2Overview of Topic Diffusion & Active transport Osmosis Enzymes & optimum temperatureControl and Feedback systemsHomeostasis and temperatureWhat happens if you get too hot or too cold?Homeostasis and water balanceHormones and water balanceKidneys
4ObjectivesExplain how diffusion and active transport work
5Smells and liquids spreading out Why can you smell cooked food from a distance?Why does the colour of concentrated fruit drink change when it is added to water?Why can you smell perfume or aftershave when someone walks past you?
6DiffusionDiffusion is the net movement of particles from a region of high concentration to a region of low concentration (concentration gradient).Only happens in gases or a substance in solution.It occurs because the particles move around and bump into each other and begin to spread out.
7Changing concentrations Boardworks GCSE Additional Science: BiologyMovement In and Out of CellsChanging concentrationsDuring diffusion molecules move from an area of high concentration to an area of low concentration often through a partially permeable membrane.Diffusion is a passive process which means that no energy is needed.highconcentrationlowMolecules diffuse until they are evenly spaced apart and equilibrium is reached.
8Concentration Gradient The difference between the concentration in each area is called the concentration gradient.The bigger the concentration gradient the faster the rate of diffusion will occur.WHAT ELSE DO YOU THINK WOULD AFFECT THE RATE OF DIFFUSION?
9Net MovementAt lower concentration gradients the rate appears slower because particles from the other side may be moving too.Because particles may move from either side we must consider the net movement of particles.Net movement = particles moving in -particles moving out
11Why is diffusion so important? Diffusion is an essential process that is going on inside your body right now and keeping you alive!Diffusion occurs in the organ systems that control your breathing, circulation, digestion and other life processes.
12Active Transport Active transport is the opposite to diffusion. Its when particles move from a region of low concentration to a region of high concentration.It requires energy to do this as it is going against the concentration gradient.high concentrationdiffusionactive transportlow concentration
13What is active transport? Boardworks GCSE Additional Science: BiologyMovement In and Out of CellsWhat is active transport?Substances can move passively in and out of cells by diffusion until the concentration on both sides of the cell membrane reaches an equilibrium. Once they have reached equilibrium they will not appear to move anymore. 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.
14Questions What is diffusion? What is active transport? What is the difference between diffusion and active transport?What is a partially permeable membrane?Why does oxygen diffuse into the blood from the lungs?Why does food diffuse into the blood from the intestines?
21What is osmosis? Osmosis is a special type of diffusion. Diffusion involves gas or dissolved molecules, but osmosis only involves the movement of water molecules.watermoleculeOsmosis occurs across a semi-permeable membrane which has tiny holes in it.These holes are small enough for water molecules to pass through but larger molecules cannot pass through.
22What happens during osmosis? watermoleculesemipermeable membraneOsmosis is the movement of water molecules from a region of high water concentration (dilute sol’n) to a region of low water concentration (conc sol’n) across a semi-permeable membrane.
23Dilute vs. concentrated Boardworks GCSE Additional Science: BiologyMovement In and Out of CellsDilute vs. concentrated.During osmosis, water molecules diffuse from pure water or dilute solution to more concentrated solutionsDilute solutions have a high concentration of water molecules.Concentrated solutions have a low concentration of water molecules.pure waterdilute solutionconcentrated solution
24Osmosis and animal cells Boardworks GCSE Additional Science: BiologyMovement In and Out of CellsOsmosis and animal cellsAnimal cells do not have a cell wall. This means they respond differently than plant cells to the gain and loss of water.In dilute solutions, water moves into the cell causing the cell to swell up and burst. This is called lysis.In concentrated solutions, water moves out from the cell from the cytoplasm, and causes the cells to shrivel and shrink.
27ObjectivesDescribe what an enzyme is and what conditions they work best in
28Boardworks GCSE Additional Science: Biology Enzymes What are enzymes?Enzymes are proteins. They are biological catalysts – they speed up the chemical reactions that take place inside all cells, but without being used up in the process.There are many thousands of different types of enzyme, and each one catalyses (speeds up) a different reaction.They are specific to each reaction due to their ‘lock and key’ structure.
