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 (plant cells and bacteria)
  • Cytoplasm
  • Mitochondria
  • Ribosomes
  • Chloroplasts (plant cells)
• 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 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 system
• 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 taken for starch to be broken down against temperature or pH
• Food tests

  • Iodine for starch
  • Benedict's solution for sugars
  • Biuret's reagent for proteins
  • Ethanol for lipids
• Breathing vs respiration

  Breathing provides oxygen for respiration to occur in cells
• Gas exchange in lungs

  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 prevent backflow
  • Pacemaker cells control heart beat
• Blood vessels

  • Arteries carry oxygenated blood away from heart, veins carry deoxygenated blood towards heart
  • Capillaries allow fast diffusion
• Coronary arteries supply heart muscle with oxygen</b>
• 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
• Heart valves

  Can become faulty, resulting in backflow, and may need to be replaced with artificial ones
• Blood

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

  An example of a non-communicable disease, where the cause comes from inside the body
• Examples of non-communicable diseases

  • Cardiovascular disease
  • Autoimmune conditions (like allergic reactions)
  • Cancer
• Communicable disease

  Caused by a pathogen (virus, bacteria, or fungus) that enters the body and causes an infection
• 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