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Cell: Basic unit of life Adult human contains ~75 trillion cells Cells are very diverse in size, shape, function › Ex: Neuron – long thin axons coupled with cell body – serve to move electric signals throughout body › Ex: Red Blood Cell – doughnut-shaped, small, carry oxygen to organs Two types: › 1) Prokaryotic › 2) Eukakryotic Prokaryotic cell: › Do NOT contain nucleus › DNA found in cytoplasm › Do NOT contain membrane-bound organelles › Simpler › Smaller (usually unicellular) Eukaryotic cell: › DOES contain nucleus › DNA found in nucleus › DOES contain membrane-bound organelles Ex: mitochondria, ER, golgi, lysosomes, vacuole › More complex › Larger size (usually a part of a multicellular organism) ALL cell contain: › Cell/plasma membrane a membrane which encloses to cell Serves to protect cell from pathogens and permit molecules to pass into cell › Cytoplasm Houses the cells organelles and genetic material › Ribosomes Protein synthesis takes place here › DNA/RNA Genetic material Also called plasma membrane Boundary that separates cell’s contents from the external environment Actively functioning component of cell › Regulates the movement of substances in and out of the cell › Helps cells to adhere to other cells (important in forming tissues) Characteristics: › 1) Thin, flexible › 2) Outpockets and infoldings (increase surface area) › 3) Selectively permeable (only allows some molecules in/out) Structure: › 1) Lipid bilayer Two layers of phospholipids Tails face inward (fat-like; hydrophobic – water hating) Heads face out (phosphate; hydrophilic – water loving) › 2) Cholesterol Keeps membrane fluid in cold weather › 3) Proteins Structure and cell communication › 4) Carbohydrates Cell communication Membrane proteins: › Transmembrane/integral: Help to transport ions and other molecules Structure › Peripheral/Extensions: Connection of organelles to membrane Structure Cell communication › CAM Cellular adhesion molecule Guides a cell’s interactions with other cells Ex: CAMs help white blood cells move to injury Contains organelles Contains cytoskeleton › Network of protein fibers that form a support system Usually slightly neutral pH Serves to help cells communicate signals Called ER Two types: › Smooth: No ribosomes found on surface (appears smooth) Contains enzymes important in lipid synthesis, absorption of fat, metabolism of drugs › Rough Contains ribosomes Site of protein synthesis – sends items to smooth ER and Golgi for further processing Site of protein synthesis Two types: › 1) Attached (to rough ER) › 2) Free (found floating in cytoplasm) Parts: › Protein › RNA molecule (rRNA – ribosomal RNA) Stacks of membranebound sacs Takes in proteins › Then, refines, packages › › › › and delivers final proteins Arrive to Golgi enclosed in vesicles Vesicles fuse with Golgi As move through Golgi, the proteins are modified chemically When reach outermost layer, packaged again in vesicles and shipped Major sites of cellular respiration (breakdown food to form energy - ATP) Can reproduce Contain own DNA Contains outer and inner membrane › Inner membrane folds inward to form cristae (fingers) Matrix: inner space Many mitochondria found in muscle cells (which require a LARGE amount of energy) Lysosomes: › Tiny sacs containing enzymes that break down nutrient molecules, foreign particles, broken organelles Peroxisomes: › Tiny sacs containing enzymes that catalyze the synthesis of bile acids, detox hydrogen peroxide, breakdown lipids, detox alcohol › Abundant in liver and kidney Cilia: › Tiny hairs › Assist in movement › Move fluids (like mucus) over tissues Flagella: › Tail-like extensions › Assist in movement › Usually cells contain single flagella › Ex: sperm Membrane-bound sacs formed by cell membrane folding inward Used for storage of macromolecules, water, toxins, pigments Thin, thread-like strands within cytoplasm Integral part of cytoskeleton Microfilaments: › Actin proteins › Provide cell movement (contraction, cilia/flagella) Microtubules: › Tubulin protein › Thicker Functions: › House genetic material › Direct all cell activities Enclosed by nuclear membrane (lipid bilayer) › Contain pores which allow molecules to exit Found within nucleus: › Nucleolus: small, dense organelle made of RNA and protein, forms ribosomes › Chromatin: loosely coiled fibers of DNA and proteins (chromosomes) Cell membrane is semi-permeable Rely upon concentration gradients to move › Def: difference in concentration between two areas › Continually