B2 - organisation

• Enzymes


  Essential for helping us break down the large molecules that we eat into the much smaller soluble molecules that we can absorb through our intestinal lining
• Main groups of nutrients to be broken down

  • Carbohydrates
  • Proteins
  • Fats
• Carbohydrates


  Found mainly in foods like pasta, potatoes and rice, used by the body mainly as an energy source
• Starch


  The main type of carbohydrate, broken down by the enzyme amylase into smaller sugars such as maltose
• Amylase


  1. Made in the salivary glands of the mouth

  2. Made in the pancreas

  3. Made in the small intestine

  4. Acts to break down starch
• Proteins


  Found in things like nuts, meats and beans, broken down by protease enzymes into amino acids
• Proteases


  1. Made in the stomach (called pepsin)

  2. Made in the pancreas

  3. Made in the small intestine

  4. Break down proteins into amino acids
• Fats/Lipids


  Found in foods like cheese, oils and chocolate, broken down by lipase enzymes into glycerol and fatty acids
• Lipases


  1. Made in the pancreas

  2. Made in the small intestine

  3. Break down fats/lipids into glycerol and fatty acids
• All digestive enzymes are made by the pancreas and the small intestine, with amylase also being made by the salivary glands and proteases also being made in the stomach
• how does bile help with the digestion of lipids

  It emulsifies the lipids
• Digestive system


  What it does, how it works, and the different organs involved
• Humans have to eat loads of food which is mostly used for energy so that we can move about and keep our metabolism running
• Main groups of nutrients needed

  • Carbohydrates (like starch and glucose)
  • Proteins
  • Fats
• Role of digestion


  To break all this food down into tiny pieces so that we can absorb it into our body cells
• Digestion process


  1. Physical breakdown (chewing)

  2. Chemical breakdown by enzymes
• Mouth


  1. Food placed in mouth

  2. Broken down physically by chewing

  3. Saliva released from salivary glands

  4. Saliva contains salivary amylase to break down carbohydrates
• Esophagus


  Food swallowed and passes down
• Stomach


  1. Muscular sac that contracts to push and mix food

  2. Produces pepsin enzyme to break down proteins

  3. Produces hydrochloric acid to kill bacteria and provide right environment for pepsin
• Small intestine


  1. Digested food absorbed into bloodstream

  2. Site of most digestion

  3. Produces digestive enzymes

  4. Pancreas produces and releases digestive enzymes into small intestine

  5. Gallbladder releases bile to neutralize stomach acid and emulsify fats
• Small intestine lining


  • Villi (finger-like projections) to increase surface area
  • Single layer of surface cells for short diffusion distance
  • Good blood supply to maintain concentration gradient
• Large intestine


  1. Absorbs excess water from leftover material

  2. Stores feces in rectum until removal
• Recap of digestive process order

  • Food placed in mouth
  • Chewed and mixed with saliva
  • Swallowed down esophagus
  • Enters stomach
  • Pushed into small intestine
  • Digested and absorbed into bloodstream
  • Leftover material enters large intestine
  • Water absorbed, feces stored in rectum
• How are alveoli adapted for efficient gas exchange?

  Their walls are only one cell thick or There are many of them giving a large total surface area
• what does the artery do 


  carries the blood away from the heart
• what does the vein do

  carries the blood back into the heart
• what is the purpose of the alveoli having a large surface area


  to allow gas exchange to occur at a faster rate
• what does the oxygen do in the blood stream

  diffuses into the blood stream and binds to the haemoglobin in red blood cells to be transported
• Translocation


  Plants transport sugars made through photosynthesis in leaves to rest of plant
• Phloem cells


  Arranged end to end to form long columns called phloem tubes to transport cell sap (water and sugar)
• what features does the phloem have and its role

  • Have small pores/gaps between adjacent cells to enable movement of cell sap
  • Can transport substances in either direction (up or down the plant)
• Transpiration


  Movement of water from roots to leaves driven by evaporation of water from leaves
• Xylem tubes


  Made up of column of dead xylem cells with no ends, forming one long hollow tube strengthened with lignin to transport water and mineral ions from roots to leaves
• Transpiration stream


  Chain of water molecules pulled up the plant as water evaporates from leaves
• Bright light intensity


  More photosynthesis, more stomata open, higher rate of transpiration
• Nighttime (no photosynthesis)


  Stomata closed, very little transpiration
• Warmer temperature


  Water particles have more energy, higher rate of transpiration
• High airflow


  Water molecules quickly blown away, higher concentration gradient, higher rate of transpiration
• High humidity


  Lower concentration gradient, lower rate of transpiration
• Main components of blood

  • Red blood cells
  • White blood cells
  • Platelets
  • Plasma