science

• 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, passive process
• 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
• 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
• Measuring enzyme activity


  1. Mix enzyme and substrate

  2. Measure time for reaction to complete at different temperatures/pH

  3. Plot time against temperature/pH to find optimum
• Food tests


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


  Provides energy for cells, different to breathing
• Gas exchange


  1. Air moves down trachea to alveoli

  2. Oxygen diffuses into blood

  3. 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 and ventricle, left atrium and ventricle, thicker walls on left side
• Blood vessels


  Arteries carry oxygenated blood away from heart, veins carry deoxygenated blood towards heart
• Coronary arteries supply the heart muscle with oxygen
• Cardiovascular disease


  Non-communicable disease, caused by internal factors
• Communicable diseases are caused by external factors like pathogens
• Coronary artery


  Delivers blood to the heart muscle to supply oxygen
• Coronary heart disease (CHD)


  Occurs when coronary arteries are blocked by fatty deposits, causing a heart attack
• 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 components


  • Plasma
  • Red blood cells
  • White blood cells (combat infections)
  • Platelets (clot wounds)
• Cardiovascular disease (CVD)


  Non-communicable disease caused by factors within the body, e.g. obesity, diet, 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
• Plant organs


  • Leaves (photosynthesis)
  • Roots (water and mineral absorption)
  • Meristem (new cell production)