Transcript cell - TeacherWeb

CYTOLOGY:
Cell structure and
function
Robert Hooke
 The first person to
identify and see
cells. 1665.
 Coined the term
“cell”
The cell theory
 Cells are the basic units of life.
 All living things are made up of cells.
 All cells are produced by existing cells.
Cell types.
 They are either
PROKARYOTIC or
EUKARYOTIC cells.
 Karyon means
‘kernal’
 Eu means ‘true’
 Pro means “before”
Prokaryotic Cells
 Kingdoms:
1. Eubacteria
2. Archaebacteria
 Characteristics:
1. lack a nuclear membrane.
2. have no membrane-bound
organelles.
3. “naked” genetic material.
Prokaryotic Cell - Bacteria
Eukaryotic Cells
 Kingdoms:
1. Protista
2. Fungi
3. Plantae
4. Animalia
 Characteristics:
1. have a nuclear membrane around
genetic material “nucleus”
2. have specialized membrane-bound
organelles
Eukaryotes Prokaryotes
DNA
Size
Organization
linear strands within
membrane-bound nucleus
single circle in “nucleoid
region
5-100 µm
0.2-10 µm
often multicellular, some have
usually single-celled,
cell walls (no peptidoglycan) some have peptidoglycan
cell walls
Metabolism
usually need oxygen to exist
may not need oxygen to
exist
Organelles
membrane bound organelles
like mitochondria
no organelles, different
ribosomes
Examples
plants, animals, protists, fungi
bacteria, archaea8
Eukaryotic Animal Cell
Eukaryotic Plant Cell
Cellular Evolution
 Current evidence indicates that eukaryotes
evolved from prokaryotes between 1 and 1.5
billion years ago.
 Two theories:
1. Infolding theory
2. Endosymbiotic theory
1. Infolding Theory
 The infolding of the prokaryotic plasma
membrane gave rise to eukaryotic organelles.
2. Endosymbiotic theory
 Endosymbiosis refers to
one species living within
another - the host.
 Theory - the movement of
smaller photosynthetic
(chloroplast) and
heterotrophic
(mitochondria)
prokaryotes into larger
prokaryotic host cells.
Cytoplasm
 Entire region between the nuclear membrane
and the cell (plasma) membrane.
 This includes all organelles!
 Buildings, factory layout, matrix
cytoplasm
Cytosol
 The semi-fluid
medium found in
the cytoplasm.
 This does not
include the
organelles.
 School grounds,
city area.
Nucleus
 A double membrane
organelle which
contains the coded
instructions for making
proteins.
 Found only in
eukaryotes.
 Contains DNA, also
called chromatin.
(Blueprints)
 principal, mayor, control
center
Nucleolus
 Spherical region in
nucleus.
 Produces the
ribosomes.
 Sometimes more than
one nucleolus present.
 Training center, machine
shop
nucleolus
Ribosomes
 Nuclear and cytoplasmic
organelle.
 Composed of 60%
protein and 40%
ribosomal-RNA (rRNA).
 Site of protein synthesis.
 Either free or attached.
 Machines, teachers, law
enforcers
Endoplasmic Reticulum
(ER)
 Extensive membranous
network of tubules and
sacs.
 Two distinct regions:
A. Rough
endoplasmic reticulum
(RER).
B. Smooth
endoplasmic reticulum
(SER).
Endoplasmic Reticulum
A. Rough endoplasmic reticulum (RER).
1. Studded with ribosomes.
2. Site of protein modification.
 Classrooms, assembly line, roadway
B. Smooth endoplasmic reticulum (SER).
1. Synthesizes lipids, phosolipids and steroids.
2. Detoxifies drugs, alcohol and poisons.
 Detox center, water treatment plant, detention
hall.
Golgi Apparatus, Body or
Complex
 A stacked, flattened
membranous
organelle of sacs.
 Modifies, stores
and routes
products from the
ER to the plasma
membrane.
 Shipping department,
post office
Lysosomes

Membrane-enclosed bag of hydrolytic
enzymes (digestive enzymes).

Functions:




Phagocytosis - intracellular digestion
Autophagy - engulfs other cellular organelles
Apoptosis – Programmed cell death
Janitors, recycling bins
Vacuoles
 Large membraneenclosed sacs for
cellular storage.
 Three types:
1. Food vacuole
(lysosomes attach)
2. Contractile vacuole
(Protozoans)
3. Central Water
Vacuole (mature plant
cells)
 Water pump, storage
sheds, refrigerator.
Cell Membrane
 The boundary of every cell, also called the plasma
membrane.
 Semi-permeable, acts as a selective barrier.
 Fence with gates, moat with bridges, security
system
Cell Wall
 Strong fibers
surrounding plant,
fungi, some protista
and most bacteria
cells.
 Composed of
polysaccharides and
proteins, gives the cell
shape.
 Boundary lines, open
fences, structural
supports.
Mitochondria
 A doubled membrane cellular organelle with its
own circular DNA found in both plants and
animals.
 It is the site of cellular respiration, an oxygen
requiring process that uses energy extracted from
organic macromolecules (like glucose) to
produce energy for the cell in the form of ATP.
 Power plant, generator, battery.
Mitochondria
Chloroplast
 A doubled membrane cellular organelle with its
own circular DNA found only in plants.
 The site of photosynthesis, a carbon dioxide
requiring process the uses light energy (sun)
and water to produce glucose, which the cell will
use for energy.
 Cafeteria, restaurants, solar panels.
Chloroplast
There is always an
exception……
Elysia chlorotica
Cytoskeleton
 Network of fibers through out the cytoplasm.
 Aids in cellular support and movement.
• Framework, scaffolding, roadways
Cilia and Flagella
 Extensions of the
plasma membrane.
 Used for movement
or to move food to
an oral groove.
Plastids (I)
 Primary function of plastids is to
store molecules.
 One molecule that they store is
pigment; pigments give fruits
and vegetables an orange or red
color.
 Plastids also store
photosynthetic products like
starch. Chloroplasts are plastids.
 Potatoes, for example, have
many plastids in their cells.
 Warehouses, study halls,
storage drums.