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Exam 1- BSCI 1510

Terms in this set (58)

The human genome contains approximately ______ genes.
25,000
What does comparison of 16S rRNA nucleotide sequences provide an "evolutionary clock" for determining how long ago different species diverged?
Mutations accumulate at a relatively constant rate over long periods of time
Oxygen has __ unpaired electrons in its outer shell and therefore has a valency of _
2,2
Hydrolysis of 1 mole ATP releases sufficient energy under standard conditions to
raise the temperature of 1 kilogram (or 1 liter) of water approximately ____ degree(s)
7.3
The formula C6H12O6 describes ___.
glucose, fructose, mannose, galactose
h functional group is ionized at neutral pH and carries +1 positive charge?
amino
he movie GATTACA, people are given a numerical score based on the
"quality" of their DNA sequence. You decide to make a sequel to this movie
where people are scored based on the quality of their RNA sequence (their
transcriptome). What would be an appropriate name for your movie?
GAUUACA: T=U in RNA
Protein kinases in animal cells typically phosphorylate substrate proteins on ____ residues
Ser, Thr or Tyr
Each amino acid in a polypeptide chain has the same backbone structure except
proline
The Km of an enzyme for its substrate is defined the concentration of the substrate that is required to produce the _________ velocity of the enzyme
half-maximal
reducing agents used in the laboratory can break disulfide bonds between two cysteine residues. For a single polypeptide chain, which level of protein structure would potentially be most directly affected by the reducing agent?
tertiary
The active site of chymotrypsin has a catalytic triad composed of His57, Asp102 and Ser195. What role does the serine hydroxyl group play in catalysis of a peptide bond in the substrate?
-it will donate its proton to form the new amino terminus in the product
-Ionization allows the O to initiate a nucleophilic attack on the substrate carbonyl
carbon.
-It forms a transient covalent bond with substrate.
-The oxygen anion receives a proton from water to reform the hydroxyl
during hydrolysis of the second product
n the reaction CH4+ 2O2-->CO2+ 2H2O, which molecule is getting reduced?
O2
During glycolysis, the 3-carbon intermediate glyceraldehyde 3-phosphate is _________by the transfer of 2 electrons to _____
oxidized, NAD+
How should your body respond to a drop in blood glucose concentration during a short fasting period?
pancreatic cells secrete glucagon, which stimulates glycogenolysis in the liver.
Which part of the cholesterol molecule orients close to the water/lipid interface of the membrane bilayer
the hydroxyl
Which molecule, or ion, would be most likely to spontaneously diffuse across a phospholipid bilayer without the aid of a specific transport mechanism?
Oxygen (O2)
In glycolysis, ___ ATPs are invested in the first three steps of the pathway, a total of ___ATPs are produced for a net gain of ____ ATPs per glucose.
2, 4, 2
List the other energy rich products generated and how many are produced per glucose
2 NADHs, 2 Pyruvates
Which enzyme in glycolysis is subject to feedback inhibition by one of the end products?

Do you think this inhibitor is a competitive inhibitor or a noncompetitive inhibitor?

What is the likely fate for glucose entering the glycolytic pathway if this enzyme is fully inhibited?
Phosphofructokinase (PFK)

Noncompetitive

It will be converted to glycogen and stored in the cell
Draw a two amino acid peptide with side chains "R". Indicate the peptide bond with an arrow and draw a box around the group of atoms that form a plane. Assume the peptide is in a neutral pH 7.0 solution and label any ionized groups with the charge
L, Leu
Leucine
Q, Gln
Glutamine
F, Phe
Phenylalanine
H, His
Histidine
D, Asp
Aspartic Acid
Do you think the amino acid substitution in the mutant caused a significant problem in the folding of this enzyme? Why or why not?
No, the mutant enzyme can still catalyze the enzymatic reaction with the same Vmax. It must be folded well enough to form the active site.
What do you think is the specific consequence of the amino acid substitution in the mutant enzyme that could explain the data shown in the graph
There must be a subtle change that weakens the ability of the enzyme to bind its substrate. Perhaps a weak bond in the substrate binding site is lost or the fit of the substrate to the active site is less precise.
The pancreas secretes insulin in response to high blood glucose levels. Insulin stimulates muscle and adipose cell to take up glucose, and inhibits two pathways in the liver that prevent this organ from releasing glucose into the blood. What two pathways would insulin inhibit in the liver?
Gluconeogenesis (glucose synthesis) glycogenolysis (glycogen breakdown)
lipids that are good at forming phospholipid bilayers
Phosphatidylcholine, Phosphatidylserine, Sphingomyelin
What properties of lipids allow them to spontaneously form a bilayer
Amphipathic (hydrophilic headgroup and hydrophobic fatty acyl tails) and cylindrical shape that allows side-by-side packing to form bilayer sheets.
What is the Cori cycle and how does it help you complete a 400 meter dash?
During vigorous exercise, muscles will be depleted of oxygen and will produce substantial ATP anaerobically from glycolysis, but also accumulate lactate as a byproduct as NADH is recycled to NAD+ in the reaction shown above. The Cori cycle is the movement of lactate through the bloodstream from muscles to the liver, where it is converted to glucose by gluconeogenesis. Glucose returns to the muscles where it enters glycolysis and is used to produce ATP and lactate to complete the cycle. This cycle shifts the metabolic burden from muscles to the liver and allows sufficient ATP production in muscles, along with lactate removal, so you can complete the 400 meter dash.
Why are viruses not considered to be living
They cannot reproduce on their own and are metabolically inert
Human beings have about _________ different human cell types.
200
You shake out a few crystals of salt (Na+Cl-) from a salt shaker into beaker and decide you want to break the ionic bonds holding the crystals together. What is the simplest, safest, cheapest and most energy efficient way to do this
Add room temperature water to the beaker
Which of the following functional groups is hydrophobic?

