Cell Membranes and Transport
Homeostasis Homeostasis is the balance cells must maintain with their surrounding environment. Cells maintain homeostasis by controlling what enters and exits the cell.
Hydrophilic Hydrophobic The Cell Membrane Made of a bilayer of phospholipids Phospholipids have a hydrophobic tail (water fearing) and hydrophilic head (water loving). Proteins are embedded in the membrane to help move materials in-and-out of the cell. Hydrophilic Hydrophobic
The membrane is called a fluid-mosaic – why?
Draw Me! The Cell Membrane Figure 7-12 The Structure of the Cell Membrane The Cell Membrane Section 7-3 Outside of cell Inside (cytoplasm) Cell membrane Proteins Protein channel Lipid bilayer Carbohydrate chains Draw Me!
The Cell Membrane Cell membranes are SELECTIVELY PERMEABLE – what does this mean? The cell membrane has some control over what can cross it, so that only certain molecules either enter or leave the cell. Ex. The strainer lets water pass through, yet keeps the pasta in. It is selectively permeable.
Passive Transport Movement of molecules across the cell membrane that DOES NOT USE ENERGY. Materials move from an area of HIGH CONCENTRATION to an area of LOW CONCENTRATION.
Diffusion Diffusion – Movement of molecules through the cell membrane A type of PASSIVE TRANSPORT because it DOES NOT USE ENERGY.
Diffusion Checkpoint What direction will the molecules move?
Diffusion Checkpoint Pt. 2 Diffusion Checkpoint Pt. 2 When is equilibrium reached? EQUILIBRIUM is reached when concentrations are equal on both sides of the cell membrane.
Osmosis Osmosis – diffusion of WATER molecules through the cell membrane (passive transport) Water always diffuses from an area of LOW SOLUTE CONCENTRATION to an area of HIGH SOLUTE CONCENTRATION. OR High Water Concentration to Low Water Concentration Solute is…..??
Osmosis
Osmosis – Driven by Solute Concentration Osmosis – Driven by Solute Concentration Hypotonic solution – solute concentration is lower on the outside of the cell than inside the cell. Water moves INTO the cell Hypo= low, below normal
Osmosis – Driven by Solute Concentration Osmosis – Driven by Solute Concentration Hypertonic solution – solute concentration is higher on the outside of the cell than inside the cell. Water moves out of the cell Hyper= excessive
Osmosis – Driven by Solute Concentration Osmosis – Driven by Solute Concentration Isotonic solution – solute concentration is equal on both sides of the cell membrane. Water diffuses in-and-out equally Iso= equal or the same
Osmosis and Plant Cells Osmosis and Plant Cells Plant cells require a hypotonic environment so water moves into the cell and the cell swells Swelling of the cell builds up turgor pressure
Osmosis and Plant Cells Osmosis and Plant Cells Plant cells in hypertonic environments lose water and the cell shrivels up. Shriveling of the cell is called plasmolysis.
Class Demo! Osmosis Checkpoint What would happen to animal cells in hypotonic and hypertonic environments? Class Demo!
Osmosis For example, marine fish:
Complete Osmosis Pre-Lab Work
Recall – Osmosis – WHAT WILL HAPPEN TO THE CELL???
Facilitated Diffusion Facilitated Diffusion Facilitated diffusion - moves molecules in-and-out of the cell using a carrier protein (passive transport) Why would molecules need help from a carrier protein? Too big Charged Can not dissolve in the phospholipid bilayer.
Active Transport Active transport - movement of molecules across the cell membrane that requires energy. Can move materials from an area of LOW CONCENTRATION to an area of HIGH CONCENTRATION. (Opposite of diffusion)
Active Transport Why does your body need to use active transport? Na+/K+ pumps for neuron function SWEET Video Animation of Sodium/Potassium Pumps
Endocytosis Large molecules can be engulfed by cells in a process called ENDOCYTOSIS. (Active transport) Pinocytosis - process of engulfing a liquid. (“Cell drinking,”) Phagocytosis - process of engulfing a solid. (“Cell eating,”)
Endocytosis
Exocytosis – release material from the cell Exocytosis – release material from the cell