Cell Membrane

Question 1

What are the functions of a cell membrane?

Answer 1

Physical isolation:
-Physical barrier separating ICF and ECF (phospholipid bilayer)
-Separates cell from environment

Regulation of exchange with the environment
-Controls entry, elimination and release

Communication between the cell and its environment
-Contain proteins that allow for responding or interacting with external environment

Structural support
-Proteins in the membrane are used to make cell-to-cell connections (tissue) and to anchor the cytoskeleton

Question 2

What is the composition of a cell membrane

Answer 2

Lipids:
-Phospholipids are the bulk of the lipid component of cell membrane
-Sphingolipids forms lipid rafts
-Cholesterol is positioned between phospholipid heads to add viscosity and help make membrane impermeable to small water-soluble molecules

Proteins:
-Integral proteins (transmembrane and lipid anchored) have a wide variety of functions
-Peripheral proteins attach to integral proteins to participate in cell signaling and attachment of cytoskeleton

Carbohydrates:
-Glycoproteins and glycolipids form protective coat (glycocalyx) and participate in cell to cell regocnition/interaction

Question 3

What are the three types of lipids found in the cell membrane?

Answer 3

-Phospholipid: Major lipid
-Sphingolipids: Lipid rafts
-Cholesterol: Increases viscosity and decreases permeability

Question 4

What are the two types of cell membrane proteins?

Answer 4

-Integral proteins
-Peripheral proteins

Question 5

What do integral proteins include and what are their roles?

Answer 5

Transmembrane proteins
Lipid anchored proteins (commonly associated with sphingolipids)
-Directly to fatty acid
-External GPI anchor: sugar-phosphate chain (glycosylphosphatidylinositol)

Roles:
-Membrane receptors
-Cell adhesion molecules
-Transmembrane movement (channels, carriers, pores, pumps)
-Enzymes
-Mediators of intracellular signaling

Question 6

What do peripheral proteins include and what are their roles?

Answer 6

Noncovalently bond to integral proteins
Loosely attached to phospholipid head

Roles:
-Participate in intracellular signaling
-Form submembranous cytoskeleton

Question 7

What are the two types of body compartments?

Answer 7

-Anatomical: The body cavities
-Functional: Body fluid compartments

Question 8

What are the cavaties included in the anatomical body compartments and what do they include?

Answer 8

Cranial cavity (skull):
-Brain (primary control center)

Thoracic cavity:
-bounded by the spine and ribs
-diaphragm forms the floor
-Contains heart that is enclosed by pericardial sac
-Contains two lungs enclosed in separate pleural sacs

Abdominopelvic cavity:
-peritoneum lines abdomen and surrounds stomach, intestines, liver, pancreas, gallbladder and spleen
-Kidneys lie outside abdominal cavity
-Pelvis contains reproductive organs, urinary bladder and terminal portion of large intestine

Question 9

What two fluids compose the functional body compartments?

Answer 9

Extracellular fluid (ECF)
-Lies outside of the cells
-Further subdivides into blood plasma (ECF inside blood vessels) and interstitial fluids (surrounds most cells)

Intracellular fluids (ICF)
-Fluid within cells

Question 10

What are the 3 structure arrangements of phospholipids?

Answer 10

Phospholipid bilayer:
-Forms a sheet
Micelles:
-Droplets of phospholipids
-Important in digestion and absorption of fats in digestive tract
Liposomes:
-Aqueous center
-Used as a medium to deliver drugs and cosmetics

Question 11

How much fluid is in each body compartment?

Answer 11

60% of the body is water

ICF:
-Contains most amount of fluid in the body (2/3)

ECF:
-Contains 1/3 of fluid in the body
-75% in interstitial fluid
-25% in plasma