BSC 215 Week 5 Notes
BSC 215 Week 5 Notes BSC 215
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This 12 page Class Notes was uploaded by Jordana Baraad on Thursday September 8, 2016. The Class Notes belongs to BSC 215 at University of Alabama - Tuscaloosa taught by Dr. Jason Pienaar in Fall 2016. Since its upload, it has received 30 views. For similar materials see Human Anatomy & Physiology I in Biological Sciences at University of Alabama - Tuscaloosa.
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Date Created: 09/08/16
9/6 CQ 1. Cmpd has 120 carbons, 240 hydrogens, 2 oxygens. It is most likely a… Lipid (C, H, O) NOT protein/ nucleic acid, bc no N, or carbohydrates bc no 1:2:1 ratio 2. monomers of proteins are… d. amino acids LO1: Understand “cell theory” and the scientific discoveries that led to it Know a few names… Robert Hookst 1 tenet of life/ cell theory: all living things have cells Anton Van Leeuwenhoek Discovered bacteria Louis Pasteur Spontaneous generation of life 2 tenet of life: all life comes fr life; all cells come from cells • 3 tenets of cell theory 1. All living organisms are composed of cells 2. The cell is the most basic unit of life everything above cell level is life; everything below is not cellular processes 3. All cells come from preexisting cells LO2: Understand variation in and limits on cellular morphology Morphology: shape and size Shape variation Skin cells—no cell wall Bacterial cells –no nucleus Nerve cells –no cell wall; axons/ dendrites as projections Egg cell Plant cells—cell wall Size variation Egg cell (100 μm diameter) –big, not microscopic Most human cells 1015 μm diameter Some nerve cells (>1m long) LO2: Understand variation in and limits on cellular morphology Surface to Volume ratio Becomes TOO SMALL 10μm v. 30μm cube hypothetical cells Surface 10 = 100; Volume 10 =1000; Ratio S/V = 0.1 Surface 30 = 900; Volume 30 =27000; Ratio S/V = 0.03 much lower S/V ratio—not ideal bc lots rxns happen on surface want smaller size smaller vol cannot sustain chemistry CQ 3. Cell 1 has 10um width; cell 2 has 50 um width. Which cell has larger S/V ratio? A) cell 1 LO3: Know the three basic components of cells and the terminology used to describe them Extracellular space/ fluid Intracellular space/ fluid: Plasma membrane (3 domain) Cytoplasm (2 domain) cytoplasmic organelles many are membranous—increase Surface Area (SA) of cell cytoskeleton—gives structure Nucleus (3 domain) Nuclear envelope (bilayer Nucleus (houses genetic material) Only in eukaryotes; bacteria don’t have nuclei LO4: Describe how lipids, carbohydrates and proteins are distributed in a cell membrane and explain their respective functions Lipids • 98% of membrane molecules are lipids • 75% phospholipids • Amphipathic – hyrophillic side (charged, phosphate) and hydrophobic side (noncharged, fatty acid (FA) ) • Form bilayers—largest component of cell membrane spontaneous formation of micelle (hydrophilic heads protect fatty acids) liposome = larger version of micelle phospholipid bilayer = larger version of liposome FA’s interact w/ one another; phosphates interact w/ water on each side • 20 % cholesterol • Stiffen membrane steroid molecule (cholesterol in cell membrane; hormone when seen elsewhere) • 5% glycolipids • Form part of the glycocalyx Proteins • 2% of membrane molecules are protein (but 50% of mass) • Two major classes • Integral (embedded): integrated/ embedded in membrane; spans membrane • peripheral: float around in extracellular or intracellular fluid Receptors: Bind specific chemical messengers and transmit the signal into the cytoplasm Often transmit signal from hormones all the way to genes Alter gene expression Enzymes: Catalyze various metabolic reactions Channels: Allow hydrophilic molecules & water through membrane Ligand channels: molecule must bind to receptor to open channel Voltage channels: requires charge difference Mechanically gated channels: need physical change to open Identity markers: Glycoproteins distinguish “self” from “non self” Part of immune response Cell adhesion molecules (CAMS): provides strong chemical linkages btwn cells cellcell binding and mechanical connections to extracellular matrix