Prokaryotic and Eukaryotic Cells PDF

Prokaryotic and Eukaryotic Cells Mrs Cassy Ross Week 6 – Cell Biology SCI1023-N-GJ1-2021 2022 Learning Outcomes • Evolution of cells • Similarities between prokaryotic and eukaryotic cells • Differences between prokaryotic and eukaryotic cells The origin and evolution of cells • Cells are divide...

Prokaryotic and Eukaryotic Cells Mrs Cassy Ross Week 6 – Cell Biology SCI1023-N-GJ1-2021 2022 Learning Outcomes • Evolution of cells • Similarities between prokaryotic and eukaryotic cells • Differences between prokaryotic and eukaryotic cells The origin and evolution of cells • Cells are divided into two main classes, initially defined by whether they contain a nucleus • It appears that life first emerged at least 3.8 billion years ago The Cell: A Molecular Approach. 2nd edition. Cooper GM. (2000) Time scale of cell evolution • It was first suggested in the 1920s that simple organic molecules could form • Macromolecules thought to polymerise spontaneously • Little to no oxygen in the environment - The Cell: A Molecular Approach. 2nd edition. Cooper GM. (2000) - https://www.britannica.com/science/life/Evolution-and-the-history-of-lifeon-Earth Cells are the basic, structural, functional, and biological unit of all living organisms Cells that changed the earth Single cell organisms e.g. bacteria Some began making their own food using C02 in the atmosphere and energy they harvested from the sun A process called photosynthesis produced enough oxygen to change earths atmosphere Soon afterward, new oxygen breathing life forms came onto the scene Symbiosis When two different species benefit from living or working together Endosymbiosis When one organism lives inside the other The endosymbiotic theory Describes how a large host cell and ingested bacteria could easily become dependent on one another for survival Mitochondrion and Chloroplasts Responsible for their own division They have their own DNA Mitochondrion and Chloroplasts Produce enzymes and proteins required for the function Double membrane surrounds both organelles Think about shared characteristics between different organisms…. Bats and butterflies both have wings Is this evidence for them being closely related? Discuss whether the pieces of evidence in front of you support Ø Ø Ø Ø Theory 1 Theory 2 Both Or neither Data no.1 Data no.2 The diversity of life Data no.3 Data no.4 An increase in antibiotic resistant bacteria The horseshoe crab – a present day example and a fossil from 500 million years ago Data no.5 Comparison of protein sequences Life, as we know it, requires proteins. Theory 1: All living organisms evolved from a single common ancestor. Theory 2: Life evolved many times independently. (writing frame taken from: Osborne, J., Erduran, S., and Simon, S. Journal of research in science teaching 41.10 (2004): 994-1020.) How we think complex cells evolved - Adam Jacobson YouTube Similarities between eukaryotes and prokaryotes Similarities between eukaryotes and prokaryotes Prokaryotes and eukaryotes originate from the same common ancestor – so they have some features in common Blackstone N. W. (2013). Philosophical transactions of the Royal Society of London. Series B, Biological sciences, 368(1622) Similarities between eukaryotes and prokaryotes • They both have cytoplasm, cell membrane and ribosomes • All prokaryotes have a cell wall, while only some eukaryotes have a cell wall • Both have genomic DNA Eukaryotic cells What are the differences between prokaryotes and eukaryotes? Differences between eukaryotes and prokaryotes • Although eukaryotes and prokaryotes originally come from the same ancestor, they have evolved independently for a long time Prokaryotic cells vs Eukaryotic cells • • • • Comprise bacteria and archaea They typically have a diameter of 0.1–5 μm DNA is circular and can be found in a region called the nucleoid, which floats in the cytoplasm Unicellular organism • Comprise of animals, plants, fungi and protists • They have a typical diameter of 10 100 μm • Membrane bound organelles, such as nucleus and mitochondrion • Multicellular organism Ribosomes Differences between eukaryotes and prokaryotes • While some eukaryotic cell have tails like the human sperm cell, none have flagella • The cytoskeleton is much simpler in prokaryotic cells – only used in cell division • Prokaryotes have pili different to cilia in eukaryotes Sperm cell Bacterial cell with flagellum DNA and reproduction Some prokaryotes also have plasmids Prokaryotic vs Eukaryotic: The Differences | Cells | Biology | FuseSchool - YouTube o List the features found in prokaryotes but not eukaryotes. o What are the advantages provided by these features? o Why have prokaryotes not evolved complex multicellularity? o List the features that are found in eukaryotes but not prokaryotes. o What are the advantages provided by these features? You might know this from previous sessions, from Microbiology and Pathology modules… let’s refresh our minds about cell shapes! Morphology of prokaryotes • • • • • Size Shape Arrangements Motility Spore formation Can be transparent under microscope! Gram staining Size of prokaryotes • • • • • The unit of measurement used in Microbiology is Micron (μ) One micron is one thousandth of a millimetre 1/1000 It is also denoted as Micrometre (μM) One thousandth of a Micrometre is one nanometre (nm) They typically have a diameter of 0.1–5 μm Shapes of prokaryotes Bacteria come in various different shapes: • Spherical • Rod • Spiral Shape depends on cell wall Arrangements of prokaryotes Gram staining Bacilli Cocci in clusters Eukaryotic cells have different shapes Human cells have different shapes Human cells can arrange in layers Remember Eukaryotes can be divided into plants, animals, fungi, protist Major differences between plants and animals Both plants and animals have cells but the structure varies in one important way: • Plant cells have cell walls • A membrane is located inside the wall • Animal cells do not have cell walls • Walls provide rigidity that keeps plants standing and maintains their shape Remember Prokaryotes can be divided into bacteria and archaea Major differences between bacteria and archaea Bacteria Archaea Cell wall Peptidoglycan/ Lipopolysaccharide Pseudopeptidoglycan Habitat Ubiquitous and are found in soil, hot springs, radioactive Extreme and harsh environments like hot springs, salt lakes, wastewater, Earth's crust, organic matter, bodies of plants and marshlands, oceans, gut of ruminants and humans animals Cell division Metabolic pathway Binary fission, budding, fragmentation, but eubacteria have the Archaea reproduce asexually by forming pseudosporangia. unique ability to form spores to remain dormant over years, a trait Changes metabolism to bacteria-like anaerobic life using acetate that is not exhibited by Archaea as e-donor and ferrihydrite as e-acceptor, all without fermentation Follow glycolysis pathway and Kreb's cycle to break down glucose Archaea possess unique metabolic pathways, distinct from those in Bacteria Other features Thymine is present in the (transferase RNA) Thymine is absent in the tRNA (transferase RNA) RNA polymerase is simple and contains 4 subunits RNA polymerase is complex and contains 10 subunits Absence of intracellular organelles Absence of intracellular organelles Archaea do live in our bodies! • Symbiotic relationship with anaerobic bacteria • Significantly lower diversity than bacteria Why are there no disease-causing archaea? Archaea share characteristics with known pathogens • Opportunity to colonise? • Long term colonisation possibilities? Does not necessarily mean they have strong virulence It is also likely that because archaea are difficult to cultivate, it is in turn difficult to study their effects on the body Archaea and human disease… Possible involvement in pathogenesis • Periodontal disease • Irritable bowel disease/ Crohn’s disease/ Ulcerative colitis • Obesity • Atherosclerosis • Colorectal cancers Tasks: 1-Draw by yourself a prokaryotic and an eukaryotic cell 2-Write down the name of different organelles 3-Write down the function of each (in one or two words) 4-Write down a list of organisms for each cell type Some requests may need you do some research on it….take the challenge! You can do this by yourself and/or look for another student and work this out together!! You can test your understanding by explaining load concepts to your peers. Test yourself…. Multiple choice questions to practice! https://forms.office.com/Pages/ResponsePage.aspx?id=WxHSQ16ltkad97Az iOz8YHPKVJ7iwLlEi3zi7EZn_8pUMUYzOUQ2Rk1FVU9VNEpNVlExWkNJM 0JUTC4u Any questions? email me: [email protected] Thank you! Thank you