Presentation on theme: "Cell Membrane & Cellular Transport Homeostasis – the maintenance of internal stable conditions The cell membrane keeps the cell in balance."— Presentation transcript:
Cell Membrane & Cellular Transport
Homeostasis – the maintenance of internal stable conditions The cell membrane keeps the cell in balance.
Membrane Functions Provides a selectively permeable barrier around the cell. Controls the passage of substances in and out of the cell. Maintains homeostasis for the cell.
Membrane Structure Phospholipid bilayer (nonpolar) Membrane proteins: act as transport channels. Carbohydrate chains: act as ID tags for the cell. Cholesterol: provides stability for the membrane.
Phospholipid Bilayer – Phospholipids: phosphate head and lipid tail. – Phospholipid Bilayer: two layers. inside cell outside cell Lipid Tails Hydrophobic = repels water Hydrophilic = attracts water Phosphate Head Phospholipid Bilayer
The cell membrane is semipermeable, which means only some material can get in or out. Amino Acids H2OH2O SugarLipidsSalt Waste So what needs to get across the membrane? O2O2
How do you build a semi-permeable cell membrane? Channels are made of proteins. Proteins act as doors in the membrane. Bilipid Membrane Protein Channels in Bilipid Membrane
Diffusion Molecules move from HIGH to LOW concentration; this continues until equilibrium is reached. Simple diffusion: directly through membrane. Facilitated diffusion: help through a protein channel. NO energy needed!! HIGH LOW
Active Transport Cells use energy to move against concentration gradient - from LOW to HIGH. Particles that are polar (charged) must move through a protein channel. – Use protein pump – requires energy (ATP) ATP
Transport of Molecules Endocytosis: takes material into cell by cell membrane making pockets. – Phagocytosis – cell eating; cell engulfs particles – Pinocytosis – cell takes in liquid from surrounding environment. Exocytosis: process forcing contents out of the cell.
Transport Summary simple diffusion facilitated diffusion active transport ATP (Smaller molecules) (Larger molecules)
Types of Cellular Transport PASSIVE Does NOT require energy Goes with the concentration gradient (high to low) Simple Diffusion, Facilitated Diffusion ACTIVE Requires energy from ATP Goes against the concentration gradient (low to high) Active Transport, Endocytosis, Exocytosis
Osmosis movement of water across cell membrane. HIGH H 2 O LOW H 2 O
Effects of Osmosis on Cells (osmotic pressure) Hypertonic: higher concentrations of solute; less H 2 O. Isotonic: equal concentrations of solute. Hypotonic: lower concentrations of solute; more H 2 O.