linking cytoskeletons Glycocalyx • Glycolipids • Glycoproteins • Unique identifier • Guides embryonic cells to destinations (mailing addresses) • Immune functions: know not to attack own cells; recognize lack in pathogens • Adhesion functions: sugar is sticky LO5: Understand passive transport mechanisms across cell membranes Passive transport: Does NOT require external energy Using term loosely; no transport protein involved 2 ways to transport across membrane w/o energy but both ACTUALLY THE SAME—both involve particles down conc. gradient 1. Diffusion: Movement of solutes (particles)down a concentration gradient Why? • kinetic energy of random motion • Less particles to bump into at lower concentration, travel further In life, interested in diffusion across a membrane (bidirectional in/out of cell) • Cell membranes are selectively permeable ex. ethanol will go in, Na won’t—not lipid soluble • Selectivity based on: • Size: lipid soluble but can’t fit btwn molecules • Charge: small enough, but charge repels • Membrane protein specificity ex. membrane channel made just for Na—other molecs can’t BUT Still just diffusion Simple V facilitated diffusion Simple diff: particles thru membrane Facilitated diff: carrier protein or channel Still with concentration gradient Factors affecting membrane diffusion rate • Temperature • Higher kinetic energy of motion • Molecular mass • Smaller molecules diffuse faster • Concentration gradient higher concentration faster diffusion to low conc area • Membrane surface area rate measured with respect to size of cell greater surface area greater rate • Membrane permeability faster diffusion 2. Osmosis: Movement of solvent down a concentration gradient • Diffusion of Solvent (e.g. water) molecules across a membrane • I.e. water flows DOWN a concentration gradient • Dissolved solutes determine water concentrations • Hydration spheres also help water slightly charged; surrounds ions CQ 4. Which of following factors affect diffusion rates of small hydrophobic molecules? b. temperature, conc. gradient NOT ATP, bc then energy required Aquaporins • Some water always diffuses across the plasma membrane • H20 is a small, partially charged molecule • Many cells embed Aquaporin channel proteins in membranes that allow water to diffuse easily ex. kidney cells • Control osmotic rate by varying Aquaporin number LO6: Understand active transport mechanisms across cell membranes Diffusion summary • Diffusion, whether simple or facilitated is always passive transport • Always down / with a concentration gradient • No additional energy required Active transport always requires energy o Primary active transport: Membrane protein uses ATP energy directly to “pump” against concentration gradient o Secondary active transport: Membrane protein uses concentration gradient energy created by a different ATP dependent “pump” o Vesicular transport: Membrane vesicles bud off membrane to transport molecules wholesale Transport up / against a concentration gradient 9/8/16 Active transport always requires energy o Primary active transport: Membrane protein uses ATP energy (via hydrolysis)directly to “pump” against concentration gradient o Secondary active transport: Membrane protein uses concentration gradient energy created by a different ATPdependent “pump” Transport is onestep removed o Vesicular transport: Membrane vesicles bud off membrane to transport molecules wholesale *or* move big molecules Vesicle made from/ derived from cell membrane Transport up / against a concentration gradient Membrane protein pumps Uniport: moves one substance one way Cotransport: Symport: 2 substances in same direction Antiport: 2 substances in opposite direction The Sodium Potassium pump All animal cells have them Necessary for … nerve cell signaling Skeletal (skinetal)muscle contraction Heart beat Osmotic balance Also lots bacteria Antiporterlike activity (2ndary active transport) **MANTRA: 2 K’s into, 3 Na’s leave (like Mad Max: 2 man into, 1 man leave) more Na’s going out than K’s in—both pos more unpaired Cl’s inside cell outside cell more pos; inside cell more neg Na more concentrated create electrical polarity electrical current ATPase (primary active