Nucleic acids Biology A2

DNA                                        v                          RNA

-Thymine                                                       -Uracil

-Double-stranded                                         -Single-stranded

-Deoxyribose                                                -Ribose

-Only in nucleus                                            -Anywhere in cell

mRNA                                    v                           tRNA

-Longer, varied in length                              -Shorter, fixed length

-Single helix                                                 -Single strand in shape of 'clover leaf'

-No amino acid binding site                        -Amino acid binding site

-No base pairing, no hydrogen bonds        -Base pairing, hydrogen bonds

- Many condensation reactions join together deoxyribose forming a strand of DNA

- Phophodiester bonds

- Made up of 2 polynucleotide strands, they coil around each other forming a 'double helix'

- This is stabilised by hydrogen bonds between the bases

- Complementary base pairing

- Strands are anti-parrelel - one runs 3' -> 5' -> 3' other 5' -> 3' -> 5'

- Polynucleotide

- Ribose 

- Uracil 

- Everything else the same

Monomers consisting of:

- Pentose sugar (deoxyribose, ribose)

- Nitrogen-containing organic base (Adenine, Thymine, Cytosine, Guanine, Uracil)

- Phosphate group

1) Unwinding and unzipping the original DNA molecule

- DNA helicase, breaks hydrogen bonds linking the base pairs

2) Building the new polynucleotide chain

- Free nucleotides hook up with their complementary base on either of the unzipped strands (template strands)

- A new polynucleotide strand grows against each template strand

3) Seperation of the new DNA molecules

- When all the bases of each template strand have joined with free nucleotides - replication is complete

- 2 new molecules of DNA seperate

Each new molecule of DNA consists of a strand of template DNA and a strand of DNA formed from the complementary base pairing.

This ensures genetic continuity from one generation of cells to the next.

ATP = Adenosine Triosphosphate - Made up of ribose, adenine and 3 phosphate groups

ATP = ADP + Pi

The reaction is...

- A phosphorylation - when phosphate is added to another molecule

- Endothermic - A type of reaction which absorbs energy

- Catalysed by ATP synthase

The energy for synthesis of ATP comes from...

- Light in light dependent reaction

- Sugars in respiration

Energy is stored in the chemical bonds of ATP

Soluble in water.

In a hydrolysis reactionthe last phosphate group is broken - more energy is released as other bonds are formed - exothermic.

Hydrolyis of ATP is catalysed by ATP hydrolase.

Drives the processes...

- Anabolic reactions - synthesis of polymers e.g. monosaccharides to polysaccharides

- Active Transport - transport of substances against their conc gradient sodium potassium pump

- Muscle contraction - during which muscle fibres shorten 

A proportion of the energy from the hydrolysis of ATP is released as heat energy - used to mainain body temp in birds and mammals or released 

Dipolarity and hydrogen bonding

- The molecule is a dipole - oxygen has small negative charge, hydrogen has small positive charge. Water molecule has no net charge bc neg and pos charges balance

The solvent properties of water

- Water is a solvent, ions and polar molecules readily dissolve in water.

- Solutes are hydrophilic bc they readily form hydrogen bonds with water molecules

- Non polar molecules are insoluble in water (hydrophobic)

The heat capacity of water - high so is a stable environment for chemical reactions

Cohesion and surface tension - high cohesion bc molecules joined by hydrogen bonds

Vaporisation - hydrogen bonding stops molecules escaping as vapor, a lot of energy needed to break bonds