WK1 LEC3: Biopolymers (Proteins and Nucleic Acids) 낱말 카드

1. Describe the main chemical components of nucleic acids and proteins/peptides, as well as their repeating

units (backbones, bonds, and sidechains or bases).

(2Nucleic Acids

- Components:

Phosphate + Pentose Sugar + Nitrogenous base

- Backbone Bonding: Phosphate-C

Phosphodiester bond from 5' above 3' below between phosphate & C

- Base Bonding: Sugar-Base

Sugar bonds to nucleobase Glycosidic bond which allows rotation.

- Units: Nucleotide sequence is unique, and determines function. Differentiation by nitrogenous base.

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Proteins

- Components:

NCC + R group attached to alpha-carbon

- Backbone Bonding: C-N

Peptide bond between Amine & Acid FG which is energetically unfavourable, not spontaneous (>= 2 amino acids = peptide)

Peptide bond itself is flat & rigid due to resonance. C-C bond portion permits rotation -> protein folding,

- R-Group Bonding: C-R

Covalently bonded to alpha carbon. Provide shape/structure & varied properties.

- Units: Differentiation by R-Side chain polarity.

2. Identify the conventions of direction/ends of nucleic acids and proteins.

Nucleic Acids:

5' -> 3' (synthesised in this direction only)

Proteins:

N -> C (synthesised in this direction only)

3. Describe the base pairing between nucleobases and appreciate that C/G base pairing is stronger than A/T(U)

base pairing in nucleic acids.

1:1 Stochiometric Ratio of Pyrimidines and Purines (A:T, C:G = 1)

Paired double DNA strands run antiparallel.

Bonding structure of base pairs determined by H-bonds.

AT: 2 H-bonds

CG: 3 H-bonds

Hence CG > AT in terms of strength & stability, higher melting point.

4. Describe the double-helical structure of DNA and distinguish DNA from RNA in terms of structure and

stability.

DNA: (Double helix - Deoxygenated)

Structure:

- B-DNA

- Major/Minor grooves

Stability

- Bases stable except C which deaminates to U. This is repaired.

- Backbone is fairly stable

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RNA: (Single Strands - Extra OH group)

Structure:

- mRNA, tRNA, rRNA

- base pairing can occur between two RNA strand regions

Stability:

- More prone to mistakes which is OK since it's not genetic material.

- Backbone is unstable.

5. Describe how the physical and chemical properties of nucleic acids and proteins can be exploited in

experimental situations.

Sugar-Phosphate Backbone: Nucleic Acids

- Exploits the -ve charge of the phosphate and hydrophilic nature of sugar and phosphate.

Electrophoresis:

- Electric Field causes nucleic acid to move due to -ve charge. Distance depends on size of the molecule.

Ethanol Precipitation:

- Nucleic acid is neutralised via the addition of a salt to precipitate out of Ethanol solution. Ethanol is favoured to ensure nucleic acid and cation are tightly bound.

UV Absorbance:

Proteins 280nm

Nucleobases (Nitrogen Bases) 260nm

Absorbance ratios will provide information for purity =/