Life

• Individual survival– Take in, digest, eliminate nutrients– Recognize self from non-self– Recognize enemies– Repair damage

• Reproduction– Survival of species– Gene transfer

Bacteria

Archaea

Protozoa

Algae

Plants

FungiAnimals

InvertebratesVertebrates

US

UCA

Prokaryotes

Euk

aryo

tes

Sin

gle-

celle

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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, immune system

The molecules of life

• Nucleic acids (DNA, RNA)

• Proteins

• Carbohydrates

• Lipids

• Lipoproteins, glycoproteins, vitamins….

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 - within cells, between cells

• Cytokines• Signal transduction factors• Receptors• Vital for regulation of growth, cell division

Schematic metabolic cycle

Cellular 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

The Metabolome - Metabolomics

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 plasma membraneLipid bilayer

Polar

Non-polar

(Lipid)

Protein

Av. Width

7.5 nm

(75 Å)

Sugar

GlycolipidGlycoprotein

The Flu Virion

Neuraminidase

Hemagglutinin Lipid bilayer envelope

Matrix protein

• 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).

www.virustaxonomyonline.com

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 damaged, 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, mostly enveloped• adenoviruses, coronaviruses, rhinoviruses,

influenza viruses, • Transmitted by direct and indirect contact, air

(aerosols) 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

Diverse bacteriaGram positive Gram negative

More bacterial types

• 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