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Boardworks GCSE Additional Science: Biology

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Presentation on theme: "Boardworks GCSE Additional Science: Biology"— Presentation transcript:

1 Boardworks GCSE Additional Science: Biology
Movement In and Out of Cells

2 Boardworks GCSE Additional Science: Biology
Movement In and Out of Cells

3 What is diffusion? Boardworks GCSE Additional Science: Biology
Movement In and Out of Cells

4 Diffusion and concentration
Boardworks GCSE Additional Science: Biology Movement In and Out of Cells Why can the student smell the sock from a distance? The sock can be smelt because sweat and other molecules are moving away from it and spreading out in the air. This is called diffusion. Where is the smell strongest? The smell is strongest at the sock. The smell becomes weaker further away from the sock.

5 Moving molecules In which states are molecules able to diffuse?
Boardworks GCSE Additional Science: Biology Movement In and Out of Cells In which states are molecules able to diffuse? liquid (e.g. water) gas (e.g. steam) solid (e.g. ice) Molecules in liquids and gases are constantly moving and bumping into each other. This means that they tend to spread out.

6 Diffusion in action: one gas
Boardworks GCSE Additional Science: Biology Movement In and Out of Cells Teacher notes This activity could be used as a starter exercise to work on diffusion.

7 Diffusion in action: two gases
Boardworks GCSE Additional Science: Biology Movement In and Out of Cells Teacher notes This activity could be used as a starter exercise to work on diffusion.

8 Changing concentrations
Boardworks GCSE Additional Science: Biology Movement In and Out of Cells During diffusion molecules move from an area of high concentration to an area of low concentration. They are said to move down a concentration gradient. high concentration low Diffusion is a passive process which means that no energy is needed. Molecules diffuse until they are evenly spaced apart and equilibrium is reached. The rate of diffusion depends on several factors, such as the distance the particles have to travel and the difference in concentration.

9 Diffusion: true or false?
Boardworks GCSE Additional Science: Biology Movement In and Out of Cells Teacher notes This true-or-false activity could be used as a plenary or revision exercise on diffusion, or at the start of the lesson to gauge students’ existing knowledge of the subject matter. Coloured traffic light cards (red = false, yellow = don’t know, green = true) could be used to make this a whole-class exercise.

10 Boardworks GCSE Additional Science: Biology
Movement In and Out of Cells

11 Why is diffusion important to life?
Boardworks GCSE Additional Science: Biology Movement In and Out of Cells Diffusion is the main way in which substances move over short distances in organisms. What substances need to move? Oxygen, food and waste products are some of the substances that move by diffusion. In animals, how do these vital substances get to where they are needed? The substances are transported in the bloodstream, from where they can diffuse in and out of cells.

12 Diffusion and breathing
Boardworks GCSE Additional Science: Biology Movement In and Out of Cells Breathing involves the exchange of gases in the lungs; a process that occurs by diffusion. What happens when you breathe in? Oxygen in inhaled air diffuses through the lungs and into the bloodstream. The oxygen is then transported throughout the body. Carbon dioxide is the waste gas produced by respiration. Carbon dioxide diffuses from body tissues into the bloodstream and is exhaled via the lungs. Where does gas exchange take place in the lungs?

13 Structures of the respiratory system
Boardworks GCSE Additional Science: Biology Movement In and Out of Cells Teacher notes This zoom activity could be used to lead students on a step-by-step journey down to the level of the alveoli. It could also be used to review prior knowledge. Students could be asked to say where alveoli are found and then additional questions could be posed to move them up or down the hierarchy towards a more precise understanding of their location.

14 Cross-section through an alveolus
Boardworks GCSE Additional Science: Biology Movement In and Out of Cells Alveoli are the tiny air sacs at the end of the bronchioles, in which gas exchange occurs. deoxygenated blood (from body tissues) air in/out alveolus capillary Teacher notes Alveoli = plural; alveolus = singular oxygenated blood (to body tissues) red blood cell

15 How are alveoli adapted?
Boardworks GCSE Additional Science: Biology Movement In and Out of Cells Alveoli have several adaptations that help to make gas exchange very efficient: They are very thin – only one cell thick. They are covered by a network of fine capillaries, enabling gases to pass almost directly between the lungs and bloodstream. They are moist, encouraging gas molecules to easily dissolve. They have a large combined surface area, allowing large amounts of gases to be exchanged with each breath.

