Bio Topic 2

• What are the levels of organistation?


  Cell - Tissue - Organ - Organ system
• What are components of the digestive system?

  • Teeth break down food mechanically: saliva contains amylase(an enzyme)
  • Stomach contains hydrochloric acid & enzymes that chemically break down food
  • Liver produces bile which is stored in the gall bladder before going to small intestine
• What are components of the digestive system (continued)?

  • Bile emulsifies lipids to form droplets, increasing their surface area
  • Pancreas secretes amylase which breaks down starch into glucose in the small intestine
  • Water is absorbed into bloodstream in the large intestine
  • Nutrients like glucose are absorbed into the bloodstream by villi in small intestine (starch is too large)
• What are enzymes?

  Special proteins that act as biological catalysts
• What are examples of some enzymes and what do they break down?

  Carbohydrase breaks down carbohydrates into simple sugars

  Proteases break down proteins into amino acids

  Lipases break down lipids into glycerol & fatty acids

  These enzymes are specific so they only break down substrates that fit their active site.
• What is the rate of reaction and how does it affect enzymes?

  Rate of reaction (activity) increases with temperature until the enzyme denatures. The same applies for too high or low pH
• What does it mean by optimum conditions for enzymes?


  When the enzyme is working at max rate/activity
• What happens in the respiratory system?

  Air moves down the trachea into the bronchi then the bronchioles and ends up in the alveoli, the air sacs where it diffuses into the blood vessels around it
• How are the alveoli adapted to gas exchange?

  It has large surface area to allow gas exchange at a fast rate.
• What happens in the alveoli?


  Oxygen diffuses into the bloodstream & binds to the haemoglobin in red blood cells to be transported.
• What happens to carbon dioxide and water during breathing?


  It also diffuses out.
• What is our heart made of?

  A double circulatory system: blood enters heart twice every time it's pumped round
• What happens in the circulatory system?

  • Deoxygenated blood enters the vena cava into the right atrium.
  • Valve between right atrium & right ventricle prevents backflow so deoxygenated blood does not go back to the body.
  • Heart muscles contract causing deoxygenated blood to go through the pulmonary artery (to lungs) to become oxygenated
  • It comes back to the heart via the pulmonary vein into the left atrium, then left ventricle then out to the body via the aorta
• Why is the left side of the heart more thicker?

  Thicker walls withstand the high pressure needed to pump blood to the whole body
• What are the group of cells near the right atrium called & what do they do?

  The group of cells near the right atrium are called the sinotrial which is our natural pacemaker that creates electrical pulses that causes heart to contract.
• What is the circulatory system composed of?

  Artery - carries blood away from heart, has thick walls & thin lumen to withstand high pressure

  Capillary - One cell thick walls allow fast diffusion to occur between blood & cells

  Vein - Carries blood back to heart, has thin walls to prevent backflow
• What is coronary heart disease?

  When the artery supplying the blood to the heart is blocked
• What is cardiovascular disease?


  When fat builds up in the arteries that restricts blood flow?
• How can CHD & CVD be treated?

  A stent can be inserted to open up the vessel

  Statins are drugs that reduce fatty deposits
• What does blood carry?

  Red blood cells, white blood cells & platelets. Everything except oxygen is dissolved in plasma.
• What is the difference between communicable & non-communicable diseases?

  Communicable is caused by pathogens whereas the cause behind non-communicable comes from the body
• What are some examples of non-communicable diseases?

  • Diabetes
  • Heart disease/CVD/CHD
  • Liver disease
  • Lung disease/cancer
  • Cancer
• What is cancer?


  An auto-immune condition resulting from genetic mutation causing cells to multiply uncontrollably (tumour)
• What is a carcinogen?

  Something that increases the risk of developing cancer
• What is benign & malignant tumour?

  Benign does not spread whereas malignant does spread through the body.
• What are risk factors and list some examples?

  Risk factors increase the chances of developing a disease.

  Examples can be smoking, alcohol, lack of exercise and obesity
• What is the structure of a plant?

  Leaf - where photosynthesis & gas exchange occurs. Water also evaporates out

  Flower - reproductive organs

  Meristem - stem cell production

  Xylem - continuous tubes that carry water & dissolved mineral ions upwards: Transpiration (unidirectional)

  Phloem - tubes of cells that carry sugar & other nutrients to where needed: Translocation (bidirectional)

  Roots - water enters through osmosis, mineral ions via active transport
• How can rate of transpiration be increased?

  Increased air movement or temperature

  Decreased humidity

  These result in water evaporating from leaves at a faster rate
• Why are nitrates needed by plants & what happens if there's a deficiency?

  Nitrates are needed for protein synthesis. Deficiency: stunted growth
• What happens if there's a magnesium deficiency in plants?


  Chlorosis: magnesium deficiency: yellow leaves, stunted growth as less chlorophyll
• What is the structure of xylem tissue?

  Long, hollow tubes made up of dead cells strengthened by lignin
• What is the structure of phloem tissue?

  Tubes of elongated cells, which cell sap can move from one phloem cell to the next through pores in the end walls
• What is the structure of a leaf?

  Waxy cuticle - waterproof to prevent water loss through the top of leaf

  Upper epidermis - transparent to let light through

  Palisade mesophyll - where most photosynthesis occurs

  Spongy mesophyll - gaps to facilitate gas exchange (large surface area)

  Vascular bundle - xylem & phloem

  Stomata - Holes in lower epidermis to allow gases in/out including water

  Guard cells - change size to control rate of gases entering & exiting through stomata
• Why do guard cells close the stomata at night?

  Prevent water loss as less water is needed for photosynthesis