Cell Membranes Osmosis and Diffusion Functions of Membranes
Cell Membranes Osmosis and Diffusion
Functions of Membranes 1. Protect cell 2. Control incoming and outgoing substances 3. Maintain ion concentrations of various substances 4. Selectively permeable: allows some molecules in, others are kept out
Features of the cell membrane 1. Phospholipid Bilayer
Features of the cell membrane 1. Phospholipid Bilayer 2. Fluid Mosaic Model
Features of the cell membrane 1. Phospholipid Bilayer 2. Fluid Mosaic Model 3. Helps maintain homeostasis
Ex: Blood-Brain Barrier • Allows some substances into the brain, but screens out toxins and bacteria • Substances allowed to cross include: water, CO 2, Glucose, O 2, Amino Acids, Alcohol, antihistamines. HIV and bacterial meningitiscan cross the barrier.
Molecules are always Moving Molecules move randomly and bump into each other and other barriers
4 Methods of Transport Across Membranes 1. Diffusion: passive transport - no energy expended
4 Methods of Transport Across Membranes 2. Osmosis: Passive transport of water across a semi-permeable membrane
Osmosis: 3 types of solutions • Hypotonic Solution: One solution has a lower concentration of solute than another. • Hypertonic Solution: - one solution has a higher concentration of solute than another. • Isotonic Solution: - both solutions have same concentrations of solute.
Plant and Animal Cells put into various solutions
4 Methods of Transport Across Membranes 3. Facilitated Diffusion: Use of proteins to carry polar molecules or ions across
4 Methods of Transport Across Membranes 4. Active Transport: requires energy to transport molecules against a concentration gradient - energy is in the form of ATP
Types of Transport
One-Minute Essay • How and why does the cell have different types of transport in and out of the cell?
- Slides: 16