7.3 TranslationCreation of Protein

Process of Translation

Once the mRNA leaves the nucleus it enters the cytoplasm

Ribosomes form around the mRNA mRNA is fed through the Ribosome

and each codon is matched up to the corresponding tRNA anticodon

The tRNA brings the amino acids, a chain is formed

Occurs in a 5’ – 3’ direction

Transfer RNA (tRNA)

A strand of RNA that has turned into a double loop by base pairing

Each amino acid has a specific tRNA activating enzyme that binds a specific amino acid to the tRNA 20 different tRNA enzymes, each

matching up to a specific amino acid Energy from ATP is needed to

attache the amino acid to the tRNA Contains the anti-codon used to

match up to the mRNA template

Structure of Ribosomes

Ribosomes are made up of rRNA and protein

Two subunits – large and small

Three binding sites for tRNA on the surface of the ribosomes

Two tRNA molecules can bind at the same time to the ribosome.

Also a binding site for mRNA

4 phases of Translation

1. Initiation – translation begins (Start codon)2. Elongation – chain of amino acids grows3. Translocation – newly formed protein is folded 4. Termination – sequence ends (Stop codon)

Polysomes

Sometimes, one strand of mRNA can be translated by more than one ribosome at a time

This results in a polysome

Free and Bound Ribosomes

Free ribosomes – located in cytoplasm Typically synthesize proteins made for

use within the cell itselfBound ribosomes – located on the

RER Synthesize proteins primarily for

secretion or for lysosomes

Draw and label – Peptide bond between 2 amino acids

Proteins

Protein Review

Long chains of amino acidsFunctions:

Blood Muscle, tissue, hair, nails Antibodies Hormones Enzymes

4 Levels of Protein Structure

Primary Structure The number and sequence of amino

acids in a polypeptide Typically anywhere between 50 – 1,000

peptides longSecondary Structure

The regular repeating structures▪ Α-helix▪ Β-pleated sheets

4 Levels of Protein Structure

Tertiary Structure The three dimensional conformation

of a polypeptide Essentially, the 3-dimensional folded

formation of a protein Includes the intramolecular bonds

formed between amino acids Quaternary Structure

How two or more polypeptides link together to form a single protein▪ Prosthetic group – non-polypeptide

structure that some polypeptides contain

▪ Conjugated protein – Proteins with a prosthetic group

Fibrous Proteins

Long, narrow shape Insoluble in waterExamples:

Collagen – structural protein▪ Strengthens bones, tendons,

skin▪ Causes these tissues to create

long tough fibres Myosin – movement

▪ Myosin + actin cause contraction in muscle fibres

▪ Results in muscle movement

Globular Proteins

Round shaped proteins

Typically soluble in water

Examples: Haemoglobin

▪ Binds with oxygen in the bloodstream and transports to tissues

Immunoglobulin▪ Antibodies

Structure of an Amino Acid

Polar and Non-Polar Amino Acids

Polarity based on the R group Hydrophilic R groups = polar Hydrophobic R groups = non-polar

Polarity determines the location and distribution of proteins located in the cell and what function it might have Creation of hydrophilic channels through

the cell membrane Influences specificity of active sites in

enzymes

Polar amino acids are forced to stay on the internal/external of the cell wall

Non polar aminoAcids are able toCross the cell membrane And make channel proteins

Enzyme Active Sites

Polar amino acids act within the active site of an enzyme initiates a chemical reaction

Substrate and enzyme interact to form an activated complex

Weakened state allows for transitions to occur

4 Functions of Proteins

Hormones – Insulin Regulates glucose uptake

in cells Immunoglobulin –

Antibodies Immune response

Enzyme – Amylase Breaks down glucose

Gas transport – Haemoglobin Brings oxygen to the

tissues