Bio - Chapter 2

Biomacromolecules

A large organic molecule found in organisms

Protein

A functional unit made up of one or more polypeptides

Polymer

A large molecule composed of a chain of repeating smaller molecules

Proteome

All proteins in a cell or organism

Polypeptide

Polymer of amino acids residues

Monomer

A molecule that is the smallest building block of a polymer

How many amino acids

20

Where are amino acids polymerised?

Ribosome

The process of polymerisation of amino acids

1. tRNA brings amino acid

2. Hydroxyl group is broken off hydroxl group of one amino acid

3. Forms a covalent bond with a hydrogen from the amino group of another amino acid forming a water molecule

4. Amino acid residue forms peptide bond

Covalent bond

share electrons

Primary structure

Sequence of amino acids in a protein

e.g. Glu-Lys-Cys-Ser

Secondary structure

3D form of local segments of a polypeptide chain resulting from the interactions between amino acids

How is the secondary structure formed

It is formed when a polypeptide chain folds and coils by forming hydrogen bonds between amino acids, when this occurs beta-pleated sheets and helices are formed.

Teritary structure

Describes overall protein shape

How is the teritary structure formed

By forming interactions and bonds in the secondary structure between R-groups of amino acids

Quaternary structure

It is made of more than a single polypeptide chain

RNA

Single-stranded nucleic acids

Nucleotides contain

Sugar, phosphate and nitrogenous base

Nucleotides can only be added to….

3’ end

Introns

Regions of a eukaryotic gene that are removed from transcript before translation (non-coding)

Exons

Transcribed regions of a gene which are also translated (coding segments)

Are introns or exons bigger?

Introns

Transcription

1. RNA polymerase enzyme run along the template strand in a 3’ to 5’ direction unwinding the DNA and building a complementary strand of mRNA in 5’ to 3’ direction.

2. End of transcription two strands of DNA join back together (template and coding). The premature-mRNA product of transcription remains

RNA processing

1. Introns get cut out

2. Methyl cap is added to 5’ end (CH3)

3. Poly-A-tail is added to 3’ end (AAA adenine)

4. Pre-mRNA becomes mRNA

Translation

1. mRNA leaves nucleus and enters ribosme 5’ end first

2. Amino acids are carried to the ribosome by specific tRNA molecules each with an anticodon on the end

3. Anticodon of the tRNA pairs with complementray codon in the mRNA

4. Amino acids carried to ribosome are linked by peptide bonds

Degenerate

Several amino acids code for a codon

Codon

Sequence of three nucleotides

Alternative splicing

Exons from the gene are joined and introns are removed. This allows a single gene to code for more than one protein.