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Science revision (Biology (Foods and nutrition (Digestion (Food is put in…

- - - - Diet is what you eat. It provides raw materials for your body
      - These raw materials are called nutrients. They are carbohydrates, fat, protein, water, vitamins and minerals
      - The two main carbohydrates are starch and sugars
      - Nutrients provide energy, growth, repair and health
      - There are many fats such as liquid fat which is called oil. Fats and oil are sometimes called lipids
      - We also need to eat fibre which is made of plant cell walls and helps food move through the intestines, preventing constipation
      - Water is also very important as we are 65% water and it acts as a lubricant, dissolves things inside us and cools us down when we sweat
      - Tests in food
        
        Starch: 2 drops of iodine, goes blue-black if present
        
        Protein: 5 drops of biuret solution , goes purple within a few minutes if present
        
        Fats: rub sample on white paper, greasy mark visible if present
    - - Different nutrients have different uses in the body
      - When you eat food you gain mass. In everyday life, this mass is burned as fuel
      - The amount of fuel you use should be balanced to what you eat
      - The body’s primary source of fuel is carbohydrates and its secondary source is fat
      - Fats are stored in your body for energy and insulate your body keeping you warm. If carbohydrates are not used up as fuel, they will become fats
      - Energy in food is measured in kilojoules
      - This energy is released during respiration
      - Protein is important for making new cells
    - - No food contains all the nutrients you need so to get them all you have to eat a balanced diet. If you don’t have enough of one nutrient, it is called malnutrition
      - If you do not have enough of a nutrient for a long time you may face deficiency disease
      - A lack of protein could cause a ‘pot belly’
      - A lack of vitamin A could cause night blindness
      - A lack of vitamin C could cause scurvy
      - A lack of calcium/vitamin D could cause rickets
      - A lack of iron could cause tiredness
      - A very severe form of malnutrition is starvation
      - People who eat too much energy without using it as fuel become obese, which could lead to heart problems
    - - Food is put in your mouth where it is chewed and mixed with saliva, a digestive juice. This is called ingestion
      - Food enters the oesphagus which contracts, pushing the food towards the stomach
      - The food is churned up with acid and more digestive juices in the stomach
      - In the small intestine the liver adds a substance which helps to digest fats. This is where small digested molecules are absorbed
      - Food that we can’t digest goes into the large intestine, where water is removed forming a more solid material (faeces)
      - The rectum stores faeces where it is later pushed out of the anus. It takes about 24-48 hours for food to travel through the gut
      - Bacteria are micro organisms. The bacteria in your gut feed on food and can digest some foods that your bodies can’t
      - These bacteria grow and reproduce, using some of the molecules. The rest of the molecules are absorbed
      - Enzymes speed up the breaking down of large molecules into smaller ones
      - Substances that speed up reactions are called catalysts. Enzymes are biological catalysts
      - Many of the enzymes that are used to break up food are made by the body
    - - Small molecules are absorbed by the small intestine
      - Once absorbed, digested nutrients are dissolved into the blood plasma
      - Blood carries the nutrients around the body to be used
      - The particles naturally spread out in all directions (diffusion), meaning that over time, the particles will become evenly spaced apart
      - Particles move randomly, so some will travlel from the blood to the small intestine, but many more will go the other way
      - The greater the surface area, the more diffusion is possible
      - The greater the area, the more glucose can be absorbed more quickly
      - To increase its surface area, the small intestine wall is folded. It has lots of little finger shaped villi, which also have microvilli on top
      - When alcohol is drunk, fewer digestive enzymes are released. If too much alcohol is consumed over a long period of time, the villi can be damaged and can become shorter
  - - - Sporting events often have paramedics nearby in case of emergency
      - These paramedics often check oxygen saturation in the blood. It should be around 95-100% saturated. If it drops below 80%, organs may be damaged
      - Galen of Pergamon was a Roman sports paramedic. He was so successful that his ideas were used for the next 1500 years
      - He thought that the heart created heat and that we breathed in to cool ourselves down
      - John Priestly and Antoine Lavoisier realised that you only neede the oxygen in the air to keep a candle burning or a mouse alive, and that the air was 21% oxygen
      - We now now know that oxygen is needed to release energy from glucose . The release of this energy is called aerobic respiration
      - The word equation for aerobic respiration is: oxygen + glucose —> carbon dioxide + water
    - - Breathing is when muscles between the ribs and diaphragm change the size of the lungs
      - The movement of air in and out of the lungs is called ventilation
      - Inhaling is breathing in and exhaling is breathing out
      - The lungs need to be kept clean in order for them to work properly
      - Some cells in the lungs create a sticky liquid called mucus which traps dirt, dust and microorganisms
      - Tiny hairs on other cells, called cilia sweep the mucus into the gullet where it can be swallowed
      - The chemicals and heat in cigarettes stop the cilia from working, making mucus collect in the lungs
      - Some oxygen in the air enters your blood in the lungs and at the same time, some CO² in the blood plasma enters the air in the lungs. This is called gas exchange
      - Gas exchange occurs by diffusion
