All Paper 1 (Science Shorts)

• 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 area or initial drop
• 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 various cell types
• Diffusion


  Movement of molecules/particles from high to low concentration, down concentration gradient, no energy input
• 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 at different temperatures or pH

  2. Test for starch presence over time

  3. Plot time to complete reaction 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 in cells
• Gas exchange in lungs

  1. Air moves down trachea to alveoli

  2. Oxygen diffuses into blood

  3. Carbon dioxide diffuses out
• Circulatory system


  Double circulatory system, deoxygenated blood enters right side of heart, oxygenated blood leaves left side
• Heart has thicker walls on left side to pump blood to whole body
• Blood vessels


  Arteries carry oxygenated blood away from heart, veins carry deoxygenated blood towards heart
• Coronary arteries supply the heart muscle with oxygen
• Stents


  Tubes inserted into blood vessels to keep them open
• Cardiovascular disease


  Non-communicable disease caused by factors within the body
• Communicable diseases are caused by pathogens that can be transmitted between individuals
• Coronary artery


  Delivers blood to the heart muscle to supply oxygen
• Heart attack


  Caused by blockage of coronary arteries, also called coronary heart disease (CHD)
• Stents


  Little tubes inserted into blood vessels to keep them open and allow blood flow
• Statins


  Drugs that reduce cholesterol and fatty deposits
• Faulty heart valves


  Result in backflow, can be replaced with artificial ones
• Blood


  Carries plasma, red blood cells, white blood cells, and platelets
• White blood cells


  Combat infections
• Platelets


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

  An example of a non-communicable disease, caused by factors within the body
• Communicable disease

  Caused by a pathogen that enters the body, can be viral, bacterial, or fungal
• Type 2 diabetes


  Caused by obesity and too much sugar
• Carcinogen


  Anything that increases the risk of cancer