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 (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 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
• Digestive system processes

  • Acid in stomach
  • Bile and enzymes in small intestine
  • Emulsification of fats
• 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 to complete reaction against temperature or 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 from breathing which supplies oxygen
• Gas exchange in lungs

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

  2. Oxygen diffuses into blood, carbon dioxide diffuses out
• Parts of the circulatory system

  • Right atrium
  • Right ventricle
  • Pulmonary artery
  • Pulmonary vein
  • Left atrium
  • Left ventricle
  • Aorta
• Arteries


  Carry oxygenated blood away from the heart, have thick walls
• Veins


  Carry deoxygenated blood towards the heart, have thin walls and valves
• Coronary arteries supply the heart muscle with oxygen
• Stents


  Tubes inserted into blood vessels to keep them open
• 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
• Carcinogens


  Anything that increases the risk of cancer
• Cancer


  Result of damaged cells dividing uncontrollably, leading to tumours. Benign cancers don't spread, malignant cancers do.