MY Biology- Paper 1

• All life consists of cells
• Light microscope

  • Can see cells and nucleus, but not subcellular structures
• Electron microscope

  • Can see finer details and subcellular structures, has better resolving power and higher resolution
• Calculating cell size

  1. Measure image size

  2. Divide by magnification
• Cell types

  • Eukaryotic cells
  • Prokaryotic cells
• Eukaryotic cells


  • Have a nucleus containing DNA
• Prokaryotic cells

  • Don't have a nucleus, DNA is in a ring called a plasmid or floating free called a chromosomal
• Cell structures

  • Cell membrane
  • Cell wall (plant cells and bacteria)
  • Cytoplasm
  • Mitochondria
  • Ribosomes
  • Chloroplasts (plant cells)
  • Vacuole (plant cells)
• Enzymes

  Biological catalysts that break down larger molecules into smaller ones
• Enzymes

  • Specific to certain molecules (lock and key principle)
  • Rate of activity increases with temperature until denaturation
  • Have an optimum temperature and pH
• Enzyme activity practical

  1. Mix enzyme and substrate

  2. Measure time for reaction to complete at different temperatures or pH

  3. Plot graph to find optimum
• Food tests

  • Iodine for starch
  • Benedict's solution for sugars
  • Biuret reagent for proteins
  • Ethanol for lipids
• Diffusion

  Movement of molecules from high to low concentration, down a concentration gradient, passive process
• Osmosis

  Diffusion of water across a semi-permeable membrane
• Osmosis practical

  1. Cut equal potato cylinders

  2. Weigh and place in sugar solutions

  3. Reweigh after time

  4. Calculate percentage change in mass

  5. Plot graph to find no change concentration
• Active transport

  Movement of substances against a concentration gradient, using energy
• Cell division

  • Mitosis
  • Meiosis
• Mitosis

  • Genetic material duplicated, cell divides into two identical cells
• Meiosis

  • Genetic material halved, four genetically different cells produced
• Stem cells

  Unspecialised cells that can develop into different cell types
• Nervous system

  • Central nervous system (brain and spinal cord)
  • Peripheral nervous system (nerves)
• Reflex arc

  1. Receptor detects stimulus

  2. Sensory neuron carries signal to spinal cord

  3. Signal bypasses brain, goes straight to effector
• Parts of the brain

  • Cerebral cortex
  • Cerebellum
  • Medulla oblongata
• MRI scans


  Magnetic resonance imaging, used to safely see brain activity
• Eye

  • Accommodation - lens changes shape to focus light
  • Pupil changes size to control light intensity
  • Cornea, lens, retina with rods and cones
• Myopia

  Shortsightedness
• Hyperopia


  Longsightedness
• Reproduction

  • Sexual (meiosis)
  • Asexual (mitosis)
• Genome

  All the genetic material in an organism
• Gene

  Section of DNA that codes for a specific protein
• Genotype


  Genetic code stored in DNA
• Phenotype

  How the genetic code is expressed in an organism's characteristics
• Nucleotides are the monomers in DNA, there are 4 types: A, T, C, G</b>
• A sequence of 3 nucleotides codes for an amino acid
• Harmful mutations can change a gene so the resulting protein doesn't function properly
• Genotype


  The code stored in your DNA
• Phenotype


  How the genetic code is expressed in your characteristics and physiology
• Monomers between DNA strands

  • Nucleotides
  • Made from sugar and phosphate group
  • 4 types: A, T, C, G
• A and T always match, C and G always match in the DNA sequence
• Codon

  A sequence of 3 bases that codes for an amino acid