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Unformatted text preview: oncentration).
– Molecules diffuse along their own concentration
gradient, independent of other molecules.
– Diffusion rates are higher at higher temperatures.
– Diffusion rates are faster when the concentration
gradient is greater.
– Thicker barriers slow diffusion. 3. (a) Channel-mediated facilitated diffusion, i.e through
a protein channel in the membrane that creates a
(b) Carrier mediated facilitated diffusion, i.e. the
molecule is aided across the membrane by a
carrier protein specific to the molecule being
transported. 4. Aquaporins are protein channels in the membrane 1. Phagocytosis is the engulfment of solid material by
endocytosis whereas pinocytosis is the uptake of
liquids or fine suspensions by endocytosis. 2. Phagocytosis examples (any of):
• Feeding in Amoeba by engulfment of material
using cytoplasmic extensions called pseudopodia.
• Ingestion of old red blood cells by Kupffer cells in the liver. • Ingestion of bacteria and cell debris by neutrophils and macrophages (phagocytic white blood
cells). 3. Exocytosis examples (any of):
• Secretion of substances from specialized secretory Concentration gradients are maintained by constant
use or transport away of a substance on one side of
a membrane (e.g. use of ADP in mitochondria and by
production of a substance on one side of a membrane
(e.g. production of CO2 by respiring cells). 5. Exocytosis and Endocytosis (page 28) Biozone International 2009 Photocopying Prohibited Anatomy and Physiology Name: Cellular junctions (given)
Location: At cell membrane surface, connecting
Function: Depends on junction type but basically cell
adhesion and communication.
Gap junction: Act as communication channels
Tight junction: Prevent leakage of extracellular fluid
from layers of epithelial cells.
Desmosome: Fasten cells together.
Visible under LM: No. specific to water molecules. This is faster (less
resistance) than diffusion through the membrane. 6
cells in multicellular orga...
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This document was uploaded on 01/28/2014.
- Winter '13