Transcript File
Moving Cellular Materials SOL BIO 4.d Fluid Mosaic Model: A mosaic is a structure made up of many different parts. The plasma membrane of a cell is composed of different kinds of macromolecules. Phospholipid bilayer Passive Transport: • PASSIVE TRANSPORT- DOES NOT require energy to move materials through the cell membrane 3 types of passive transport • Diffusion • Osmosis • Facilitated diffusion 1. DIFFUSION- molecules of a substance will move from an area of high concentration to an area of low concentration, down the concentration gradient, until they reach equilibrium • Diffusion occurs in cells when substances (O2,CO2, salts, sugars, amino acids) that are dissolved in H2O move from an area of higher concentration to an area of lower concentration. DIFFUSION Osmosis 2. OSMOSIS (diffusion of water)-the movement of water molecules through a semi-permeable membrane from an area of greater water concentration or pressure to an area of lesser water concentration or pressure down the concentration gradient OSMOSIS 3 Types of concentration involved in osmosis • Hypertonic- too much solute, not enough water; if a cell is placed in this solution, cell will shrink & wrinkle • Hypotonic- too much water, not enough solute; if a cell is placed in this solution, cell will swell up, expand • Isotonic- equal parts water and solute; water moves in & out of the cell in dynamic equilibrium OSMOSIS 3 Types of Passive Transport: OSMOSIS Facilitated diffusion 3. FACILITATED TRANSPORT- requires transport proteins in the cell membrane to move materials into and out of the cell either because the molecules that are transported are too big or they are polar (act against the nonpolar fatty acid tail of the lipid bilayer) FACILITATED TRANSPORT Factors that effect diffusion 1. Temperature – The rate of diffusion increases with the increase of temperature 2. Pressure- when pressure increases the rate of diffusion increases 3. Concentration – the rate of diffusion is effected by the concentration of the substances. It always takes place from higher to lower concentration. Active Transport: • ACTIVE TRANSPORT- requires ENERGY, ATP, to move materials through the cell membrane • Work against concentration gradient • Molecules move from low to high cocentration Active Transport: 3 Types of Active Transport: • ENDOCYTOSIS- requires ENERGY to move materials INTO the cell membrane • EXOCYTOSIS- requires ENERGY to move materials OUT OF the cell membrane • Ion pumps – Sodium –potassium pump and proton pumps Active Transport: Active Transport: Active Transport: This is an example of Active Transport through sodium potassium pumps. Here sodium is taken outside of the cell, and potassium is brought inside the cell against concentration gradient.