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 Fibers of the extracellular matrix Glycoprotein Carbohydrate (of glycoprotein) Microfilaments of the cytoskeleton Phospholipid Cholesterol Proteins CYTOPLASM Glycolipid

Membranes are selectively permeable 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

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

- 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 Passive transport – the movement of substances without the cell using energy or doing work; by diffusion across a membrane EQUILIBRIUM Molecule of dye Membrane EQUILIBRIUM

In osmosis, water travels from an area of lower solute concentration to an area of higher solute concentration Osmosis is the passive transport of water Hypotonic solution Solute molecule HYPOTONIC SOLUTION Hypertonic solution Selectively permeable membrane HYPERTONIC SOLUTION Selectively permeable membrane NET FLOW OF WATER Solute molecule with cluster of water molecules Water molecule

Unequal distribution of particles, called a concentration gradient, is one factor that controls osmosis. What 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.

Terms used to compare two areas of concentration HypotonicHypertonic I sotonic

Section 8.1 Summary – pages Osmosis in action

5% solute 10% solute

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. Cells in an isotonic solution H2OH2O H2OH2O Water Molecule Dissolved Molecule

Cells in a hypotonic solution In a hypotonic solution, water enters a cell by osmosis, causing the cell to swell. H2OH2O H2OH2O Water Molecule Dissolved Molecule

Cells in a hypertonic solution In a hypertonic solution, water leaves a cell by osmosis, causing the cell to shrink. H2OH2O H2OH2O Water Molecule Dissolved Molecule

Draw in your notebook and label Hypotonic, Hypertonic, Isotonic AB C

The control of water balance (osmoregulation) is essential for organisms ISOTONIC SOLUTION HYPOTONIC SOLUTION HYPERTONIC SOLUTION (1) Normal (4) Flaccid (2) Bursting = Lysing (5) Full = Turgid (3) Shriveled = crenulated (6) Shriveled = plasmolyzed ANIMAL CELL PLANT CELL Plasma membra ne

ANIMAL CELLS --- red blood cells

Plant Cells in an isotonic solution A plant cell has its normal shape and pressure in an isotonic solution. “flaccid” state vacuole Cell wall 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.

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 isotonic pond water

Elodea with 10% salt solution added

Elodea in 10% NaCl solution demonstrates that water has moved _______ _ the cells. (out of / into)Elodea in 10% NaCl solution demonstrates that water has moved _______ _ the cells. (out of / into) ?

ISOTONIC SOLUTION HYPERTONIC SOLUTION HYPOTONIC SOLUTION

Section 8.1 Summary – pages Passive Transport in Action

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.

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 Transport(carrier) proteins facilitate(help) diffusion across membranes Solute molecule Transport protein Carrier protein- specialized

ACTIVE TRANSPORT

Moves large or polar molecules or ions. Transport proteins can move solutes across a membrane against a 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 Active transport – when cells must use energy to move substances across the membrane

Active transport moving two different solutes across a membrane Transport protein 1 FLUID OUTSIDE CELL First solute First solute, inside cell, binds to protein Phosphorylated transport protein 2 ATP transfers phosphate to protein 3 Protein releases solute outside cell 4 Second solute binds to protein Second solute 5 Phosphate detaches from protein 6 Protein releases second solute into cell Example of Active Transport

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

To move large molecules or particles through a membrane –a vesicle may fuse with the membrane and expel its contents (exocytosis) Bulk transport of large molecules FLUID OUTSIDE CELL CYTOPLASM

–or the membrane may fold inward, trapping material from the outside (endocytosis)

Types of Endocytosis Pseudopod of amoeba Food being ingested Plasma membrane Material bound to receptor proteins PIT Cytoplasm Cell “eating” PHAGOCYTOSIS Cell “drinking” PINOCYTOSIS Liquid droplets of water or oil/fat being taken in

Macrophage White Blood Cell – cell “eater”

Old Red Blood Cells