Lecture 11: Cell Basics Notes PDF

11 Cell Basics mmmure : Notes - What factors does it take to make a cell? 1. Information All cells contain DNA (the hereditary material of genes) and RNA (provides info necessary to build. Various proteins), these are the cell’s primary machinery Central Dogma:...

11 Cell Basics mmmure : Notes - What factors does it take to make a cell? 1. Information All cells contain DNA (the hereditary material of genes) and RNA (provides info necessary to build. Various proteins), these are the cell’s primary machinery Central Dogma: Because of the lack of nuclei (Enucleation: Mechanism by which maturing RBCs eject their nucleus) and organelles, mature red blood cells (RBCs) don’t contain and DNA and cannot synthesize any RNA Consequence: RBCs cannot divide and have limited repair capabilities Due to this, RBCs evolved to accommodate maximum hemoglobin carrying capacity During development, most cells in multicellular organisms will become specialized due to differentiation This creates different specific cell types and is how various tissue of the body (organs, muscle, etc.) are produced 2. Chemistry When and how the building blocks of life (Nucleic Acids, Lipids, and Amino Acids) appeared in the history of Earth Miller-Urey Experiment: Chemiscal experiment that simulated the conditions thought to exist on early Earth to test the chemical origin of life Oparin’s and Haldane’s Primordial Soup Hypothesis: Putative conditions on primitive Earth favoured chemical reactions that synthesized more complex organic compounds from simpler inorganic precursors Chemical origin of life = ABIOGENESIS Nitrogen, Carbon Dioxide, + Energy —> Simple Organic Ammonia, Methane, Water, (Electricity, UV) Compound and Hydrogen gas  Conclusion: Amino acids (the building blocks of protein) can be generated in conditions that mimic those of early Earth Follow-up: Later experiments have shown that other chemical reactions can generate simple sugars, the bases found in nucleotides, and the lipids needed to form primitive membranes 3. Compartments Usually defined by a single or double lipid layer membrane Examples of cellular compartments include: mitochondria, chloroplasts, the nucleus, vesicles, and the endoplasmic reticulum Compartments play fundamental roles: - Establish physical boundaries and enable the cell to carry out different metabolic activities - Generate a micro-environment to spatially and temporally regulate biological processes The Discovery of Cells: The discovery of cells was discovered by Robert Hooke (1635-1703) using an early model of the microscope He contributed to the improvement of the microscope and coined the term “cell” The Cell Theory: The credit for developing the Cell Theory is given to two scientists: Matthias Jakob Schleiden and Theodor Schwann They postulated two of three tenets of the Cell Theory: 1. All living organisms are composed of one or more cells 2. The cell is the most basic unit of life Later on, Rudolf Virchow added the third tenet: 3. Omnis cellula-e-cellulla (All cells come from cells) Basic Properties of Cells: 1. Highly COMPLEX and ORGANIZED 2. Actively controlled by a GENETIC program 3. Can REPRODUCE - make copies of themselves 4. Assimilate and utilize ENERGY 5. Carry on many CHEMICAL reactions (enzymes) 6. Engage in MECHANICAL activities 7. Respond to STIMULI 8. Capable of SELF-REGULATION 9. They EVOLVE Prokaryotic vs Eukaryotic Cells: Is said to be the most important distinction among groups of organisms Prokaryotes were the only form of life on Earth for millions of years until more complicated eukaryotic cells came into being through the process of evolution Examples of Prokaryotes: Archea, Bacteria Typical Features of Prokaryotes Single-cell organism Size: 1-10 micrometers No nucleus or organelles Ribosomes are present but small Reproduce asexually Genetic material found in nucleoid - not a true chromosome but rather DNA arranged in a circular fashion (plasmid) Organisms that have Eukaryotic Cells include: Protozoa (single-celled eukaryotes), Fungi, Plants, and Animals Typical Features of Eukaryotic Cells Found in multicellular organisms, but can be unicellular as well (Protozoa) Size: typically 10-100 micrometers Have nucleus and organelles Ribosomes are large Genetic martial found in nuclear compartment and arranged as chromosomes Eukaryotic Cells: Animal vs Plant: Not all eukaryotic cells have the same components, important distinctions exist for instance between animal and plant cells Plant cells have cell walls (rigid barrier made of polysaccarides) while animal cells do not Plant cells have vacuoles (contribute to the structural rigidity of the plant cell and maintain the pressure against the cell walls) animal cells do not Plant cells contain chloroplasts (used for photosynthesis) animal cells do not Plant cells have plasmodesmata (connect neighbouring plant cells together so that they can communicate) animal cells do not