loss of electrons from one substance is called oxidation, and the addition of electrons to another substance is known as reduction. C6h12o6 + 6 o2 6 co2 + 6 h2o + energy (atp + heat) How is the formation of a polar covalent bond an example of an oxidation- reduction reaction? (pg. 166, paragraph 3, sentence 1 and figure 9. 3) not all redox reactions involve the complete transfer of electrons from one substance to another; some change the degree of electron sharing in covalent bonds. How does the potential energy in an electron relate to its association with an electronegative atom? (pg. 166, paragraph 5) an electron loses potential energy when it shifts from a less electronegative atom towards a more electronegative one: what are the roles of dehydrogenase and the coenzyme nicotinamide adenine dinucleotide (nad+) in catabolic pathways? (pg.