work to reach a state of equilibrium (uniform concentration) Two types of cellular movement: › 1) Passive transport: No energy required Ex: diffusion, osmosis, facilitated diffusion, filtration › 2) Active transport Energy required Ex: exocytosis, endocytosis, proton pumps Passive transport (no energy use) Molecules/Ions spread from regions where they are more concentrated to less concentrated Can occur if: › Membrane allows it › Concentration gradient exists Ex: oxygen and carbon dioxide moving in/out of blood Animation Passive transport (no energy use) Molecules/Ions spread from regions where they are more concentrated to less concentrated Can occur if: › Membrane allows it › Concentration gradient exists › Membrane proteins assist(change shape when molecule attaches) Ex: movement of glucose and amino acids Animation Passive transport (no energy use) WATER molecules spread from regions where they are more concentrated to less concentrated Can occur if: › Membrane allows water (but usually not other molecules) to pass through › Concentration gradient exists Solution can be: › Hypertonic: Higher osmotic pressure inside More water –less solutes - on inside of the cell Result: water rushes OUT, cell shrinks › Hypotonic: Lower osmotic pressure inside Less water – more solutes – on inside of the cell Result: water goes IN, cell expands Solution can be: › Isotonic: Same osmotic pressure on body sides Molecules CONTINUE TO MOVE Net concentration of water and solutes does not change! Animation Passive transport (no energy use) Molecules are FORCED from regions where they are more concentrated to less concentrated Usually used to separate solids from water Relies upon hydrostatic pressure (created by weight of water due to gravity) to force molecules Teacher Demo (applesauce and water) Requires use of energy (ATP molecules) Also requires the use of special membranebound proteins to assist molecule movement › Carrier proteins (change shape when molecule attaches) Moves particles AGAINST concentration gradient (low to high) May use up to 40% of cell’s energy Ex: Proton pump, Na/K pump, movement of nutrients into cells that line intestines Requires use of energy (ATP molecules) Molecules too large to enter cell through passive transport Molecules are packaged inside vesicles (using infolding of cell membrane) Molecule moves INWARD Three forms: › Phagocytosis: Cell “eating” Take in solid particles (bacteria, debris) › Pinocytosis: Cell “drinking” Take in liquid particles (water w/ dissolved items) › Receptor-mediated: Moves specific kinds of particles into cell Proteins extend to outer surface where they form receptors Bind to ligands Requires use of energy (ATP molecules) Molecules too large to leave cell through passive transport Molecules are packaged inside vesicles and SECRETED OUT Molecule moves OUTWARD Series of changes cell undergoes from its formation to its division Rate of cell cycle depends upon checkpoints and stimulation › Ex: restriction checkpoint Determines cell’s fate (division, resting, death) › Cancer: inability of cell to respond to checkpoints, cells divide uncontrollably › Stimulation: cells will divide spontaneously when hormone or growth factor triggers it Ex: development of milk during pregnancy Includes: › Interphase: preparatory phase Grows, makes copies of organelles, obtains nutrients replicates DNA Three stages: G1, S, G2 Includes: › Mitosis: Nuclear division Phases: Prophase, Metaphase, Anaphase, Telophase Prophase: chromosomes condense (become visible), centrioles migrate to opposite ends, nuclear envelope disappears Metaphase: chromosomes line-up in middle, spindle fibers attach to centromeres Anaphase: chromosomes separate, cell elongates Telophase: final stage, chromosomes unwind (go back to chromatin), nuclear envelope reforms (prophase in reverse!) Includes: › Cytokinesis: Cytoplasmic division Animals: Cell membrane begins to constrict, pinch inward Creates cleavage furrow Uses microfilaments to contract and pinch › Animation Differentiation: › Def: Process of cell specialization › Cell gains function/structure Stem cells: › Def: cells who have NOT gained specialization, divide frequently › Divides through mitosis continually (two options) 1) Forms 2 daughter cells 2) One daughter cell and one progenitor cell Progenitor cell: partially specialized cell Apoptosis: › Cell that does not divide or specialize › Cell death › Normal part of development Ex: fetus – rids hands of webbing › Could also be due to injury or disease Ex: sunburn (peeling skin)