Membrane & Fibrous Proteins Flashcards
Where can a membrane protein be located?
Outside, through or on the inner-surface of the cell
What are the two main functions of membrane protein in tissues?
- Critical to give your cells identity
- Moving nutrients and waste in/out of the cell
Where are peripheral membrane proteins found?
In and out of the cell (NOT THROUGH)
Name the 3 ways peripheral membrane proteins bind to the membrane.
1) Lipid tail, which inserts into the membrane
2) Protein-protein interactions (anchored to membrane)
3) Electrostatic interactions with phospholipid head group
Where are integral membrane proteins located?
INSERT completely (partly inside and outside the cell)
What are the functions of integral membrane proteins?
They can shut down/turn on the expression of a gene
What do you need to traverse the lipid bilayer?
A transmembrane domain that traverses the lipid bilayer
What are TMDs made up of? (Transmembrane domain)
JUST hydrophobic amino acids
What is the Kyte-Doolittle plot’s function?
To plot hydrophilicity as a function of residue number.
To figure out the function, where it acts
What does above 0 mean? And below?
Above: hydrophobic (TMD)
Below: hydrophilic
Are fibrous proteins soluble in water?
They are non-soluble
What is the function of a-keratin?
Tough, rigid (nails, horns)
What is the structure of a-keratin?
Cross-linked a-helices
What is the function of collagen?
Tensile strength (tendons, cartilage)
What is the structure of collagen?
Cross-linked triple helices
What is the structure of silk fibroin?
Non-covalently held B-sheets and van der waals
What is the function of silk fibroin?
Soft, flexible (non-stretchy)
What gives a-keratin its great strength?
Covalent disulfide bonds
Describe the 4 steps it takes to become a-keratin.
1) Alpha helix (long)
2) Two alpha-helices intertwine
3) Binds with another a-helix intertwined in a head to tail fashion (protofilament)
4) + Intertwinning and disulfide bridges (protofibril)
The single a-keratin subunit is ____ handed.
Right
Two subunits of a-keratin will form a ____ handed a-helix.
Left
A-keratin is rich in ____? What does that explain?
Non-polar amino acids (hydrophobic), explains why it wraps around
What is collagen important for?
Connective tissue (tendons, cartilage, bones)
What is a collagen chain rich in?
Glycine and Proline
One collagen chain is _____ handed.
Left
Three intertwined collagen chains are ____ handed.
Right
Name a characteristic of collagen’s triple helix bond.
Higher tensile strength than a steel wire of equal cross section
What force holds collagen together?
Hydrogen bonds
A lack of what can affect collagen strength? Why?
Vitamin C, less hydroxy proline, less strength
What makes aging skin rough?
The number of crosslinks in your skin increases as you age
Explain how fibrils are laid in the tendon, cornea, and skin.
Tendon (linear)
Cornea (criss-cross)
Skin (random)
What influences the strength of collagen fibrils?
The way fibres are laid down.
What do proteins sometimes require to function?
Cofactor
Name 2 protein cofactor groups.
Prosthetic groups and metals
What are prosthetic cofactor groups made of?
Organic compounds
Name 4 ways protein structure can be denatured.
1) Heat/Cold
2) Extremes in pH
3) Organic solvents
4) Detergents
How would you transform straight hair into curly?
Reducing agent that cleaves the disulfide bonds between the a-keratin. Curler mechanically changes the structure, oxidizing agent promotes the formation of a set of disulfide bonds
CURLY HAIR HAS MORE DISULFIDE BONDS
Is a-keratin made of a-helices? Is collagen?
a-keratin: yes
collagen: NO, a chains
What do TMDs require for solubility in aqueous solutions? Why?
- Require detergents or organic solvents
- Because they are hydrophobic
