2-Organisation

• cell organisation in order, from least to most complex:

  1. organelles
  2. cells
  3. tissues
  4. organs
  5. organ systems
  6. organisms
• function of cell organisation:

  1. organelles- subcellular structures that form a cell
  2. cells- come in different type of specialised cells
  3. tissues- group of similar cells that work together to carry out a particular function
  4. organs- group of different tissues that work together to carry out a particular function
  5. organ systems- group of different organs that work together to carry out a particular function
  6. organism- formed by multiple organ systems
• enzymes are needed because chemical reactions are slow and increasing temp to speed up reaction has some issues:

  • requires a lot of energy
  • can damage cells
  • speed up non-useful reactions
• a catalyst is a substance that increases the speed of a reaction without being changed or used up
• enzymes are known as biological catalysts and are large proteins so are made up of long chains of amino acids
• enzymes have active sites which are complementary to certain substrates to be able to catalyse a reaction
• the two models of enzyme action:

  • lock and key model- that the substrate has to fit perfectly into the active site
  • induced fit model- the active site changes shape slightly to be complementary to the substrate
• how temperature and pH affect the functioning of enzymes:

  • high temperature/high or low pH- break apart enzyme bonds, active site changes shape and slows down reaction, enzyme unable to bind to substrate so it has been denatured
• the optimum temperature or pH is when the rate of reaction is fastest
• the three digestive enzymes are:

  • amylase
  • protease
  • lipase
• what the digestive enzymes break down:

  • amylase- breaks down carbohydrates(starch) into maltose(smaller sugars) and further by maltase into glucose
  • protease(pepsin, trypsin)- breaks down protein into amino acids
  • lipase- breaks down fats(lipids) into glycerol and fatty acids
• where the digestive enzymes are made:

  • amylase- salivary glands, pancreas, small intestine
  • protease- stomach, pancreas, small intestine
  • lipase- pancreas, small intestine
• bile helps with the digestion of lipids as it emulsifies(breaks down) them which increases the surface area for lipase enzymes to break them down
• digestive system pathway:

  1. mouth
  2. gullet/ oesophagus
  3. stomach
  4. small intestine
  5. large intestine
  6. rectum
• digestive system function:

  1. mouth- chewing, release of saliva from salivary glands that contains enzyme amylase
  2. stomach- contracts muscular walls, produces pepsin, produces hydrochloric acid(kills bacteria, provides right pH for pepsin)
  3. small intestine- digest, absorb digested food into blood stream
  4. large intestine- absorbs excess water
• small intestine:

  • pancreas- secretes digestive enzymes (pancreatic juices) to the small intestine
  • gallbladder- secretes bile into small intestine which neutralises acids from the stomach, emulsifies fats
  • bile is made in the liver but stored in the gallbladder
• the lining of the small intestine is an exchange surface adapted to it's function:

  • villi- increase surface area so food absorption is quicker, they have a single layer of cells which decreases the distance of absorption, they have a good blood supply which maintains the concentration gradient
• the digestive system has two functions:

  • digestion- breaking down food molecules
  • absorption- absorbing food molecules
• food tests required practicals:

  • Benedict's test- sugars
  • Iodine test- starch
  • Biuret test- proteins
  • Ethanol test- lipids(fats and oils)
• Benedict's food test:

  • tests for reducing sugars
  • no sugars present- solution stays blue
  • sugars present- solution turns brick red
• Iodine food test:

  • tests for starch
  • no starch present- solution stays orange-brown
  • starch present- solution turns blue-black
• Biuret food test:

  • tests for protein
  • no protein present- solution stays clear or blue
  • protein present- solution turns pink
• Ethanol food test:

  • tests for fats
  • no fats present- solution stays clear
  • fats present- milky white presence appears in solution
• lung and gas exchange pathway for oxygen and carbon dioxide:

  1. mouth/nose
  2. trachea (windpipe)
  3. bronchi
  4. bronchioles
  5. alveoli
• alveoli are adapted to be the site for gas exchange so rate of diffusion is increased:

  • walls are 1 cell thick like the capillaries next to them
  • large surface area (lots of alveoli)
  • moist walls which allows gases to dissolve
• breathing rate is number of breaths divided by time (minutes)
• the journey of the blood around the body:

  • body
  • vena cava
  • right atrium
  • right ventricle
  • pulmonary artery
  • lungs
  • pulmonary vein
  • left atrium
  • left ventricle
  • aorta
  • body
• valves prevent the blood from flowing backwards
• the left ventricle has thicker walls because it has to pump the blood all the way around the body
• • arteries carry blood away from the heart- pulmonary artery, aorta
  • veins carry blood to the heart- vena cava, pulmonary vein
  • capillaries exchange nutrients, oxygen and waste products with body tissues
• pacemaker cells are found in the right atrium
• the coronary arteries supply the heart muscle with oxygen and nutrients
• arteries:

  • carry blood at high pressure
  • thick walls made up of muscle and elastic tissue
  • have a narrow lumen
• veins:

  • carry blood at low pressure
  • have thin walls and a large lumen
  • contain valves
• capillaries:

  • carry blood at low pressure
  • walls are permeable
  • walls are one cell thick
• rate of blood flow is volume (ml) divided by time (mins)
• the blood consists of:

  • red blood cells
  • white blood cells
  • platelets
  • plasma
• function and structure of red blood cells:

  • carry oxygen from the lungs to the body's tissues
  • biconcave disk shape to increase surface area to absorb oxygen
  • no nucleus to carry more haemoglobin (red pigment) and oxygen
  • haemoglobin binds to oxygen
  • they make up half of our blood
• function and structure of white blood cells:

  • has nucleus
  • engulf pathogens through phagocytosis
  • produce antibodies to bind and help destroy pathogens
  • produce antitoxins to neutralise toxins produced by pathogens
  • make up less than one percent of the blood
• function and structure of platelets:

  • no nucleus
  • made up of fragments of cells
  • clots cuts to prevent pathogens from entering blood (cause infection) and to stop blood loss