biology paper 1 full notes

• 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 (in plants and bacteria)
  • Cytoplasm
  • Mitochondria
  • Ribosomes
  • Chloroplasts (in plants)
• 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 unpaired 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 various cell types
• Diffusion


  Passive movement of molecules/particles from high to low concentration
• Osmosis


  Diffusion of water across a semi-permeable membrane
• Osmosis practical


  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
• Digestive system processes


  • Acid in stomach
  • Bile and enzymes in small intestine
  • Nutrients absorbed by villi
• Enzymes


  Biological catalysts that are specific to certain substrates
• Enzyme activity practical


  1. Mix amylase and starch at different temperatures or pH

  2. Test for starch using iodine every 10 seconds

  3. Plot time to complete reaction against temperature or pH
• 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 to alveoli

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


  Double circulatory system, deoxygenated blood enters right side of heart, oxygenated blood leaves left side
• Coronary arteries supply the heart muscle with oxygen</b>
• Cardiovascular disease


  Non-communicable disease caused by factors within the body, e.g. cholesterol buildup
• 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
• Heart valve replacement


  Artificial heart valves can replace faulty ones to prevent backflow
• 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
• Communicable disease


  Caused by a pathogen (virus, bacteria, fungus, or parasite) that enters the body
• 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
• Photosynthesis


  Process in plant cells that uses chlorophyll, light energy, carbon dioxide, and water to produce glucose
• Transpiration


  Process of water evaporating from leaves, causing more water to be drawn up from the roots
• Xylem


  Long continuous tubes that transport water and minerals up the plant
• Phloem


  Convey cells that transport sugars, food, and sap up and down the plant
• Chlorosis


  Yellowing of leaves due to magnesium deficiency and lack of chlorophyll
• Leaf structure


  • Waxy cuticle
  • Upper epidermis
  • Palisade mesophyll
  • Spongy mesophyll
  • Vascular bundle
  • Lower epidermis with stomata