Organisation

• Principles of Organisation

  1. A group of similar cells makes up a tissue

  2. A group of tissues makes up an organ

  3. A group of organs makes up a system

  4. A group of systems make up an organism
• Enzymes

  Biological catalysts that help the reactions that occur in our bodies by controlling the rate of reaction
• Enzymes

  • They are large protein molecules made up of long chains of amino acids that are "folded" to create a certain shape
  • The enzyme's shape helps another molecule "fit" into it ("lock and key")
  • The shape can be destroyed ("denatured") by high temperatures or the wrong pH
• Active site

  The part of the enzyme that the substrate binds to
• The point of the digestive system

  To break down our food into small molecules which the body can then use to make carbohydrates, lipids and proteins
• Enzymes in digestion

  1. Enzymes can be produced by the body to help digestion

  2. When they come into contact and react with food they break it down into smaller pieces which can then pass into the bloodstream
• Amylase (produced in the mouth, pancreas and small intestine) breaks starch down into glucose
• Protease (produced in the stomach, pancreas and small intestine) breaks proteins down into amino acids
• Lipase (produced in the pancreas and small intestine) breaks fats down into fatty acids and glycerol
• Enzyme table

  • Organ Enzyme Substrate/food Product pH
  • Mouth/pancreas Amylase Starch Maltose 7.5
  • stomach pepsin proteins Polypeptides 2
  • s. intestine Carbohydrase Carbohydrates glucose 8/9
  • s. intestine lipase Lipids/fats Fatty acids and glycerol 8/9
  • s. intestine Proteases Proteins Amino acids 8/9
  • pancreas Proteases Proteins Amino acids 8/9
  • pancreas lipase Lipids/fats Fatty acids and glycerol 8/9
  • pancreas Amylase Starch Maltose 8
  • Liver, *bile, Emulsifies fats, Neutralises stomach acid
• Food tests

  • Fat /lipid, Sudan III test, Transparent, colourless, goes to Milky/ cloudy, Translucent mark, Forms red ring, +
  • Starch, Iodine, brown, goes to Blue-black(positive),
  • Protein, Biuret test, blue, purple(positive),
  • Glucose, Benedict's solution, Blue, Green/orange/red(positive), +
• Bile

  A chemical produced in the liver and stored in the gall bladder that has two functions: it neutralises stomach acid and produces alkaline conditions for enzymes to work in, and it emulsifies ("breaks down") fats
• Diffusion in the lungs

  The Lungs have the following adaptions for gas exchange:

  1. large surface area from many alveoli
  2. thin alveoli walls
  3. good ventilation with air
  4. good blood supply
• Circulatory system

  The system responsible for pumping blood around the body, which contains glucose and oxygen that are needed for cells to produce energy through respiration
• "Double Circulation"

  1. Blood gets pumped from the right ventricle in the heart to the lungs and picks up oxygen

  2. The blood is then taken back to the heart

  3. The left ventricle of the heart then pumps the blood to the intestine (where oxygen and glucose are removed) and to the rest of the body

  4. After the oxygen and glucose have been removed for respiration the blood is sent back to the heart and starts again
• The Heart (in more detail)

  1. Deoxygenated blood enters through the vena cava into the right atrium

  2. It's then pumped through the tricuspid valve into the right ventricle

  3. It's then pumped through a valve up to the lungs through the pulmonary artery

  4. Oxygenated blood from the lungs enters through the pulmonary vein into the left atrium

  5. It's then pumped through a valve into the left ventricle

  6. It's then pumped out of the aorta to the rest of the body
• Heart beat

  Normally controlled by a group of pacemaker cells on the right hand side of the heart that produce small electrical impulses that cause the heart to contract
• Arteries

  Carry high pressure blood away from the heart, have smaller lumen and no valves. also have elastic fibres to stretch against pressure
• Veins

  Carry low pressure blood back to the heart, have thinner, less elastic walls and have valves to prevent backflow of blood
• Capillaries

  Have thin walls (one cell thick) to allow glucose and oxygen to pass through, used to connect arteries to veins. cells have pores which allow plasma to leak out and form tissue fluid
• The four parts of blood