16 What happens in the alveoli?
Boardworks GCSE Additional Science: Biology Movement In and Out of Cells Teacher notes This four-stage animation shows how oxygen and carbon dioxide are exchanged in the alveoli. Suitable prompts could include: Start: What is special about the shape of the alveoli and their position to the capillary blood supply? Stage 1: Why is the blood arriving at the lungs deoxygenated? Stage 2: What colour is haemoglobin? Stage 3: Which other substances are produced during respiration? Stage 4: Approximately what percentage (approx). of exhaled air is carbon dioxide? (4%)

17 Diffusion and digestion
Boardworks GCSE Additional Science: Biology Movement In and Out of Cells Carbohydrates, proteins and fats are made up of large molecules that cannot be readily absorbed by the body. Digestion breaks down large food molecules into smaller molecules 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.

18 How is the small intestine adapted?
Boardworks GCSE Additional Science: Biology Movement In and Out of Cells The wall of the small intestine is lined with many tiny finger-like projections called villi. These are very thin and increase the surface area of the small intestine, both of which increase the speed of diffusion. capillary network villus small intestine blood vessels

19 Diffusion and the small intestine
Boardworks GCSE Additional Science: Biology Movement In and Out of Cells How does the initial concentration of dissolved food molecules in the small intestine compare with the concentration of the blood in the villi? The concentration of dissolved food molecules is higher in the small intestine than in the blood entering the villus. This means that the dissolved food molecules diffuse from the small intestine into the blood, moving from higher to lower concentration. glucose

20 Diffusion and the placenta
Boardworks GCSE Additional Science: Biology Movement In and Out of Cells The placenta is an organ that develops in the uterus of female mammals during pregnancy. The umbilical cord connects the placenta to the fetus. The placenta enables nutrients and oxygen to pass from the mother to the fetus by diffusion, and waste substances to diffuse from the fetus back to the mother. The placenta can filter out certain molecules and bacteria, but is unable to stop many harmful substances such as alcohol, chemicals and some types of virus from reaching the fetus.

21 Diffusion and the placenta
Boardworks GCSE Additional Science: Biology Movement In and Out of Cells How does the placenta work? blood to mother low in O2/nutrients, high in CO2/waste umbilical cord placental villi increase surface area for diffusion umbilical artery blood from mother high in O2/nutrients, low in CO2/waste umbilical vein

22 Diffusion and nerves impulses
Boardworks GCSE Additional Science: Biology Movement In and Out of Cells A synapse is a junction between two neurones across which electrical signals must pass. synaptic cleft neurotransmitter neurotransmitter receptor nerve impulse Neurotransmitter molecules diffuse from vesicles towards the neurotransmitter receptors, moving from an area of high concentration to low concentration.

23 Boardworks GCSE Additional Science: Biology
Movement In and Out of Cells

24 What is osmosis? Boardworks GCSE Additional Science: Biology Movement In and Out of Cells 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 visking tubing filled with a solution and placed in a beaker of pure water. partially- permeable membrane (visking tubing) water glucose

25 Dilute vs. concentrated
Boardworks GCSE Additional Science: Biology Movement In and Out of Cells During 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 water dilute solution concentrated solution

26 Predicting osmosis Boardworks GCSE Additional Science: Biology
Movement In and Out of Cells Teacher notes This drag and drop activity provides the opportunity for informal assessment of students’ understanding of osmosis.

27 Osmosis in action Boardworks GCSE Additional Science: Biology
Movement In and Out of Cells Teacher notes This activity could be used as a starter exercise to work on osmosis.

28 Osmosis and cells Boardworks GCSE Additional Science: Biology Movement In and Out of Cells Plant 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. plasma membrane cell wall red blood cell plant cell

29 Osmosis and plant cells
Boardworks GCSE Additional Science: Biology Movement In and Out of Cells Teacher notes This activity could be used to check students’ understanding of the effects of osmosis on plant cells.

30 Osmosis and animal cells
Boardworks GCSE Additional Science: Biology Movement In and Out of 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 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.

31 Osmosis and animal cells
Boardworks GCSE Additional Science: Biology Movement In and Out of Cells Teacher notes This activity could be used to check students’ understanding of the effects of osmosis on red blood cells.

