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, use aseptic technique

  3. Calculate culture size from area or initial drop
• 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 into different cell types
• Diffusion

  Movement of molecules/particles from high to low concentration, down concentration gradient, passive process
• 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 % change in mass

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

  Using energy to move substances against a concentration gradient
• 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

  2. Test for starch every 10 seconds with iodine

  3. Plot time taken for starch breakdown against temperature or pH

  4. Find optimum conditions
• 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 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 artery

  Supplies heart muscle with oxygen and nutrients
• 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
• Benign cancer

  Doesn't spread through the body, relatively easy to treat