BSC 114 Lecture Notes - Lecture 2: Hydrogen Bond, Ionic Compound, Kinetic Energy

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plumtermite154

29 Aug 2016

School

University of Alabama

Department

Biological Sciences

Course

BSC 114

Professor

Daryl W.Lam

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Document Summary

Abundance of water is the main reason for life on earth o o. Life only occurs where there is liquid water available: most cells are surrounded by water and are comprised of roughly 70%-95% water, approximately 70% of the earth"s surface is covered by water. Roughly 97% of that water is salt water in oceans: only common substance to exist in the natural environment in all 3 physical states of matter o. Structure is highly polar because of oxygen"s higher electronegativity compared to that of hydrogen. Allows water molecules to interact with other polar or charged molecules. The electrons of its polar covalent bonds spend more time near the oxygen than the hydrogen atom o. Polarity allows water molecules to form hydrogen bonds with each other and other polar compounds. Hydrogen bonds are weak- the are constantly broken and reformed. One water molecule can make up to 4 hydrogen bonds with other water molecules and other polar compounds.

Related Questions

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

BSC 114 Lecture Notes - Lecture 2: Hydrogen Bond, Ionic Compound, Kinetic Energy

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