Biology topic 2

• Cells make up all living things
• A tissue is a group of specialised cells with a similar structure and function
• Organs are formed from different tissues working together to produce a specific function, for example, the stomach
• Organs are organised into organ systems, such as the digestive system
• Enzymes are biological catalysts that can break up large molecules and join small ones, they have a specific active site where the substrate binds
• Enzymes require an optimum pH and temperature to function properly
• Carbohydrases convert carbohydrates into simple sugars, proteases convert proteins into amino acids, and lipases convert lipids into fatty acids and glycerol
• Bile is alkaline to neutralise stomach acid and emulsifies fats in the small intestine
• Blood vessels include arteries, veins, and capillaries, each with specific functions in blood circulation
• Blood is made up of plasma, red blood cells, white blood cells, and platelets, each with specific functions in the body
• The lungs are part of the gas exchange system, with structures like trachea, bronchi, bronchioles, and alveoli for oxygen exchange
• The heart is an organ in the circulatory system with a double circulatory system, pumping deoxygenated and oxygenated blood to different parts of the body
• Coronary heart disease is a non-communicable disease caused by blockages in coronary arteries, leading to reduced blood flow to the heart
• Solutions for heart issues:

  • Stents (metal mesh tubes inserted in arteries) keep arteries open to allow blood flow
  • Stents are effective in lowering the risk of a heart attack
  • Stents have a quick recovery time from surgery
  • Risks of stents include heart attack during the procedure, infection following it, and blood clots forming near the stent (thrombosis)
  • Statins are drugs that decrease LDL (bad) cholesterol levels
  • Statins reduce the risk of strokes, coronary heart disease, and heart attacks
  • Statins increase HDL (good) cholesterol levels
• • Cons of statins include the need for continuous intake, potential side effects, and delayed effects as it only slows down cholesterol deposition
• Faulty heart valves:

  • Replacing with a biological valve (from pigs or cattle) works well but only lasts 12-15 years
  • Replacing with a mechanical valve lasts long but requires constant medication to prevent blood clotting
• Heart failure can be solved with a heart transplant:

  • Heart transplant requires a donor who has recently died
  • Artificial heart may be used while waiting for a donor
  • Artificial hearts are less likely to be rejected by the immune system
  • Surgery for heart transplant temporarily exposes the body to infection
• Extreme blood loss can be solved by giving artificial blood:

  • Artificial blood is a salt solution that can keep people alive even if they lose ⅔ of their red blood cells
  • Artificial blood gives time for the body to produce new blood cells
  • Artificial blood can only be used for short periods, then a blood transfusion is needed
• Cancer:

  • Cancer results from changes in cells leading to uncontrollable growth and division, forming a tumour
  • Tumours can be benign (non-cancerous) or malignant (cancerous)
  • Lifestyle risk factors for cancer include smoking, obesity, UV light exposure, and viral infections
  • Genetic risk factors for cancer include inheriting certain genes that increase cancer risk
• Plant tissues:

  • Epidermal tissue covers the whole plant and has a waxy cuticle to reduce water loss
  • Palisade mesophyll tissue has many chloroplasts for rapid photosynthesis
  • Spongy mesophyll tissue has air spaces for gas exchange
  • Xylem transports water and mineral ions
  • Phloem transports food substances
  • Meristematic tissue is found at the tips of shoots and roots and can differentiate into different types of plant cells
• Plant organ system:

  • Roots, stem, and leaves form a plant organ system for substance transport
  • Translocation moves food substances in the phloem
  • Transpiration is the loss of water vapor from leaves and stems
  • Guard cells surround stomata and control their opening and closing
• Factors affecting transpiration rate:

  • Increase in temperature leads to faster evaporation and transpiration
  • Increase in relative humidity reduces the rate of diffusion and transpiration
  • Increased air movement (wind) speeds up diffusion and transpiration
  • Increase in light intensity leads to more stomata opening for gaseous exchange and increased transpiration
• The cons of statins include

  The need for continuous intake