Unit 2 - Organisation

• Adaptations of muscle cells

  • Can contract because they contain special protein fibers which can change their length
  • Packed full of mitochondria which provide the energy needed for contraction
• Digestion is required because all of the nutrients in food are too large to be absorbed into the bloodstream.
• During digestion, large food molecules are broken down into small molecules by enzymes, allowing them to be absorbed into the bloodstream.
• Digestion Process


  1. Food is chewed in the mouth

  2. Enzymes in the saliva begin to digest starch into smaller sugar molecules

  3. Esophagus to the stomach

  4. Enzymes begin the digestion of proteins

  5. Stomach contains hydrochloric acid to help enzymes digest proteins

  6. Churning stomach muscles turns the food into a fluid, increasing surface area for enzymes to digest

  7. Pancreas releases enzymes to continue digestion of starch and protein, and begin digestion of lipids

  8. Liver releases bile which speeds up the digestion of lipids, and also neutralises acid released from the stomach

  9. Food molecules produced by digestion are absorbed into the bloodstream in the small intestine

  10. Large intestine absorbs water into the bloodstream
• Uses of products of digestion

  • Build new carbohydrates, lipids and proteins
  • Some glucose produced is used in respiration
• Proteases are found in the stomach, pancreatic fluid and the small intestine
• Amylases are found in the saliva and pancreatic fluid
• Lipases are found in the pancreatic fluid and small intestine
• Bile is made in the liver and stored in the gall bladder
• Steps for preparing for a food test:

  1. Take the food sample and grind with distilled water using a mortar and pestle
  2. Transfer paste to a beaker and add more distilled water. Stir so chemicals in food dissolve in water
  3. Filter the solution to remove suspended food particles
• Adaptation of small intestine for absorption:

  • 5m in length, provides a very large surface area for absorption of the products of digestion
  • Interior covered with millions of villi - increase surface area
  • Microvilli on villi increase surface area even further
  • Villi have good blood supply to maintain a steep concentration gradient
  • Thin membrane on villi for short diffusion path
• A fish has a single circulatory system as such:

  This is a problem because the blood loses a lot of pressure as it passes through gills before reaching organs. This means blood travels to organs relatively slowly, delivering less oxygen.

  
• Label the picture of the human blood:

  A) Plasma (liquid part)

  B) Red blood cells

  C) White blood cells

  D) Platelets

  
• Blood plasma transports:

  1. soluble digestion products (e.g. glucose) from small intestine to other organs
  2. carbon dioxide (from aerobic respiration) from organs to lungs to be breathed out
  3. waste-product urea from the liver to the kidneys to be excreted in urine
• Adaptations of a red blood cell

  • Contain oxygen-carrying molecule hemoglobin
  • No nucleus - more room for hemoglobin
  • Biconcave disc - greater surface area so oxygen diffuses in and out rapidly
• Adaptation of a white blood cell:

  • Nucleus which contains DNA which encodes instructions needed by white blood cells to do their job
• Uses of donated blood:

  • To replace blood lost during injury
  • Some people are given platelets extracted from blood to help in clotting
  • Proteins extracted from blood can also be useful (e.g. antibodies)
• Problems with donated blood:

  • Chance of immune system rejecting blood and death - make sure blood type is the same
  • Risk of infection and diseases via blood - blood is screened for infections
• Coronary heart disease:

  1. Layers of fatty material build up inside the coronary arteries, causing them to narrow
  2. Reduced flow of blood through arteries means a lack of oxygen for the heart muscle
  3. In extreme cases this results in a heart attack, where the heart is starved of oxygen
• Statins are drugs which reduce the level of cholesterol in the blood, slowing down the rate of fatty materials building up in the arteries
• Pros of statins:

  • Have been proven to reduce risk of coronary heart disease - effective
  • Reduce levels of bad cholesterol, and can increase levels of good cholesterol in the blood
• Cons of statins:

  • Unwanted side effects, e.g. liver problems
  • Must be taken regularly and long-term; less effective if someone forgets to take them
  • Can take a while to start having an effect
• A stent is a tube inserted into the coronary artery to keep it open
• Pro of stent:

  • Allows blood to flow normally through artery
  • Effective at reducing risk of heart attack
  • Relatively simple
  • Lasts a while
• Con of stent:

  • Will not prevent other regions from narrowing - doesn't treat underlying causes of disease
  • Risk of blood clots occurring
• Mechanical valves can last a lifetime, but they increase the risk of bloodclots. Patients therefore have to take anticlotting drugs.
• Valves from animals do not last as long and need to be replaced, but patients don't need to take drugs
• Heart failure: when patients' hearts cannot pump enough blood around the body
• Cons of heart transplant:

  • Not enough to treat every patient
  • Must take drugs to stop heart from being rejected by immune system
  • Chance of infection
• Cons of artificial hearts:

  • Increase risk of blood clotting
  • Not a long-term solution
• Label the lungs:

  A) Trachea

  B) Bronchi

  C) Bronchiole

  D) Alveoli

  
• Tumour: uncontrolled growth and mitosis of cells
• Benign tumour:

  Growths of abnormal cells found in one area usually contained within a membrane

  Do not invade other parts of the body
• Malignant tumour (cancer):

  • Invade neighbouring tissues
  • Move in the bloodstream to spread to other parts of the body to form secondary tumours
• Genetic cancers:

  • Breast cancer
  • Prostate cancer
  • Large intestine
• Cancers linked to lifestyle:

  • Smoking - lung cancer
  • UV light - skin cancer
  • Alcohol - mouth and throat cancer
• Health: state of physical and mental well-being
• A correlation does not prove cause, it simply suggests it may be linked.
• Causal mechanism: A mechanism that explains the relationship between two variables.
• Carcinogen: A substance that can cause cancer.