BIOL 107 Part B - Cell Membranes and Transport (Questions))

Why are cells small?

1. Surface area to volume ratio must be small enough to import nutrients and export waste products

2. Cells specialize to perform certain functions

Humans have ___ types of cells.

200

What is the structure of the plasma membrane?

Phospholipid bilayer, with the hydrophobic tails of the phospholipids pushing together and the hydrophilic heads facing water outwards

Why is the phospholipid bilayer flexible?

The phospholipids are not actually attached to one another, only held together by hydrophobic interactions

Why do phospholipid bilayers form spontaneously?

It is energetically favourable for a sealed compartment to be formed in order to ensure no hydrophobic edges are exposed to water

Describe the fluidity of plasma membranes.

Remains moderately fluid until it reaches a temperature in which it solidifies

How does the saturation of the hydrocarbon tails of phospholipid bilayers affect their fluidity?

Phospholipids with unsaturated tails enhance membrane fluidity because their kinked tails prevent proper packing, while phospholipids with saturated tails pack together to decrease membrane fluidity

How does cholesterol moderate fluidity of the plasma membrane?

Prevents leaking at moderate temperatures by by reducing phospholipid movement (reducing fluidity); prevents solidification at low temperatures by disrupting the regular packing of phospholipids

Peripheral membrane proteins (are/are not) embedded into the phospholipid bilayer.

Are not

Integral membrane proteins have a hydrophobic region made of ___ coiled into ___ secondary structure.

Stretches of nonpolar amino acids, alpha helix

What are the functions of transmembrane proteins?

Transport, enzymatic activity, signal transduction, glycoproteins as identification tags for cell-cell recognition, intercellular joining, attachment to the cytoskeleton and extracellular matrix

What are the characteristics of animal cell plasma membranes?

Contain phospholipids, membrane proteins, cholesterols, membrane carbohydrates

H, A, and B antigens in human blood cells are ___.

Glycolipids

D antigens in human blood cells are ___.

Integral membrane proteins

Patients can receive blood transfusions from blood types that ___.

Do not contain antigens they don’t already have

What are the characteristics of plant cell plasma membranes?

Have a cell wall for protection, contain just phospholipids and membrane proteins

What are the characteristics of prokaryote cell plasma membranes?

Have a cell wall for protection, contain just phospholipids and membrane proteins

Cells want to increase membrane surface area because ___.

More membrane means more membrane proteins to be able to carry out essential functions

What are the ways in which cells increase membrane surface area?

Outfoldings, infoldings, internal membranes