The Cell Membrane BE ABLE TO: Identify the parts and its structure Importance in eukaryotic cells Describe its functions
The plasma membrane of an animal cell Glycoprotein Carbohydrate (of glycoprotein) Fibers of the extracellular matrix Glycolipid Phospholipid Cholesterol Microfilaments of the cytoskeleton Proteins CYTOPLASM
Membranes can hold enzymes that function in metabolism and many chemical reactions • Membrane parts play a role in cellular communication • Membrane is a phospholipid bilayer w/ embedded proteins • Some proteins form cell junctions- • Connections between cells • Most transport special substances across the membrane • Membranes are selectively permeable
Importance in Eukaryotes: • Membranes organize the chemical reactions making up • metabolism • Create “compartments” w/in organelles to isolate one • reaction from another Cytoplasm
2 MAJOR CATEGORIES OF CELLULAR TRANSPORT Passive & Active
Passive transport – the movement of substances without the cell using energy or doing work; by diffusion across a membrane -Move from areas of high concentration to areas of lower concentration -Move “with” the concentration gradient -3 types of Passive Transport: • Simple diffusion • Osmosis • Facilitated diffusion Molecule of dye Membrane EQUILIBRIUM EQUILIBRIUM
Osmosis is the passive transport of water Hypotonicsolution Hypertonic solution • In osmosis, water travels from an area of lower solute concentration to an area of higher solute concentration Selectivelypermeablemembrane Solutemolecule HYPOTONIC SOLUTION HYPERTONIC SOLUTION Water molecule Selectivelypermeablemembrane Solute molecule with cluster of water molecules NET FLOW OF WATER
What controls osmosis? • Unequal distribution of particles, called a concentration gradient, is one factor that controls osmosis. Before Osmosis After Osmosis Water molecule Sugar molecule Selectively permeable membrane
Knowing the tonicity of a solution allows you to predict what will happen to cells and organisms in certain environments.Tonicity is the relative concentrations of two areas; a means of comparing [ ]’s.
Hypotonic Hypertonic Terms used to compare two areas of concentration Isotonic
Section 8.1 Summary – pages 195 - 200 Osmosis in action
hypertonic hypotonic! 10% solute 5% solute
Cells in an isotonic solution • Most cells are subject to osmosis because they are surrounded by water solutions. • In an isotonic solution, the concentration of dissolved substances in the solution is the same as the concentration of dissolved substances inside the cell. • In an isotonic solution, water molecules move into and out of the cell at the same rate, and cells retain their normal shape. H2O H2O Water Molecule Dissolved Molecule
Cells in a hypotonic solution • In a hypotonic solution, water enters a cell by osmosis, causing the cell to swell. H2O H2O Water Molecule Dissolved Molecule
Cells in a hypertonic solution • In a hypertonic solution, water leaves a cell by osmosis, causing the cell to shrink. H2O H2O Water Molecule Dissolved Molecule
Draw in your notebook and label Hypotonic, Hypertonic, Isotonic A B C
The control of water balance (osmoregulation) is essential for organisms ANIMALCELL (3) Shriveled = crenulated (1) Normal (2) Bursting = Lysing PLANTCELL Plasmamembrane (6) Shriveled = plasmolyzed (5) Full = Turgid (4) Flaccid HYPERTONIC SOLUTION ISOTONIC SOLUTION HYPOTONIC SOLUTION
Plant Cells in an isotonic solution Cell wall • A plant cell has its normal shape and pressure in an isotonic solution. • “flaccid” state vacuole membrane
Plant Cells in a hypotonic solution • Plant cells swell beyond their normal size as pressure increases. • Increasing “turgor pressure” on cell walls • Will become “turgid” What has happened to the vacuole? Notice the arrangement of the organelles compared to the isotonic?
Plasmolysis Anim. Plasmolysis in Elodea Cells
Plant Cells in a hypertonic solution • Plant cells lose pressure as the plasma membrane shrinks away from the cell wall. • Plasmolysed What has happened to the membrane of the cell? Why? What happened to the vacuole? Why? Cell membrane Empty space
Elodea in 10% NaCl solution demonstrates that water has moved _______ _ the cells. (out of / into) ?
HYPOTONIC SOLUTION ISOTONIC SOLUTION HYPERTONIC SOLUTION
Passive Transport in Action Section 8.1 Summary – pages 195 - 200
Facilitated Diffusion • Diffusion with “help” • Some substances can diffuse through special protein ports • No energy required • High [ ] to Low[ ] • Example: glucose enters by Fac. Diff.
Solutemolecule Transportprotein Transport(carrier) proteins facilitate(help) diffusion across membranes • Small nonpolar molecules diffuse easily through the phospholipid bilayer; CO2 and O2 • Many other kinds of molecules must pass through specialized protein pores by facilitated diffusion Carrier protein- specialized
Active transport – when cells must use energy to move substances across the membrane • Moves large or polar molecules or ions. • Transport proteins can move solutes across a membrane againsta concentration gradient; • low to high • Must use active transport • Proteins act as “pumps” • Requires cell to do work • uses energy in the form of ATP
FLUIDOUTSIDECELL Phosphorylated transport protein Transportprotein • Active transport moving two different solutes across a membrane Firstsolute 1 First solute, inside cell, binds to protein 2 ATP transfers phosphate to protein 3 Protein releases solute outside cell Second solute Example of Active Transport 4 Second solute binds to protein 5 Phosphate detaches from protein 6 Protein releases second solute into cell
PARAMECIUM Problem: Lives in Fresh Water Hypertonic to environment Water constantly diffuses into cytoplasm Single cell – no cell wall Can burst –lyse! How to get rid of excess? Pump it out! Use a Contractile vacuole! Requires energy – ACTIVE!
BULK TRANSPORT –LARGE MOLECULES, FOOD, AND OTHER SUBSTANCES ARE PACKAGED IN MEMBRANE-BOUND SACS CALLED A VESICLE AND MOVED ACROSS THE MEMBRANE. • TYPES OF BULK TRANSPORT: • ENDOCYTOSIS, • PINOCYTOSIS, • PHAGOCYTOSIS • EXOCYTOSIS
FLUID OUTSIDE CELL CYTOPLASM Bulk transport of large molecules • To move large molecules or particles through a membrane • a vesicle may fuse with the membrane and expel its contents (exocytosis)
or the membrane may fold inward, trapping material from the outside (endocytosis)
Types of Endocytosis Liquid droplets of water or oil/fat being taken in Pseudopod of amoeba Food being ingested Plasma membrane Material bound to receptor proteins PIT Cytoplasm Cell “eating” PHAGOCYTOSIS Cell “drinking” PINOCYTOSIS