29The ‘Lock and Key’ model Boardworks GCSE Additional Science: BiologyEnzymesThe ‘Lock and Key’ modelEach enzyme binds to a specific molecule called the reactant or substrate.The part of the enzyme to which the reactant binds is called the active site. It is a very specific shape and the most important part of the enzyme.Photo credit: JC Revy / Science Photo LibraryThe image shows a molecular computer graphics image of ribonuclease A, an enzyme involved in the destruction of messenger RNA (mRNA) in the cytoplasm of bacteria. At left is its substrate, shifted away from the active site. Enzymes are biological catalysts, proteins that speed up the rates of reactions within cells. Each enzyme is specific for a particular reaction; interaction occurs (typically as a weak bond) between an active site on the enzyme & a reactant (or substrate) due to the arrangement of mutually attractive groups of atoms. This image displays the molecular surface (blue) & polypeptide chain: colours are used to represent the polarity of constituent amino acids.Only the substrate that matches the active site can bind to the enzyme. This is why we call it the lock and key model.
30What happens at the active site? Boardworks GCSE Additional Science: BiologyEnzymesWhat happens at the active site?++↔↔enzymesubstrate+enzyme-substrate complex↔products
33Why do enzymes speed up reactions? Boardworks GCSE Additional Science: BiologyEnzymesWhy do enzymes speed up reactions?Enzymes speed up reactions by lowering the activation energy (Ea) of a reaction. The activation energy is the energy needed to start a reaction. Different reactions have different activation energies.Ea without enzymereaction (time)energy (kJ)Ea with enzymeTeacher notesSee the ‘Energy Transfer’ and ‘Rates of Reaction’ chemistry presentations for more information on activation energy.
34How else can we speed up reactions? Another way to speed up chemical reactions is to increase the temperature. If the temperature gets too high though, the enzyme will stop working.Human body Optimum Temp = 37°C
35Factors affecting enzymes Boardworks GCSE Additional Science: BiologyEnzymesFactors affecting enzymesEnzymes work at an optimum temperature and pH.If the temperature and pH changes from an enzyme’s optimum level, the shape of the enzyme irreversibly changes.This affects the shape of the active site and means that the enzyme will no longer work. When this happens we call the enzyme denatured.denaturednormalheatpH
36Enzyme Questions What are enzymes also known as? What do enzymes do to biological reactions?What do we call the special shape on an enzyme molecule?What are enzymes made of?What is created when an enzyme and substrate combine together?What is lost when an enzyme is denatured?Write down two factors that can cause denaturing.
37CAUTION – VERY HOT WATER!! Enzyme PracticalPut 5cm starch solution and 1cm amylase (enzyme) in a boiling tubeRepeat this for 5 boiling tubesPlace each boiling tube in a different condition and leave for 15 minutesConditions are:Ice (0°C), Room temp (20°C), 40°C, 60°C and 80°C.CAUTION – VERY HOT WATER!!
38Enzyme PracticalAfter 15 minutes remove the test tube from the water bath and place in a test tube rack.Then add a few drops of iodine to each solution and observe the reaction.Record the results in a table.See if you can draw any conclusions about the temperature amylase likes to work at.
39Results Temperature Group 1 Group 2 Group 3 Group 4 Group 5 Group 6 20 20406080
41Starter Activity List your senses Tick which ones you used coming into the roomHow would you tell the temperature of a cup of water without a thermometer?
42ObjectivesDescribe how a control and feedback system work
43How does this greenhouse maintain its temperature? If its too cold...A receptor detects the temperature, which sends a message to a processing centre (computer), which triggers a response in the effector, which in this case turns heaters onAnd if its too hot... A receptor detects the temperature, which sends a message to a processing centre (computer), which triggers a response in the effector, which in this case opens ventilation flaps to allow cooling.
44The same thing happens in the human body STIMULUS is the change your body detectsRECEPTORS in the body detect a change inside or outside of the bodyCENTRAL NERVOUS SYSTEM (CNS) co-ordinates the body’s response, made up of brain and spinal cordEFFECTORS cause a response by moving part of the body or secreting a hormoneExample...RECEPTORIn your earsEFFECTORMuscles contract so you turn to look at them(CNS)STIMULUSFriend shouts you
45Write a control and feedback flow diagram for each of these situations You touch a hot pan on a cookerYou prick your finger on something sharpYour friends shouts your name and you turn round to look at them
46What is the central nervous system? Boardworks GCSE Science: BiologyElectrical SignalsWhat is the central nervous system?The central nervous system (CNS) is made up of the brain and spinal cord.cerebral hemispherecerebellumspinal cord
47Boardworks GCSE Science: Biology Electrical Signals What are reflexes?Reflexes are fast, automatic protective biological control systems that link a stimulus to a response.Reflex reactions happen without you having to think about them – they are involuntary. This is because the central nervous system (CNS) sends electrical signals to the muscles before the brain can pick up the message.Many reflexes such as sneezing and focusing your eyes occur naturally, but other reflexes can be learned, i.e. conditioned responses.
