2Boardworks High School Science Homeostasis Saving energy?Boardworks High School ScienceHomeostasisSayid has decided to save energy by staying in bed all day.How much of his energy do you think this will save?Surprisingly, the answer is only about 30%.The other 70% keeps his body temperature at 37 °C (98.6 °F), and the solutions around his cells at just the right concentration.
4Boardworks High School Science Homeostasis Keeping comfortableBoardworks High School ScienceHomeostasisTeacher notesThis three-stage animation can be used to introduce the concept of homeostasis in terms of responding to change in external conditions.
5The organs of homeostasis Boardworks High School ScienceHomeostasisTeacher notesThis activity could be used as a starter exercise to work on homeostasis.
6Boardworks High School Science Homeostasis Why is water important?Boardworks High School ScienceHomeostasisThe human body is about 60-70% water.Water molecules and ions constantly move in and out of cells, and are essential for all life processes.Dehydration (loss of too much water from the body) damages cells.How is water gained and lost?Water is produced by the body during respiration, and absorbed from food and drink.Water is lost from the body in exhaled air, sweat, urine and feces.
8Boardworks High School Science Homeostasis What is osmosis?Boardworks High School ScienceHomeostasisOsmosis is the diffusion of water molecules from a low concentration solution to high concentration solution, across a partially-permeable membrane.A partially-permeable membrane has holes in it that permit water molecules through but are too small to allow larger molecules through. Osmosis can be demonstrated using dialysis tubing filled with a solution and placed in a beaker of pure water.partially- permeablemembrane(dialysis tubing)waterglucose
9Dilute vs. concentrated Boardworks High School ScienceHomeostasisDuring osmosis, water molecules diffuse from pure water or dilute solution to more concentrated solutions.Dilute solutions have a high concentration of water molecules.Concentrated solutions have a low concentration of water molecules.pure waterdilute solutionconcentratedsolution
10Boardworks High School Science Homeostasis Predicting osmosisBoardworks High School ScienceHomeostasisTeacher notesThis drag and drop activity provides the opportunity for informal assessment of students’ understanding of osmosis.
11Boardworks High School Science Homeostasis Osmosis in actionBoardworks High School ScienceHomeostasisTeacher notesThis activity could be used as a starter exercise to work on osmosis.You may need to allow the simulation to run for a minute or so before the water molecules on either side of the membrane are roughly equal.
12Remember what the cell membrane looks like: Boardworks High School ScienceHomeostasis
13Boardworks High School Science Homeostasis Osmosis and cellsBoardworks High School ScienceHomeostasisPlant and animal cells are surrounded by a partially-permeable plasma membrane. This allows water and other small molecules to diffuse across.Plant cells additionally have a strong cell wall surrounding the membrane which offers support and protection.plasmamembranecell wallred blood cellplant cell
14Osmosis and plant cells Boardworks High School ScienceHomeostasisTeacher notesThis activity could be used to check students’ understanding of the effects of osmosis on plant cells.
15Osmosis and animal cells Boardworks High School ScienceHomeostasisAnimal cells do not have a cell wall. This means they respond differently to plant cells to the gain and loss of water.In dilute solutions, osmosis can cause animals cells, such as red blood cells, to swell up and burst. This is called lysis.In concentrated solutions, water loss causes the cells to shrink. When this happens to red blood cells, it is called crenation.
16Osmosis and animal cells Boardworks High School ScienceHomeostasisTeacher notesThis activity could be used to check students’ understanding of the effects of osmosis on red blood cells.
17Factors that affect Passive Transport: Boardworks High School ScienceHomeostasisWhether a molecule can move through the membrane depends on:the size of the moleculethe type of molecule (polar or nonpolar, ions, etc.)Molecules move by one of the following methods: diffusion, facilitated diffusion, or osmosis.
18Egg in hypertonic solution Boardworks High School ScienceHomeostasisWater moved out of the egg to try to dilute the solutes outside of the egg and make the external environment have a higher water concentration to match the inside.Chicken egg in syrup
19Egg in hypotonic solution Boardworks High School ScienceHomeostasisWater moved into the egg to reduce the water concentration compared to solutes outside of the egg and make the external environment have a lower water concentration to match the inside.Chicken egg in tap water (or vinegar)
20Osmosis and animal cells Boardworks High School ScienceHomeostasisIn order to remain healthy, animal cells need to maintain an isotonic water balance. This means that the water concentration both inside and outside the cell are equal.hypothalamusThe concentration of water and salt in the blood are controlled by the kidneys.The kidneys are controlled by the portion of the brain called the hypothalamus.
22Boardworks High School Science Homeostasis Waste removalBoardworks High School ScienceHomeostasisSeveral organs are important in removing waste from the body.The lungs remove carbon dioxide.The liver converts excess protein into urea.The skin provides a surface for small amounts of water and salt to move out of the body.The kidneys remove unwanted substances such as urea, excess water and salt.
23Boardworks High School Science Homeostasis What is urea?Boardworks High School ScienceHomeostasisExcess amino acids in the body are broken down by the liver, producing a waste substance called urea.This process is important because it converts toxic ammonia to urea, which is done using carbon dioxide.Once formed, urea is transported by the circulatory system to the kidneys.Teacher notesThe kidneys typically filter about 1,500 liters of blood every day.The kidneys filter the blood, removing urea and excess water and salt, which forms urine. Urine is stored in the bladder before being excreted from the body.
24What are the different parts of a kidney? Boardworks High School ScienceHomeostasis
25Boardworks High School Science Homeostasis Labeling the kidneyBoardworks High School ScienceHomeostasis
26How does the kidney work? Boardworks High School ScienceHomeostasisTeacher notesStage 1: Filtration occurs as an increased blood pressure forces smaller substances through the capillary wall into the Bowman’s capsule. The glomerulus is a ball of blood vessels.Stage 2: In the first coiled tubule (proximal convoluted tubule) most reabsorption is by active transport. The cells of the first coiled tubule are packed with mitochondria, and have large brush borders to increase the surface area for reabsorption.Stage 3 & 4: Substances move out of the loop of Henle by passive diffusion. The cells of the loop of Henle are thin, with no brush border and relatively few mitochondria.Stage 5: The collecting duct carries water to the ureter.
27Boardworks High School Science Homeostasis Stages in the nephronBoardworks High School ScienceHomeostasis
28Controlling water content Boardworks High School ScienceHomeostasis
29Regulating water content Boardworks High School ScienceHomeostasis
31Boardworks High School Science Homeostasis Which sample?Boardworks High School ScienceHomeostasis
32Controlling blood glucose Boardworks High School ScienceHomeostasisBetween meals, blood glucose levels are topped up from stored deposits in the liver and muscles.After a meal, blood glucose rises but quickly returns to normal. Where does the excess go? Why not leave it in the blood?Excess glucose makes the blood plasma and tissue fluid around cells too concentrated. This can severely damage cells, for example, causing crenation in red blood cells.However, low blood sugar levels can be equally as dangerous, as it can make cells swell up and burst. This is called lysis.