Protein Structure And Function Flashcards
Function of amino acids
Make up proteins
Amino acid functional groups
Carboxylic acid
Amine (nh2)
What is a zwitterion
Possesses both positive and negative negative charges simultaneously creating a molecule which overall bears no net charge
What happens to the carboxylic acid of the amino acid with increasing ph
Deprotonated
NH3+ AND COO-
What is the isoelectric point
Point at which amino acid has no net charge
Enantiomers
Non superimposable mirror images
What are the 4 R groups of amino acids
Hydrophobic
Hydrophilic
Acidic
Basic
Bonds between peptides and proteins
Amide/peptide bonds between amino acid monomers in a condensation reaction
What are the levels of protein structure
Primary- amino acid sequence
Secondary- 3D structure formed by hydrogen bonds
Tertiary- 3D structure formed by non covalent interactions and disulphide bonds
Quaternary- association of multiple polypeptide subunits
What are the ends of the amino acids in a polypeptide chain called
N- terminus to C-terminus
Types of secondary structures
Alpha helix
Beta pleated sheets
Explain beta pleated sheets
Hydrogen bonds form between peptide chains next to each other in the sheet
Parallel= hydrogen bonds to each other run in the same direction
Anti parallel = peptide chain run in opposite directions
Explain beta pleated sheets
Hydrogen bonds form between peptide chains next to each other in the sheet
Parallel= hydrogen bonds to each other run in the same direction
Anti parallel = peptide chain run in opposite directions
Tertiary structure
Folded structure of polypeptide chain to form a 3D shape with noncovalent and covalent interactions
Non covalent= ionic, hydrogen, hydrophobic and London
Covalent= disulphide
Describe disulphide bonds
Covalent single bonds between 2 cysteines
INTRAmolecular= within a single polypeptide chain
INTERmolecular= between different polypeptide chains
Quaternary structure
Two or more polypeptides with non covalent interactions
Each polypeptide is called a subunit and the protein is called oligomeric
List the 7 protein functions
1) catalysis= enzyme
2) genomic= dna associated proteins (histones) that regulate chromosome structure and gene expression
3) defence= proteins(antibodies) to fight infection
4) movement= contractile proteins (actin and myosin) for muscle contraction
5) structure= proteins which define cell shape and support tissues (collagen and elastin)
6) transport= proteins which carry molecules around body (haemoglobin) and membrane proteins that control transport in and out of cell
7) signalling= hormones which convey signals between cells and receptors which receive signals
Protein + what binds? + where does it bind?
Enzyme + substrate + active site
Receptors + ligand + binding site
Antibody + antigen + binding site
What are enzymes
Catalyse chemical reactions
Lowers activation barrier
Role of histone genomic protein
Condense nuclear dna into chromatin
Positive charge on histones neutralises the negative charge on dna which enables it to pack closely together to fit into the nucleus
Structure of antibodies
Quaternary structure held by disulphide bonds
Antigen binding site is variable between different antibodies
Role of movement proteins (actin and myosin)
Head groups on myosin use energy from atp hydrolysis to form and break bonds with actin filaments
Myosin slide alongs actin filament= muscle contraction
Role of structural proteins (collagen)
Long fibre of insoluble protein
Each strand is a alpha helix and wind together to form a fibre
Cross links with lysine side chains= ‘super secondary structure’
Sickle cell anaemia
Mutation in the beta subunits
Causes haemoglobin to aggregate
Sickle shape
Block narrow blood vessels and interfere with blood flow
