Answer the following questions

Biomolecules

6. Distinguish between nitrogenous base and a base found in inorganic chemistry.

Nitrogenous base

• Organic molecule containing Nitrogen and has some chemical properties of a base.

• Nitrogen is an odourless, colourless & tasteless gas so reacts easily with other elements

• This reactivity makes it an important part in compounds necessary for life

• 2 types

Purine

^|→ Adenine

^|→ Guanine

Pyrimidine

^|→ Thyamine

^|→Cytosine

^|→ uracil

• Chemistry of nitrogenuous bases is key in the functioning of DNA (allows complementary base pairing)

Base in inorganic chemistry

Inorganic base is a substance they are metal oxides or hydroxides. Base is also a substance that can donate pair of electrons to other elements to form new molecule.

Characters of a base

• Base is soapy or slimpy substance bitter in taste

• React with acid-precipitate to form salts

• Turn red litmus to blue

7. What are the factors affecting the rate of enzyme reaction?

Enzymes being bio-molecules sensitive to environmental condition

(i) Temperature

• Heating increases molecular motion-quicken enzyme reaction

• Optimum temperature is the temperature that promote maximum activity

(ii) pH

• Change in the pH^– leads to an alteration of enzyme shape (active site)

• Extremes of pH^– denatures enzymes

• Optimum pH^– is that at which the maximum rate of reaction occurs

(iii) Substrate concentration

For a given enzyme concentration, the rate of reaction increase with increasing substrate concentration

(iv) Enzyme concentration

The rate of reaction is directly proportional to enzyme concentration 

8. Briefly outline the classification of enzymes

Classification of enzymes

Enzymes are classified into six groups based on their mode of action.

9. Write the characteristic feature of DNA

• Double stranded-anti parallel 5'-3'-one strand,3'-5'-another strand .

• 5'-end has phosphate group

3'-end has ‘OH’ group

• The two sugars protrude from the base pair is

^|→ 120° for narrow angle

^|→ 240° for wide angle

• A complete turn of helix at 360° has 10 bases the single turn distance 3.4 nm so each base has 0.34nm this was proved by x-ray crystallography study of DNA

• The width of DNA is 20° & a pitch of about 34 Ǻ

• Thermodynamic stability of double helix & specificity of base pairs is due to

a. Hydrogenbonds between complementary bases

b. Stacking interaction between bases is perpendicular to the direction of helical axis

c. Electron cloud interactions (II-II) between bases in a helical stacks

• Phospho diester linkages

• It give polarity

• It form strong covalent bonds

• It gives strength and stability to the polynucleotide chain

• Plectonemic chain:

• the two strands are wrapped around each in a helix impossible to move them apart

• Paranemic coiling:

2 strands lie along side easier to pull apart

Types 3-(based on the helix and distance between each turns)

A DNA, B DNA & Z DNA.

10. Explain the structure and function of different types of RNA

I. mRNA (messenger RNA)

• single stranded

• carries a copy of instructions to carryout amino acid assembling & protein synthesis

• unstable

• 5% of total RNA

• In Prokaryotes - it is (polycistronic) carrying coding sequence for many polypeptides

• In Eukaryotes - (monocistronic) contain information for only one polypeptide

II. tRNA (transfer RNA)

• single stranded clover shaped with 4 arms highly folded -3 D structure

• translates the code from mRNA and transfers amino acid to ribosomes (to built proteins)

• unstable (also known soluble RNA)

• 15% of total RNA

III r RNA (ribosomal RNA)

• single stranded

• make up the 2 sub units of ribosomes

• metabolically stable

• 80% total RNA

• A polymer with varied length from 120 - 3000 nucleotides & give ribosomes their shape

• Genes of rRNA employed for phylogenetic studies