CYTOLOGY
Cytology
• Living organisms are made up of cells.
• Either PROKARYOTIC or EUKARYOTIC cells.
A. two major cell types
B. distinguished by structural organization
• See table on handout for differences.
• Plant, Animal and Bacteria Cell Models at
http://www.cellsalive.com/
Prokaryotic Cells
• Kingdoms:
1. Monera (Eubacteria)
2. Archaea (Archaebacteria)
• Characteristics:
1. lack a nuclear membrane
2. have no membrane-bound organelles
Prokaryotic Cell - Bacteria
Eukaryotic Cells
• Kingdoms:
1. Protista
2. Fungi
3. Plantae
4. Animalia
• Characteristics:
1. have a nuclear membrane
2. have membrane-bound organelles
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!
cytoplasm
Cytosol
• The semi-fluid medium found in the
cytoplasm.
• This does not include the organelles.
Nucleus
• Conspicuous membrane-bound cellular
organelle in eukaryotes.
• Contains the genes (DNA).
nucleus
Nucleolus
•
•
•
•
Spherical region in nucleus.
Found in non-dividing cells.
Has nuclear organizers and ribosomes.
Sometimes more than one nucleolus present.
nucleolus
Ribosomes
• Nuclear and cytoplasmic organelle.
• Composed of 60% protein and 40% ribosomalRNA (rRNA).
• Site of protein synthesis.
• Polyribosome or polysome.
incoming
large
subunit
1
2
3
4
5
6
7
mRNA
incoming
small subunit
polypeptide
Endomembrane System
• Eukaryotic organelles that are formed of
interrelated membranes.
1. nuclear envelope (membrane)
2. endoplasmic reticulum
3. transport vesicles
4. golgi apparatus (complex)
5. lysosomes
6. vacuoles
7. plasma (cell) membrane
1. Nuclear Membrane
• Encloses the nucleus.
• A double membrane perforated with
pores through which materials enter and
leave the nucleus.
2. Endoplasmic Reticulum
• Extensive membranous network of tubules
and sacs called cisternae.
• Two distinct regions:
A. Rough endoplasmic reticulum (RER).
B. Smooth endoplasmic reticulum (SER).
2. Endoplasmic Reticulum
A. Rough endoplasmic reticulum (RER).
1. Studded with ribosomes.
2. Site of protein synthesis
B. Smooth endoplasmic reticulum (SER).
1. Synthesizes lipids, phosolipids and steroids.
2. Detoxifies drugs, alcohol and poisons.
3. Transport Vesicles
• A membrane organelle that transits
materials from one part of the cell to another.
• ER → Golgi apparatus
• Golgi apparatus → plasma membrane
4. Golgi Apparatus (Complex)
• A stacked, flattened membranous
organelle with sacs called cisternae.
• Modifies, stores and routes products
from the ER to the plasma membrane.
5. Lysosomes
• Membrane-enclosed bag of hydrolytic enzymes
(digestive enzymes).
• Functions:
1. intracellular digestion - phagocytosis.
2. Autophagy - engulfs other cellular organelles.
6. Vacuoles
• Large membrane-closed sac for cellular
storage.
• Three types:
1. Food vacuole (lysosomes attach)
2. Contractile vacuole (Protozoans)
3. Central Vacuole (mature plant cells)
7. Plasma (Cell) Membrane
• The boundary of every cell.
• Approximately 8 nm thick.
• Separates the living cell from its nonliving
surroundings.
• Acts as a selective barrier. Hydrophobic region
Hydrophilic
region
Mitochondria
• A doubled membrane cellular organelle with its
own circular DNA found in both plants and
animals.
• It is the site of cellular respiration, a catabolic,
exergonic, oxygen requiring process that uses
energy extracted from organic macromolecules
(like glucose) to produce ATP.
Mitochondria
Outer
membrane
Inner
membrane
Inner
membrane space
Matrix
Cristae
Chloroplast
• A doubled membrane cellular organelle with its
own circular DNA found in photosynthetic plants.
• The site of photosynthesis, an anabolic,
endergonic, carbon dioxide requiring process
the uses light energy (sun) and water to
produce organic macromolecules (glucose).
Chloroplast
Stroma
Outer Membrane
Inner Membrane
Thylakoid
Granum
Microbodies
• Two types:
1. Peroxisomes: produces and
degrades hydrogen peroxide (H202).
2. Glyoxysomes: fat-storing tissue of
germinating seeds.
Cytoskeleton
• Network of fibers through out the cytoplasm.
• Aids in cellular support and movement.
• Composed of three components:
1. Microfilaments - globular protein (actin)
- support and cellular contraction
2. Intermediate filaments - fibrous protein
- support
3. Microtubles - globular protein (tubulin)
- support and cell motility
Centriole
• Composed of microtubules.
• Arranged in a 9 + 0 pattern.
• Remember:
Animal cells only!
• Helps organize microtuble assembly during
cell division (mitosis and meiosis).
Cilia and Flagella
• Extensions of the plasma membrane.
• Microtubular core (9 + 2 pattern).
• Attached by a basal body (identical to centriole).
Cell Wall
• Strong cellulose fibers surrounding plant
cells and some bacteria only!
• Composed of polysaccharides and
proteins.
Intercellular Junctions
• Junctions where anchoring and communication
takes place between cells.
• Plants:
plasmodesmata
• Animals:
tight junctions
anchoring junctions
communicating junctions