CLASSIFICATION OF LIVING ORGANISMS Most Familiar organisms are made from Eukaryotic Cells e.g....
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Transcript of CLASSIFICATION OF LIVING ORGANISMS Most Familiar organisms are made from Eukaryotic Cells e.g....
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
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
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)
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.
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.
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
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)