Biology paper 1

• Microscopes


  Normal light microscope can see cells and nucleus, electron microscope can see subcellular structures in more detail
• Calculating cell size


  1. Measure image size

  2. Divide by magnification
• Eukaryotic cells


  Have a nucleus where DNA is found (e.g. plant and animal cells)
• Prokaryotic cells


  Don't have a nucleus, DNA is in a ring called a plasmid
• Subcellular structures


  • Cell membrane
  • Cell wall
  • Cytoplasm
  • Mitochondria
  • Ribosomes
  • Chloroplasts
  • Vacuole
• Bacterial binary fission


  1. Number doubles every 10 minutes

  2. Practical: Grow culture on agar plate using aseptic technique

  3. Calculate culture size from area or initial drop
• Diploid cells


  Have 23 pairs of chromosomes
• Haploid cells


  Have 23 single chromosomes
• Mitosis


  1. Genetic material duplicated

  2. Nucleus breaks down

  3. Chromosomes pulled to opposite sides

  4. New nuclei form
• Specialised cell types


  • Nerve
  • Muscle
  • Root hair
  • Xylem
  • Phloem
  • Stem cells
• Diffusion


  Movement of molecules/particles from high to low concentration, down concentration gradient, passive
• Osmosis


  Diffusion of water across a semi-permeable membrane
• Practical: Osmosis


  1. Cut potato cylinders

  2. Weigh and place in sugar solutions

  3. Reweigh after a day

  4. Calculate % change in mass

  5. Plot against concentration to find no change point where it crosses the x-axis
• Active transport


  Using energy to move substances against a concentration gradient
• Digestive system processes


  • Acid in stomach
  • Bile and enzymes in small intestine
  • Emulsification of fats
• Enzymes


  Biological catalysts, specific to certain substrates, work on a lock and key principle
• Practical: Enzyme activity


  1. Mix amylase and starch

  2. Test for starch every 10 seconds with iodine

  3. Plot time to complete reaction against temperature or pH

  4. Find optimum conditions
• Food tests


  • Iodine for starch
  • Benedict's solution for sugars
  • Biuret's reagent for proteins
  • Ethanol for lipids
• Breathing and gas exchange

  1. Air moves down trachea, bronchi, bronchioles to alveoli

  2. Oxygen diffuses into blood, carbon dioxide diffuses out
• Double circulatory system


  Blood enters heart twice per cycle, deoxygenated blood to lungs, oxygenated blood to body
• Blood vessel types


  • Arteries (thick walls, narrow lumen)
  • Veins (thin walls, valves to prevent backflow)
  • Capillaries (one cell thick walls)
• Coronary artery


  Supplies heart muscle with oxygen and nutrients
• Stents


  Tubes inserted into blood vessels to keep them open
• Examples of non-communicable diseases

  • Coronary heart disease
  • Autoimmune conditions
  • Cancer
• Communicable diseases are caused by pathogens from outside the body
• Coronary artery


  Delivers blood to the heart muscle to supply oxygen
• Heart attack


  Occurs when coronary arteries are blocked by buildup of fatty deposits, causing coronary heart disease (CHD)
• Stents


  Little tubes inserted into blood vessels to keep them open and allow blood flow
• Statins


  Drugs that reduce cholesterol and fatty deposits
• Faulty heart valves


  Result in backflow, can be replaced with artificial ones
• Blood


  Carries plasma, red blood cells, white blood cells, and platelets
• White blood cells


  Combat infections
• Platelets


  Clump together to clot wounds and stop bleeding
• Cardiovascular disease (CVD)


  An example of a non-communicable disease, caused by factors within the body
• Communicable disease


  Caused by a pathogen that enters the body, can be viral, bacterial, or fungal
• Type 2 diabetes

  Can be caused by obesity and too much sugar
• Carcinogen

  Anything that increases the risk of cancer
• Cancer

  Caused by damaged cells dividing uncontrollably, leading to tumors
• Benign cancer


  Doesn't spread through the body, relatively easy to treat
• Malignant cancer


  Cancerous cells spread through the body, much worse