Organisation

• Organelles

  subcellular structures that form a cell

  eg - nucleus
• Cells

  different cells = specialised

  multiple organelles = single cell

  different shapes and sizes, with different numbers of organelles

  eg muscle cells
• tissue

  a group of similar cells that work together to carry out a particular job

  eg muscle tissue
• organs

  a group of different tissue that work together to perform a particular job

  eg stomach
• organ system

  a group of different organ that work together to perform a particular function

  eg digestive system
• organisms

  multiple organ systems working together to form an organisms

  eg humans
• organelle -> cell -> tissue-> organs -> organ system -> organism
• enzymes

  most chemical reactions are too slow - too speed up we increase temperature - negative side effects;

  • requires a lot of energy
  • can damage cells
  • can speed up unuseful reactions

  instead we use a catalyst - a substance that increases the speed of a reaction without being used up or changed in the process
• enzymes

  a particular type of catalysts made by living organisms

  'biological catalysts'

  • large proteins (long chains of amino acids)
  • different shapes (unique) - catalysts are particular to a reaction
  • break down food chemically
• how do enzymes work?

  active site - unique shape - complementary to the substrate of the reaction

  if a substrate doesn't fit the active site, the reaction won't be catalysed - this allows enzymes to be really specific about which reaction the speed up

  A) substrate

  B) active site

  C) enzyme

  
• enzymes - lock and key model (original)

  scientists thought that the substrate had to fit perfectly into the active site
• enzymes - induced to fit model (realistic)

  the enzymes actively changes shape slightly as it binds to the substrate

  A) complementary

  B) substrate

  C) enzyme

  
• enzymes can -

  build large molecules from binding molecules together;

  A) two substrates

  B) active site

  C) enzyme

  D) enzyme-substrate complex

  E) enzyme - use again

  F) product

  
• enzymes can -

  be used to break down large molecules into smaller molecules;

  A) substrate

  B) active site

  C) enzyme-substrate cimplex

  D) enzyme - use again

  E) 2 products

  
• factors that effect enzymes - temperature

  too high temperatures (45'C permanent damage) can break the bonds holding enzymes together - active site changes shape

  if it changes too much, the enzyme won't be able to bind to the substrate ( not complementary) - they have denatured

  optimum temperature - where reactions is at its highest rate (37'C) - all enzymes have optimum temperature, different enzymes have different temps
• factors that effect enzymes - pH

  pH - measure of acidity - too high or too low = low rate of reaction - changes the active sites shape (changes too much, the enzyme won't be able to bind to substrates )

  optimum pH - here enzyme works best - depends where the enzyme works -

  • most enzymes = 7pH (neutral)
  • stomach = 2pH
• Food groups

  biological molecules = nutrients

  foods have a mix of different nutrients in them

  food is measure in calories - cal or kcal
• carbohydrates

  starchy foods - bread, pasta

  energy source - chemical reactions, movement
• lipids

  fats (solid at rooms temperature) and oils (liquid at room temperature)

  provide long term energy

  keep us warm - insulated

  protect our organs

  olive oil, avocado's, fruit and nuts, fish, dairy products
• Proteins

  nuts and seeds, meat and fish, lintels and beans

  growth and repair

  can be used for energy - don't have enough carbohydrates or lipids
• Vitamins

  organic

  A - leaf - eyes and skin and hair

  C - citrus fruit - prevent scurvy

  D - sun and eggs and fish - absorbs calcium
• minerals

  inorganic

  calcium - mild - strong bones

  iron - red meat, spinach, beans - important for haemoglobin (red blood cells)
• fibre

  types of carbohydrates - body doesn't absorb

  helps move food through the intestines

  wholemeal foods
• water

  chemical reactions

  most of our body is water - around 70%

  continuously loosing water - need to replace it
• how much you eat depends on

  activity levels

  age

  pregnancy
• biological molecules

  nutrients (needed for growth, repair and metabolism)

  found in living organisms produced by cells

  • carbohydrates
  • protiens
  • lipids
• biological molecules - carbohydrates

  carbon

  hydrogen

  oxygen

  come in different sizes

  smallest = simple sugars (glucose) - monomers

  complex carbohydrates (polymers - starch) - have chemical bonds that can be broken down by enzymes in the mouth and small intestines
• monomer and polymers

  monomers can join together to make polymers
• biological monomers - proteins

  carbon

  hydrogen

  oxygen

  nitrogen

  long chains of amino acids bonded together

  amino acid = monomer

  proteins = polymer

  enzymes in the stomach and small intestine break down proteins into amino acids
• biological molecules - lipids

  carbon

  hydrogen

  oxygen

  fats and oils

  single glycerol molecules attached to 3 fatty acids (the fatty acids vary in length - this determines whether the lipid is a fat or oil at room temperature)

  enzymes break down lipids in the small intestine
• digestive enzymes

  enzymes are essential in breaking large molecules into small soluble molecules that can be absorbed through intestine lining

  • carbohydrase
  • protease
  • lipase
• carbohydrates are broken down by carbohydrase's

  starch - broken down by amylase into a maltose molecule - maltase breaks maltose into glucose

  carbohydrase's are made in the;

  • small intestine
  • pancreas
  • salivary glands
• proteins are broken down by protease

  they break down proteins into amino acids

  examples - pepsin and trypsin

  protease's are made in;

  • stomach (pepsin)
  • small intestine
  • pancreas
• lipids are broken down by lipase

  lipids are broken down into glycerol and fatty acids

  lipase is made in;

  • pancreas
  • small intestine
• bile

  neutralises acids

  emulsifying fats - increases the surface area for lipase enzymes to break them down

  gall bladder (stores)

  made in liver

  helps with lipid digestion
• digestive system

  break down food so we can absorb through intestine lining

  physical and chemical breakdown

  mouth - oesophagus (gullet) - stomach - small intestine - large intestine - rectum
• mouth

  physical breakdown (chewing)

  realises saliva from the salivary glands - salivary amylase
• swallow through the oesophagus (gullet)
• stomach

  contacts muscular walls to mix foods

  produces pepsin (protease enzyme - breaks down proteins)

  produces hydrochloric acid - kills bacteria and creates the right environment for pepsin to be produced
• small intestine

  digested food is absorbed into the bloodstream across lining (exchange surface is adapted - Villi)

  most digestion takes place

  produces enzymes to aid digestion