Cell TypesCell Types

Viruses: The KingdomViruses: The Kingdom--less Organismsless Organisms

These incredibly small, but simple structures are not alive and have no known origin. (influenza)

What is a Virus?What is a Virus?

A tiny particle made up of genetic material (DNA or RNA) that can invade and replicate within a living host.

Why are Viruses not Why are Viruses not Considered Living?Considered Living?

They do not respire, eat, excrete, or reproduce.By itself, a virus can not do anything.Viruses affect every living cell known, from man to bacteria.

Virus StructureVirus Structure

There are two main types of virus structure.

1. Enveloped2. Unenveloped

Types of VirusesTypes of VirusesThere are three

main types of Viruses1. DNA Viruses2. RNA Viruses3. Retroviruses

Cell Types• Living organisms are made up of

cells.

• Either PROKARYOTIC or EUKARYOTIC cells.

A. two major cell typesB. distinguished by structural organization

Prokaryotic Cells• Kingdoms:

1. Monera (Eubacteria)2. Archaea (Archaebacteria)

• Characteristics:1. lack a nuclear membrane2. have no membrane-bound organelles

Prokaryotic Cell - Bacteria

Eukaryotic Cells

• Kingdoms:1. Protista2. Fungi3. Plantae4. Animalia

• Characteristics:1. have a nuclear membrane2. have membrane-bound organelles

Eukaryotic -Animal Cell

Eukaryotic -Plant Cell

Cytoplasm• Entire region between the nuclear membrane

and the cell (plasma) membrane.• This includes all organelles!

cytoplasm

Nucleus• Conspicuous

membrane-bound cellular organelle in eukaryotes.

• Contains the genes (DNA).

nucleus

Nucleolus• Spherical region in nucleus.• Makes ribosomal RNA.• 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.• Polyribosome or polysome.

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.

4. Golgi Apparatus (Complex)

• A stacked, flattened membranous organelle with sacs called cisternae.

• Modifies, stores and routes productsfrom 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

Hydrophilicregion

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

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

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.

• 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 communicationtakes place between cells.

• Plants: plasmodesmata

• Animals: tight junctionsanchoring junctionscommunicating junctions