CYTOLOGYCYTOLOGY

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% ribosomal-

RNA (rRNA).• Site of protein synthesis.

incominglargesubunit

incomingsmall subunit polypeptide

mRNA1 2 3 4 5 6 7

Endomembrane System

• Eukaryotic organelles that are formed of interrelated membranes.1. nuclear envelope (membrane)2. endoplasmic reticulum3. transport vesicles4. golgi apparatus (complex)5. lysosomes6. vacuoles7. 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.

MitochondriaMatrix

Innermembrane

Outermembrane

Innermembrane space 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

Outer Membrane

Inner Membrane

Stroma

Granum

Thylakoid

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.

• 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.