biology paper 1

• Eukaryotic cells

  Cells that contain their genetic material enclosed in a nucleus
• Eukaryotic cells

  • Have a nucleus containing the genetic material (DNA)
  • Have a cell membrane around the edge of the cell
  • Have cytoplasm within the cell membrane
• Prokaryotic cells

  Cells that do not have their genetic material enclosed in a nucleus
• Prokaryotic cells

  • Do not have a nucleus, their genetic material is a single loop of DNA
  • May have small rings of DNA called plasmids
  • Have a cell membrane
  • Have a cell wall
  • Have cytoplasm
• 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, use aseptic technique, calculate growth rate
• 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
• Stem cells

  • Unspecialised, found in embryos and plant meristems
  • Can specialize into different cell types
• Diffusion

  Movement of molecules/particles from high to low concentration, down concentration gradient, passive
• Osmosis

  Diffusion of water across a semi-permeable membrane
• Measuring osmosis

  1. Cut equal potato cylinders

  2. Weigh and place in sugar solutions

  3. Reweigh after a day

  4. Calculate % change in mass

  5. Plot against concentration to find no change point
• Active transport

  Using energy to move substances against a concentration gradient
• Tissues

  • Heart tissue
  • Digestive tissue
• 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 to complete reaction at different temperatures/pH

  3. Plot graph 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, 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
• Blood vessels

  • Arteries have thick walls, veins have valves
  • Capillaries are one cell thick
• Coronary artery

  Supplies heart muscle with oxygen
• Non-communicable diseases

  Caused by internal factors, e.g. cardiovascular disease, allergies, cancer
• Communicable diseases

  Caused by external pathogens, e.g. infections
• 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