Membrane Protein and Composition patr 2

Question 1

What are proteins and why is it difficult to incorporate into lipid core of membrane ?

Answer 1

Polypeptides and because of the hydrophobic effect

Question 2

What does Patterns of Hydrophobiicty help determine folding of proteins in water ?

Answer 2

Yess helps determine folding f proteins inw ater

Question 3

What about alpha helixes ?

Answer 3

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

Question 4

Why are Alpha helixes abundant in proteins ?

Answer 4

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.

Question 5

What about beta sheets ?

Answer 5

In the βsheet adjacent peptide chains run in opposite (parallel) directions. The H bond forms between peptides in different strands.

Question 6

Name the ways proteins attaches to the cell membranes ?

Answer 6

• Single Alpha helixes
• Multiple Alpha Helix
• Rolled up B sheet
• ## Peripheral indirectly

Question 7

How can integral membranes proteins be extracted ?

Answer 7

Dissolving the membrane in detergents.

Question 8

proteins in cytoskeleton of the cells

Answer 8

The membrane proteins might be bound to the underlying cytoskeleton of the cells.

This gives membrane mechanical strength and to the cells specific shapes

Question 9

Red blood cells proteins

Answer 9

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.

Question 10

What do Detergents do ?

Answer 10

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 .

Question 11

What is diffusion ?

Answer 11

Process of passive transport in which molecules move from one area of high concentration to an area of lower concentration

Question 12

What is the strategy for transport for molecules which cannot pass through the lipid bilayer ?

Answer 12

Diffusion

Question 13

What are some of the transport proteins which can transfer polar molecules (ions, sugars, amino acids, nucleotides) across the cell membrane.?

Answer 13

Transporter and Channel Proteins

Question 14

What are some of the factors which might affect diffusion ?

Answer 14

Temperature
Concentration gradient
Mass of molecules

Question 15

What does the Lipid Bilayer restrict ?

Answer 15

Passage of Polar molecules

Question 16

What does the barrier function as ?

Answer 16

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

Question 17

What are Transporters ?

Answer 17

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

Question 18

Passive Transport

Answer 18

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

Question 19

What controls the movement of molecules across membrane ?

Answer 19

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

Question 20

What do Couple carriers do ?

Answer 20

Involve either the simultaneous transfer of a second solute in the same direction perform by symporter or known as co .

symport and anti port