CellsThe Basic Unit of Life

Are all Cells Alike?All living things are made up of cells. Some organisms are made of only one cell. Other organisms are made of many cells.

1. What are the advantages of a one-celled organism?

2. What are the advantages of an organism that is made of many cells?

Cell Theory – Life is Cellular

1. All living things are made of cells.

2. Cells are the basic unit of structure and function in living things.

3. New cells come from pre-existing cells.

B. Exceptions to Cell Theory

1. Viruses and Bacteriophage

Tobacco MosaicVirus

Influenza Virus

Section 19-3

Head

Tail sheath

DNA

Tail fiber

RNA

Capsidproteins

RNACapsid

Surfaceproteins Membran

eenvelope

Protein Coat

Nucleic Acid Core

Can Change Shape

(Bacteria) (Plants) (Humans)

T4 Bacteriophage

Virus Characteristics Not cellular Made of protein coat (capsid) surrounding … A nucleic acid (DNA or RNA) core Classified by shape – can be very complex Are PATHOGENIC – disease causing Are all OBLIGATE PARASITES

Must live off of a host Host is harmed Parasite benefits Virus is specific to species of host Virus is specific to cell type once in host

Viral Life Cycle

Lytic Cycle

Lysogenic or Latent

Cycle

Bacteriophage DNA

Bacterialchromosome

New phage produced by cells.

Bacteriophage enzyme lyses the bacterium’s cell wall, releasing new bacteriophage particles that can attack other cells

Bacteriophage attaches to host bacterium

Bacteriophage DNA inserts itself into bacterial chromosome

Bacteriophage DNA (prophage) may replicate with bacterium for many generations

Bacteriophage DNA (prophage) can exit the bacterial chromosome

Bacteriophage DNA enters cell

Prophage

Viral DiseasesAIDSCoxsackie VirusCroupDengue VirusEbola Hemorrhagic FeverHerpes Simplex (Genital Herpes,Cold Sores)

Hanta Hemorrhagic FeverHepatitis (A,B,C,D,E)InfluenzaMeaslesMumpsRubella (German Measles)MeningitisMononucleosis/Epstein-Barr (Herpes)

Conjunctivitis (Pink Eye)PneumoniaPolioRabiesSARSChicken Pox/Shingles (Varicella)Yellow FeverRSVPapilloma VirusSmall Pox

Herpes Viruses

Varicella Zoster

Herpes Simplex

Chicken Pox

Shingles

Cold Sore

MMR

Rubella

MumpsMeasles

Polio

Dr. Jonas Salk (~1954)First vaccination campaign

Small Pox Extremely contagious –

airborne particles (Variola) Eradicated by massive

vaccination campaign. The last naturally occurring

outbreak was in Somalia on 26th October 1977.

Vaccinations halted about 25 years ago.

2 (???) samples remain, one on Vector (lab in Siberia, one in CDC (Georgia)

Bioterrorism???

Treatment of Viral Diseases Cannot be cured Must be prevented Vaccines given before virus exposure Vaccines come in two varieties:

weakened or “dead” fragments

Cause the body to develop “immune memory” Never get the same virus twice. Except when:

Very young at time of first exposure (boosters) Get a very mild infection the first time Get very sick later in life (immunocompromised)

Edward Jenner (~1798)First vaccineUsed cow pox to vaccinate (vacca = cow in Latin) against small pox

Exception #2 to Cell Theory2. Cell Organelles

Organelles are structures within cells that do the work of the cell – “little organs”

a. Some carry out life functions independently of the cell they are part of.

- Reproduction- Heredity- Metabolism (convert energy)

b. Their structure also suggests that they are/were independent life forms.

Ex. Mitochondrion

OuterMembrane

Inner Membrane

Christae

Matrix

Ex. Chloroplast

Exception #3 to Cell Theory3. The First Cell

?

Types of CellsProkaryotic Cells (Prokaryotes)

General Characteristics- smallest type of cell , 1-5 μm in diameter

- most common cell type- lack nucleus- cell wall present around the cell

membrane- diverse: eubacteria, archaebacteria- archaebacteria ancestors of our cells???- classified by shape …