transport) Up to 30% of cellular energy used for Na/K pumps Sodium potassium pump Diagram: NOT the Na/K pump; describes what happens after—channels open, and then… arrows rep diffusion Green: K; orange: Na 1. Na binds to pump by ATP phosphorylation 2. phosphorylation shape change 3. Shape change good for binding K ions (2) 4. release phosphate ions shape change back 5. K released Primary & secondary active transport • Sodium potassium pump is an example of primary active transport • Uses ATP as an energy source • Secondary active transport uses concentration gradients of cotransported molecules as an energy source • e.g. Sodium gradient Secondary active transport: Glucose symporter 1. Na/K pump creates ion gradient 2. 2 protein: Naglucose symport transporter loading glucose from ECF Na/K pump uses so much E bc used for so many processes Vesicular transport • Movement of large particles or many molecules simultaneously through membranes in membrane derived vesicles • Endocytosis (vesicular transport into cell) •Phagocytosis (“cell eating”) “eats” bacterial or cancer cell internalize w/ vesicle destroy w/ lysosome • Pinocytosis (“cell drinking”) if cells don’t get water fast enough, bring in lots water wholesale • Receptor mediated endocytosis (“specific molecule transport”) most prevalent type proteins good at recognizing shape; informs this mechanism only molecules w/ correct shape enter (ex. hormones) • Exocytosis (vesicular discharge out of cell) Receptor mediated transport: e.g. Low Density Lipoprotein (LDL) uptake from bloodstream Molecules bind to specific receptors on plasma membrane. Receptors cluster Receptors sink inwards to form Clathrincoated pit Clathrincoated pit containing molecules separates from membrane to form clathrin coated vesicle o Complete internalization o Part of membrane internalized; need to keep replenishing membrane Cytoskeleton and Organelles Learning Outcomes Endomembrane system means all connected Dynamic cytoskeleton—can be reorganized/ remodeled Essential for cellular motion Centrioles; microvilli, cilia, flagella—3 stick out; all dependent on cytoskeleton Cellular Ultrastructure Able to start learning w/ advent of electron microscopy Major advances in resolution of 1cell imgs Plasma membrane Nucleus—largest organelle; Nuclear envelope Ribosomes—some free, some embedded in rough ER Translate genetic material protein If it’s alive, it has ribosomes—viruses don’t have them to translate gen code Mitochondria **fav test question: what’s evidence that mitochondria were once freeliving? Endosymbiant theory Ev #1 Outer membrane has lipids sim to eurkaryotes Inner membrane has lipids sim to bacteria Tells us that ancient endocytosis Inner = orig Outer = remnant of vesicle Golgi complex: modify protein Endoplasmic reticulum: creates SA to embed proteins/ ribosomes Translate/ encode “hydrophobic highway” LO1: Describe the structure and function of each organelle Most ATP made btwn inner and outer membrane Folds: cristae Don’t confuse w/ cistanae— **Mitochondrial DNA: evidence #2 remnants of bacterial genome Ev #3: has own ribosomes Ev #4 in genetic sequencing—don’t need to know Much more like bact Mitochondria • Powerplant of the cell • Specialized for ATP synthesis • Double membrane • Inner membrane forms cristae (folds) • Surrounds matrix • DNA, ribosomes • Endosymbiotic theory = reason for own dna/ ribosomes remnants of original bacterial ancestor LO1: Describe the structure and function of each organelle • Ribosomes • Specialized for protein synthesis using mRNA and tRNA • Large and small protein subunits • Free in cytosol or bound to rough ER and nuclear membranes fixation in ER impmRNA knows where to go (fixed address) Endoplasmic reticulum nucleus has inner membrane and outer membrane continuous w/ rough Er then smooth ER ribosomes lost along the way • Network of cisternae (tubules) continuous with outer nuclear membrane • Rough ER • Studded with ribosomes • Protein folding • Membrane factory • Combines integral proteins and lipids in “prefabricated” cell membrane sections fairly constant cell function, despite cell type variation • Smooth ER • No ribosomes • main job: Calcium ion storage function varies dep