32 Osmosis and animal cells
Boardworks GCSE Additional Science: Biology Movement In and Out of 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. hypothalamus 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. Teacher notes See the ‘Homeostasis’ presentation for more information on osmoregulation.

33 Boardworks GCSE Additional Science: Biology
Movement In and Out of Cells

34 Movement in and out of cells
Boardworks GCSE Additional Science: Biology Movement In and Out of Cells Substances move in and out of cell by passive and active transport. Which methods of transport are illustrated? Teacher notes This illustration contains several discussion points relating to movement in and out of cells, including: Rats escaping from prison This section of the illustration represents diffusion. The rats are running from the prison through the gaps in the fence (representing a partially-permeable membrane). The rats are running from an area of high concentration (inside the prison) to an area of low concentration (outside the prison), i.e. along a concentration gradient. Prison guard watering wilted flowers This section of the illustration represents osmosis. The water being sprayed from the hosepipe represents water particles moving from an area of high concentration to an area of low concentration (the parched soil), i.e. along a concentration gradient. Objects being passed through the wire fence This section of the illustration represents active transport. The bags represent cellular substances and the fence represents a partially-permeable membrane. The bags are being passed from an area of low concentration (outside the prison) to high concentration (inside the prison), i.e. against a concentration gradient.

35 What is active transport?
Boardworks GCSE Additional Science: Biology Movement In and Out of Cells Substances can move passively in and out of cells by diffusion until the concentration on both sides of the cell membrane reaches an equilibrium. Substances can continue to move in and out of a cell using a process called active transport. During active transport, protein carriers in the cell membrane ‘pick up’ particles and move them against the concentration gradient. As the name suggests, active transport requires energy from the cell, which is made available by respiration.

36 What is active transport?
Boardworks GCSE Additional Science: Biology Movement In and Out of Cells Teacher notes This two-stage animation shows how substances are transported across the cell membrane. Suitable prompts could include: Start: What kind of molecules are transported by active transport? (e.g. sodium and potassium in muscle cells) Stage 1: Which process provides the energy for active transport? (respiration)

37 Active transport in plants
Boardworks GCSE Additional Science: Biology Movement In and Out of Cells Plants need to absorb mineral elements such as nitrogen, phosphorus and potassium from the soil for healthy growth. When the concentration of minerals in soil is lower than inside the plant, active transport is used to absorb the minerals against the concentration gradient. What would happen if the plant relied on diffusion to absorb minerals? minerals The cells would become drained of minerals because they would travel down the concentration gradient.

38 Active transport in humans
Boardworks GCSE Additional Science: Biology Movement In and Out of Cells 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. glucose Active transport is used to continue the transport of the small amounts of remaining nutrients against the concentration gradient.

39 Boardworks GCSE Additional Science: Biology
Movement In and Out of Cells

40 Glossary (1/2) Boardworks GCSE Additional Science: Biology Movement In and Out of Cells active transport – The movement of molecules against a concentration gradient, and which requires energy. alveoli – The tiny air sacs at the end of the bronchioles in which gas exchange takes place in mammals. concentration gradient – The difference in concentration across a given area. crenation – The shrinking of animal cells in response to water loss by osmosis. 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.

41 turgid – The state caused by high water uptake in plant cells.
Glossary (2/2) Boardworks GCSE Additional Science: Biology Movement In and Out of Cells partially-permeable membrane – A membrane that allows only certain sized molecules to pass through it. placenta – The organ that transports oxygen, nutrients and waste products to and from the developing fetus. turgid – The state caused by high water uptake in plant cells. villi – Tiny finger-like projections on the inner surface of the small intestine, across which nutrients diffuse.

42 Anagrams Boardworks GCSE Additional Science: Biology
Movement In and Out of Cells

43 Which process? Boardworks GCSE Additional Science: Biology
Movement In and Out of Cells Teacher notes This completing sentences activity could be used as a plenary or revision exercise on movement in and out of cells. Students could be asked to write down the missing words in their books and the activity could be concluded by the completion on the IWB.

44 Multiple-choice quiz Boardworks GCSE Additional Science: Biology
Movement In and Out of Cells Teacher notes This multiple-choice quiz could be used as a plenary activity to assess students’ understanding of movement in and out of cells. The questions can be skipped through without answering by clicking “next”. Students could be asked to complete the questions in their books and the activity could be concluded by the completion on the IWB.


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