Download Golgi apparatus

Chapter 4
A View of the Cell
Cell History
• The microscope was invented in the 17th
century
• Using a microscope, Robert Hooke
discovered cells in 1665
• All living things are made of cells (cell
theory)
Cell Theory
• All cells come from preexisting cells
• The cell is the basic unit of
organization of organisms.
• All organisms are made up of one or
more cells.
• The light microscope enables us to see the
overall shape and structure of a cell
Image seen by viewer
Eyepiece
Ocular
lens
Objective lens
Specimen
Condenser lens
Light source
• Electron microscopes were invented in the 1950s
• They use a beam of electrons instead of light
• The greater resolving power of electron
microscopes
– allows greater magnification
– reveals cellular details
• Scanning
electron
microscope
(SEM)
• Scanning
electron
micrograph of
cilia
• Transmission
electron
microscope
(TEM)
• Transmission
electron
micrograph of
cilia
Cell sizes vary with their function
• Below is a list of the most common units of
length biologists use (metric)
• Cell size and
shape relate
to function
Cell Types
• There are two kinds of cells: prokaryotic and
eukaryotic
• Prokaryotic cells are small, relatively simple cells
– They do not have a nucleus
• A prokaryotic cell is enclosed by a plasma
membrane and is usually encased in a rigid cell
wall
– The cell wall
may be covered
by a sticky
capsule
Prokaryotic
flagella
Ribosomes
Capsule
Cell wall
– Inside the cell
are its DNA and
other parts
Plasma
membrane
Pili
Nucleoid region
(DNA)
Eukaryotic cells are partitioned into
functional compartments
• All other life forms are made up of one or more
eukaryotic cells
• These are larger and more complex than
prokaryotic cells
• Eukaryotes are distinguished by the presence of a
true nucleus
• An animal cell
Smooth
endoplasmic
reticulum
Nucleus
Rough
endoplasmic
reticulum
Flagellum
Not in most
plant cells
Lysosome
Centriole
Ribosomes
Peroxisome
Microtubule
Cytoskeleton
Intermediate
filament
Microfilament
Golgi
apparatus
Plasma membrane
Mitochondrion
• The plasma membrane controls the cell’s contact
with the environment
• The cytoplasm contains organelles
• Many organelles have membranes as boundaries
– These compartmentalize the interior of the cell
– This allows the cell to carry out a variety of activities
simultaneously
• A plant cell has some structures that an animal
cell lacks:
– Chloroplasts
– A rigid cell wall
Nucleus
Rough
endoplasmic
reticulum
Ribosomes
Smooth
endoplasmic
reticulum
Golgi
apparatus
Microtubule
Not in
animal
cells
Central
vacuole
Intermediate
filament
Chloroplast
Microfilament
Cell wall
Mitochondrion
Peroxisome
Plasma membrane
Cytoskeleton
The nucleus is the cell’s genetic
control center
• The largest organelle is usually the nucleus
• The nucleus is separated from the cytoplasm by
the nuclear envelope
• The nucleus is the cellular control center
– It contains the DNA that directs the cell’s activities
NUCLEUS
Chromatin
Nucleolus
Two membranes
of nuclear
envelope
Pore
ROUGH
ENDOPLASMIC
RETICULUM
Ribosomes
•The endomembrane system is a collection of
membranous organelles
–These organelles manufacture and distribute
cell products
–The endomembrane system divides the cell into
compartments
–Endoplasmic reticulum (ER) is part of the
endomembrane system
Rough endoplasmic reticulum makes
membrane and proteins
• The rough ER manufactures membranes
• Ribosomes on its surface produce proteins
Transport vesicle
buds off
4
Ribosome
Sugar
chain
1
Polypeptide
3
Secretory
(glyco-) protein
inside transport
vesicle
Glycoprotein
2
ROUGH ER
• Smooth ER synthesizes lipids
• In some cells, it regulates
carbohydrate metabolism and
breaks down toxins and drugs
SMOOTH ER
ROUGH
ER
Nuclear
envelope
Ribosomes
SMOOTH ER
ROUGH ER
•The Golgi apparatus
consists of stacks of
membranous sacs
–These receive and
modify ER products,
then send them on to
other organelles or to
the cell membrane
• The Golgi apparatus
Golgi apparatus
Golgi
apparatus
“Receiving” side of
Golgi apparatus
Transport
vesicle
from ER
New
vesicle
forming
“Shipping”
side of Golgi
apparatus
Transport vesicle
from the Golgi
Lysosomes digest
the cell’s food
and wastes
LYSOSOME
• Lysosomes are
sacs of digestive
enzymes budded
off the Golgi
Nucleus
• Lysosomal enzymes
– digest food
– destroy bacteria
– recycle damaged organelles
– function in embryonic development in
animals
Rough ER
Transport vesicle
(containing inactive
hydrolytic enzymes)
Plasma
membrane
Golgi
apparatus
Engulfment
of particle
Lysosome
engulfing
damaged
organelle
“Food”
LYSOSOMES
Food
vacuole
Digestion
• Plant cells
contain a large
central vacuole
– The vacuole has
lysosomal and
storage functions
Central
vacuole
Nucleus
• Protists may have contractile vacuoles
– These pump out excess water
Nucleus
Contractile
vacuoles
ENERGY-CONVERTING
ORGANELLES
• Chloroplasts are found in plants and some
protists
• Chloroplasts convert solar energy to chemical
energy in sugars
Chloroplast
Stroma
Inner and outer
membranes
Granum
Intermembrane
space
•Mitochondria carry out cellular respiration
MITOCHONDRION
–This
process
uses the
chemical
energy in
food to
make ATP
for cellular
work
Outer
membrane
Intermembrane
space
Inner
membrane
Cristae
Matrix
THE CYTOSKELETON AND
RELATED STRUCTURES
The cell’s internal skeleton helps
organize its structure and
activities
• A network of protein fibers makes up the
cytoskeleton
• Microfilaments of actin enable cells to change
shape and move
• Intermediate filaments reinforce the cell and
anchor certain organelles
• Microtubules
– give the cell rigidity
– provide anchors for organelles
– act as tracks for organelle movement