The type of macromolecule found in highest concentration on a weight basis in a
ID: 142806 • Letter: T
Question
The type of macromolecule found in highest concentration on a weight basis in a HeLa cell is
protein.
lipid.
polysaccharide.
nucleic acid.
water
Co and Zn ions are required by humans in
microgram amounts.
gram or near gram amounts.
kilogram amounts.
d. milligram amounts.
Which description best characterizes the length of a hydrogen bond between water molecules?
About the same length as the calculated van der Waals distance for two water molecules.
About the same length as a covalent O----H bond.
Shorter than a covalent O---H bond.
Longer than a covalent O---H bond, but shorter than the calculated van der Waals distance between water molecules.
Which of the following statements about water is not true?
Water will hydrogen bond into highly ordered structures or "cages" around non-polar molecules.
The electron-rich oxygen atom of one water molecule can interact with an electron-poor hydrogen on another water molecule to form a hydrogen bond.
Water is a key player in the energetics of the hydrophobic effect.
In an ice crystal water molecules pack into open lattices consisting of five-membered oxygen rings.
At 25 degrees celsius liquid water is about 85% as hydrogen bonded as the water in ice, with each molecule in an average of 3.4 hydrogen bonds.
Which of the following is the strongest?
Ionic interactions
Permanent dipole - permanent dipole interactions
London dispersion forces
Co-linear hydrogen bonds
Which of the following is the best explanation for the hydrophobic effect?
It is caused by the attraction of hydrophobic groups for each other.
It is an entropic effect caused by the tendency of hydrophobic groups to increase their entropy by associating with other hydrophobic groups.
It is an entropic effect, caused by the tendency of water molecules to increase their entropy by excluding hydrophobic groups, which they must otherwise surround with highly ordered structures.
It is caused by the attraction of water for hydrophobic groups.
It is an entropic effect, caused by the tendency of water molecules to increase their entropy by forming highly ordered structures around the hydrophobic groups.
Which of the following is NOT defined as a buffer? (pKa PIPES-H+ = 6.76; pKa MOPS-H+ = 7.15; pKa HEPES-H+ = 7.47)
0.15 M MOPS, pH 6.50
0.05 M HEPES-H+ / 0.04 M HEPES
0.20 M PIPES, pH 7.97
0.01 M HEPES, pH 7.30
protein.
lipid.
polysaccharide.
nucleic acid.
water
Co and Zn ions are required by humans in
a.microgram amounts.
b.gram or near gram amounts.
c.kilogram amounts.
.d. milligram amounts.
Which description best characterizes the length of a hydrogen bond between water molecules?
About the same length as the calculated van der Waals distance for two water molecules.
About the same length as a covalent O----H bond.
Shorter than a covalent O---H bond.
Longer than a covalent O---H bond, but shorter than the calculated van der Waals distance between water molecules.
Explanation / Answer
1. Based on weight, protein is found in highest concentration in HeLa cells. Total dry weight of a HeLa cell is 400pg out of which protein is 300pg, DNA-15pg and RNA-30pg. (pg - picograms).
2. Zn ions are required by humans in milligrams. An adult human requires 8-11mg of Zn a day in diet. On the other hand Co or Cobalt is required in microgram amounts of around 5-8mcg a day.
3. Length of hydrogen bond between water molecules is longer than the covalent O-H bond but shorter than the Van der Waals distance. Hydrogen bond length is 1.88A, covalent O-H bond length is 0.96A and calculated van der waal radii is 2.82A. (A - Angstrom or 10-10m)
4. The last statement "In an ice crystal water molecules pack in open lattices of five-membered oxygen rings" is wrong. Water molecules form layers of 6-membered hexagonal ring in the molecular structure of ice.
5. Ionic interactions or ionic bonds are the strongest of the four given. Bond dissociation energy or the energy required to break a bond is given here. Higher the value, stronger is the bond.
6. Option D. Hydrophobic interaction is an entropic effect which occurs due to disruption of the hydrogen bonds between molecules of liquid water by a nonpolar or hydrophobic molecule. A hydrocarbon chain or a similar nonpolar molecule is unable to form hydrogen bonds with water. Such a non-hydrogen bonding subsatnce, when introduced to water causes disruption of the hydrogen bonds between water molecules. The hydrogen bonds are then reoriented tangentially to minimize disruption of the H-bonded network of water molecules, and this leads to the formation of structured water cage around the nonpolar or hydrophobic group.
Ionic 250-400 kcal/mol dipole-dipole 0.5-2 kcal/mol London disp forces <1 to 15 kcal/mol H-bond 4-50 kcal/mol (5 for water)Related Questions
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