BIO 361 Lecture Notes - Titration Curve, Chemical Polarity, Acid Dissociation Constant

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carminedinosaur561

17 Feb 2019

School

Stony Brook University

Department

Biology

Course

BIO 361

Professor

Stephen Glynn

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Document Summary

Lecture 2: water and buffers. Describe how the structure of water creates a polar molecule with the capacity to hydrogen bond. Water is tetrahedral polar molecule. One water molecule can donate two h and accept two h. Strength of an h- bond depends on orientation of honor and acceptor. The hydrophobic effect is the tendency of water to minimize its contacts with hydrophobic groups. Dissolving non- polar in non- polar is entropically driven. Understand the relationship between ph, [h+], and pka ph = - log[h+] pk = - logk. Henderson- hasselbalch is used to calculate the ph of weak acids pk"s are disassociation constants. Determine whether a particular weak acid can act as a buffer at a given ph. Buffers are solutions that can resist changes in ph. Lecture 3: amino acids: describe the structures, sizes, polarities and charges of the 20 naturally occurring amino acids. Side chain is large & organic.

Related Questions

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 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.

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

1. Use the following definitions and phrases to describe to which molecules of life and their subunits it belongs:

a. Energy-storing molecule, typically water soluble - b. Subunits are called monosaccharides â c. Used to speed chemical reactions - d. Subunits are joined to each other with peptide bonds - e. Most prevalent molecule in cell membranes - f. Some of them function as hormones - g. Used for storing, transmitting, and executing genetic information - h. Subunits are nucleotides

2. Weak hydrogen bonds between water molecules are responsible for the many properties of water. Acidity is expressed as pH. Buffers stabilize pH. a. What characteristics of water molecule makes it polar? Provide two examples why this property is important in microbiology. b. What is the role of buffers in living organisms, including microbes? c. What must be added to pure water to decrease OH- and/or H+ concentration, respectively

3. Carbohydrates serve as storage molecules and structural material. Lipids are hydrophobic molecules; phospholipids are main component of cell membranes. Protein has a complex structure based on identity and sequence of amino acids. Nucleic acids (DNA and RNA) are genetic station of storage information and for synthesis of proteins. ATP serve as the main energy source in the living cell. a. Name the subunits (building blocks) of carbs, simple lipids, proteins, and nucleic acids b. What level of protein structure is described as an alpha helix? c. If DNA is placed in boiling water, what and how the molecule would change?

BIO 361 Lecture Notes - Titration Curve, Chemical Polarity, Acid Dissociation Constant

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