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© Boardworks Ltd 20091 of 9. © Boardworks Ltd 20092 of 9 Saving energy? Sayid has decided to save energy by staying in bed all day. Surprisingly, the.

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Presentation on theme: "© Boardworks Ltd 20091 of 9. © Boardworks Ltd 20092 of 9 Saving energy? Sayid has decided to save energy by staying in bed all day. Surprisingly, the."— Presentation transcript:

1 © Boardworks Ltd 20091 of 9

2 © Boardworks Ltd 20092 of 9 Saving energy? Sayid has decided to save energy by staying in bed all day. Surprisingly, the answer is only about 30%. How much of his energy do you think this will save? The other 70% keeps his body temperature at 37 °C (98.6 °F), and the solutions around his cells at just the right concentration.

3 © Boardworks Ltd 20093 of 9 What is homeostasis? The body uses so much energy, even during sleep, because it must maintain a constant internal environment. This process of keeping things the same is called homeostasis. A series of automatic control systems ensures that the body maintains a constant temperature and steady levels of water, ions and blood sugar. Homeostasis allows the body’s cells to work at their optimum.

4 © Boardworks Ltd 20094 of 9 Keeping comfortable

5 © Boardworks Ltd 20095 of 9 The organs of homeostasis

6 © Boardworks Ltd 20096 of 9 Why is water important? The human body is about 60-70% water. 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. How is water gained and lost? 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.

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8 © Boardworks Ltd 20098 of 9 What is osmosis? water glucose partially- permeable membrane (dialysis tubing) Osmosis 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.

9 © Boardworks Ltd 20099 of 9 Dilute vs. concentrated Concentrated solutions have a low concentration of water molecules. Dilute solutions have a high concentration of water molecules. During osmosis, water molecules diffuse from pure water or dilute solution to more concentrated solutions. pure water dilute solution concentrated solution

10 © Boardworks Ltd 200910 of 9 Predicting osmosis

11 © Boardworks Ltd 200911 of 9 Osmosis in action

12 © Boardworks Ltd 200912 of 9 Remember what the cell membrane looks like:

13 © Boardworks Ltd 200913 of 9 Osmosis and cells Plant and animal cells are surrounded by a partially- permeable plasma membrane. This allows water and other small molecules to diffuse across. plant cell red blood cell cell wall Plant cells additionally have a strong cell wall surrounding the membrane which offers support and protection. plasma membrane

14 © Boardworks Ltd 200914 of 9 Osmosis and plant cells

15 © Boardworks Ltd 200915 of 9 Osmosis and animal cells Animal cells do not have a cell wall. This means they respond differently to plant cells to the gain and loss of water. In concentrated solutions, water loss causes the cells to shrink. When this happens to red blood cells, it is called crenation. In dilute solutions, osmosis can cause animals cells, such as red blood cells, to swell up and burst. This is called lysis.

16 © Boardworks Ltd 200916 of 9 Osmosis and animal cells

17 © Boardworks Ltd 200917 of 9 Factors that affect Passive Transport: Whether a molecule can move through the membrane depends on: the size of the molecule the type of molecule (polar or nonpolar, ions, etc.) Molecules move by one of the following methods: diffusion, facilitated diffusion, or osmosis.

18 © Boardworks Ltd 200918 of 9 Egg in hypertonic solution Water 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

19 © Boardworks Ltd 200919 of 9 Egg in hypotonic solution Water 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)

20 © Boardworks Ltd 200920 of 9 Osmosis and animal cells In 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. The 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. hypothalamus

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22 © Boardworks Ltd 200922 of 9 Waste removal The lungs remove carbon dioxide. The liver converts excess protein into urea. The kidneys remove unwanted substances such as urea, excess water and salt. Several organs are important in removing waste from the body. The skin provides a surface for small amounts of water and salt to move out of the body.

23 © Boardworks Ltd 200923 of 9 What is urea? Excess amino acids in the body are broken down by the liver, producing a waste substance called urea. Once formed, urea is transported by the circulatory system to the kidneys. 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. This process is important because it converts toxic ammonia to urea, which is done using carbon dioxide.

24 © Boardworks Ltd 200924 of 9 What are the different parts of a kidney?

25 © Boardworks Ltd 200925 of 9 Labeling the kidney

26 © Boardworks Ltd 200926 of 9 How does the kidney work?

27 © Boardworks Ltd 200927 of 9 Stages in the nephron

28 © Boardworks Ltd 200928 of 9 Controlling water content

29 © Boardworks Ltd 200929 of 9 Regulating water content

30 © Boardworks Ltd 200930 of 9 Analysing urine Changes in the colour, clarity, pH and the presence of certain substances in urine can help doctors diagnose medical conditions: Protein or red blood cells in urine can indicate kidney damage or disease, as these substances would not normally filter through the glomerulus. Glucose in urine is often an indication of diabetes. A person with diabetes will have a high level of glucose in the blood.

31 © Boardworks Ltd 200931 of 9 Which sample?

32 © Boardworks Ltd 200932 of 9 Controlling blood glucose Between 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.


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