2 Cell Membrane: Function: Maintain homeostasis. This is also called equilibrium.Allow passage of some molecules while preventing the passage of othersThis is called being “Selectively permeable” or “semi-permeable”
3 Semipermeable Membrane The Plasma Membrane4/20/2017Semipermeable MembraneSmall molecules and larger hydrophobic molecules move through easily.e.g. O2, CO2, H2OG. Podgorski, Biol. 1010
4 Semipermeable Membrane The Plasma Membrane4/20/2017Semipermeable MembraneIons-hydrophilic molecules larger than water, and large molecules such as proteins do not cannot pass through the membrane without help.G. Podgorski, Biol. 1010
5 Membrane structure: Composed of a phospholipid bilayer Have a phosphate head which is polar- does react with waterHave a fatty acid (lipid) tail that is non-polar- does not react with waterTogether these make up the membrane
6 The outside of the membrane is hydrophobic- which means it does react with water The inside of the membrane is hydrophilic- which means it does not react with water
7 Contains proteins within its structure Integral proteins (transport proteins)- which allow the passage of molecules to large too pass through the membrane without helpPeripheral proteins- aid in signaling for the cell to communicate with other cells
8 Cell Structure:Make up a metaphor for the phosphate heads of the membrane and the lipid tails of the membrane.The cell’s structure allows it to maintain homeostasis in different situations.
9 Concentration Gradient Concentration gradients occur when there is a higher amount of solutes in one area of solution then in another.Molecules will tend to travel from areas of high concentration to areas of lower concentrations
10 Passive transport Molecules flow with or down a concentration gradient No energy requiredTwo types:DiffusionEx. OsmosisFacilitated Diffusion
12 Facilitated Diffusion Diffusion for molecules that are not lipid soluble or are too large to pass through the membrane.Carrier proteins change shape to aid these molecules across the membraneNo Energy Required.Example: Glucose, Fructose
13 OsmosisDiffusion involving water moving from high solute concentrations to low solute concentration.Water can move freely across the membraneNo energy required.
14 Osmosis There are three different types of osmotic solutions: HypotonicisotonicHypertonic
15 Hypotonic Solution Higher concentration of solutes within the cell More free water outside the cellWater moves into the cellThe cell becomes swells or gets largerHypo Hippo- it gets big and swells.
16 Hypertonic Solution Higher concentration of solute outside the cell More free water in the cellWater moves out of the cellCell shrinks
17 Isotonic solution Solutions are equal between the two areas Water moves both directions to keep the solutions at an equilibrium.
19 Three different Osmotic Solutions Hypotonic- higher concentration of solutes in the cellHypertonic- higher amount of water inside the cellIsotonic – equal amount of solutes inside and outside the cell
20 Example- Plants:In a hypotonic solution plant cell’s membrane is pushed against the cell wallTurgor PressureIn a hypertonic solution a plant cell’s membrane will shrink within the cell wallPlasmolysisCauses wilting when plants dehydrate
21 Turgor Pressure Plant cell become engorged with water Gives plant the stiffness in their stem
22 Plasmolysis Plant cell membrane shrinks from the cell wall Causes plant to wilt.
23 Active TransportMolecules are transported against the concentration gradient by proteinsRequires energy (ATP)Example: Sodium-Potassium PumpA protein that transfer Na+ and K+ ions up the gradientCell has a high Na+ concentration outside the cell and a high K+ concentration inside the cell
24 Active transport Enodcytosis: Exocytosis: cells engulf substances that are too large to enter the cell by passing through the cell membranecellular wastes are removed from sacs at the cell’s surface
25 Exocytosis- moving things out. The Plasma Membrane4/20/2017Exocytosis- moving things out.Molecules are moved out of the cell by vesicles that fuse with the plasma membrane.This is how many hormones are secreted and how nerve cells communicate with one another.copyright cmassengaleG. Podgorski, Biol. 1010
26 The Plasma MembraneExocytosis4/20/2017Exocytic vesicle immediately after fusion with plasma membrane.copyright cmassengaleG. Podgorski, Biol. 1010
27 The Plasma Membrane4/20/2017Large molecules move materials into the cell by one of three forms of endocytosis.copyright cmassengaleG. Podgorski, Biol. 1010
28 Pinocytosis- Most common form of endocytosis. The Plasma Membrane4/20/2017Pinocytosis-Most common form of endocytosis.Takes in dissolved molecules as a vesicle.G. Podgorski, Biol. 1010
29 Pinocytosis- Cell forms an invagination The Plasma Membrane4/20/2017Pinocytosis-Cell forms an invaginationMaterials dissolve in water to be brought into cellCalled “Cell Drinking”copyright cmassengaleG. Podgorski, Biol. 1010
30 Example of Pinocytosis The Plasma Membrane4/20/2017Example of PinocytosisTransport across a capillary cell (blue).mature transport vesiclepinocytic vesicles formingcopyright cmassengaleG. Podgorski, Biol. 1010
31 Receptor-Mediated Endocytosis The Plasma Membrane4/20/2017Receptor-Mediated EndocytosisSome integral proteins have receptors on their surface to recognize & take in hormones, cholesterol, etc.copyright cmassengaleG. Podgorski, Biol. 1010
33 Endocytosis – Phagocytosis The Plasma Membrane4/20/2017Endocytosis – PhagocytosisUsed to engulf large particles such as food, bacteria, etc. into vesiclesCalled “Cell Eating”copyright cmassengaleG. Podgorski, Biol. 1010
34 The Plasma Membrane4/20/2017Phagocytosis - Capture of a Yeast Cell (yellow) by Membrane Extensions of an Immune System Cell (blue)copyright cmassengaleG. Podgorski, Biol. 1010
35 So to review the three types of Endocytosis are: PhagocytosisPinocytosisReceptor mediated Endocytosis.
36 The Plasma Membrane4/20/2017Exocytosis The opposite of endocytosis is exocytosis. Large molecules that are manufactured in the cell are released through the cell membrane.copyright cmassengaleInside CellCell environmentG. Podgorski, Biol. 1010
37 What are the three different types of active transport? Protein pumpsEndocytosisExocytosis
38 Cell TransportPassive transport: molecules travel along the concentration gradientNo energy requiredActive Transport: molecules are transported against the concentration gradientenergy required