Physiology Test 1
Which number represents the mass of one water molecule in grams? 18/(6*1023) (6*1023)/18 18*(6*10-23)
18/(6*1023) ***Explanation: 6*1023 molecules of water have a mass of 18 g. 1 molecule has a mass 6*1023 times smaller, or 18/(6*1023) grams
The smallest size that is clearly visible under an optical microscope is close to...
250 nm
A baby crab from Notes 1 has grown 3 times longer (variants) without changing its shape. Its volume (area) has increased by
3^3 = 27
4 ug/ml =
4 mg/l
What are the two main parameters that determine concentrations at equilibrium?
Delta E and T
Think of an example of non-specific inactivation of an enzyme
Denaturation by heat
Two atoms have the same numbers of electrons but different numbers of protons. What can you say about them?
Different elements, at least one of them is ionized
If the energy of cis-2-butene increased for some reason, how would that affect the reaction rates and the equilibrium?
Formation of trans-butene will be accelerated, and more of it will be present at equilibrium
How would you classify a hydrogen atom H?
Free radical
Why do denatured proteins become less water-soluble?
From exposure of normally buried hydrophobic residues
What is the main difference between tight junctions and gap junctions?
Gap junctions allow passage of small molecules, tight junctions do not
. Which of these molecules should be able to pass through a gap junction? (Amyloid, Hexokinase, Glucose, Potassium ion)
Glucose and Potassium ions
Give an example of monosaccharide, disaccharide, polysaccharide.
Glucose, sucrose, glycogen
What makes uncooked egg whites sticky?
Glycoproteins
The reason water has a high boiling temperature is...
Hydrogen bonds
Is it correct that kon for Fe2+-myoglobin-O2 is larger than koff?
Quantities expressed in different units cannot be compared
What medical procedures make use of free radical reactions?
Radiation therapy, photodynamic therapy, sterilization by hydrogen peroxide
How can you explain repulsion between a hydrophobic solvent and a hydrophilic solute?
Reduction in energy upon separation
Two atoms have the same numbers of protons but different numbers of electrons. What can you say about them?
Same element, at least one of them is ionized
One atom has 37 protons, 37 electrons, and 85 neutrons. Another atom has 37 protons, 37 electrons, and 87 neutrons. They are:
Same elements, different isotopes
What type of tests are commonly used to see if cells are alive?
Tests for impermeability of the plasma membrane to hydrophilic molecules
Leucine is less soluble in water than glycine T/F
True
What could be the units of Vmax?
nmol/(ml*s)
What could be the units of K(sub)m?
nmol/ml
1 % correspond to how many g/L?
1 % = 1 g/100 mL = 10 g/L
Compare concentrations of hydrogen ions at pH 1 and pH 4
1000 times larger at 1
pH difference by 3 units correspond to [H+] difference by ... ?
1000-fold
Kilo is larger than milli by
10^6
You have 15 L of water. Which of these represents its volume in liters? 15x10^-3 15x10^-6 15x10^-9
15x10^-6
"The turnover numbers can range from single digits to millions per second". What do you think it depends on?
Activation energy
What are amyloids?
Aggregates of misfolded protein
Which group binds H+ stronger: carboxyl or amino?
Amino groups bind H+ stronger
Does binding of any ligand to a receptor produce a biological response?
Antagonists are ligands but do not elicit a response.
Do liquids with higher surface tension tend to bead or to spread?
Bead
From a book: "... calcium is buffered by calmodulin and troponin". Calmodulin and troponin are proteins; but what does it mean, "calcium is buffered"?
By analogy with hydrogen ion buffers: calmodulin and troponin bind calcium and decrease its free concentration.
Explain how soap works.
By providing connection between hydrophobic dirt and water
What are the two main parameters that determine reaction rates?
E(subscript a) and T
How would you interpret n < 1 in a Hill equation?
Each subsequent bound ligand decreases the affinity of the remaining unoccupied sites
Fill in the missing word in the sentence: "A common misconception is that soap ... the water's surface tension. Actually, soap does the exact opposite" (Choose between "increases" and "decreases")
Increases
What does enzymatic energy coupling achieve?
It ensures that the energy released from ATP hydrolysis is not wasted in heat but used to drive the needed reaction.
What is the difference between liposomes and micelles?
Liposomes have an interior lipid-free volume, micelles don't
How would you tell whether a binding curve represents cooperative binding or is drawn on a logarithmic scale?
Logarithmic curves never cross zero. They are also symmetric around k(subscript)d
Suppose you have the same molar concentrations of chemical S with molecular mass 250 and of chemical L with molecular mass 2500. What can you say about their mass per volume concentrations?
Mass per volume concentration of L is 10 times higher **Explanation: It would take 250 g/L of S and 2500 g/L of L to make 1 M. Thus, the same molar concentration would correspond to a 10 times larger mass of L than of S.
Which of the following structures are surrounded by a membrane: ribosomes, mitochondria, nuclei, nucleoli, cytoskeleton, lysosomes?
Mitochondria, nuclei, lysosomes.
What is the origin of surface tension?
Molecules on the surface have a higher energy than when surrounded by similar molecules
What is the typical mechanism of the end-product inhibition?
Negative allosteric regulation
Is water the only molecule that forms hydrogen bonds?
No
Strong acids bind hydrogen more strongly than do weak acids: is that correct?
No
If k(sub)d for compound A is smaller than k(sub)d for compound B, what (if anything) can be said about their association and dissociation rates?
Nothing certain
What is 6x10-23?
Nothing- The number of molecules in 1 mole is 6x10^23 , not 6x10^-23.
What type of molecule is Tyr-Gly-Gly-Phe-Leu?
Oligopeptide
How would the binding curve be affected if the receptors were upregulated?
The curve would not change if plotted as q against [L]. It would stretch vertically if plotted as the total amount of bound ligand against [L]
Explain the meaning of E(subscript)a
The energy that must be added to the molecule for a reaction to occur
What is Q(subscript)10?
The factor by which a reaction is accelerated when temperature increases by 10 degrees Celsius.
What is a rate-limiting reaction?
The slowest one in a chain of reactions
If enzymes accelerate both forward and reverse reactions, why are the effects of kinases and phosphates different?
They catalyze slightly different reactions: phosphates release free phosphate and kinases use ATP.
What makes a molecule or an atom free radical?
Unfilled outer shell of electrons
Can a non-catalyzed reaction be faster than a catalyzed one?
Yes, because at high concentrations of reagents, enzymatic rates level off but noncatalyzed reaction rates continue to increase.
Which of the following would be legitimate units for kd: mole, g/L, M?
g/L and M (they are the units of concentration)
Which kd is higher: for the carboxyl or for the amino group?
kd is higher for the carboxyl group
If [H+] = 1 nM then pH = ?
pH 9
What is isoelectric point?
pH at which a molecule is electrically neutral
What is the concentration of [H+] at pH 2? pH 3?
pH2 = 10 mM, pH 3= 1 mM
Which pKa is higher: for the carboxyl or for the amino group?
pKa is higher for the amino group
