Topic Notes Import

• Valid method and data


  It will answer the question being asked
• Designing experiments


  1. Identify independent variable

  2. Identify dependent variable

  3. Identify control variables

  4. Repeat experiment

  5. Control experiment
• Accurate measurements


  • Choose equipment with better resolution
  • Take repeated measurements
  • Identify and account for errors
• Precision


  Results are similar when repeated
• Accuracy


  Measurements are close to the true value
• Errors are not mistakes, they are due to equipment and experimental design
• Taring (zeroing) a balance is an example of calibration
• Parallax error occurs if you do not read volumes with the measuring cylinder at eye level
• Burning food to determine energy content has a lot of heat energy radiated into the surroundings, which is a source of error
• Table organisation


  Independent variable in first column, measurements of dependent variable, calculations
• Results of calculations should be recorded with the lowest number of significant figures used to record measurements
• Units should be in column headings
• If independent variable is numerical, record it and associated data in sequence from lowest to highest
• Data should be recorded with a consistent number of decimal places
• Graphs


  • Title
  • Labelled axes with units
  • Plotted data points
  • Line of best fit
  • Anomalous results identified

  
• Evaluating a method involves considering how to improve it, checking precision, identifying anomalous results, and improving reliability
• Counting ladybird larvae and adults separately would improve the investigation
• Repeating the investigation at the same times each week would improve reliability
• Using a thermostatic water bath would improve temperature control
• Accurate results


  Close to the true value
• Using equipment with better resolution increases accuracy
• Equipment for different measurements

  • Metre ruler for height
  • Voltmeter for current
  • Stopwatch for sprint time
  • Newton meter for force
  • Lab balance for mass
  • Gas syringe for gas volume
  • Thermometer for temperature
  • Small measuring cylinder for small liquid volumes
  • Litmus indicator for pH

  
• Repeating an experiment multiple times allows checking for a pattern and identifying anomalous results
• Doing an experiment only once does not provide reliable, precise data
• Anomalous results are those that don't fit the overall pattern
• Improving reliability involves repeating the experiment multiple times
• Table


  Organises data to make it easier to use
• Table for enzyme activity experiment

  • Temperature
  • 3 readings
  • Average
• Bar chart


  Shows nutrient content of different foods

  
• Line graph


  Shows growth of a microbe under controlled conditions
• Topics covered


  • Cell structures and functions
  • Similarities and differences between plant and animal cells
  • Genome and genes
  • Chemical composition of biomolecules
  • Enzyme function and regulation
  • Levels of organisation in organisms
  • Cell differentiation
  • Features of eukaryotes and prokaryotes
  • Pathogens

  
• Cells


  Made of millions (or billions) of different cells
• Cell


  • Cell membrane surrounding a liquid called the cytoplasm
  • Organelles - small structures which carry out functions (jobs) needed to keep the cell alive
• The diagram shows the structure of plant and animal cells. What are the differences between them?

  
• What are the functions of the different parts of cells?
• Nucleus


  • Controls the activity of the cell (by making proteins)
  • Contains the chromosomes - strands of DNA which carry the genes (each gene codes for a protein)
• Cell membrane


  • Boundary between the cytoplasm and the cell's surroundings
  • Controls what substances enter and leave the cell (selectively permeable)
• Cytoplasm


  Jelly-like liquid where chemical reactions occur
• Mitochondria


  Carries out some reactions of aerobic respiration, producing ATP (energy carrier molecule)
• Ribosomes


  Synthesise (assemble) proteins from amino acids