CELL MEMBRANE CELL TRANSPORT CELL MEMBRANE Cell membrane

CELL MEMBRANE & CELL TRANSPORT

CELL MEMBRANE Cell membrane vs. cell wall Cell Membrane All cells have cell membranes Flexible barrier Function: maintain homeostasis within the cell Cell Wall

CELL MEMBRANE STRUCTURE • Many names… cell membrane, plasma membrane, phospholipid bilayer • Phospholipid bilayer – two layers of phospholipids protein channel with Cell embedded proteins Layer 1 Membrane Layer 2 lipid bilayer protein pump

CELL MEMBRANE STRUCTURE Phosopholipid Bilayer Hydrophilic head – “water loving” attracts water Hydrophobic tail – “water fearing” repels water Creates a constant push and pull

CELL MEMBRANE STRUCTURE Phosopholipid Bilayer Small materials can pass easily: 1. Push and pull of water 2. Porous nature 3. Vibrating phospholipids, creating openings

CELL MEMBRANE STRUCTURE “Fluid Mosaic Model”: explains the structure of the cell membrane Proteins and other embedded materials “float” within the cell membrane

CELL MEMBRANE STRUCTURE Carbohydrate Chain Cholester ol Phospholipi d Bilayer Transport/Channel Proteins Membrane Protein

CELL MEMBRANE FUNCTION - “Gatekeeper” - Semipermeable : Allows certain materials in and out of the cell - Nutrients IN - Waste OUT - CELL TRANSPORT: MOVEMENT OF MATERIALS IN AND OUT OF CELLS

CELL TRANSPORT - The movement of materials in and out of cells (cell transport) … can be passive or active - Passive Transport: Does NOT require energy - Active Transport: Requires energy

CELL TRANSPORT Passive Transport - Does NOT require energy - Movement of materials from HIGH LOW - “with the concentration gradient” - Diffusion, Osmosis, Facilitated Diffusion

CELL TRANSPORT Active Transport - REQUIRES the use of energy - Movement of materials from LOW HIGH - “against the concentration gradient” - Endocytosis and Exocytosis

PASSIVE TRANSPORT DIFFUSION Diffusion: movement of small particles from high to low until equilibrium is reached

PASSIVE TRANSPORT DIFFUSION Diffusion: movement of small particles from high to low until equilibrium is reached Particles are small enough to pass through the porous cell membrane

PASSIVE TRANSPORT - OSMOSIS Osmosis: the diffusion of water across a selectively permeable membrane Outside Cell Water will travel from HIGH concentration LOW concentration Inside Cell

PASSIVE TRANSPORT - OSMOSIS Osmosis: the diffusion of water across a membrane Water travels from high low Osmosis will take place until equilibrium is reached 25% sugar 75% water 60% sugar 40% water 50% sugar 50% water

PASSIVE TRANSPORT - OSMOSIS Osmosis: the diffusion of water across a membrane Water will move in and out of cells when they are placed in various solutions

PASSIVE TRANSPORT - OSMOSIS Isotonic Solution – equal amount of solute in and out of cell. Water moves in and out of cell in equal amounts Cell size does not change

PASSIVE TRANSPORT - OSMOSIS Hypertonic Solution – higher concentration of solute outside cell. Water diffuses out of cell through osmosis. Cell shrinks/shrivels in size.

PASSIVE TRANSPORT - OSMOSIS Hypotonic Solution – higher concentration of solute inside cell. Water diffuses into cell through osmosis. Cell expands and can even burst.

PASSIVE TRANSPORT – FACILITATED DIFFUSION Facilitated Diffusion – Diffusion of larger molecules which must be “helped” through the membrane by traveling through channel proteins & carrier proteins High Low! outside of cell No energy! inside of cell Glucose molecules

Outside cell Inside cell “bridge” squeezing motion

ACTIVE TRANSPORT REVIEW Active Transport - REQUIRES the use of energy - Movement of materials from LOW HIGH - “against the concentration gradient” - Endocytosis and Exocytosis

ACTIVE TRANSPORT ENDOCYTOSIS Endocytosis – the movement of large molecules INTO the cell Low High Requires energy

ACTIVE TRANSPORT ENDOCYTOSIS Molecule “bumps” into cell membrane Cell membrane wraps around and engulfs particle Creates a temporary vesicle/vacuole for transport

ACTIVE TRANSPORT ENDOCYTOSIS Examples: - Your white blood cells use energy to engulf bacteria - An amoeba bumps into something tasty!

A WHITE BLOOD CELL CHASING A BACTERIUM HTTPS: //WWW. YOUTUBE. COM/WATCH? V=JNL ULOJUHSQ

ACTIVE TRANSPORT EXOCYTOSIS Exocytosis – the movement of large molecules OUT OF the cell Low High Requires energy

ACTIVE TRANSPORT EXOCYTOSIS The golgi body plays a major role in the secretion (release) of proteins and other materials through exocytosis