48What types of common reflexes do you know? Boardworks GCSE Science: BiologyElectrical SignalsTeacher notesThis illustration contains several discussion points relating to reflexes, including:the girl who has burnt her hand on the hot oven doorthe boy who is sneezingthe short-sighted boy squinting at the boardthe long-sighted girl looking at the piece of paper
49Boardworks GCSE Science: Biology Electrical Signals What are neurones?Neurones are specialised cells that conduct electrical impulses through the body.A nerve is a bundle of many nerve fibres enclosed within a protective sheath. Nerve fibres are the long axons of neurones together with any associated tissues.nerve fibrenerve
50Definitions Stimulus – Changes that receptor cells detect. Receptors – Cells that detect changes inside or outside the body.Sense organs – organs that contain receptor cells.Effectors – Organs in the body that cause a response. They can be muscles or glands.
51Boardworks GCSE Science: Biology Electrical Signals Interpreting signalsHow can you find your reaction time?Extend your arm over the edge of a table and have a partner hold a ruler between your fingers at the 0 cm mark.The partner drops the ruler – catch it between your fingers and thumb as quickly as possible.Repeat the test 10 times, recording the results and calculate the mean (average) distance. Then convert the distance into a reaction time.Teacher notesThe following table contains data to convert distance into a reaction time:Distance on ruler Time5 cm sec (100 ms)10 cm sec (140 ms)15 cm sec (170 ms)20 cm sec (200 ms)25.5 cm sec (230 ms)30.5 cm sec (250 ms)43 cm sec (300 ms)61 cm sec (350 ms)79 cm sec (400 ms)99 cm sec (450 ms)
52Converting distance to Reaction time Distance on ruler Time5 cm sec (100 ms)10 cm sec (140 ms)15 cm sec (170 ms)20 cm sec (200 ms)25.5 cm sec (230 ms)30.5 cm sec (250 ms)43 cm sec (300 ms)61 cm sec (350 ms)79 cm sec (400 ms)99 cm sec (450 ms)
53to part of the body called an effector organ e.g. muscle or gland The brain or spinal cord co-ordinate a responseResponseInformation is sent as an electrical signals called impulsesImpulse travels along nerve cells called sensory neurone.Receptor detects changeImpulses send a message along a motor neuroneStimuli
54Information is sent as an electrical signals called impulses Receptor detects changeStimuliImpulse travels along nerve cells called sensory neurone.The brain or spinal cord co-ordinate a responseto part of the body called an effector organ e.g. muscle or glandImpulses send a message along a motor neuroneResponse
56Boardworks GCSE Additional Science: Biology Homeostasis Saving energy?Sayid 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, and the solutions around his cells at just the right concentration. The body uses so much energy, even during sleep, because it must maintain a constant internal environment.
57ObjectivesExplain how your body regulates temperature
58HomeostasisThe way our body keeps its internal conditions constant is called Homeostasis.We have many different feedback systems to control the conditions of our body such as; temperature, water levels, blood sugar etc.We are constantly making and losing heat, and temperature levels have to be maintained at 37°C for our body to work properly.
59Inside our bodyThe inside of our head and torso is known as our core as it contains our vital organs such as brain, heart, lungs.Inside the core is where our body is the warmest because this is where most of the heat from respiration is produced.This heat is transferred to our arms and legs through our blood to keep the warm too.They often feel cold because they don’t make much heat themselves and lose heat easily because they have such a large surface area.
