Transcript Introduction to Cell Structure and Function.

Introduction to Cell
Structure and Function
Lecture By Dr. Dirk M. Lang
Dept. of Human Biology
Faculty of Health Sciences
University of Cape Town
South Africa
Phone: ++27-21-406 6419
E-Mail: [email protected]
08/2007
Cellular
Structures
and Their
Functions
are
Complex…
I. Definition of a Cell:
• Basic structural and functional units
of life
• The smallest units that display the
characteristics of life, i.e.
reproduction, metabolism, response
to stimuli
Prototypes of Cells:
II. Cell Structure Detail
III. General Subdivisions of a Cell
A. Nucleus
(regulatory
center of the
cell)
C. Cytoplasm
(everything
between the
plasma membrane
and the nuclear
compartment)
B. Plasma
Membrane
(selectively
permeable
boundary
between the
cell and the
environment)
Organelles are individual
compartments in the cytoplasm
The Nucleus
A.
D.
(Ribosome
synthesis)
C.
(Chromosomes with
DNA that regulate all
cell activities)
(Phospholipid bilayer
with nuclear pores =
membrane barrier to
control what
enters/leaves nucleus)
B.
(Proteins
embedded in the
nuclear
envelope; most
substances must
pass through
the pores to
enter or leave
the nucleus)
The Plasma Membrane
Structure: phospholipd bilayer with proteins
embedded in and attached to the inner
(intracellular) and outer (extracellular) surfaces
The Plasma Membrane
Most
substances
must use
proteins to
gain access
to cell;
proteins are
selective
Lipids
move
freely
through
bilayer
Function: “selectively permeable” barrier; main
responsibility is to ensure that the composition of
extracellular fluid is not the same as the
composition of the intracellular fluid
The Plasma Membrane
Serves as
attachment
site for the
cytoskeleton
Function (continued): phospholipids are liquid at
body temperature so membrane functions as a
“fluid mosaic”
The Plasma Membrane
(continued)
Glycocalyx: protein and carbohydrate
coat covering the extracellular surface of
the plasma membrane
•
•
Allows attachment to other cells
Allows the cell to interact with the
environment
The Cytoplasm
Cytoskeleton:
network of
protein fibers
extending
throughout
the cytoplasm
Flagellum
Cytoplasm: water
with dissolved
salts, nutrients,
enzymes; site of
many chemical
reactions
Organelles:
“little
organs”found
throughout
cytoplasm
Functions of the Cytoskeleton
• Provides
support and
structure
for the cell
• Very
dynamic,
always
remodelled
• Important in
cellular
reproduction
Functions of the
Cytoskeleton (continued)
Important in cell
movement:
•
Cilia - short and
numerous
• Flagella - long,
single
(Moveable portions of
the cytoskeleton that
project from the
surface of the cell)
Organelles
•
Separate compartments within the
cytoplasm formed by membranes
•
Each organelle has a specific
function in the cell
The Mitochondrion
“Thread
granule”;
contained
by double
membrane
Function of Mitochondrion
Major source of cell’s energy:
•
Energy is taken from sugar, stored in
molecule called ATP (adenosine
triphosphate)
•
Requires oxygen to make this exchange
(aerobic metabolism)
The Ribosomes
Sites of protein synthesis; function in the cytoplasm,
but are assembled in the nucleolus
Free: unbound
Bound:
attached to the
endoplasmic
reticulum;
produce
proteins for
export and for
the plasma
membrane
in the
cytoplasm;
produce
proteins for
use inside the
cell
The Cytomembrane System
•
System of tubes and chambers formed by
membranes
•
Extensively distributed throughout the fluid
cytoplasm
•
Involved in synthesis, modification, processing
and packaging of cellular lipids and proteins
1. Endoplasmic Reticulum (ER)
“within the
cytoplasm
network”,
system of
tubes and
sacs formed
by
membranes
Endoplasmic Reticulum (ER)
a) Rough: with bound ribosomes
• modifies proteins produced by the ribosomes
b) Smooth: without bound ribosomes
• doesn’t modify proteins
• functions in lipid synthesis, drug
detoxification, carbohydrate metabolism
2. The Golgi Apparatus
A series of flattened sacs formed by
membranes, functions in final lipid and protein
processing prior to use by the cell
The Golgi Apparatus
•
Proteins get shuttled from the ER to one
end of the Golgi
•
In each sac, different modifications are
made (proteins get individually tailored)
•
Proteins get sorted and shipped off to
their destination (like the post office of
the cell)
3. Vesicles
Small membrane-bound structures that
transport proteins and lipids around the
cell
•
Little transporters that shuttle their contents
from one organelle to another
•
When they contact the appropriate organelle,
they fuse with its outer membrane and release
their contents inside
•
Same for plasma membrane, allowing the
export of materials from the cell (exocytosis)
4. The Lysosome
Membrane-bound vesicle that contains
digestive enzymes or toxic chemicals
•
Merges with vesicles containing food particles,
invading bacteria
•
Harsh chemicals and enzymes degrade the
food or bacteria, without harming rest of cell
Interaction of
ER and Golgi:
Vesicle
trafficking