on cell type Calcium ion storage (e.g. muscles) • Detoxification reactions (e.g. liver) adapts to manage substance abuse • Lipid synthesis (phospholipids, cholesterols) LO1: Describe the structure and function of each organelle Golgi apparatus • Small system of cisternae • job: Synthesizes carbohydrates • Adds carbohydrates to proteins received from ER (glycoproteins) enclose proteins in transport vesicles lipidderived membrane fr membrane enclosing protein Specialized Associated Structures Goal: understand difference btwn peroxisomes and lysosomes Peroxisomes Diff #1: Produced by rough ER Contains oxygen free radicals Dangerous to cell; OK in enclosed organelle Oxidizes toxic substances (like ethanol) to hydrogen peroxide (H2O2) Functions: Breaks down fatty acids Reincorporate products into phospholipidsrecycling Synthesizes some phospholipids Lysosomes Diff #1: Produced by Golgi apparatus Functions: Contain acid hydrolases to digest bacteria & worn out cell components Relatively large Diff #2: peroxisomes break down small things; lysosomes break down larger things LO2: What is the endomembrane system and how does it function? Smooth ER: detox, store Ca, add lipids to growing proteins Peroxisomes = accessory struct Golgi apparatus: add carbs to growing proteins Lysosomes = accessory sruct LO2: What is the endomembrane system and how does it function? SER: lipid synth some degraded by peroxisomes RER: folding/ modification SER and RER proteins Golgi apparatus Some degraded by lysosomes Packaged in transport vesicles PM Some exocytosized LO3: Describe the structure and function of the cytoskeleton Fluorescent protein used for tagging in imgs Actin and tubulin = main cytoskeleton components Blue = cell nucleus Most cells have one nuc; count nuceli to count # cells (7 in img) Actin Lots concentrated directly beneath cell membranes Used to tell cell shape—cuboidal in this figure Tubulin Can rearrange Forms mitotic spindle, dragging DNA to new cells shifts mitochondria Microtubule highway LO3: Describe the structure and function of the cytoskeleton Cytoskeletons crucial to cell existence Shape function Experiments to synthesize cell failed until 3D print cytoskeleton Gives cells characteristic shape & size (e.g. artificial cells) Provides structural support for membrane, nucleus & organelles (e.g. holds mitochondria in place) Perform specialized functions (e.g. phagocytosis—restructuring to grab molecules to be phagocytosized) Allows for movement of whole cells, and movement of organelles within cells (e.g. mitosis, cilia & flagella) cytoskeleton allows flagella to beat LO3: Describe the structure and function of the cytoskeleton 3 types of protein filaments make up animal cell cytoskeletons (know funct and diameter) • Microfilaments (red) • Protein = actin 79 nm = d • Intermediate filaments (blue) • Protein depends on tissue (e.g. keratin in hair & nails) keratin makes you waterproof reason for fingers wrinkling in water: nerves activating muscles to increase grip if nerves severed, no wrinkles (ev for muscle contraction) 10 < d < 25 nm—gives intermediate name • Microtubules (green) • Protein = tubulin 20 nm = d LO3: Describe the structure and function of the cytoskeleton Microfilaments (Actin) • Form terminal web • Extend into microvilli (support & “milking”) can pull microvilli and whatever’s attached into cell • Intermediate filaments (Various proteins) • Give cell shape (stiff) • Purely structural role • Microtubules (Tubulin) • Radiate from centrosomes, hold organelles in place centrosomes controlle microtubules’ movements • Act as “railway tracks” for organelle movement • Axonemes (motors) of cilia & flagella, mitotic spindles (special instance of microtubules) • Some remodel (spindles) dragging chromosomes some don’t (axonemes for beating flagella) depending on function Cellular Extensions Microvilli v cilia Microvilli: Increase SA Find actin Cilia: bigger, more mobile Find tubulin protein Crosssection of axoneme in bottom left of cilia pic Flagellum (only in sperm cell) Structure almost exactly like cilia axoneme Pseudopodia: Actin filaments extend cell surface Directed by tubulin
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