The Cellular Basis of Life PDF

Preview

Summary

Download The Cellular Basis of Life PDF

Description

The Cellular Basis of Life (http://nie.lk/pdffiles/other/eOM%20U02ChemicalCellular.pdf)     

The Origins of Life Introduction to prokaryotic and eukaryotic cells Endosymbiont theory Overview of cell structure and size Biodiversity of living organisms

How did life on Earth arise? • Number of different theories • Vitalism – Religion, pre-scientific – Urea • Oparin-Haldene – Primordial soup – Coacervates or amino acids – Urey-Miller What is RNA? How does it differ to DNA? • Genetic material – RNA – Orgel, Crick, Cech – Ribozyme – RNA enzymes – RNA world theory • Self-replicating RNA • PNA (polyamide/peptide nucleic acid) Compartmentalisation • Coacervates – Oparin ‘Protocells’ • Making cells from ‘scratch’ • Montmorillonite – Catalyst and RNA • Growing protocells which could divide and compete • Replicating RNA Hydrothermal vents/metabolism • Ability to metabolise more important than ability to replicate • Vents found to be populated with a variety of organisms • Temperature and pH • Proton gradients • Energy then allowed molecules such as RNA to be produced • Cells formed and moved into the sea

All at once? – Experiments ‘too clean’ – In early life things were not as pure but still functioned – Metals, sulphur – UV radiation – Ponds and pools more likely than deep sea Last Universal Common Ancestor (LUCA) • Last organism/species from which life on Earth which is believed to originate • Genomic analysis – Hydrogen metabolism – Use of proton gradients – Close to Origin of Life? – More favoured theory at present Eukaryote An organism consisting of a cell or cells in which the genetic material is DNA in the form of chromosomes contained within a distinct nucleus Bacteria A member of a large group of unicellular microorganisms which have cell walls but lack organelles and an organized nucleus, including some which can cause disease Archaea Microorganisms which are similar to bacteria in size and simplicity of structure but radically different in molecular organization Differences Between Archaea and Bacteria Bacteria Archaea • Prokaryote • Prokaryote • Cell wall made of • No peptidoglycan in cell wall peptidoglycan • Histones present • No histones • 70S ribosome (different shape) • 70S ribosome • Not sensitive to antibiotics • Sensitive to antibiotics Archaea • Previously grouped with bacteria – Carl Woese 1977 • Lipids unique • More advanced methods have determined more similar to eukaryotes than bacteria • Extremophiles – Example Methanobrevibacter smithii – Human gut

Prokaryotes • Different shapes • 1-10µm • Binary fission Structure • Cell wall • Plasma membrane • Circular DNA • Plasmids • Cytoplasm • Ribosomes • Various appendages Eukaryotes • Large variety of functions • 5-100µm • True nucleus • Linear DNA • Membrane bound organelles • No cell wall • Cytoskeleton

Cell Organelles Ribosomes • Can be free or attached to the ER – Also found in mitochondria and chloroplasts • Comprised of two units Endoplasmic Reticulum • Continuation of the nuclear membrane • Smooth or rough Golgi Apparatus • Flattened sacs • Forms part of the network of the endomembrane system Lysosomes • Hydrolytic enzymes

Peroxisomes • Oxidative enzymes Vacuoles • Variety of functions dependent on the cell type Mitochondria • Similar size to bacterial cell • Double membrane • Mitochondrial DNA Chloroplasts • Three membranes – Thylakoid – Chlorophyll • Similar size to bacteria – Similar to cyanobacteria • Circular DNA

Endosymbiotic Theory • Chloroplasts and mitochondria are similar in size to bacteria – Ribosomes – DNA • Engulfment, incomplete digestion – Double membrane • Chloroplast – Photosynthesising prokaryote • Mitochondria – Aerobic prokaryote Multicellular Organisms • Symbiotic theory – Endosymbiosis extended • Syncytial theory

– Multiple nuclei • Colonial theory – Aggregates of the same species Taxonomy The branch of science concerned with classification, especially of organisms

Overview of Cell Structure & Size...