Download cells: The living units

Chapter 3a
Overview of the
cell, and structure
of the plasma
membrane

http://www.youtube.com/watch?v=gFuEo2cc
TPA



The cell is the basic structural and
functional unit of life
Amoebas are
single-cellular
Humans, dogs, trees are
multi-cellular


Human body
has 50 to 100
Trillion cells
200 types


First to observe cells
Robert Hooke in 1600s
(1665)
(he observed cork)
–
Anton van Leeuwenhoek observes
single cell organisms in pond water
1674
1838 Matthias Schleiden
concludes all plants are made
up of cells
1839 Theodor Schwann
concludes all animals are
made up of cells

1855
Rudolph
Virchow
proposed
all cells
come
from
existing
cells

These discoveries were very
important, before ‘cell theory’
which includes all these
discoveries, people accepted the
theory of spontaneous generation
Four
concepts
that are known
as the
Cell Theory


1. A cell is the basic structural and
functional unit of life.
2. The activity of an organism
depends on the individual and
collective activities of its cells


3. Principle of complementarity,
(its function depends on its form)
4. Continuity of life has a cellular
basis






Cubelike
Tilelike
Disk-shaped
Spherical
Branching
Cylindrical
Figure 3.2


All cells are composed chiefly of
carbon, hydrogen, nitrogen,
oxygen, and trace amounts of
several other elements
All cells have the same basic parts
and some common functions

Human cells have 3 Main Parts

1. Plasma membrane


2. Cytoplasm


Outer boundary of the cell
Intracellular fluid packed with organelles
3. Nucleus

Controls cellular activities


Separates intracellular fluids from
extracellular fluids
Plays a dynamic role in cellular
activity


Thin, Double layer (bilayer) of
lipids with imbedded, dispersed
proteins
Bilayer consists of phospholipids,
cholesterol, and glycolipids
Phospholipids have hydrophobic
and hydrophilic bipoles
 Each phospholipid molecule has a
polar ‘head’ that is charged and is
hydrophilic
 Each phospholipid molecule has a
nonpolar ‘tail’ made of 2 fatty acid
chains and is hydrophobic

Hydro = water
 Philic = loving
 Phobia = hating
 Polar heads are attracted to water
so they lie on the inner and outer
surfaces of the membrane
 Nonpolar tails avoid water and line
up in the center of the membrane




Plasma membranes also have
proteins, glycolipids, glycoproteins,
and cholesterol
20% of all membrane lipid is
cholesterol
Cells recognize one another by
markers made out of glycoproteins
called Glycocalyx


Small extensions of the
plasma membrane that
project from a free, or
exposed cell surface
Increases surface area

Most often found on the surface of
cells that function in absorption like
intestinal and kidney cells
Next time!
Study guide check
pages 53 – 55 after
next lecture.

http://video.google.com/videoplay?docid=7204725871954420481