chapter 6.3: membranes regulate the traffic of molecules college prep biology mr. martino
Post on 01-Apr-2015
221 Views
Preview:
TRANSCRIPT
Chapter 6.3: Membranes regulate the traffic of
molecules
College Prep BiologyMr. Martino
6.3 Cell Membranes Cell membranes make
the E in chemical bonds available for metabolic reactions Kinds and amounts of
substances different on either side of membrane – membrane is selectively permeable
CO2, O2, water, and small nonpolar molecules move easily across
Large, polar molecules and ions do not move freely across
These require various proteins
Concentration Gradients Brownian Motion –
continuous random movement of particles due to temp. differences
Concentration gradient: the difference in conc. of particles on one side of a membrane as opposed to the other
Diffusion
Diffusion: the tendency for particles to move from areas of high concentration to areas of low conc.
Molecules naturally move “with” conc. Gradient
Diffusion is fastest when gradient is steep
Active transport: requires E to move substances across a membrane Transport
protein pumps the substance against the conc. gradient
Usually use ATP
Movement of Water
Osmosis: the diffusion (passive transport) of water Hypertonic
Solution: has a higher conc. of solutes than the cell
Water will leave cells and cells will shrivel
Hypotonic Solution: had a lower conc. of solutes than the cell
Water will rush into cells and cells will swell
Turgor (hydrostatic) pressure: the internal force pushing outward in plant cells Cell wall prevents
the uptake of too much water
Isotonic Solution: the conc. of particles inside the cell is = to the conc. of the particles outside the cell Movement
continues – just no net movement
Endocytosis and Exocytosis
Exocytosis: process of how cells export bulky materials from the cytoplasm Ex. Tear and insulin
formation Endocytosis: process of how
cells import macromolecules Phagocytosis: cellular
eating Pinocytosis: cellular
drinking Receptor-mediated
endocytosis: highly specific due to receptor proteins
top related