Proteins Flashcards
Primary Protein Structure
- linear string of AAs
- determined by nucleic acids/genes encoding this protein
- bonded by peptide bonds (strong)
- determines the structure of mature proteins
Secondary Protein Structure
- first level of folding
- twist upon themsleves to make tertiary structure
- weak non-covalent bonds
- structures include: alpha helixes, Beta sheets, & Beta turns
Tertiary Protein Structure:
- final shape of peptide
- forms mature protein shape
- weak non-covalent bonds
- provides additional stability
- reduces surface area available to solvents
- process of folding usually requires chaperones but can at times occur without assistance
- structures are normally a combination of hydrophobic inside and hydrophillic outside
Two types of Protein Structures
Fibrous & Globular
Proteibn Structure: Fibrous
- polypeptide chains runnig paraellel to eachother, twisted
- H-bonds hold strands together, covalen bonds form between starnds
- structural proteins e.g. in bone/connective tissue (collagen, keratin)
Protein Structure: Fibrous
- polypeptide chains runnig paraellel to eachother, twisted
- H-bonds hold strands together, covalent bonds form between starnds
- structural proteins e.g. in bone/connective tissue (collagen, keratin)
Protein Structure: Globular
- most proteins
- polar outside, non-polar inside
- many a-helix & b-helix sheets
- aurface generally constructed from loops and tight turns
- surface elements can interact with other molecules/proteins
- basis for ezymatic substrate interactions/cell signalling/immune responses
- water on the protein surface stabalises protein due to hydrophillic molecules interacting with the water
Quanternary Protein Structure:
- multiple tertiary structures bonded together to form a protein complex
- not all proteins have quanternary structures, some just tertiary
- weak non-covalent bonds
- each individual polypeptide = a subunit
- provides stability
- brings catalytic sites together
Types of non covalent bonds defining structures include:
- Hydrogen bonds
- Hydrophillic interactions
- Electrostatic Bonds
- Van der Waals forces
Hydrogen Bonds
- most common
- provides structure
Hydrophobic Interactions
- form between non-polar side chains
- minimises hydrophilia
- drives protein folding
Van der waals forces:
- very weak force
- aids in stability
When folded correctly what biological functions to proteins perform
- transport
- catalytic
- scaffold
- regulatory
What happens when misfolding of proteins occur?
- these will often be destroyed by cellular processing
- this processing may not alwyas be able to remove all of this protein which can contribute to disease (e.g. alzheimer’s)
Biomembranes Structure:
- composed of lipd & protein bilayer
- approx. 50% of bilayer is lipid
- lipid provides membrane structure
- protein provides membrane function
- approx. 5nm thick
Types of membrane proteins
- integral proteins
- peripheral proteins
- lipid anchored proteins
Membrane Proteins - Integral Proteins:
- embedded in membrane
- cant be released by changing pH or salt
Membrane Proteins - Peripheral Proteins:
- globular proteins
- electrostatic and H bonds for interactions
Membrane Proteins - Lipid Anchored Proteins
- attached to protein; not embedded
- covalently linked, reversible
- ancor can modulate activtity of protein
