Life

• Individual survival

• Reproduction

Bacteria

Archaea

Protozoa

Algae

Plants

FungiAnimals

InvertebratesVertebrates

US

UCA

Prokaryotes

Euk

aryo

tes

Sin

gle-

celle

d

Cell Functions• Maintenance

– Recovery of energy from nutrients– Storage of energy– Synthesis of correct proteins and other cell

components

• Perpetuation of self– DNA replication– Cell division

• Specialized functions– e.g. muscle, blood, nerve cells

The molecules of life

• Nucleic acids (DNA, RNA)

• Proteins

• Carbohydrates

• Lipids

• Lipoproteins, glycoproteins, vitamins….

• DNA, the blueprint for the cell– Four bases, A,C,G,T– The order of the bases dictates amino acid sequence in proteins -

“codes for synthesis of proteins”

• Double strand, coiled in Double Helix– Arranged in chromosomes– About 1 yard total in each human cell

• Inside nucleus• RNA takes instructions from nucleus to endo-plasmic

reticulum where proteins are made

DNA RNA Protein

DNA + DNA

Translation protein synthesis

DNA ReplicationCell division

The ProteomeThe ProteomeProteomicsProteomics

GenomicsGenomicsThe GenomeThe Genome

Transcription

PROTEINS

• Chains of amino acids

• Structural elements - cell walls, membranes

• Catalysts - enzymes

• Communication devices - within cells, between cells• Cytokines• Signal transduction factors• Receptors

–Vital in regulation of cell growth, replication

Schematic metabolic cycleCellular components

Nucleic acids, Carbohydrates, Protein,

Fat

Metabolic intermediates

NADPHNADP+

Work

TransportAssemblyMovementHeat

ATP

ADP + Pi

Food

Carbohydrates, Fats, Glucose,

Proteins

Wastes

CO2, H2O, lactic acid

ATP

ADP + Pi

NAD+

NAD+

NADH

NADH

Viruses

• 0.02-0.3 micrometers diameter• Genetic material: ss or ds DNA, RNA • Protein coat• Some enzymes• Lipid envelope – enveloped/non enveloped

viruses• Nomenclature semi-systematic

– Hepatitis A Virus, HAV

• Need host cell for replication

The Flu Virion

• Envelope: lipid bilayer membrane + glycoproteins, typically acquired from host cell membranes

• Capsid (protein coat): multiple copies of 1 or more proteins in an array

Life-cycle of virus

• Particle, virion

• Infects host cell

• Genetic material uses host’s replication apparatus to produce new viral components (capsid, core proteins, genetic material)

• Components assemble into viral particles, exit host cell, sometimes lysing host cell

• Each type of virus has its own specific host

• Viruses that colonize bacteria are bacteriophage viruses (bacteriophages).

Viruses in the Environmment• Must be able to survive outside host cell• Non-enveloped viruses are more persistent than

enveloped viruses– lipid envelope more easily damages, protein

coat confers stability • Enteric viruses are almost all non-enveloped

– Hepatitis A, poliovirus, noroviruses, rotaviruses – transmitted by direct and indirect contact, fecally

contaminated water, food, fomites and air. • Respiratory viruses: adenoviruses, coronaviruses

– transmitted by direct and indirect contact, air and fomites (some also by water and food).

Unicellular organisms

• Bacteria - procaryotes

• Protozoa

• Algae - eucaryotes

• Fungi

Procaryotic Cell (left) and Eucaryotic Cell (right)

Procaryotes: Bacteria and Others

Unicellular organisms

Simple internal organization

Multiply by binary fission

Diameter ~0.5-1.0 micrometer

Envelope: cytoplasmic membrane, cell wall & capsule (polysaccharide)

Some have appendages:

flagella: for locomotion

pili: attachment to other cells for genetic transfer; virus receptor site

Standard Linnean nomenclature: Genus species

Bacterial types

• Gram positive• Gram negative• Aerobes• Anaerobes• Facultative aerobes• Rods (bacilli)• Spherical (cocci)• Comma-shaped (vibrios)• Spiral (spirochetes)

