BIOC 385, BIOC EXAM 2 || All Questions Answered
Correctly.
The Light Harvesting Complex (LHC) molecules are arranged to facilitate correct answers
Resonance energy transfer to the reaction center
Which statement below best describes the glycoconjugate structure of bacterial cell walls?
correct answers Peptidoglycans with multiple strands of hexosamine polysaccharide chains
linked together.
What is the energy source for sustaining the electrochemical proton gradient in chloroplasts;
what is the biochemical function of this gradient? correct answers D. Photon absorption;
production of ATP via chloroplast ATP synthase complex
Why is photorespiration a bigger problem for plants at high temperatures, and which enzyme is
responsible for this wasteful process? correct answers Ratio of soluble O2 : CO2 is increased;
Rubisco
Calculate the DG value (actual change in free energy) at 37 .C for the aldolase reaction, which
converts fructose-1,6-bisphosphate (F-1,6-BP) to glyceraldehyde-3-phosphate (GAP) and
dihydroxyacetone-phosphate (DHAP), given the DG.' value for this reaction of +23.8 kJ/mol and
the
concentrations of these metabolites at steady state; F-1,6-BP = 10 mM, GAP = 0.02 mM, DHAP
= 0.02 mM. correct answers DG = +23.8 kJ/mol + (8.315 x 10-3 kJ/mol•K) • (310K) • ln (2 x 10-
5M) (2 x 10-5M)
1 x 10-2M
DG = +23.8 kJ/mol + (8.315 x 10-3 kJ/mol•K) • (310K) • (-17.73)
DG = +23.8 kJ/mol + (-43.9 kJ/mol))
DG = - 20.1 kJ/mol
The figure at the right shows the cellular processes that
synthesize, secrete, and recognize glycoconjugates in eukaryotic cells.
Correctly Identify these three types of proteins, a) a lectin protein, b)
hexose transport protein, c) a glycoprotein. correct answers a) 4; b) 1; c) 3
What type of antibody or antibodies is/are found in the plasma of a person with type A blood?
correct answers B antibodies
Calculate the Energy Charge of a cell when the levels of ATP, ADP, and AMP are all equal to
1 mM; is this value for the Energy Charge within the physiological range? correct answers EC=
0.5; no, the cell's energy charge does not fall within physiological range.
What is the advantage of using methicillin compared to using penicillin as an antibiotic? correct
answers Methicillin is resistant to beta-lactamase activity.
,Glycogen phosphorylase is an enzyme that catalyzes the rate-limiting
step in glycogen degradation. The catalytic activity of this enzyme is stimulated by
phosphorylation. What is the best description of this type of enzyme regulation? correct answers
covalent modification
Why are C4 plants better adapted to hot climates than C3 plants? correct answers They can
capture CO2 and store it during times that O2 levels are high and minimize photorespiration.
Raffinose-series oligosaccharides are hard for humans to digest because: correct answers humans
do not have the enzyme a-1,6-glycosidase necessary to hydrolyze the glycosidic bonds
Which statement below best describes the reason why the Cori Cycle has a net cost of 4 ATP
for each glucose that is regenerated? correct answers Because it requires an investment of 6 ATP
equivalents to generate glucose from lactate in the liver but
the recovery of ATP in conversion of glucose to lactate in muscle is only 2 ATP.
Photons first enter the Z scheme via which molecule? correct answers chlorophyll P680
Two reduced plastoquinol molecules (PQBH2) are oxidized in the PQ cycle
for every 2 H2O that are oxidized by the oxygen evolving complex (OEC). How many
protons are translocated into the thylakoid lumen by the PQ cycle? correct answers 4 protons
Using the DG.' values for the reactions shown below, what is the DG.'
value for the conversion of phosphoenolpyruvate to 3-phosphoglycerate in the gluconeogenesis?
correct answers Phosphoenolpyruvate <--> 2 Phosphoglycerate DG.' = -1.7 kJ/mol
3-Phosphoglycerate <--> 2-Phosphoglycerate DG.' = +4.6 kJ/mol
2-Phosphoglycerate <--> 3-Phosphoglycerate DG.' = -4.6 kJ/mol
Phosphoenolpyruvate <--> 2-Phosphoglycerate DGº' = -6.3 kJ/mol
Explain why 8 photons need to be absorbed by photosynthetic eukaryotic plants in order to
transfer 4 electrons obtained from the oxidation of H2O through the photosynthetic Z scheme.
correct answers Absorption of 4 photons by PSII leads to 4 e- being transferred from 2 H2O
through the Z scheme to
plastocyanin; 4 more photons need to be absorbed by PSI in order to generate 2 NADPH from 2
NADP+
A continual supply of reduced glutathione is required to protect red blood cells against the toxic
effects of vicine, which is found at high levels in fava beans. Why would individuals with a
defect in the
enzyme glucose 6-phosphate dehydrogenase (G6PDH) be susceptible to vicine-induced
hemolytic anemia? correct answers A G6PDH deficiency leads to insufficient NADPH to protect
against vicine-induced anemia.
