Proteins Flashcards
How many genetically amino acids are there?
20
What are the 4 basic categories of natural amino acids?
Acidic, basic, uncharged polar and non-polar
What are examples of acidic proteins?
Aspartic acid and glutamic acid (AG)
What are examples of basic proteins?
Lysine, arginine and histidine (LAH)
What are examples of uncharged polar proteins?
Asparagine, glutamine, serine, threonine and tyrosine (AGSTT)
What are examples of non-polar proteins?
Glycine, alanine, valine, leucine, isoleucine, proline, phenylalanine, methionine, tryptophan and cysteine (GAVLIPPMTC)
How to proteins function?
By interacting with other biomolecules
What are the functions of protein?
Movement, protection, transport, enzymes, receptors, structural, storage, hormones and control of gene expression
What protein groups can be charged at biological pH?
Alpha-amino group, alpha-carboxyl group and R groups of some amino acid residues
What is the basic structure of proteins?
Unbranched linear polymer of L-amino acid residues linked by peptide bonds forming a polypeptide
What is the primary structure of proteins?
The sequence of amino acids in a polypeptide chain which is determined by gene encoding
What is the function of primary structured proteins?
They allow versatility in protein structure and function
What is the secondary structure of proteins?
The spatial arrangement of amino acid residues that are near each other in the linear sequence
What is an amino acid residue?
What remains of each amino acid after water is removed from the peptide
What are the 2 examples of secondary protein structures?
Alpha helices and beta sheets
What are alpha helices?
Telephone cord shape held in place by H bonds between the N-H group and the C=O group of each amino acid in the turn of the helix
What are beta sheets?
Pleated structure held together by H bonds between amide groups of linear polypeptide chains
What is the tertiary structure of proteins?
The spatial arrangement of amino acid residues that are far apart in the linear chain
What does the tertiary structure depend on?
Van der Waals, ionic interactions, H bonding, disulphide bridges and hydrophobic interactions
What is the quaternary structure of proteins?
The spatial arrangement of individual polypeptide chains in a multi-subunit protein
What are the properties of the quaternary structure?
Contains more than one polypeptide, can be fibrous or globular
What causes a loss in 3D structure?
Denaturation
What is denaturation?
Loss of 3D structure due to acid, heat or solvents. The primary structure is unaffected, while the secondary and tertiary structures are
What does denaturation cause?
A decrease in solubility and a loss of function
What is renaturation?
The gain of 3D structure
What is the structure of fibrous proteins?
Beta-pleared sheet due to the interaction of many individual protein chains
What determines the function of fibrous proteins?
It’s structure
Where do fibrous proteins occur?
Bone matrices, muscle fibres, tendons and connective tissue
What are examples of fibrous proteins?
Collagen, eleastins, keratins and fibrinogen
What is the structure of globular proteins?
Clumped into a ball
What are the functions of globular proteins?
Enzymes, messengers (hormones), transporters, amino acid storage and structural function
What is an example of globular proteins?
Haemoglobin
What are the 3 different types of modified proteins?
Glycoproteins, lipoproteins and metalloproteins
What are glycoproteins?
They are carbohydrates that have joined to proteins which are formed by post-trasnlational modification. They are important integral membrane proteins and play a role in cell-cell interactions
What are lipoproteins?
They are lipids joined to proteins. They transport water-insoluble fats in the blood e.g. HDL and LDL
What are metalloproteins?
They are metals joined to proteins. They are used for enzymes, storage, signalling and transport
What are examples of protein disorders?
Sickle cell anaemia, FH and scurvy
What cases sickle cell anaemia?
One amino acid change
What causes FH?
Decrease in LDL receptors
What causes scurvy?
Weakened collagen
What is an alpha-keto-acid?
The C skeleton of an alpha-amino-acid
What is the difference between an alpha-keto-acid and an alpha-amino acid?
Alpha-keto-acids have been deaminated, although they have the same structure. The H and amino groups have been removed and replaced by an O group. The carbonyl and R groups are still there
