biology paper 1 summary

• 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
• 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 size of culture from initial drop or area not grown
• Diploid cells


  Have 23 pairs of chromosomes
• Haploid cells


  Have 23 chromosomes (not in pairs)
• 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
• 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 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
• 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 taken for starch to be broken down against temperature or pH

  4. Find optimum temperature or pH
• Food tests


  • Iodine for starch
  • Benedict's solution for sugars
  • Biuret's reagent for proteins
  • Ethanol for lipids
• Respiration


  Provides energy for cells, uses oxygen
• Gas exchange


  1. Air moves down trachea, bronchi, bronchioles 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
• Heart structure


  • Right atrium, right ventricle, left atrium, left ventricle
  • Valves to prevent backflow
  • Electrical pulses from pacemaker cause contraction
• Blood vessels


  • Arteries carry oxygenated blood away from heart, veins carry deoxygenated blood towards heart
  • Arteries have thicker walls, veins have valves
• Coronary artery


  Supplies heart muscle with oxygen
• Stents


  Tubes inserted into blood vessels to keep them open
• Heart valves


  Can be replaced with artificial ones
• Non-communicable diseases


  Caused by factors within the body, e.g. cardiovascular disease, allergies, cancer
• 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


  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, which reduces fatty deposits
• Faulty heart valves


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


  Carries plasma, red blood cells, white blood cells (combat infections), and platelets (clot wounds)
• Cardiovascular disease (CVD)


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

  • Cardiovascular disease
  • Autoimmune conditions
  • Cancer
• Communicable disease


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


  Anything that increases the risk of cancer