Science Learner Book: Respiration PDF

## Respiration ### Why we need oxygen - Respiration is a series of chemical reactions that happens inside every living cell. - Aerobic respiration uses oxygen. - Cells produce carbon dioxide as a waste product. - Oxygen is taken into the lungs when breathing. - Oxygen from the air goes into the blo...

## Respiration ### Why we need oxygen - Respiration is a series of chemical reactions that happens inside every living cell. - Aerobic respiration uses oxygen. - Cells produce carbon dioxide as a waste product. - Oxygen is taken into the lungs when breathing. - Oxygen from the air goes into the blood and is delivered to every cell in the body. - The blood takes carbon dioxide back to the lungs. - The organs that help with taking oxygen out of the air, and getting rid of carbon dioxide, make up the respiratory system. ### The structure of the human respiratory system - The white spaces in the diagram are the 'tubes' (bronchi and bronchioles) that air moves through. | Structure | Description | |-----------------|-----------------------------------------------------------| | Entrance to nose | | | Entrance to mouth| | | Voice box (larynx) | | | Windpipe (trachea)| Contains rings of cartilage | | Lung | | | Bronchiole | | | Bronchus | | | Air sacs | | | Rib bone | | | Muscles between ribs (intercostal muscles) | | | Diaphragm | | ### Air sacs - The photograph shows a tiny part of the lungs, seen through a powerful microscope. - The holes are called air sacs or alveoli. - There are also many tiny blood vessels wrapped around the air sacs. - These blood vessels are capillaries. ### The structure of an air sac - The air sac has a wall made of one layer of very thin cells. ### Gas exchange in the air sacs - Oxygen goes into the blood and carbon dioxide goes into the air. - Oxygen from the air inside the air sac diffuses into the blood capillary. - Blood in the capillary comes from the heart and contains a small amount of oxygen and a lot of carbon dioxide. - Oxygen dissolves in the blood and combines with haemoglobin. - The oxyhaemoglobin lets go of its oxygen and gives it to the cells. - Carbon dioxide from the blood diffuses into the air in the air sac. ### Breathing - The intercostal muscles contract, pulling the ribs upwards and outwards. - The muscles in the diaphragm contract, pulling the diaphragm downwards. - This increases the volume inside the chest cavity. - The pressure inside the chest cavity and lungs decreases. - Air moves into the lungs to fill the extra space. - The intercostal muscles relax, allowing the ribs to drop down. - The muscles in the diaphragm relax. - This decreases the volume inside the chest cavity. - The pressure inside the chest cavity and lungs increases. - Air is squeezed out of the lungs. ### Plasma - Plasma is the liquid part of blood. It is mostly water. - Red and white blood cells are transported around the body in the blood plasma. - Plasma also has many other different substances dissolved in it. - Glucose is dissolved in blood plasma and is transported from the digestive system to every cell. - Carbon dioxide dissolves in blood plasma and is transported to the lungs. ### Red blood cells - Red blood cells are unusual cells. - They do not have a nucleus. - They do not have mitochondria. - They are full of a red pigment called haemoglobin that makes blood look red. ### Delivering the requirements for respiration in cells - Every cell in the body needs glucose and oxygen, and the carbon dioxide and water that the cell makes must be taken away. - The blood moves around the body inside blood vessels. - The heart pumps constantly to keep the blood moving. ### What is blood? - Most of the cells in our blood are red blood cells. - An adult person has at least 20 trillion red blood cells in their body. - There are about five million of them in every $1cm^3$ of your blood. - There are not many white blood cells, but some of them may be quite a lot bigger than the red blood cells. ### Using energy to stay alive - Our bodies need energy for many different reasons: - To move around. - To send electrical impulses along neurones. - To keep warm. - The food we eat, especially carbohydrates, provides energy. - Carbohydrates are broken down to glucose. - Glucose is transported around the body in the blood and used by cells to get energy. ### Releasing energy from glucose - The energy in glucose is locked up inside it. It has to be released from the glucose before your cells can use the energy. - This is done by tiny structures called mitochondria found inside each cell. - Mitochondria release energy from glucose through aerobic respiration. - Aerobic means that it uses oxygen. - The word equation for aerobic respiration is: $glucose + oxygen → carbon \ dioxide + water$ - Just a little bit of energy is released at a time – just enough for the cell’s needs. ### The haemoglobin helps the red blood cells to transport oxygen. - Oxygen from the alveoli in the lungs diffuses into the blood. - Oxygen then diffuses into the red blood cells where it combines with haemoglobin. - This forms a very bright red compound called oxyhaemoglobin. - Oxyhaemoglobin lets go of its oxygen and gives it to the cells. - Red blood cells do not have a nucleus or mitochondria which allows for more space for haemoglobin. ### White blood cells - White blood cells are easy to distinguish from red blood cells. - They always have a nucleus. - Some bacteria and viruses can cause illness when they get into the body. - These bacteria and viruses are called pathogens. - White blood cells help to defend us against pathogens. - Some kinds of white blood cell can change their shape, and push their cytoplasm out to make ‘fingers' that can capture a pathogen, then produces chemicals that kill and digest the pathogen. - Other types of white blood cells produce chemicals that kill pathogens. - These chemicals are called antibodies. - The antibodies stick onto the pathogen and sometimes kill it directly or glue lots of the pathogens together so that they cannot move. This makes it easy for other white blood cells to capture and kill the pathogens. ### Comparing solubility - Solubility is the amount of a solute that can be dissolved in 100g of solvent at 20°C. - A saturated solution is one which will not dissolve any more solute. - Most solutes will dissolves more quickly and easily in hot water than in cold water. ### Solubility - A solid that dissolves in a solvent (such as water) is said to be soluble. - Solids that don't dissolve in water are insoluble. - A saturated solution is one which will not dissolve any more solute. ### Think like a scientist: Solubility in water - This investigation will determine which solute is most soluble in water. - The solute will be tested at room temperature. - The