61How is temperature controlled? Boardworks GCSE Additional Science: BiologyHomeostasisHow is temperature controlled?Body temperature is monitored and controlled by temperature receptors in the skin and brain.These receptors detect changes in the temperature of blood flowing through those areas.The part of the brain that detects changes is called the hypothalamus.The skin has temperature receptors in its nerves.If body temperature changes from 37°C, the hypothalamus and skin receptors send out electrical signals that trigger actions to change the temperature back to 37°C
62Body TemperatureTemperature detectors in the skin detect the external temperatureTemperature detectors in the brain detect the blood temperatureThe brain processes this information and coordinates a responseEffectors (muscles and sweat glands) carry out the response
64Keeping WarmYour muscles cause you to shiver (rapid contraction and relaxation of the muscles) to create heat.Goosebumps are caused by the tiny muscles at the base of body hairs pulling the hairs erect. The upright hairs trap an insulating layer of air, which helps reduce heat loss.
65Boardworks GCSE Additional Science: Biology Homeostasis Keeping WarmBlood vessels in the skin get narrower. This is called vasoconstriction. (this is why you look pale)This is when the blood vessels sink into the body to keep the blood warm.This is caused by contraction of the muscular wall of the blood vessels. This reduces the volume of blood flowing near the skin surface, and reduces the amount of heat lost from the body.
66Keeping Cool You sweat and heat evaporates from your sweat. Hairs lie flat so air is not trapped.Blood vessels in the skin get wider this is called vasodilation. (this is why you go red)This allows a larger volume of blood to flow near the skin surface, transferring heat to the environment.
71ObjectivesDescribe what happens if your body gets too hot or too cold
72What happens if your body is not 37°C If the temperature falls too low, reactions become too slow for cells to survive.If the temperature gets too high, the body’s enzymes are at risk of denaturing.
73If you get too hot - Heatstroke If your temperature goes over 40°C you can get heat stroke.You will be dehydrated, dizzy, confused and sick. You will look sweaty and pale, even though your skin is hot and dry and your not sweating much because your body is trying to conserve water.It happens easily to people who are ill (sickness and diarrhoea), people who have taken ecstasy and people who are not used to the heat.
74If you get too hot - Heatstroke To treat a person with heatstroke it is important to cool them down as quickly as you can.Put them in a bath of cold water. If you cant do that cover them in a wet sheet and keep the sheet wet.Give them water to drink.They must be seen by a doctor as soon as possible.
75If you get too cold - Hypothermia If your temperature goes below 35°C you have hypothermia. If it drops lower than 30°C you will pass out and be at risk of death.You will be shivering, confused, drowsy, have slurred speech, lose coordination and have cold, dry, pale skin.It doesn’t just happen in snowy places it can also happen in water, in wind and rain and even indoors! Elderly people are most at risk if their houses are cold and they don’t move around a lot.
76If you get too cold - Frostbite Your arms and legs don’t generate as much heat as the core of your body. They also lose heat easier.When its cold the blood flow is less to those areas due to the body concentrating blood flow to vital organs, as well as due to vasoconstriction.This means they are more at risk of getting too cold, and can develop frostbite.
77If you get too cold - Hypothermia To treat a person with hypothermia it is important to warm them up as quickly as you can.This can be done by taking them to a warm place and wrapping them n blankets and warm clothes. You can also give them something warm to drink.If they are wearing wet clothes, remove them and give them warm, dry clothes.
78TaskDesign an advice leaflet giving advice to people who are off on a trekking expedition in the desert.Remember deserts are really hot during the day and really cold during the night, so you will need to give advice on what to do to stay at the right temperature, and what to do if you get too hot or cold.
81ObjectivesExplain how your body regulates water balance
82Boardworks GCSE Additional Science: Biology Homeostasis Why is water important?The human body is about 60-70% water.Water molecules constantly move in and out of cells, and are essential for all life processes. Dehydration is the loss of too much water from the body and it damages cells.Teacher notesSee the ‘Movement In and Out of Cells’ presentation for more information on cells and osmosis.Water is produced by the body during respiration, and absorbed from food and drink.Water is lost from the body in exhaled air (breathing), sweat, urine and faeces.
83How are water levels controlled? Boardworks GCSE Additional Science: BiologyHomeostasisHow are water levels controlled?Water levels are monitored by the receptors in the hypothalamus.Receptors inside the hypothalamus detect changes in the concentration of salt in the blood.The higher the salt level the lower the water level. That’s why salty food makes you thirsty.
