View
270
Download
0
Category
Tags:
Preview:
Citation preview
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
Recommended