      - The lungs are adapted for gas exchange by having about 700,000,000 small pockets called aveoli. This give the lungs a large surface area meaning it can occur faster
      - Aveoli have walls only 1 cell thick. The blood capillaries surrounding them also have thin walls. These thin walls allow diffusion to occur quickly and easily
    - - When oxygen gets into the blood, it enters red blood cells, where it sticks to molecules of haemoglobin, making them change from dark browny-red to bright red
      - From the lungs, blood enters the heart to be pumped around the body through blood vessels called arteries ,which divide into tiny capillaries
      - In the capillaries, blood gradually leaves the red blood cells and dissolves in the plasma. This leaks out through tiny holes in the capillaries and forms tissue fluid
      - This tissue fluid carries oxygen to the cells . Plasma has glucose and other nutrients dissolved in it, meaning that they are also in the tissue fluid
      - Water products from cells dissolve in the tissue fluid and return to other capillaries which link up with veins. These veins then lead to the heart
      - When you exercise, your muscle cells work harder and release more energy using aerobic respiration. They need more oxygen and glucose
      - Your breathing rate increases to get more oxygen in your blood and your heart beats faster
    - - If you hold your breath, the amount of CO₂ in your blood plasma increases. If this reaches a certain level, your brain causes breathing to occur
      - Our muscle cells can store some oxygen
      - During strenuous exercises oxygen is used faster than it is replaced. Then anaerobic respiration occurs. This does not involve oxygen. Glucose —> lactic acid.
      - Anaerobic respiration does not release as much energy from glucose as aerobic respiration and it also causes your muscles to tire much more quickly
      - Lactic acid from the muscles enters the blood and is carried to the gut, where it converts back to glucose . This process needs a lot of energy
      - After exercise you need extra of oxygen for different processes. This lack of oxygen is known as EPOC - Excess Post-exercise Oxygen Consumption
      - Your breathing and heart rate remain high after exercise in order to regain the necessary amount of oxygen
  - - - An organism is a living thing, which means it carries out 7 processes, (MRS GREN)
      - Organisms are all based on cells. If an organism has many cells, it is multicellular. Unicellular organisms are also known as microorganisms as they are too small to see with the naked eye
- - - - The Earth moves around the sun at around 100,000km/h
      - The gravity from the sun keeps the earth from flying away
      - The force of gravity gets weaker the further away the objects are
      - The moon is an example of a natural satellite
      - Artificial satellites are put into orbit by humans they often serve purposes such as transmitting tv programs and photographing the surface.
      - If you climbed Mount Everest you would weigh 1 N less than you do now because you would be further away from the Earth
      - Weight (N) = mass (kg) x gravitational field strength (N/kg)
- - - - A fuel, such as hydrogen, is a chemical substance which stores energy, ready to be transferred later
      - In a chemical reaction, a reactant is the substance that reacts and a product is the result of it. Energy is not a substance and therefore is not part of a word equation
      - Hydrogen can react with oxygen if there is a form of energy like a match or spark to start off the reaction, which then continues without need of additional energy input
      - In combustion, useful energy is used as heat, sometimes light and, if the reaction is very vigorous, sound
      - Some fuels are known as fossil fuels if they were produced from oil that was formed from living organisms that died millions of years ago
      - A wooden splint that has been lit, will make a popping sound of hydrogen is present in a test tube
    - - If a substance reacts with oxygen it forms a compound known as an oxide. This process is called oxidation
      - Many metals react with oxygen to produce metal oxide
    - - When carbon burns in lots of air, only CO₂ is formed. This is called complete combustion
      - However, if there is not enough air, incomplete combustion occurs. The products are CO₂, CO and soot
      - Many products of burning fuels in engines are pollutants due to impurities in the fuel
      - Sulfur dioxide and nitrogen oxide are two common acidic gases
    - - Most of the energy that is causing the earth to heat up is transferred by the Sun, because some of this energy is trapped beneath the earths atmosphere
      - This warming effect is called global warming and without it the earth would be inhabitable
      - Global warming is increasing because more fossil fuels are being used which creates more CO₂, blocking energy from the sun
      - Global warming can lead to climate change, causing more droughts/floods/storms etc.
  - - - John Dalton’s atomic theory
        
        All matter is made of tiny particles called atoms
        
        The atoms in an elements are all identical
        
        In compounds, each atom of an element is always joined to a fixed number of atoms of other elements
        
        Atoms are indestructible and can be neither created nor destroyed
        
        During chemical reactions, atoms rearrange themselves to form new substances
      - Properties of elements
        
        Colour
        
        Melting point
        
        Boiling point
        
        Density
        
        Strength
        
        Flexibility
        
        Heat conduction
        
        Electricity conduction
      - Physical changes, like physical properties, only involve 1 substance. These changes are often easy to reverse
      - The idea that all matter is made up of particles is over 2400 years
    - - In physical changes, no new substances are formed, unlike in chemical reactions , which are much more difficult to reverse
      - The chemical properties of a substance describe how it reacts with other substances