Transport Topic 8

Transport: Absorption & Circulation of materials End products of digestion enter body cells

Structure of the Cell Membrane: Cell membrane is the “security guard” of the cell Semi/Selectively permeable Regulates movement of materials into & out of the cell Phospholipid bi-layer

The Cell Membrane

Phospholipids form 2 layers Phosphate “heads” are hydrophilic They can touch water outside and inside (cytoplasm) the cell Lipid “tails” are hydrophobic They face inward to avoid touching water

Fluid Mosaic Model: Model of the cell membrane Small molecules pass through easily Ex: amino acids, monosaccharides, glycerol, fatty acids, water & gases Large molecules don’t pass through easily, they must be broken down Ex: carbs., lipids & proteins

Cell Membrane http://www.susanahalpine.com/anim/Life/memb.htm

Methods of Transport: Two Types of Transport Passive Transport Active Transport

1. Passive Transport: No energy needed Diffusion Osmosis

A. Diffusion: Materials move from High  Low Concentration Continues until equilibrium is reached Video: http://www.stolaf.edu/people/giannini/flashanimat/transport/diffusion.swf

Diffusion of Sugar in Water

Diffusion of a Dye in Water

Diffusion of a Solute Across a Cell Membrane

Diffusion of Gases Across a Cell Membrane

B. Osmosis: Diffusion of water Movement from High  Low Concentration

ACTIVE TRANSPORT Energy is required Materials move from Low  High Concentration

Cell engulfs undissolved material A. Phagocytosis: Cell engulfs undissolved material http://www.stolaf.edu/people/giannini/flashanimat/cellstructures/phagocitosis.swf

Cell membrane pinches in and absorbs dissolved molecules B. Pinocytosis: Cell membrane pinches in and absorbs dissolved molecules http://student.ccbcmd.edu/~gkaiser/biotutorials/eustruct/pinocyt.html

Endocytosis Exocytosis Materials move into the cell Materials move out of the cell

Passive or Active Transport? Active Passive

Effects of Osmosis on a Cell Isotonic Solution: Solution has same concentration of dissolved substances as cell Hypotonic Solution: Solution has a lower concentration of dissolved substances than cell Hypertonic Solution: Solution has a higher concentration of dissolved substances than cell

How does a change in salt concentration affect a cell?

Adding a Salt Solution to a Cell Concentration of water is higher inside cell Water flows out of cell High –> Low Concentration Cell’s cytoplasm shrinks!!!

SALT shrinks! Water rushes out!

Salt shrinks- water rushes out

Adding Distilled (Pure) Water to a Cell Concentration of water is higher outside the cell Water flows in the cell Cell bursts/ruptures

Cell SWELLS!

Let’s Review…

Transport in Lower Organisms: In ameba & paramecium Transport by diffusion, osmosis & cyclosis

Intracellular Transport: Transport inside the cell Cyclosis- circular motion of the cytoplasm Endoplasmic Reticulum Diffusion, Osmosis, Phagocytosis & Pinocytosis

What process is being shown?

Transport in Plants: Vascular tissue- Roots- Xylem-transports water Phloem- transports food Roots- Provide anchorage into soil Absorb water

Capillary Action: Pulls water up into the xylem tubes Adhesion- attraction between water molecules and the xylem tube Cohesion- attraction between water molecules

Capillary Tube