A. Hydroxyl B. Phosphate C. Amino D. Carboxyl E. Methyl
Methyl
Polysaccharides (or carbohydrates) are important in biology because they ______.
-are used to store energy.
-can provide structural support.
-mediate molecular recognition events.
-play important roles in metabolism
Synthesis of a macromolecule from monomer building blocks is an energy demanding process that often requires "activation" of the monomer by attachment to a carrier prior to assembly. What carrier is used during glycogen synthesis to link glucose to the polymer?
UTP
Which two amino acids are most likely to form an ionic bond
Aspartic acid and Lysine
Weak, noncovalent bonds between amino acid side chains are responsible for what aspects of a protein structure
Tertiary and quaternary
Proteins are synthesized on ribosomes from ________.
the amino terminus to the carboxyl terminus
The infectious type of Creutzfeld-Jacob disease is caused by a change in a normal human protein called PrPC into an altered form called PrPSC. What causes this change?
An infectious PrPSC prion templates a conformational change in PrPC to form PrPSC
Which of the following conditions allow an enzyme to catalyze a chemical reaction that has a positive ∆H (an exothermic reaction).
The enzyme can bring a negative attitude into the mix
Noncompetitive inhibitors of enzymes typically _______
use an allosteric mechanism where binding to a regulatory site alters the conformation of the active site so substrate cannot bind.
When we eat a hamburger, what happens to the protein in the meat we are consuming?
-It is broken down to amino acids in our stomachs and intestines.
-The amino acids are absorbed and used directly to make our own proteins.
-The amino acids are broken down to acetyl-CoA and TCA cycle intermediates.
-We use amino acid breakdown products to make ATP by oxidative phosphorylation
During glycolysis of one glucose molecule, _____ ATPs are invested in the first three steps, and _______ ATPs are produced for a net yield of _____ ATPs.
2, 4, 2
In glycolysis, when glucose is converted to pyruvate, most of the energy in glucose is
retained in pyruvate
Omega-3 fatty acids found in nature have ___________
A double bond 3 carbons from the methyl group (last carbon).
How is water used by chymotrypsin to help cleave a peptide bond?
Water is used to hydrolyze a covalent bond between substrate and enzyme.
only 20 amino acids are found in nature. True or False? Explain.
False. While 20 amino acids are genetically encoded, proteins are
subject to posttranslational modifications that generate many more amino acids.
For example, phosphoserine, phosphothreonine and phosphotyrosine
lipids that are NOT built on a glycerol backbone
cholesterol, diacyglycerol, phosphatidylethanolamine
Where did the phosphate originally come from that
is being transferred from phosphoenolpyruvate onto ADP to synthesize ATP?
The phosphate originally came from ATP (catalyzed by
either hexokinase, glucokinase or phosphofructokinase)
People with sickle cell anemia inherit the mutation from both parents and so the
mutation is present in the genome of every cell of the body. Why are only the red
blood cells affected by the mutation?
Hemoglobin is only expressed in red blood cells
based on the chemical properties of the Glu and Val side chains, where are these
amino acids normally found in the folded structure of a water soluble protein? (4)
Glu is polar and charged so it should be at the surface
Val is hydrophobic and so it should be in the interior of the protein away from
water
hOW then do you think the presence of valine at position 6 contributes to the
aggregation of hemoglobin when oxygen levels are low? (4
Glu6Val not alter the secondary or tertiary structure of the beta hemoglobin
subunit and so it is likely that the valine is occupying a position on the surface
of hemoglobin and is exposed to water. This mutation, combined with a small
conformational change accompanying dissociation of oxygen, allows
hemoglobin tetramers to start to aggregate into large fibers. Aggregation is
driven by the hydrophobic effect to bury Val in the aggregates away from
water
What level of protein structure is being altered to cause the disease symptoms?
Quaternary Structure
List Three potential causes of the obesity epidemic in the US that were discussed in
class
increased consumption of fructose because of the use of high
fructose corn syrup as a sweetener. Fructose has a greater tendency to be
stored as fat (because of the unique metabolism of fructose in our liver)
2. Increased consumption of simple carbohydrates in our diet (~50 grams per
day more than 30 years ago).
3) The presence of
trans
fatty acids in the food we eat from chemical
hydrogenation of vegetable oils (not broken down for energy very well).
4) Changes to microbiome in our guts (increased births by cesarean section
and increased antibiotic use)
5) Not discussed, but a more sedentary population is also frequently blamed.
following statement is true or false? (Explain why). The glycolytic reaction
described by glucose + ATP-->
glucose 6-phosphate + ADP is called an irreversible
reaction because the cell cannot convert glucose 6-phosphate to glucose + free
phosphate.
False. It is called irreversible because hexokinase cannot catalyze the reverse
reaction to synthesize ATP (too large of a positive ∆G). The cell has another enzyme acting in gluconeogenesis (Glucose-6-phosphate
phosphatase) that catalyzes this reaction.
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