Transcript animal cell
The CELL SURFACE AND CYTOSKELETON 3-D Journey Chapter 5 The Cell Membrane and Cell Function Cell Membrane recognizes “self” Organ rejection Name tags of proteins, carbs and lipids Key: Blue “egg shaped” forms = cell membrane Brown forms = proteins Green “chain-like” form = sugars Cells do not have “telepathic” abilities. They must actually come in contact with each other via these sugars in order to communicate their needs and recognize one another. Cytoskeleton Cell’s interior scaffolding Protein fibers Cytoskeleton + cell membrane Cells framework Organizes interior of cell Distinguishes on cell from another A. Cell Membrane Structure Cell membrane is a phospholipid bilayer embedded with mobile proteins. – Sandwich-like layering repels both charged and uncharged particles Proteins Phosphate head of phospholipid is hydrophilic. Fatty acid tails are hydrophobic. CM Structure, con’t Proteins – embedded Passageway for water soluable molecules and ions Also act as carriers CM Structure, con’t Fluid mosaic – everything moves within the layer CM Structure, con’t Receptors – glycoproteins on or within the membrane surface CM Structure, con’t Ratios of proteins to phospholipids reflect health Upset = sickness Multiple sclerosis – not enough fat in cell membranes (cell that are supposed to create mylin TaySachs – excess lipid in cell membrane (cells that build TOO MUCH mylin Layers of plasma membrane wrapped around an axon Diffusion: Passive Flow Across a Membrane General terms: Aquaeous solution – homogeneous mixture of solute + solvent (water) Concentration – how much solute is in the solvent Diffusion, con’t Diffusion moves substances from high to low concentration Membranes are selectively permeable Oxygen, water and carbon dioxide freely cross membranes Diffusion, con’t Heat increases the rate of diffusion – kinetic energy is increasing Diffusion, con’t Concentration gradient – differences in concentration from low to high or vice-versa Other types of gradients: pH Electrical Pressure ions Diffusion, con’t Dynamic equilibrium – equal movement back and forth Osmosis The diffusion of water MUST be across a membrane Controlled by solute concentration inside and outside the cell Solutes can’t move, so water does Osmosis, cont Tonicity Isotonic-solutes inside and outside have the same concentration Osmosis, con’t Hypotonic – hypertonic Relative terms Can refer to inside or outside of cell • Hypotonic - solution with the lower solute concentration. • Hypertonic - solution with the higher solute concentration. Red blood cell example Pg 70 What is effect of immersing an animal cell in a hypertonic or hypotonic solution? Cells in solutions What is effect of immersing a plant cell in a hypertonic or hypotonic solution? Cell immersed in hypertonic solution Cell immersed in hypotonic solution Osmosis, con’t Contractile vacuole – organ that regulates water movement in single cell critter (see video on previous slide) Turgor pressure – how plant cells regulate how much water can flow into cell – water forced against the cell wall Transport Proteins Channels Allow Passive Movement at a faster Rate Forms an opening (tube) for solutes to pass through Charge and size regulate what passes FAST -100 million ions or molecules /second Form of facilitated diffusion Transport Proteins, con’t Carriers move cargo from one side to the other Carrier protein binds to ion or molecule Protein changes shape and forces particle to other side of membrane Can be passive (no ATP- therefore another facilitaed diffusion) or active- uses ATP Passive facilited 100-1000 per ssecond Active – can move against the gradient Transport Proteins, con’t Pumps use energy to move molecules or ions against a gradient Sodium potassium pump Transport Proteins, con’t Pumps, con’t Co-transport- see diagram (figure 5.11) pg 72 Creates gradient Gradient used to transport substance Symporter molecule responds to gradient movement Transport Proteins, con’t Vesicles perform mass movements by packaging substances Exocytosis – fluids and large particles out of cell Ex. Sperm – releases enzymes that penetrate egg Transport Proteins, con’t Vesicles, con’t Endocytosis – capture large molecules and fluid on surface and move into cell Pinocytosis – just water or solutes and water Phagocytosis – captures and destroys debris, small organisms, bacteria Endosome – phagocytic vesicle fuses with a lysosome Transport Proteins, con’t Vesicles, con’t Endocytosis, con’t Receptor mediated endocytosis Receptor protein binds to ligand, membrane indents, pulling ligand into the cell Ex. Liver cells take in cholesterol this way Transport Proteins, con’t Trancytosis – combination of endo and exocytosis Moves particles from one side of the cell to another The Cytoskeleton Tubules and filaments guide organelle movement, provide shape and link molecules The cytoskeleton, con’t Compare Microtubules and both filaments (figure 5.14 pg 75 aka microfilaments The cytoskeleton, con’t Microtubules – hollow, thick elements made of the protein tubulin- protein dimmers (pairs) Length adjustable + or – molecules of tubulin Number and arrangement changes based on cell cycle (spindles) Cancer treatments – some effect tubule assembly The cytoskeleton, con’t Other Functions: • move chromosomes apart during cell division • form cilia & flagella •Cilia- have wave-like motion •9 microtubule pairs around a central pair (9+2) pattern •Dynein – connects inner and outer proteins (wheel-like) pg 76 The cytoskeleton, con’t • • Bad dynein arrangement leads to disease Clean respiratory track, move egg down fallopian tube, single celled critters swim Leads to Alzheimer’s plaques and tangles The cytoskeleton, con’t Flagella 9+2 arrangement but longer Whiplike – propulsion Sperm cells – humans 1, cycad tree - thousands The cytoskeleton, con’t Another function – track-way in cell Moves organelles and proteins within Squid color changes – rearrange pigment The cytoskeleton, con’t Microfilaments - long, thin elements made of the protein actin. Not hollow Smaller than microtubules Functions: • Strength to cells – withstand stretching and bending) • connect cells to each other • move vesicles & organelles within cytoplasm • Muscle contractions • Actin and myosin interact in sliding filament The cytoskeleton, con’t Intermediate filaments - elements with diameters in between that of microtubules & microfilaments. Made of various proteins (ie. keratin) Dimers entwined into coiled rods Functions: • maintain cell shape • Inner framework of cell • connect cells to each other & to underlying tissue (skin cells) • Epidermolysis bullosa • Intermediate filaments abnormal – skin blisters easily Cell Signaling and Response Cell to Cell communication Intercellular Junctions Structures that connect cells of multicellular organisms to form tissues Cell Signaling and Response, con’t . Animal cell Connections- types depend on functions Tight Junctions - cell membranes of adjacent cells are fused, creating a tight seal – like a belt Create sheets Ex. cells lining small intestine; cells lining capillaries in brain Cell signaling and Response, cont Blood vessels (capillaries) in brain (400 mile-blood brain barrier) Lipids are chemically soluble – heroin, valium, nicotine, cocaine, alcohol Oxygen passes Water soluble – different pathway Cell Signaling and Response, con’t Desmosomes - intermediate filaments weld cell membranes of adjacent cells together in isolated spots. hold skin cells in place (cell to extrcellular matrix) Ex. skin cells Cell Signaling and Response, con’t Gap Junctions - channels that link the cytoplasm of adjacent cells, allowing exchange of materials. Ex. heart muscle cells, and muscle cells in digestive track Cell Signaling and Response, con’t Cell Walls add structure and allow interactions Around cells of bacteria, archaea, fungi, algae and plants Provide shape and volume AND interact Cell Signaling and Response, con’t Cell walls, con’t Composition depends on function of cell, surrounding or life cycle of cell Plants – mostly cellulose and pectin (like glue) Cell Signaling and Response, con’t CW is layers. Oldest layer is most outside layer Where cell walls meet: middle lamella Plasmodesmata – link plant cells (tunnels to cells) Cell Signaling and Response, con’t Cell Adhesion Process that uses membrane proteins called cellular adhesion molecules (CAMs) to direct the migration of cells. Various CAMs function in sequence to: • guide WBCs to injury sites • guide embryonic cells to help form placenta • establish nerve connections involved in learning & memory CAMs directing WBCs to injury sites. Cell Signaling and Response, con’t . Signal Transduction Process by which cells receive, amplify, & respond to outside stimuli.