CLASSIFICATION OF LIVING ORGANISMS

Most Familiar organisms are made from Eukaryotic Cellse.g.

plants

animal

fungi – including yeasts

protists – protozoa (animal-like single celled) e.g. paramecia

-algae (plant-like single/multi celled) e.g. algae

http://www.cellsalive.com/cells/cell_model.htm

vesicle

nucleolus

lysosome

cytoplasm

nucleusPinocytotic vesicle

Centriole

Food vacuole

Smooth endoplasmic reticulum

Lysosome)

Plasma membrane

Cytoplasm

Mitochondrion

Nuclear membrane

Nuclear pore

Chromatin

Nucl;eolus

Rough ER

Ribosome

Golgi Body

Secretory vesicle

Smooth ER Large vacuole

Vacuole membrane

ribosome

Golgi body (dictyosome)

Plasmadesmata

Secretory vesicle

Nuc

leol

usN

ucle

ar p

ore

Chr

omat

inN

ucle

ar m

embr

ane

Chloroplast

Mito

chondrio

nC

ell m

embr

ane

Cell wall

Rough ER

Organelle P/A? Function

Nucleus(nuclear poreNucleolus)

NucleusNucleolusNuclear pore

Mitochondrion CristaeMatrix

Rough Endoplasmic Reticulum

R.E.R.Ribosome

Smooth Endoplasmic reticulum

Golgi Body

Lysosome

Centriole

Chloroplast

Large Vacuole

Organelle P/A? Function

Nucleus(nuclear poreNucleolus)

Nucleus Controls the cell, contains DNA in the form of chromsomes (chromatin)

Nucleolus Manufactures ribosomes, contains a lot of rRNA

Nuclear pore Allows transfer of materials between nucleus and cytoplasm (esp. mRNA

Mitochondrion Site of aerobic respiration

Cristae Electron transfer chain, produces majority of ATP

Matrix KREB’s Cycle

Rough Endoplasmic Reticulum

R.E.R. Transports proteins synthesized on the ribosome around cell in particular to Golgi for packaging for secretion

Ribosome Site of protein synthesis, mRNA translation

Smooth Endoplasmic reticulum

Site of synthesis of some other macromolecules in particular lipids

Golgi Body Packaging of macromolecules, especially proteins (enzymes, hormones, neurotransmitters) for excretion from the cell

Lysosome Contain digestive enzymes (e.g lysozyme), low pH,Digest macromolecules , involved in autophagy.

Centriole Found in pairs, made of microtubules,Organizes spindle fibres on which chromsomes align during cell division.

Chloroplast Site of photosynthesisLight reactions –grana (thylakoid) membranes,Dark reaction – stroma

Large Vacuole Large storage vesicle, containing cell salts, pigments.

• Plasmodesmata are channels found in plant cells which allow direct cytoplasmic connection between adjacent plant cells.

• Middle Lamella –layer of “glue” between adjacent plant cells which holds them together. Contains pectins.

• Nucleosome – DNA string wrapped around a histone protein bead. Necessary to allow DNA to be packaged efficiently into the small volume of the nucleus

Prokaryotic cells

Helicobacter pylori-

Stomach uclersMycobacterium tuberculosis –

Tuberculosis

Nesseiria meningitiis –

Meningitis

Yersinia pestis –

Black death (plague)

Bacteria 0.5-100m, Eukaryotes 10- 100 m

Streptomyces coelicolor.

The bacterium and its relatives produce most of the natural antibiotics in current use, including tetracycline and erythromycin. They also generate compounds that are used to treat cancer and suppress the immune system.

An Electron Micrograph of a bacterium

Bacteria are much more simply constructed – no membrane bound organelles

COMMON BACTERIA SHAPES

•Spherical (coccus)

•Rod shaped (bacillus)

•Spiral (spirochaetes, helicobacter)

BASIC BACTERIAL STRUCTURES

flagellae

cytoplasmpili

(fimbriae)

Major difference between prokaryotic cells and eukaryotic cells

PLASMA MEMBRANE

Same as all membranes (bilipid layer)

Phospholipid composition may differ between bacteria and eukaryotic cells.

•The CytoplasmNo compartmentalisation (no internal mebranes ie. No ER)All chemical reactions occur within it.Efficient regulation of biochemistry needed (Jacob Monod).

Contains ribosomes (free floating) responsible for protein synthesis –

different from eukaryotic ribosomes – antibiotics (chloramphenicol, tetracycline, streptomycin) can specifically target them.

ON OFF OFF

Repressor molecule

No Enzyme is produced

ON ON ON

LACTOSEEnzyme is produced

The Bacterial “Chromosome” - NucleoidA single, circle of DNA. Packaged by folding – to reduce volume.

FunctionsContains genetic information.

Codes for bacterial proteins.

ReplicationBacteria reproduce by dividing (asexual)

DNA must be replicated

DNA simply copied (no MITOSIS - no chromosomes).

Extrachromosomal DNA – Plasmids

StructureCircular DNA, smaller than nucleoid.

Size~ 1000 - 200, 000 bp (c.f. 4,000,000 base pairs)

1-700 copies.

FunctionNot normally essential,

Gives some advantage

e.g. antibiotic resistance.

e.g. conjugative plasmids - Allow exchange of DNA between bacteria

– antibiotic resistance can jump from one bacterial species to another.

The Cell Wall

General Properties

Cell wall resists swelling due to osmotic entry of water

Prevents osmotic lysis

Maintains shape

Structure and synthesis unique to prokaryotes.

The chemical structure of peptidoglycan

The NAM, NAG and amino acid side chain form PEPTIDOGLYCAN Covalently bonded (strong) to form a repeating polymer.

The polymer is further strengthened by covalent cross links (peptide bridges) between amino acids.

NAM – N acetyl muramic acid

NAG – N acetyl glucosamine

Two basic types of bacterial cell wall structures – GRAM +ve

Gram +ve cells peptidoglycan is:

heavily cross-linked

very thick

(peptidoglycan accounting for 50% of weight of cell

and 90% of the weight of the cell wall)

20-80 nm thick.

Two basic types of bacterial cell wall structures – GRAM -ve

In GRAM –ve (G-) bacteria

peptidoglycan much thinner

15-20% of the cell wall

intermittently cross-linked.

Gram positive (G+) cells are purple and Gram negative (G-) cells are red.

GRAM STAINING

Lysozyme ( tears and saliva) -attacks peptidoglycan. It hydrolyzes the NAM - NAG linkage.

Cell Wall

Freely permeable to solutes, the openings in the mesh are large and all types of molecules can pass through them.

Penicillin inhibits cells wall synthesis.

The G+ cell wall is very sensitive to the action of lysozyme and penicillin.

Penicillin is antibiotic of choice for infections caused by G+ organisms.

e.g. Streptococcus pyrogenes which causes strep throat.

Bleu D’avergne

BACTERIAL MOTILITY

Flagellum (ae) – used for movement

FLAGELLUM

FIMBRIAE

Fimbriae/ pili –concerned with cell adhesion

Special SEX pili – enable transfer of plasmids from one bacteria to another – can on occasion cross species.

e.g staphylococcus - MRSA

SUMMARY

No true membrane bound nucleus – rather a nucleoid (folded)

No membrane bound organelles/ no compartmentalisation

Many free floating ribosomes

Cell walls made of peptidoglycan (G+/ G-)

Mucilaginous capsule can be present

Flagellae (movement)

Pili./ Fimbrae are other extracellular protrusions (adhesion/ transfer)