Bacteria in the Environment

Some bacteria form spores:

– highly resistant to physical and chemical agents and

– very persistent in the environment

Pathogenic Bacteria

Pathogenic bacteria possess structures or chemical constituents that contribute to virulence properties – Outer cell membrane of Gram

negative bacteria: endotoxin (fever producer)

– Exotoxins– Pili: for attachment to cells and

tissues– Invasins: to invade cells

Unicellular Eucaryotes:

• More complex internal organization:

– organelles: discrete nucleus, mitochondria

• Wide range of sizes: 2 micrometers and larger

Protozoa• Unicellular; non-photosynthetic; flexible cell membrane;

no cell wall; some are parasites, have complex life-cycles • Wide range of sizes and shapes; 2 micrometers to 2 mm• Disease-causing:

– Amoebae: Entamoeba histolytica– Flagellates: Giardia lamblia– Ciliates: Balantidum coli– Sporozoans: Plasmodium vivax– Coccidians: Cryptosporidium parvum– Microsporidia – Cyclosopora cayetanensis

Cryptosporidium parvum oocysts: ~5 m diameter

Acid fast stain of fecal preparation

Wet mount by differential interference contrast microscopy

Giardia lamblia cyst: ~10 x 8 micrometers

More Protozoans: Fungi

Fungi (yeasts and molds):•non-photosynthetic• immotile; •rigid cell wall

Molds:•grow as branched, interlacing chains or filaments (hyphae) called mycelia

•Yeasts:• do not form mycelia •grow as single cells that bud •sexual reproduction possible

Mitospores (conidia) of Penicillium, one of the asexual Ascomycota

Yeasts

Algae

• Photosynthetic• Rigid cell wall • Simple plants, protists,

protozoa, plancton, derived from cyanobacteria ?

• Wide range of sizes and shapes – 2 micrometers and larger

• Some algae are harmful– Algal booms

• Toxins– Anabaena, anatoxins

Nostoc

Helminths (Worms)

• Multicellular animals• Some are human and/or animal

parasites • Eggs pass via human and animal

excreta to water, food, soil.• Several major groups:

– Roundworms, Nematodes eg. Ascaris, Trichinella spiralis, hookworms

– Flatworms Platyhelminthes: Cestodes (tapeworms): pork, beef tapeworms, and Trematodes (flukes) eg Schistosomes

– Annelids (leeches)

Necator (hookworm)

eggs

adult

• Eggs hatch in soil• Infective stage: larvae• Penetrate skin, migrate to

blood, lungs, trachea • or are ingested• Adults mature in intestine• Attach to intestinal walls

– anemia– Necator americanus ,

Ancylostoma duodenale (hookworm)

Trematodes

• Schistosomes (blood flukes)

• Liver fluke

Cestodes

• Head (scolex) attaches to tissue– beef tapeworm,

Taenia saginata– pork tapeworm (T.

solium)

• Grows in intestine

http://www.marvistavet.com/html/body_tapeworm.html

Multicellular organisms

• Plants

• Animals– Invertebrates– Vertebrates

The plasma membraneLipid bilayer

Polar

Non-polar

(Lipid)

Protein

Av. Width

7.5 nm

(75 Å)

Sugar

GlycolipidGlycoprotein

The cell cycle

GG11

SS

GG22

MMGG00

AA

Mitosis (Cell division)

Different cell types

• Connective tissue, fibroblasts• Endothelial cells, lining of blood

vessels• Epithelial cells, “outside” of several

tissues• Hepatocytes, liver cells• Some cell populations are continually

being renewed (turnover), others are “permanent”

Rat fibroblasts

Cell renewal• Renewal by

duplication - proliferation– eg endothelial

cells– pancreas– hepatocytes ?

• Renewal by differentiation of stem cells– eg skin, intestinal

wall, blood cells

Cell reproduction, cell development

“Generic” Specialized

Stem cells Differentiated cells

Pluripotent stem cells Different types of

differentiated cells

Totipotent (embryonic) stem cells Organs, organisms ?