01:377:213 Lecture Notes - Lecture 19: Lipid Bilayer, Extracellular Fluid, Cell Membrane
I. Intro
A. The cell theory has three basic concepts: (fundamental unit for all living things)
1. Cells are the structural “building blocks” of all plants and animals
2. Cells are produced by the division of preexisting cells
3. Cells are the smallest structural units that perform all vital functions
B. Trillions of cells in body
1. Millions/billions of cells work at once to perform function
C. Responding to changes in environment
D. There are two types of cells in the body
1. Sex cells
a) Also called germ cells or reproductive cells
b) Sperm of males
c) Oocytes of females
2. Somatic cells
a) All the other cells in the body that are not sex cells
II. Cellular Anatomy
1. Each cell is like a person and we can only describe it in general
B. The Plasma Membrane (cell membrane or plasmalema)
1. Extremely thin, 6-10nm
2. Four major functions
a) Physical isolation
(1) Lipid bilayer creates physical barrier from extracellular
fluid
b) Regulation of exchange with the environment
(1) Some substances go in and out like ions, nutrients, waste
and secretory products
c) Sensitivity
(1) First part of cell affected by change in extracellular fluid
(2) Has receptors for cell to recognize and respond to
molecules in environment
(3) Any change affects all cellular activities in cell
d) Cell-to-cell communication, adhesion, and structural support
(1) Specialized connections between other membranes allow
cells to attach to each other to give tissues a stable structure
3. Components of the Plasma Membrane
(1) Chemicals vary upon cells functions
b) Phospholipids
c) Proteins
d) Glycolipids
e) Sterols like cholesterol
4. Phospholipid bilayer
a) Phospholipid molecules are arranged with heads on outside and
tails inside
b) Dissolved ions and water soluble compounds cannot cross tails
because they’re hydrophobic
c) This isolation is important because the composition of cell is very
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