85Controlling water levels Sweating, Excreting & breathing make you have less water in your bloodTo get back to normal blood levels you don’t make much urine and need to take in more water through food and drinkNormal blood levelsDrinking, Eating & respiration make you have more water in your bloodTo get back to normal blood levels you make lots of urine and lose water by evaporation through sweat
86Questions How do we gain water? How do we lose water? What do we do if our water levels are too high?What do we do if our water levels are too low?Which organ checks what our water levels are?What are the symptoms of dehydration?
88ObjectivesExplain how hormones regulate water balance
89How are water levels controlled? Boardworks GCSE Additional Science: BiologyHomeostasisHow are water levels controlled?Water levels are monitored by the receptors in the hypothalamus.These receptors detect changes in the concentration of salt in the blood.Depending on the concentration, the hypothalamus instructs the pituitary gland to secrete more or less of the hormone ADH (anti-diuretic hormone)
90ADH and water regulation Osmoreceptors in the hypothalamus detect the low levels of water, so the hypothalamus sends an impulse to the pituitary gland which releases ADH into the bloodstream.ADH causes more water to be reabsorbed in the kidneys by making the wall of the collecting duct more permeable to water.This means less, more concentrated urine is made. It also increases thirst levels in the body, encouraging us to drink more.So, when ADH is present more water is reabsorbed and less is excreted.
91Not having enough water Low blood water level causes a high salt concentrationReceptors in the hypothalamus detect the high salt contentMore ADH is secreted into the bloodThe kidney becomes more permeable to water so more is reabsorbed.The bladder fills with a small quantity of urineNormal blood water level is achieved.
92Having too much waterHigh blood water level causes a low salt concentrationReceptors in the hypothalamus detect the low salt contentLess ADH is secreted into the bloodThe kidney becomes less permeable to water so more is absorbed.The bladder fills with a large quantity of urineNormal blood water level is achieved.
93Water regulation by ADH Too much waterToo little waterHigh blood water level causes a low salt concentrationLow blood water level causes a high salt concentrationReceptors in the hypothalamus detect the low salt contentReceptors in the hypothalamus detect the high salt contentLess ADH is secreted into the bloodMore ADH is secreted into the bloodThe kidney becomes less permeable to water so more is absorbed.The kidney becomes more permeable to water so more is reabsorbed.The bladder fills with a large quantity of urineThe bladder fills with a small quantity of urineNormal blood water level is achieved.Normal blood water level is achieved.
94Some drugs can affect the production of ADH. Drugs and ADHSome drugs can affect the production of ADH.Alcohol acts as a diuretic by reducing the amount of ADH secreted.This results in increased amounts of urine produced, which in turn can result in dehydration.Ecstasy is the opposite, it increases the amount of ADH secreted.This results in reduced amounts of urine produced, so the body is not releasing any water, yet users often drink lots.
97ObjectivesDescribe what job the kidneys do and explain how they work
98The KidneysThe blood contains many small molecules such as water, glucose, salt and urea.The kidneys filter the molecules that are not needed out of the blood.Once they have done that they reabsorb any molecules that are needed back into the blood.This happens in the kidney tubules.
99Amino AcidsAmino acids are used for growth and repair. They come from proteins which we eat.They cannot be stored if they are not used though, and have to be broken down.The liver breaks them down into a substance called urea which is filtered out by the kidneys.
100Ureter (tube that takes urine containing the waste down to bladder) KidneysKidneys are responsible for controlling water, glucose, salt and urea content.Blood inBlood outUreter (tube that takes urine containing the waste down to bladder)
102Kidneys work in 3 stages: Blood vesselTubule1. ULTRAFILTRATION - Lots of water and products of digestion are squeezed out of the blood and into tubules under pressure.2. SELECTIVE REABSORPTION – the blood takes back the things it wants (e.g. glucose and ions) even though this means going against a concentration gradient.3. WASTE – excess water, excess ions and any urea are now removed through the ureter
103Questions to answerWhich part of the body monitors water levels and how does it do it?How do we gain and lose water?How do we overcome not having enough water?How do we over come having too much water?How do the kidneys work?What effect do drugs and alcohol have on water levels?
106What conditions do Enzymes work best in? Revision BrainstormOsmosisDiffusionActive TransportWhat do Enzymes do?What conditions do Enzymes work best in?
107Responses Can you write responses for each of these situations? StimulusReceptorCNSEffectorResponseCan you write responses for each of these situations?You knock an object off the table and go to pick it upYou have an itch on your head and scratch itYou feel warm so you take your jumper off