,Fructose-2,6-bisphosphate (F-2,6-BP) is an allosteric regulator that controls flux through the
glycolytic and gluconeogenic pathways. Levels of F-2,6-BP increase in the cell in response to
insulin and
decrease in response to glucagon. Choose the number corresponding to the correct underlined
answer. correct answers Insulin (1) / Glucagon (2) signaling in liver cells leads to the
phosphorylation of PFK-2/FBPase-2, which
activates PFK-2 (3) / FBPase-2 (4) activity of the enzyme and dephosphorylation (5) /
phosphorylation (6) of
fructose-2,6-BP. The net result of increased (7) / decreased (8) levels of F-2,6-BP in liver cells is
to
stimulate flux through the gluconeogenic pathway by lowering the levels of this allosteric
inhibitor of the
enzyme FBPase-1 (9) / phosphofructokinase-1 (10). Glucagon (11) / insulin (12) signaling
stimulates protein
phosphatase-1 in liver cells leading to the activation of the PFK-2 (13) / FBPase-2 (14) domain
(Answer: 2, 4, 5, 8, 9, 12, 13)
T is the less active form of an allosteric enzyme and R is the more active form of enzyme.
What happens to the value for the ratio of [inactive enzyme]/[active enzyme] when the substrate
concentration decreases relative to high substrate levels? correct answers the ratio is increased
What are biochemical properties of enzyme active sites? Choose the TWO best answers. correct
answers ~ Enzyme active sites provide optimal orientation
~ Enzyme active sites exclude excess solvent.
Match the general type of carbohydrate in the first column (a-f) with the best specific example
of that carbohydrate in the second column (1-6). Record your answer in the order from a through
f. correct answers Type of carbohydrate Specific example
____ a. Disaccharide 1. Fructose
____ b. Disaccharide heteropolymer 2. Raffinose
____ c. Monosaccharide 3. Syndecan
____ d. Oligosaccharide 4. Lactose
____ e. Proteoglycan 5. Chitin
____ f. Glycoprotein 6. Lectin
(Answer: 4, 5, 1, 2, 3, 6)
Choose the statement that describes what the actual change in free energy (DG) tells you
about an enzymatic reaction, which cannot be determined by the standard free energy (DG.')
change. correct answers The direction of the reaction under steady state conditions
The term greenhouse effect refers to the idea that correct answers the temperature of the earth is
increasing because of heat trapped by gases such as CO2.
What must be the chemical property of the electron acceptor molecule that is reduced by
, electron transfer when chlorophyll photooxidized? Choose the one best answer. correct answers
The acceptor molecule must have a higher reduction potential than chlorophyll (more positive).
How are plants able to stay alive in the absence of light? correct answers Mitochondria use
carbohydrates as an energy source for cellular respiration
Choose the best statement below that accurately describes O-linked
glycan to a protein. correct answers Glycan forms an O-glycosidic bond involving the anomeric
carbon of the oligosaccharide and a Ser or
Thr residue on the protein.
Heparin has one of the highest negative
charge densities ever found in a biomolecule and is
used commercially to prevent blood clotting. Heparin
binds to and activates antithrombin, thereby inhibiting
the blood clotting cascade. An accidental heparin
overdose can be fatal. How does infusion with
protamine sulfate, a cationic protein, counteract the effects of a heparin overdose? correct
answers The positively charged protamine sulfate binds to the negatively charged heparin and
inactivates it
The mitochondrial electron transport system and the photosynthetic electron transport system
are different in many ways. In what way are they similar? correct answers Electrons are
transferred from one electron carrier to the other by redox reactions in both systems
What is the role of most chlorophyll molecules in
a photosynthetic membrane? correct answers to serve as light-harvesting antennae
Which one of the following is involved in the breakdown of glycogen? correct answers inorganic
phosphate
Which enzyme catalyzes the formation of alpha(1,6) linkages during glycogen synthesis? correct
answers branching enzyme
The activation of glycogen phosphorylase will lead to a(n) ____ in blood glucose concentrations
and is stimulated by the hormone _____. correct answers increase; glucagon
Because muscles lack receptors for glucagon, what hormone activates muscle glycogen
phosphorylase? correct answers epinephrine
Given that ΔG°´ for the glycogen phosphorylase reaction is +3.1 kJ/mol, what factors in the cell
make the actual free energy change (ΔΔΔG) favorable? correct answers Pi being much greater
than glucose-1-P
Sort the following into activators or inhibitors of glycogen synthase. correct answers Activates:
Insulin and protein phosphatase 1
