Biology paper 1

• Cell structures


  • Cell membrane
  • Cell wall (plant cells and bacteria)
  • Cytoplasm
  • Mitochondria
  • Ribosomes
  • Chloroplasts (plant cells)
• Diploid cells


  Have 23 pairs of chromosomes
• Specialised cell types


  • Nerve
  • Muscle
  • Root hair
  • Xylem
  • Phloem
• Osmosis


  Diffusion of water across a semi-permeable membrane
• Measuring 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 sugar concentration to find no change point
• 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 that are specific to certain substrates
• Measuring enzyme activity


  1. Mix enzyme and substrate

  2. Test for remaining substrate every 10 seconds

  3. Plot time taken to complete reaction against temperature or pH

  4. Find optimum conditions
• Stents


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


  Drugs that reduce cholesterol and fatty deposits
• Blood


  Carries oxygen, nutrients, white blood cells, and platelets
• Cardiovascular disease (CVD)


  Non-communicable disease caused by factors within the body, e.g. obesity, diabetes, smoking
• Benign cancer


  Doesn't spread through the body and is relatively easy to treat
• Plant organs


  Leaves, roots, meristem
• Transpiration


  Water evaporating from leaves, increased by higher temperature, lower humidity, and more air movement
• Leaf structure


  • Waxy cuticle to prevent water loss
  • Palisade mesophyll layer for photosynthesis
  • Spongy mesophyll layer for gas exchange
  • Vascular bundles (xylem and phloem)
  • Stomata controlled by guard cells
• Pathogens


  Viruses, bacteria, fungi, and protists that can cause communicable diseases
• Fungi


  Cause infections like athlete's foot
• Protists


  Single-celled parasites that can cause diseases like malaria
• Immune system defences


  • Skin, mucus, acid, enzymes
  • White blood cells (lymphocytes, phagocytes)
  • Antibodies that bind to antigens
• Vaccines


  Expose the immune system to a dead or inert version of a pathogen to build immunity
• Aerobic respiration


  1. Occurs in mitochondria

  2. Converts glucose and oxygen into carbon dioxide and water (releases energy)
• Fermentation


  Converts glucose into ethanol and carbon dioxide (e.g. in yeast)
• Metabolism


  Sum of all chemical reactions in a cell or organism, including respiration, synthesis, and breakdown