Cell Transport Notes PDF

 CELLULAR TRANSPORT How do cells move nutrients, products and wastes in and out of the cell? Why is this traffic across the membrane so important? HOMEOSTASIS  HOMEOSTASIS Why is homeostasis important for cells? Living cells depend on the movement of chemicals around...

 CELLULAR TRANSPORT How do cells move nutrients, products and wastes in and out of the cell? Why is this traffic across the membrane so important? HOMEOSTASIS  HOMEOSTASIS Why is homeostasis important for cells? Living cells depend on the movement of chemicals around the body. Chemicals such as oxygen, carbon dioxide and dissolved food need to be transported into and out of cells. This is done by the processes of diffusion and osmosis and active transport. These processes depend on the body's water and salt balance, which are maintained by homeostasis HOMEOSTASIS Cells are filled and surrounded by watery fluid. This fluid helps solids move around inside, outside the cell and cross the cell membrane. CELL MEMBRANE  CELL MEMBRANE The cell membrane controls what moves in and out of the cell. Semi-permeable membrane Cell membranes only allow some solutes (solids) to move across it. Movement across the membrane depends on size and type of the solute (solid). TYPES OF TRANSPORT  Down the Low High concentration concentration concentration gradient Low High Up the concentration concentration concentration gradient DIFFUSION PASSIVE TRANSPORT  DIFFUSION The process by which molecules spread from areas of high concentration, to areas of low concentration. When the molecules are even throughout a space - it is called EQUILIBRIUM  DIFFUSION AND DIGESTION Carbohydrates, proteins and fats are made up of large molecules that cannot be absorbed by the body. Digestion breaks down large nutrient molecules into simpler forms such as glucose, amino acids and fatty acids that can be easily absorbed. In which part of the digestive system is most food absorbed? Small food molecules are usually absorbed in the small intestine, diffusing across the intestine wall and into the bloodstream.  DIFFUSION AND DIGESTION Only some food molecules are small enough to diffuse through glucose the villi and into the bloodstream. Fats, fat-soluble vitamins and glucose can move into the bloodstream by diffusion. These small molecules diffuse from the small intestine into the blood, moving from higher to lower concentration. OSMOSIS PASSIVE TRANSPORT  OSMOSIS Osmosis - the diffusion of water (across a membrane) Water will move in the direction where there is a high concentration of solute (and hence a lower concentration of water). A simple way to remember is: Salt is a solute, when it is concentrated inside or outside the cell, it will draw the water in its direction. This is also why you get thirsty after eating something salty.  OSMOSIS AND DIGESTION In order to remain healthy, animal cells need to maintain homeostasis in water balance. This means that the water concentration both inside and outside the cell are equal. In the large intestine water is absorbed back in the body cells by osmosis. This also makes the feces solid. Good bacteria in the large intestine produce vitamins like Vitamin K which is also reabsorbed by osmosis. These bacteria also produce flatus, a mixture of nitrogen and carbon dioxide, with small amounts of the hydrogen, methane, and hydrogen sulphide.  REVIEW: OSMOSIS Solution is made of solutes dissolved in a liquid or gas. Hypertonic Solution = high amount of solutes Hypotonic Solution = low amount of solutes Isotonic Solution = equal amount of solutes Dynamic Equilibrium is reached when solutes and water move across a membrane at equal rates because concentrations are equal (isotonic). Homeostasis = all living systems need to maintain perfect concentrations inside each cell  PASSIVE TRANSPORT Diffusion and osmosis do not require energy so they are called passive transport. E E D E D E R G Y N NO E N high low concentration concentration ACTIVE TRANSPORT  ACTIVE TRANSPORT Sometimes dissolved molecules are larger or at a higher concentration inside the cell than outside, but, because the organism needs these molecules, they still have to be absorbed. Active transport is the process by which dissolved molecules move across a cell membrane from a lower to a higher concentration. In active transport, particles move against the concentration gradient and therefore require an input of energy from the cell.  Down the Low High concentration concentration concentration gradient Low High Up the concentration concentration concentration gradient ACTIVE TRANSPORT AND DIGESTION glucose During digestion, the villi in the small intestine absorb the soluble nutrients. Over time, the concentration of nutrients in the villi reach an equilibrium with the concentration in the gut. Active transport is used to continue the transport of the small amounts of remaining nutrients against the concentration gradient. Amino acids are also absorbed by active transport. REVIEW  GLOSSARY active transport – The movement of molecules against a concentration gradient, and which requires energy. concentration gradient – The difference in concentration across a given area. diffusion – The movement of molecules from an area of high concentration to low concentration. osmosis – The diffusion of water molecules from a dilute solution to a more concentrated solution. partially-permeable membrane – A membrane that allows only certain sized molecules to pass through it. villi – Tiny finger-like projections on the inner surface of the small intestine, across which nutrients diffuse.  REVIEW: TYPES OF TRANSPORT Passive Transport Active Transport Molecules move from Molecules move from area of high area of low concentration to area of concentration to area of low concentration high concentration Movement is down the Movement is up the concentration gradient concentration gradient No energy needed Energy is required (ATP) Small molecules such as Large molecules, ions H2O, O2 and CO2 NEXT TOPIC: BIOMOLECULES