BIOL1020 Module 1 - Cell Biology

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University of Queensland
Dr Paul Ebert

Module 1: Cell Biology The common origin of life Living things:  Have order  Adapt to their environment  Respond to their environment  Regulate their cellular and body processes  Grow and develop  Reproduce Life is based on a hierarchy It is believed all living organisms evolved from a single, common ancestor cell (roughly 2.8 billion years ago) Classification of life Eukarya Eukaryotic Archaea Common ancestor Prokaryotic Bacteria Prokaryotic Prokaryotic: refers to lack of cell nucleus  Archaea are highly metabolically adaptable  Bacteria are the supreme inhabitants of other organisms Eukaryotic: refers to presence of cell nucleus Similarities:  Plasma membrane (refers to a fluid matrix which separates the contents from its surroundings)  Cytoplasm (semi-fluid matrix which contains chemicals of cell i.e. sugars, amino acids, proteins (and organelles in eukaryotes))  Proteins and carbohydrates (the ‘workhorses’ and energy source)  Perform metabolic processes (interconversion of different forms of energy and chemical materials i.e. photosynthesis and respiration)  Produce similar structures  Contain DNA and RNA Differences  Eukaryotic cells have DNA contained inside a membrane  Eukaryotic cells have internal membranes that allow them to compartmentalize cellular processes The cell Prokaryotic cells Bacterial chromosome is a single, circular molecule Component Properties Function Chloroplasts - Contains pigment chlorophyll Site of photosynthesis (plastid) - Contains 3 membranes (outer, inner & thylakoid) - Inner membrane surrounds stroma which contains soluble enzymes, DNA and thylakoids Cytoskeleton - Set of filaments: microtubules, microfilaments, - Cell shape, cell support and cell intermediate filaments movement - Allows cells to adopt extreme shapes Vacuole - Occupies more than 30% of cell volume - Houses water, enzymes, ions, pigments and toxic metabolic byproducts - Transport of protons from cytosol to vacuole helps keep cytoplasmic pH stable - Maintains turgor pressure against cell wall - Pushes chloroplasts against the cellular membrane (closer to light) Cell wall - Rigid structure outside plasma membrane - Cell support - Consists of polysaccharides (i.e. cellulose) - Limits cellular expansion Eukaryotic cells Component Properties Function Nucleus - Surrounded by double nuclear Contains cell’s hereditary information membrane - Contains chromatin (DNA + protein) Endoplasmic - Membrane system attached to outer Outer ER: synthesis of proteins on ribosomes reticulum membrane of nucleus Ribosomes - Free in cytoplasm and attached to ER Protein synthesis and mitochondria Mitochondria - 2 membranes: outer layer smooth and Harvesting energy from food molecules inner layer folded into cristae (respiration) - Function as semi-autonomous organisms with own DNA and ribosomes Origins of eukaryotic cells  Predation  Symbiotic merge of two prokaryotic cells to form a nucleus  Invagination of cell membrane to surround the DNA Endosymbiont hypothesis: mitochondria and chloroplasts came from prokaryotic cells that developed symbiotic relationships with another cell  Mitochondria: alpha Proteobacteria  Chloroplasts: photosynthetic Cyanobacteria Cells are made of molecules Monomer  Polymer  Macromolecule Building blocks: Carbohydrates Serve as fuel and building material  Include sugars and their polymers (mono-, di- and polysaccharides) Monosaccharides: simple sugars  Used for fuel  Converted into other organic molecules or polymers  May be linear or form rings when dissolved in water – ring formation favoured Disaccharides: two monosaccharides joined by glycosidic linkage Glucose + glucose = maltose (produced by digestion of starch) Glucose + fructose = sucrose (circulates in plant sap and used as table sugar) Glucose + galactose = lactose (gives milk its sweet taste) Polysaccharides: polymers of sugar; used for energy storage and structure Starch  Consists entirely of glucose monomers  Major storage form in plants  1-4 linkages with some branching (1-6 links)  Can be digested by humans Glycogen  Consists of glucose monomers  Major storage form in animals  1-4 linkages with frequent branching (1-6 links)  Humans break it down to release glucose Cellulose  Component of cell walls in plants  1-4 linkages of beta-glucose monomers = good packing potential  100 billion tones made annually  Cannot be digested by mammals Chitin  Modified version of cellulose  Found in exoskeleton of arthropods and cell walls of fungi  Highly resistant to enzymatic digestion  Used as surgical thread Building blocks: Proteins Amino acids  polypeptides  protein Amino acids: organic molecules possessing both carboxyl and amino groups  Differ in properties due to differing side chains (R groups)  Can be non-polar, polar or electrically charged  Linked by peptide bonds Proteins made up of 20 different amino acids Four levels of protein structure 1. Primary structure 2. Secondary structure 3. Tertiary structure 4. Quarternary structure Type of protein Function Examples Enzymatic Selective acceleration of chemical Digestive enzymes: catalyze reactions hydrolysis of polymers in food Structural Support Collagen and elastin: connective tissues Keratin: protein of hair, feathers, skin Storage Storage of amino acids Ovalbumin: source of amino acids for developing embryo in egg white Casein: protein of milk; source of amino acids for baby mammals Transport Transport of substances Hemoglobin: iron-containing protein of vertebrate blood; transports oxygen from lungs to other parts of body Hormonal Coordination of an organism’s Insulin: helps regulate activities concentration of sugar in blood Receptor Response of cell to chemical stimuli Receptors in membrane of a nerve cell: detect chemical signals from other nerve cells Contractile and motor Movement Actin/myosin: responsible for muscle movement Defensive Protection against disease Antibodies: combat bacteria and viruses Building blocks: Nucleic acids Store and transmit hereditary information Nucleotides  polynucleotide  nucleic acid Genes: units of inheritance  Program the amino acid sequence of polypeptides  Comprised of nucleic acids – sequence is unique to each gene Nucleotide monomers: nucleosides + phosphate groups Nucleic acids  Deoxyribonucle
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