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(c) Knoll and Ruska

The three forms of DNA: 

1. A – DNA 

2. B – DNA and 

3. Z – DNA.

The characteristic feature of DNA. 

1. If one strand runs in the 5′ – 3′ direction, the other runs in 3′ – 5′ direction and thus are antiparallel (they run in opposite direction). The 5′ end has the phosphate group and 3’end has the OH group.

2. The angle at which the two sugars protrude from the base pairs is about 120° , for the narrow angle and 240° for the wide angle. The narrow angle between the sugars generates a minor groove and the large angle on the other edge generates major groove.

3. Each base is 0.34 nm apart and a complete turn of the helix comprises 3.4 nm or 10 base pairs per turn in the predominant B form of DNA. 

4. DNA helical structure has a diameter of 20 Å and a pitch of about 3 Å. X – ray crystal study of DNA takes a stack of about 10 bp to go completely around the helix (360°).

5. Thermodynamic stability of the helix and specificity of base pairing includes

• (a) The hydrogen bonds between the complementary bases of the double helix
• (b) stacking interaction between bases tend to stack about each other perpendicular to the direction of helical axis. Electron cloud interactions (Π − Π ) between the bases in the helical stacks contribute to the stability of the double helix.

6. The phosphodiester linkages gives an inherent polarity to the DNA helix. They form strong covalent bonds, gives the strength and stability to the polynucleotide chain.

7. Plectonemic coiling – the two strands of the DNA are wrapped around each other in a helix, making it impossible to simply move them apart without breaking the entire structure. Whereas in paranemic coiling the two strands simply lie alongside one another, making them easier to pull apart.

8. Based on the helix and the distance between each turns, the DNA is of three forms – A DNA, B DNA and Z DNA.

tRNA is the soluble RNA which is about 15% of total RNA.

DNA has thymine base, whereas RNA has uracil base. DNA has deoxyribose sugar, whereas RNA has ribose sugar.

Nitrogen base, pentose sugar and phosphate.

Prosthetic groups are organic molecules that assist in catalytic function of an enzyme. 

Example: Flavin adenine dinucleotide (FAD).

An example for following enzyme groups:

1. Transferase – Ex: Transaminase 

2. Isomerase – Ex: Isomerase 

3. Oxidoreductase – Ex: Dehydrogenase 

4. Lyase – Ex: Decarboxylase

(a) Watson and Crick

Gelatin is used in preparation of ice cream, medicinal capsules, films and photographic papers,

These are the esters of three molecules of fatty acids and one molecule of glycerol.

(a) Activation energy (enzymatic reaction) 

(b) Activation energy (non- enzymatic reaction) 

(c) Transition state 

(d) Product

Enzymes are biological catalysts produced by living cells. 

Waxes are the fatty acid esters of long chain monohydric alcohols like cityl, ceryl or mericyl. However, paraffin wax is obtained from petroleum. Plant waxes occur in cuticle whereas animals have cutaneous glands which are known to secrete wax.

Testosterone, Progesterone

The metabolic pathway has following unique features : 

(i) The interlinked metabolic traffic is very smooth and without a single mishap under healthy conditions. 

(ii) Every chemical reaction of the metabolic pathway is a catalysed reaction. 

(iii) The catalysts which hastens the rate of a given metabolic conversion are proteins. The protein which possess catalytic power are called enzymes.

DNA found in the nucleus of a living cell has necessary message for the production of all enzymes required by it. DNA forms mRNA through the process of transcription. This mRNA through the process of translation forms proteins.

Deoxyribose sugar is found in DNA

Role of DNA in the life of an organism: 

(i) DNA is known as the master molecule of the organism. It is the vehicle of the heredity and store house of all informations required for the growth, differentiation etc. 

(ii) This information in deoxyribose nucleic acid is contained in the form of blue print. 

(iii) It gives message to the cell for duplication and transcription. This message is used for protein synthesis by the cells.

(d) (iii) only

Hemoglobin an example for chromoproteins.

(C) always as organic molecule

Living State: The living state is a non-equilibrium steady-state to be able to perform work. 

(i) The living process is a constant effort to prevent falling into equilibrium and is achieved by energy input. 

(ii) The metabolism provides a mechanism for the production of energy. 

(iii) The living state and metabolism are synonymous, without metabolism there cannot exist a living state. 

(iv) A living organism works continuously so it cannot afford to reach equilibrium because a system at equilibrium cannot perform the work.

Deoxyribose Nucleic Acid.

(b) Glycogen