biology paper 1

• 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 pushes digestive enzymes into small intestine

  5. Gallbladder releases bile to neutralize stomach acid and emulsify fats
• Lining of small intestine

  • 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 moves to large intestine
  • Water absorbed, feces stored in rectum
• 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
• Blood plasma


  The liquid part of the blood
• Functions of blood plasma

  1. Transports dissolved substances around the body

  2. Transports soluble digestion products from small intestine to other organs

  3. Transports carbon dioxide from body cells to lungs to be breathed out

  4. Transports waste product urea from liver to kidneys to be excreted
• Red blood cells


  • Contain the oxygen-carrying molecule hemoglobin
  • Have no nucleus, allowing more space for hemoglobin
  • Have a biconcave disk shape, giving greater surface area for oxygen diffusion
• Function of red blood cells

  Transport oxygen from lungs to body cells
• White blood cells


  • Contain a nucleus with DNA encoding instructions for immune system functions
• Function of white blood cells

  Part of the immune system, e.g. making antibodies
• Platelets


  Tiny fragments of cells that help the blood to clot
• Fish have a single circulatory system where deoxygenated blood is pumped from the heart to the gills, becomes oxygenated, and then passes straight to the organs
• The problem with a single circulatory system is that the blood loses a lot of pressure as it passes through the gills before reaching the organs, so the blood travels to the organs relatively slowly and cannot deliver a great deal of oxygen
• Humans have a double circulatory system where deoxygenated blood is pumped from the heart to the lungs, becomes oxygenated, and then returns to the heart to be pumped to the organs
• The benefit of the double circulatory system is that the blood passes through the heart twice, allowing it to travel rapidly to the body cells and deliver the oxygen they need
• Heart


  • Organ consisting mainly of muscle tissue
  • Job is to pump blood around the body
• Chambers of the heart

  • Left atrium
  • Right atrium
  • Left ventricle
  • Right ventricle
• The atria are separated from the ventricles by valves
• Blood vessels entering and leaving the heart

  • Vena cava (brings in oxygenated blood from the body)
  • Pulmonary artery (blood passes from heart to lungs)
  • Pulmonary vein (oxygenated blood passes from lungs to heart)
  • Aorta (blood pumped from heart to body)
• Pattern of blood flow through the heart

  1. Blood enters left and right atria

  2. Atria contract, forcing blood into ventricles

  3. Ventricles contract, forcing blood out of heart

  4. Valves prevent backflow into atria
• Left ventricle


  • Has thicker muscular wall than right ventricle
  • Pumps blood around entire body, so needs greater force
• Right ventricle


  • Only pumps blood to the lungs
• Coronary arteries


  • Branch out of the aorta and spread into the heart muscle
  • Purpose is to supply oxygen to the muscle cells of the heart
• Pacemaker


  Group of cells in the right atrium that control the natural resting heart rate