Bio 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
  • Nutrients absorbed by villi
• 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 enters trachea, bronchi, bronchioles, 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 regulates heartbeat
• 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
• Cardiovascular disease


  Non-communicable disease caused by internal factors, e.g. coronary heart disease
• 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 valves can replace faulty ones to prevent backflow
• Blood components


  Plasma, red blood cells, white blood cells, platelets
• White blood cells


  Combat infections
• Platelets


  Clump together to clot wounds and stop bleeding
• Cardiovascular disease (CVD)


  Non-communicable disease caused by factors within the body
• Other non-communicable diseases


  • Autoimmune conditions, allergic reactions, cancer
• Communicable disease


  Caused by a pathogen that enters the body, leading to viral, bacterial or fungal infection
• Type 2 diabetes


  Caused by obesity and too much sugar
• Risk factors for heart disease


  Bad diet, smoking, lack of exercise, alcohol