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 containing DNA
• Prokaryotic cells


  Do not have a nucleus, DNA is in a ring called a plasmid
• Cell structures


  • Cell membrane
  • Cell wall (plant cells and bacteria)
  • Cytoplasm
  • Mitochondria
  • Ribosomes
  • Chloroplasts (plant cells)
• Bacterial binary fission


  1. Number doubles every 10 minutes

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

  3. Calculate size of culture from initial drop or area not grown
• 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


  Unspecialised cells that can differentiate into different cell types
• Diffusion


  Movement of molecules/particles from high to low concentration, down concentration gradient, no energy required
• 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 percentage change in mass

  5. Plot against sugar concentration to find no change point
• Active transport


  Using energy to move substances against a concentration gradient
• Tissues


  • Heart
  • Digestive system
• Enzymes


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


  1. Mix amylase and starch at different temperatures or pH

  2. Test for starch every 10 seconds using iodine

  3. Plot time taken for starch to be broken down against temperature or pH
• Food tests


  • Iodine for starch
  • Benedict's solution for sugars
  • Biuret's reagent for proteins
  • Ethanol for lipids
• Breathing vs respiration


  Breathing provides oxygen for respiration to occur in cells
• Gas exchange in lungs

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

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


  Double circulatory system - blood enters heart twice per cycle
• Blood vessels

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


  Supplies heart muscle with oxygen and nutrients
• Non-communicable diseases


  Caused by factors within the body, e.g. cardiovascular disease, cancer, autoimmune conditions
• Communicable diseases


  Caused by pathogens that can be transmitted, e.g. infectious diseases
• Coronary artery


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


  Caused by blockage of coronary arteries, also known as 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
• Heart valves


  Can become faulty, leading to backflow, and may need to 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, e.g. ionizing radiation
• Benign cancer

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


  Cancerous cells spread through the body, much worse