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DNAnucleusdouble helixcytoplasmBase pairscopygeneamino acidproteinA,G,C,TRibosomeW
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Learning Outcome
• Protein folding • Explain how one strand of mRNA can give
rise to many proteins by ….– Pre-transplational modificayion (process of
alternative RNA splicing)– Post-translational modification (cutting, combining
polypeptide chains, addition of groups)
Why is shape important?
Protein shape and folding .....• A string of amino acids (polypeptide chain)• Charges on the amino acid causes hydrogen
bonding either folds of coils
Further interactions between side chains (R group on amino acids)
Amino acids linked by peptide bonds to form polypeptide and then chains form 3D shapes of protein
Amino AcidsPolypeptide (chain of aa)
Coils into helix
Beta sheets
Elastin proteins
Fibril proteins
Conjugated proteins
Globular proteinsFibrous proteins
Proteins have a wide variety of structures and shapes resulting in a wide range of functions!
Elastin proteins
Fibril proteins
Conjugated proteins
Globular proteins
Fibrous proteins
Enzymes
AntibodiesHormones & recpetors
Pre
-tra
nsla
tiona
l Mod
ifica
tion
Alte
rnat
ive
splic
ing
However, multiple introns may be spliced differently in different circumstances, for example in different tissues.
3 541 2
1 2 3 5Heart muscle
1 43 5Uterine muscle
Thus one gene can encode more than one protein. The proteins are similar but not identical and may have distinct properties. This is
important in complex organisms
Post-Translation Modification
2 main methods of modification;• Cutting/Cleavage• Addition
Cleavage
Cleavage and Cutting
• Some hormones are produced in an “immature” form, and require further cutting to get the active peptide hormone.
• Pro-hormones are cut into final form by peptidases (enzyme) in the Golgi apparatus.
• Cutting usually occurs at basic amino acids (lysine, arginine)
Inhibin alpha
Inhibin alpha
processing
Molecular Addition
• Modification by adding different groups such as carbohydrate component (eg. glycoprotein for membrane)and phosphate group (eg. regulatory proteins such as p53)
• p53 is a tumour repressor protein – only needs to be active (with a phosphate group) if the cell DNA becomes damaged. •When made for active form is needed phosphorylation occurs which adds a phosphate group. •p53 then can either repair the DNA, or if not able then it causes programmed cell death (apoptosis)
Demonstrate your knowledge by summarising .....
Separating Proteins
• Process called electrophoresis• Separates on charge and size• Useful for analysis/identification and purification
Charge Separation
Size Separation
Analyze
Identify
PurifyMixture of Charged
Molecules
Positive Molecules
Negative Molecules
Electrophoresis
Definition• Electro = Charge + Phorsesis=
Carry
• Electrophoresis = Separation of charged molecules by differences in their rate of migration in an electric field.
Agarose Gel
• Mesh of gel sepeartes size
• Electrical Charge then placed across to separate.
Name 5 functions of proteins;
Name 5 functions of proteins;
• Enzymes• Structural proteins • Hormones• Antibodies• Associations with other chemicals