Shapes of Prokaryotes

Round Oval Spiral

Electron Micrographs of Bacteria

Structure of a Prokaryote

Peptidoglycan

Cell wall

Cell membrane

Ribosome

Flagellum DNA Pili

Structure of a Prokaryote

1. Cell Wall: Provide support and shape2. Cell Membrane: Control entry/exit of materials

to/from the cell3. Ribosome: Only organelle present in

prokaryotes; site of protein synthesis4. Flagellum/Cilia: Strands of protein used for

locomotion5. DNA: One large central loop of genetic

information6. Pili: Extensions of the cell membrane used for

cell attachment

Bacteria and Disease Pathogenic = disease causing; includes

some types of bacteria Species: Group of similar bacteria Strain: Smaller sub-group of species; have

many similarities (same species) but significant differences exist

May breakdown cells and tissues for food May release toxins (usually a protein) that

harm the body

Bacterial DiseasesStrep ThroatScarlet FeverRheumatic FeverDental CarriesPneumoniaPimples, Boils, ImpetigoToxic Shock SyndromeGonorrheaMeningitisPertussisAcneDiptheriaTetanusGas GangreneBotulismTrachomaChlamydia

AnthraxTuberculosisLeprosyConjunctivitisTraveler’s DiarrheaTyphoid FeverSalmonellosisShigella (Dysentery)Bubonic PlagueCholeraSyphillisThyphus FeverRocky Mountain Spotted FeverLyme DiseaseNecrotizing Fasciiitis

Anthrax: A Bacillus Bacterium

Also Presents as Inhalation Anthrax

Streptococcus: A Round Bacterium

Strep Throat

Necrotizing Fasciitis

Rheumatic FeverScarlet Fever

Staphylococcus

Impetigo

Boil

Clostridium tetani: A Bacillus Bacterium

B. burgdoferi: A Spiral Bacterium (Lyme Disease)

Looks bad, but …..

95% of all bacteria are either helpful or just there!!!

Helpful Bacteria Lactobacillus: yogurt, cheese

E. coli: lives in your large intestine

Petroleum-eating bacteria help clean up oil spills.

Biotechnology research

Treatment of Bacterial Infections Treat each exposure Re-infection always possible Some vaccines available Most infections treated with antibiotics

“anti” = against “biotic” = living Are cell poisons that prevent prokaryotic cells

from functioning Discovered by accident by Alexander Fleming

Resistance is a dangerous possibility

Controlling Bacterial Growth Sterilization

Chemicals = disinfectants Heat

Pasteurization Heat product to just below

boiling Kills most bacteria Increases shelf life

Bacteria in Nature Decomposers

Recycle nutrients within organisms – return them to the ecosystem

Sewage treatment; septic systems – purify water

Bacteria in Nature, Continued

Nitrogen Fixation Process by which plants

convert N to a usable form

Requires the presence of bacteria

Symbiosis Two different organisms living

together At least one must benefit from

relationship One benefits, other harmed =

parasitism One benefits, other not

effected = commensalism Both benefit = mutualism

N2 NH3

Legume

Soy BeansPeas

Clover

BacteriaIn Root Nodule

Types of CellsEukaryotic Cells (Eukaryotes)

General Characteristics- large cells, 100-300 μm

- have a well-defined nucleus- organelles present- more advanced than prokaryotes

Animal CellNucleus: Contains DNA;

control center of cell

Mitochondrion: Site of cellular respiration; energy production; powerhouse of the cell

Cytoplasm: Watery environment for chemical reactions of the cell

Cell Membrane: controls entry/exit of materials to/from cell; maintains homeostasis

Animal CellOther Organelles and Structures

DNA: Either as chromosomes or chromatin

Endoplasmic Reticulum: System of channels for cell transport

Nucleolus: site of RNA production; temporary

Ribosomes: site of protein production

Vacuoles: storage of waste, water, food

Cytoskeleton: Protein fibers that provide support and hold organelles in place

Lysosomes: Vacuole-shaped organelles that contain digestive enzymes

Centrioles: Protein microtubules that help during animal cell division

Golgi Apparatus: Stacks of membrane that package cell secretions (products)

Plant Cell

Cell Wall: made of cellulose; nonliving layer for structure and support

Central Vacuole: single large vacuole for water storage and support

Nucleus: contains DNA

● Plant cells lack centrioles & lysosomes

Chloroplasts: site of photosynthesis; contains the pigment chlorophyll

● They have all the other organelles found in animal cells

Comparison of Animal & Plant Cells

Animal Cells

Have well-defined nucleus with DNA

Cell membrane present

Vacuoles small and numerous

Centrioles aid in cell division

Lysosomes for digestion

Plant Cells

Have well-defined nucleus with DNA

Cell membrane present AND

Cell wall surrounds membrane One large central vacuole and

some small No centrioles – cell wall takes

over function Chloroplasts produce glucose

for the plant No Lysosomes

The End …..Cells