paper 1

Cards (85)

  • 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 where DNA is found
  • Prokaryotic cells
    • Don't have a nucleus, DNA is in a ring called a plasmid
  • Cell structures
    • Cell membrane
    • Cell wall (in plant cells and bacteria)
    • Cytoplasm
    • Mitochondria
    • Ribosomes
    • Chloroplasts (in plant cells)
    • Permanent vacuole (in plant cells)
    • Enzymes
  • Cell membrane
    Keeps everything inside the cell, semi-permeable
  • Cell wall
    Provides rigid structure (in plant cells and bacteria)
  • Cytoplasm
    Liquid in which most chemical reactions take place
  • Mitochondria
    Where respiration takes place, releasing energy
  • Ribosomes
    Where proteins are assembled or synthesized
  • Chloroplasts
    Contain chlorophyll, where photosynthesis takes place (in plant cells)
  • Permanent vacuole
    Stores sap (in plant cells)
  • Enzymes
    Biological catalysts that break down larger molecules into smaller ones
  • Enzymes
    • Specific, work on a lock and key principle
    • Rate of activity increases with temperature until active site changes shape and enzyme denatures
  • Enzyme activity experiment
    1. Mix enzyme with substrate
    2. Measure time taken for all substrate to be broken down
    3. Plot time against temperature or pH
    4. Optimum is lowest point on curve
  • Food tests
    • Iodine turns black in presence of starch
    • Benedict's solution turns orange in presence of sugars
    • Biuret reagent turns purple in presence of proteins
    • Cold ethanol goes cloudy in presence of lipids
  • Diffusion
    Movement of molecules or particles from high to low concentration, down concentration gradient, passive
  • Osmosis
    Diffusion of water across a semi-permeable membrane
  • Osmosis experiment
    1. Cut equal sized cylinders from potato
    2. Weigh and place in varying sugar solutions
    3. Reweigh after a day
    4. Calculate percentage change in mass
    5. Plot against sugar concentration, x-axis crossing point is no change in mass
  • Active transport
    Using energy to move substances through a membrane against a concentration gradient
  • Cell types
    • Nerve cells
    • Muscle cells
    • Root hair cells
    • Xylem cells
    • Phloem cells
    • Stem cells
  • Stem cells
    Unspecialised cells that can differentiate into various cell types
  • Parts of the nervous system
    • Central nervous system (brain and spinal cord)
    • Peripheral nervous system (nerves)
  • Nerve signal transmission
    1. Receptor detects stimulus
    2. Electrical signal travels to spine through sensory and relay neurons
    3. Signal crosses synapse using neurotransmitter
    4. Signal travels to brain
    5. Brain makes decision
    6. Signal travels back to effector (e.g. muscle) through relay and motor neurons
  • Reflex arc
    Electrical signal bypasses the brain and goes straight from spine to effector
  • Parts of the brain
    • Cerebral cortex (higher functions)
    • Cerebellum (motor skills, balance, coordination)
    • Medulla oblongata (unconscious actions)
  • MRI scans

    Safely show brain activity
  • Eye accommodation
    1. Ciliary muscles relax and suspensory ligaments tighten to focus on distant objects
    2. Ciliary muscles contract and suspensory ligaments slacken to focus on near objects
  • Pupil
    Changes size depending on light intensity
  • Meiosis
    1. Chromosomes duplicate
    2. Homologous chromosomes pair up and swap genes
    3. Cell divides twice to form 4 haploid cells
  • Asexual reproduction produces genetically identical offspring (clones)
  • Advantages of sexual reproduction include increased variation in offspring
  • 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
  • Harmful mutations can change a gene so much that the resulting protein doesn't function properly