Membrane Protein and Composition patr 2 Flashcards
What are proteins and why is it difficult to incorporate into lipid core of membrane ?
Polypeptides and because of the hydrophobic effect
What does Patterns of Hydrophobiicty help determine folding of proteins in water ?
Yess helps determine folding f proteins inw ater
What about alpha helixes ?
A αhelix is generated when a single polypeptide chain twists around on itself to form a rigid cylinder. A H bond forms between every fourth peptide bond, linking the C=0 of one peptide bond to the N-H of another. Note that all of the NH groups point up whereas the C=O point down. This gives polarity to the helix
Why are Alpha helixes abundant in proteins ?
αhelix are abundant in proteins located in the cell membrane because the hydrophilic polypeptide backbone is H-bonded to itself in the αhelix and shielded from the hydrophobic lipid membrane.
What about beta sheets ?
In the βsheet adjacent peptide chains run in opposite (parallel) directions. The H bond forms between peptides in different strands.
Name the ways proteins attaches to the cell membranes ?
- Single Alpha helixes
- Multiple Alpha Helix
- Rolled up B sheet
- ## Peripheral indirectly
How can integral membranes proteins be extracted ?
Dissolving the membrane in detergents.
proteins in cytoskeleton of the cells
The membrane proteins might be bound to the underlying cytoskeleton of the cells.
This gives membrane mechanical strength and to the cells specific shapes
Red blood cells proteins
The Red blood cells are biconcave and lack of nucleus and organelles. This shape results from the interaction of the plasma membrane proteins with the underlying cytoskeleton, which consists of a meshwork of the filamentous protein spectrin.
What do Detergents do ?
They disrupt the lipid bilayer and brings the proteins into solutions as proteins lipids detergent complexes .
Phospholipids in the membrane are also solubilised by detergents .
What is diffusion ?
Process of passive transport in which molecules move from one area of high concentration to an area of lower concentration
What is the strategy for transport for molecules which cannot pass through the lipid bilayer ?
Diffusion
What are some of the transport proteins which can transfer polar molecules (ions, sugars, amino acids, nucleotides) across the cell membrane.?
Transporter and Channel Proteins
What are some of the factors which might affect diffusion ?
Temperature
Concentration gradient
Mass of molecules
What does the Lipid Bilayer restrict ?
Passage of Polar molecules
What does the barrier function as ?
Allow cells to maintain concentration of solutes in its cytosol that differ from those in extracellular fluids and each of the intracellular membrane enclosed compartments
Do this to help ingest nutrients ,extret waster products and regulate intracellular ions concentrations
What are Transporters ?
Bind to specific solute to bind the specific solute to be transported and undergo a conformational change .
Alternatively expose solute binding sites one side of the membrane and then to the other to transfer solute across it
Chanells however, interact with the solute to be transported much more weakley forming continuous pores that extend across lipid bilayer
Passive Transport
Passive transport of a
•neutral solute (simplest case) •down concentration gradient •
by a transporter(or transport protein) = facilitated diffusion
No energy is required
Molecules go downhill from high to low
Not everything enters the cells through passive transport .
Even when the equilibrium is reached the particles do not stop moving across the cell membrane .
Energy is required to transport matter against potential gradient
different forms of energy may be harnessed for active transport of solutes
What controls the movement of molecules across membrane ?
Concentration gradient and electrical field gradient may both control spontaneous ion movement across a membrane
Concentration and electrical gradients can also work in opposite directions
What do Couple carriers do ?
Involve either the simultaneous transfer of a second solute in the same direction perform by symporter or known as co .
symport and anti port
