Osmosis

• The cell membrane is a phospholipid bilayer that controls what enters and exits the cell.
• Pores on the surface of the cell act as entrances and exits.
• Cell membranes are selectively permeable, allowing some substances to pass through and blocking others.
• Examples of substances that pass through the cell membrane include carbon dioxide, oxygen, glucose, and water.
• Fish and Meat (bacon) may be stored in a salty solution to prevent spoilage.
• Jams, marmalades and tinned fruits are stored in a sugary solution to prevent spoilage.
• Gal cells lose water, causing the cells to shrivel and die, preventing the food from becoming contaminated with loads of bacteria and fungi.
• The process of gal cells losing water prevents the food from spoiling.
• Examples of biological membranes include cell membranes, nuclear membranes, mitochondrial membranes, and chloroplast membranes.
• Membranes can be permeable, allowing everything in and out, selectively permeable, allowing some substances to pass through and blocking others, or impermeable, allowing nothing in and out.
• Diffusion is the movement of molecules from a region of high concentration to a region of low concentration, it is a passive process that requires no energy, and it works best over short distances.
• Examples of diffusion include oxygen and carbon dioxide moving between the alveoli and the blood, absorption of food in the intestine, and oxygen and carbon dioxide moving in and out of leaves on a plant.
• Osmosis is the diffusion of water, it is the movement of water molecules from a region of high water concentration to a region of low water concentration across a semi permeable membrane, it is a passive process.
• Examples of osmosis include absorption of water by plant root cells, opening and closing of stomata, and reabsorption of water in the nephron of the kidney.
• Active Transport is the opposite of diffusion, substances are pumped through the cell membrane against the concentration gradient.
• If plant cells are surrounded by a more concentrated solution, the water inside the cell would move out to the more concentrated solution outside, causing the cell wall to stay intact but the membrane to shrivel up away from it, a condition known as Plasmolysis.
• Bacteria and Fungi are the most common causes of food spoilage, both enclosed by a membrane.
• Reabsorption of amino acids and glucose in the nephron is an example of osmosis.
• If animal cells are in a solution that is more concentrated than their cytoplasm (hypertonic), the water may leave the animal cell and the cells shrivel up and may die, a condition called crenation.
• Osmosis is the process where water moves from an area where it is in low concentration to an area where it is in high concentration, requiring energy.
• If a cell’s contents are at the same concentration as its environment, the cell is said to be isotonic, with no net movement of water into or out of the cell.
• Animal cells that are in a less concentrated solution (hypotonic) have water entering the cell constantly, which may eventually cause it to burst or die.
• This causes the membrane to be pushed out towards the cell wall, and when cells are fully “swelled” like this with the membranes pushing against the cell wall they are described as Turgid.
• Animal cells do not have a cell wall to prevent the cell from bursting like a plant cell.
• If a food is placed in a sugary or salty solution, any bacteria or fungi present will lose the water in their cells to the more concentrated solution outside.
• If a plant cell is surrounded by a less concentrated solution, water from outside will move into the cytoplasm and vacuole of plant cells, causing the vacuole to become bigger and the cytoplasm to swell.
• Plant cell walls are fully permeable, while cell membranes are selectively permeable.
• Turgor is the pressure of the cytoplasm and vacuole against the cell wall of a plant, giving a plant cell strength and preventing the cell from bursting.
• Cells in this condition are called plasmolysed.