  • RED BLOOD CELLS - contain haemoglobin and carry oxygen around the body, have no nucleus and a large surface area
  • PLATELETS - small bits of cells that lie around waiting for a cut to happen so that they can clot (for a scab)
  • WHITE BLOOD CELLS - these help the body fight infections
  • PLASMA - a straw-coloured liquid that transports CO2 and glucose as well as taking away waste products to the kidneys
• Drugs called "statins" can be used to reduce cholesterol levels and slow down the build up of fatty material. they are good because they involve no operations, and often increase levels of HDL, but bad because they must be taken daily and may cause an allergic reaction
• Arteries can narrow due to cholesterol and other factors, and a "stent" may be needed. stents are expanding metal tubes inserted over a blockage. they are good because anyone can have them, they do not need to be checked daily, and bad because they themselves may cause blood clots and they also involve an operation with a risk of infection
• Health

  The state of physical, social and mental well being and the absence of disease
• Diseases can interact with each other when they affect the body

  • Viruses in living cells can be a trigger for cancer
  • Defects in the immune system mean that a person can catch an infectious disease more easily
  • Immune reactions (after being caused by a pathogen) can cause allergies such as skin rashes
  • Severe physical ill health can lead to depression and other mental illnesses
• Benign tumours

  Non-cancerous growths. These do not invade other parts of the body and are usually contained by a membrane
• Malignant tumours

  Cancerous (over division) growths that consist of abnormal cells, that grow uncontrollably, invade neighbouring cells, develop their own blood supply which connects to the circulatory system and spread to other parts of the body where they form secondary tumours (Metastasis)
• Causes of cancer

  • Genetic factors
  • Smoking
  • Obesity
  • UV exposure
• Examples of Plant Tissue

  • Epidermal tissue, which covers the plant
  • Palisade mesophyll, where photosynthesis occurs
  • Xylem and phloem, which are used to transport substances around the plant
  • Spongy mesophyll, where gases move through air spaces
  • Meristem tissue found at the growing tips of shoots and roots
• Transpiration

  1. Water evaporates through the stomata

  2. Water passes back into the leaf through xylem vessels by osmosis

  3. Water is then pulled upwards through the xylem tissue

  4. This is replaced by water entering from the root tissue

  5. Water enters root hair cells by osmosis to eventually replace the water lost through respiration
• Transpiration rate

  Factors that affect how quickly transpiration happens: temperature (high=more), humidity(high=less), air flow (high=more), light intensity(high=more)

  When water levels are low guard cells lose water from osmosis ad become flaccid, closing stomata and reducing rate of transpiration, they are located on the underside of leaves as it is cooler and shadier so there is less transpiration
• Xylem

  Used by the plant to transport water and soluble mineral salts from the roots to the stem and the leaves (one direction only), made of hollow tubes (no intercellular walls) strengthened by lignin, cells are dead
• Phloem

  Tubes used by the plant to transport dissolved sugars to the whole plant for respiration and storage (all directions), contains porous intercellular walls known as sieve plates, still very few subcellular structures like xylem, has a cytoplasm
• The Role of Bacteria in Digestion

  • Breaking down substances we can’t digest (like cellulose)
  • Supplying essential nutrients
  • Synthesising vitamin K
  • Providing competition with any harmful bacteria to restrict their growth
• Metabolism

  The sum of all reactions happening in an organism
• For all food tests

  • break up food with a pestle and mortar
  • transfer to a test tube and add distilled water
  • mix with a glass rod
  • filter the mixture using filter paper and a funnel
  • add a few drops of distilled water and respective indicator
  • observe for colour changes
• Difference in the Benedict's food test

  Is heated in a water bath at 80 degrees for five minutes
• Benefits of a double circulatory system

  • Blood travelling through the small capillaries in the lungs loses a lot of pressure which reduces the speed at which it can flow
  • By returning oxygenated blood to the heart from the lungs, the pressure can be raised before sending it to the body, meaning cells can be supplied with oxygenated blood more quickly
• Adaptations of the heart

  1. walls of ventricles are thicker than those in the atria
  2. wall of the left ventricle is thicker than the wall of the right ventricle
  3. two sets of valves prevent backflow of blood
  4. two sides of the heart are separated by the septum
  5. made of special cardiac muscle that fatigues less
  6. coronary arteries supply the heart with a lot of blood
• Adaptations of the Leaf

  1. large surface area for light and diffusion
  2. thin walls for diffusion
  3. chlorophyll absorb light energy
  4. Stomata and guard cells open and close to change how much water and gas leaves/enters the leaf
  5. network of veins transports substances
  6. thin waxy cuticle protects leaf while allowing light
  7. palisade cells at the top of the leaf and with large surface area
  8. spongy layer allows for air spaces and diffusion
  9. vascular bundles support the stem and leaf