CLASS: M13A
DATE: 21.08.2013
TITLE: Transport across membrane
OBJECTIVES: To investigate the effect of concentration of blackcurrant squash on osmosis in chipped potatoes.
INTRODUCTION: In biology, osmosis is defined as the diffusion of solvent molecules (usually water molecules) across a semi-permeable membrane from a region of lower solute concentration to a region of higher solute concentration. Osmosis is of great importance in biological processes where the solvent is water. The transport of water and other molecules across biological membranes is essential to many processes in living organisms. The pressure exerted by the molecules of the solvent on the membrane they pass through is called osmotic pressure. Osmotic pressure is the energy driving osmosis and is important for living organisms because it allows water and nutrients dissolved in water to pass through cell membranes. There are three types of condition that involves osmosis which is hypotonic, hypertonic and isotonic. In a hypotonic solution, the water will move into the cell due to the outside of the cell having a lower solute concentration than the inside of the cell. When an animal cell is placed in a hypotonic surrounding (lower solute concentration), the water molecules will move into the cell causing the cell to burst and haemolysed. When plant cell is placed in a hypotonic solution, water molecules diffuse into the cell and the plant cells remain turgid because the cell wall prevents bursting. In a hypertonic solution, water will move outside of the cell due to the outside of the cell is having a higher solute concentration than the inside of the cell. When an animal cell, a red blood cells is exposed to a hypertonic surrounding (higher solute concentration) the water will leave the cell causing the cell to shrink and it is said to undergoes crenation. If a
References: http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/diffus.html#c3 http://www.thefreedictionary.com/osmosis http://www.biology-online.org/dictionary/Osmosis Longman Pre-U Text STPM Biology Volume 1 (page 41 & 44) Biology HL Student Handbook Year 1 page 165-166