Unit 2 Cell Membrane

What does the plasma membrane maintain?

Homeostasis

How does the plasma membrane maintain an internal balance within the cell?

By controlling what enters and exits the cell

What can generally enter the cell easily?

Small and nonpolar molecules

What are the components of the cell membrane?

Phosphate group, proteins, carbohydrates, and cholesterol

What does the plasma membrane separate?

The internal cell environment from the external environment

What is another term for the external environment of the cell?

Extracellular matrix

What is the plasma membrane comprised primarily of?

Phospholipids

What are phospholipids as a result of their hydrophilic head and hydrophobic tail?

Amphipathic

What does selective permeability refer to?

The ability of membranes to regulate the substances that enter and exit

How are the hydrophilic heads of phospholipids oriented?

Towards aqueous environments

How are the hydrophobic tails of phospholipids oriented?

Inwards and thus away from aqueous environments

What are the two major categories of proteins in the plasma membrane?

Integral and peripheral proteins

What are integral proteins?

Proteins that are embedded into the lipid bilayer

What may integral proteins also be referred to as?

Transmembrane proteins

What term describes the nature of integral proteins towards water?

Amphipathic

What are peripheral proteins?

Proteins that are not embedded into the lipid bilayer

What type of protein are peripheral proteins considered?

Surface protein

How are peripheral proteins bonded?

Loosely to the surface

What two functions of proteins in the cell membrane are important for cellular communication?

Signal transduction and cell-to-cell recognition

Peripheral proteins can function in enzymatic activity in regards to the cell membrane.

True

What kind of proteins are responsible for the transport function of the cell membrane?

Transport proteins

What are membrane carbohydrates important for?

Cell-to-cell recognition, cell sorting, and cell organization in tissue and organ development 

What are glycolipids?

Carbohydrates bonded to lipids 

What are glycoproteins?

Carbohydrates bonded to proteins

What of membrane carbohydrates are most abundant?

Glycoproteins

How do carbohydrates attach to proteins?

By attaching to the R-group of an amino acid on a protein

What is cholesterol?

Sterol found between phospholipid molecules

How is the polarity of cholesterol described?

Nonpolar

What is the structure of cholesterol?

4 fused rings

What does cholesterol help stabilize?

Membrane fluidity

What does cholesterol maintain membrane fluidity at?

High and low temperatures

What does cholesterol do at high temperatures?

Reduce movement

Why does cholesterol reduce movement at high temperatures?

Because it gets tangled with fatty acid chains

What does cholesterol do at low temperatures?

Reduce tight packing of phospholipids

What is the fluid mosaic model?

A model that describes the structure of cell membranes

What does the term fluid refer to in regards to the cell membrane?

How the cell membrane can move and shift

Why can the cell membrane move and shift?

It’s held together by weak hydrophobic interactions

How do phospholipids move?

Laterally

What distance do most phospholipids move on average per second?

2 nanometers

What do some large proteins do within the cell membrane?

Drift among the phospholipids

What affects fluidity?

Temperature

What happens to the cell membrane as temperature cools?

Gets more solid and phospholipids become more tightly packed

What, in addition to cholesterol, can help maintain fluidity at low temperatures?

Unsaturated hydrocarbon tails

Why do unsaturated hydrocarbon tails help maintain fluidity at low temperatures?

Kinked tails prevent tight packing of phospholipids

What is the mosaic of the fluid mosaic model comprised of?

Many macromolecules