number of spatulas of solute that will dissolve in a set volume of water will be measured. ### Solutions - A solution is made when a solute is dissolved in a solvent. - A concentrated solution has more particles of the solute dissolved in it than a dilute solution. ### Think like a scientist: Making different concentrations of a solution - This investigation involves accurately measuring specific volumes of concentrated food dye solution and water to create a dilute solution. ### All solutions are transparent and colorless. - You can still see through a solution even if it is colored, for example, the copper sulfate solution is blue. - A liquid such as milk is not transparent. It is opaque. ### Examples of dissolving - Sugar in black tea (solvent) - Instant coffee in hot water (solvent) - Nail polish in nail polish remover (solvent) ### Examples of melting - Butter in a frying pan - Ice cream on a warm day - Candle wax as the candle burns ### What is a solution? - When you place a lump of sugar in water, the sugar seems gradually to disappear. - The substance that dissolves is called the solute. - The substance that it dissolves into is called the solvent. - A solution is a mixture. - When the sugar has dissolved, the sugar and water mixture is the colourless solution. ### How to make a solution - Sugar crystals are visible because they are made of lots of groups of vibrating particles that are tightly packed together. - Water particles vibrate and slide past one another, bumping into the vibrating sugar particles. - The sugar particles are separated and mixed up with the water particles. - The water particles eventually separate all the sugar particles and they are no longer in groups and are too small to be seen. ### Comparing different substances - Scientists may use a large piece of chromatography paper and place spots of different items alongside each other. - The solvent can move up through all the samples at the same time. ### Chromatography - Scientists use chromatography to study the dyes used in food. - Some food dyes contain only one substance and are a pure substance. - Other food dyes contain a mixture of substances. - Public health scientists may also use chromatography to check that the colourings used in products such as hair dye or ink in pens are not harmful. ### Colours in ink - Black colored ink is a mixture of different coloured inks. - This can be shown by using paper chromatography. - The different coloured inks that make up the black ink separate out as the water moves up the paper. - The resulting image on the paper is called a chromatogram. - The coloured inks separate because the water dissolves them. - Water is the solvent. - The different kinds of ink particles are carried different distances because not all the ink particles have the same solubility. ### Dissolving salt in water - This experiment involves determining how the temperature of the water affects how much salt will dissolve. - The independent variable is the temperature of the water. - The dependent variable is the number of spatulas of salt that dissolve. - The control variables are the volume of water that is used. ### Other solvents - Water is not the only solvent. - Some substances that are insoluble in water will dissolve in other solvents. - Oil paint is not soluble in water. - It is soluble in methanol (methylated spirits). - Nail polish is not soluble in water, but is soluble in propanone (acetone). ### Comparing the solubility of different salts - The graph shows the solubility of three salts at a range of temperatures. - The general trend for the solubility of all three salts is that solubility increases with increasing temperature. ### Distance/time graphs - Scientists use graphs to describe how two variables are related. - A graph is more useful than words for describing movement because it is easier to see trends and patterns and information about the whole journey can be seen easily. - A distance/time graph shows the journey of an object by plotting a measure of distance on the vertical axis and a measure of time on the horizontal axis. ### Speed - Speed is the rate at which an object is moving. - Average speed is calculated in the same way as speed. - The equation for speed can be used in a formula triangle. - This means the equation can be used to calculate: - The distance travelled, if you know the speed and the time taken. - The time taken, if you know the speed and the distance travelled. ### Units of speed - There are many different units of speed. - The standard unit for speed is metres per second. ### Calculating speed - The way you calculate speed is linked to the unit metres per second, m/s. - Speed can be calculated by dividing the total distance travelled by the total time taken. ### Changing direction - Unbalanced forces can also make objects change direction. - When the ball contacts the tennis racket, the ball pushes on the tennis racket and the ball changes direction because the hitting force must be larger than the force from the ball. - This can be shown in a force diagram. - When an object moves in a circle, its direction is always changing. - A constant unbalanced force is needed to keep an object moving in a circle. ### Slowing down - Unbalanced or unequal forces can also make moving objects slows down. - A parachute makes a falling object slow down. - When an object is falling quickly, the parachute causes a force of air resistance that is larger than the weight of the object. - This force becomes balanced again and the object falls at a constant speed. ### Balanced or unbalanced? - Objects are not moving if the forces acting on them are balanced. - These forces are equal in size and opposite in direction. - There could be more than two forces acting on the object. - The forces acting on the rock are: - Weight force - Contact force - Friction force - Wind force ### Turning effects of forces - When you push down on a door handle, the handle turns. - When you push down on the pedal of a bicycle, the crank arm turns. - When you pull on a door, the door turns toward you. - These are all examples of forces that cause an object to turn. - The object that turns is called a lever. - The point around which the lever turns is called the pivot. ### Calculating moments - The moment of a force describes its the turning effect of a force. - The moment of a force depends on: - The size of the force (the bigger the force, the bigger the moment) - The distance between the position where the force acts and the pivot (the greater the distance, the greater the moment). - The equation to calculate the moment of a force is: moment = force × distance ### Balancing - A seesaw is a type of lever. - A seesaw will be balanced when the moments on both sides of the pivot are equal and opposite.