biology

• Organisms have to produce offspring (children) in order for their species to survive
• 1. They Grow and Develop
• Cells

  Tiny building blocks that organisms are made up of
• Cells

  • Can be eukaryotic or prokaryotic
  • Eukaryotic cells are complex, and include all animal and plant cells
  • Prokaryotic cells are smaller and simpler e.g. bacteria
• Organelles


  Tiny structures within cells that can only be seen using a powerful microscope
• Organelles in a typical animal cell

  • Nucleus
  • Cytoplasm
  • Ribosomes
  • Cell membrane
  • Mitochondria
• Organelles in a typical plant cell

  • Chloroplasts
  • Vacuole
  • Cell wall
• Similar cells are organised into tissues
• Tissue


  A group of similar cells that work together to carry out a particular function
• Organ


  A group of different tissues that work together to perform a function
• Organ system


  Organs working together to do a different job
• Plants, animals and fungi are eukaryotic organisms
• Features of plants


  • Multicellular
  • Have chloroplasts and can photosynthesise
  • Have cell walls made of cellulose
  • Store carbohydrates as sucrose or starch
• Features of animals


  • Multicellular
  • Don't have chloroplasts and can't photosynthesise
  • Don't have cell walls
  • Have some kind of nervous coordination
  • Can usually move around
  • Store carbohydrates as glycogen
• Features of fungi


  • Some are single-celled, others have a body called a mycelium
  • Can't photosynthesise
  • Have cell walls made of chitin
  • Feed by saprotrophic nutrition
  • Store carbohydrates as glycogen
• Protoctists


  Single-celled and microscopic, some have chloroplasts and are similar to plant cells, others are more like animal cells
• Bacteria


  Single-celled, don't have a nucleus, have a circular chromosome of DNA, some can photosynthesise, most feed off other organisms
• Viruses


  Particles rather than cells, smaller than bacteria, can only reproduce inside living cells, infect all types of living organisms, have a protein coat around genetic material (DNA or RNA)
• Pathogens are organisms that cause disease, including some fungi, protoctists, bacteria and viruses
• Enzymes


  Biological catalysts produced by living things that increase the speed of chemical reactions without being changed or used up
• Enzymes reduce the need for high temperatures and only speed up useful chemical reactions
• Bacteria


  The plural of bacterium
• Enzymes are chemical reactions that make you work. And enzymes are what make them work
• Enzymes


  Catalysts Produced by Living Things
• Enzymes


  1. Living things have thousands of different chemical reactions going on inside them all the time

  2. These reactions need to be carefully controlled to get the right amounts of substances in the cells

  3. You can usually make a reaction happen more quickly by raising the temperature, but this would speed up the unwanted reactions too

  4. So living things produce enzymes that act as biological catalysts

  5. Enzymes reduce the need for high temperatures and only speed up the useful chemical reactions in the body (metabolic reactions)

  6. Enzymes are all proteins made up of chains of amino acids folded into unique shapes
• Enzymes


  • They increase the speed of a reaction, without being changed or used up in the reaction
  • They are very specific - they usually only speed up one reaction because the substrate has to fit the active site of the enzyme, like a key in a lock
• Just like you've got to have the correct key for a lock, you've got to have the right substrate for an enzyme. If the substrate doesn't fit, the enzyme won't catalyse the reaction
• Enzymes


  • They need just the right conditions to work properly
  • They have an optimum temperature and pH that they work best at
• Changing the temperature


  Changes the rate of an enzyme catalysed reaction
• As temperature increases


  The rate of the reaction increases
• If it gets too hot

  Some of the bonds holding the enzyme together break, changing the shape of the active site so the substrate won't fit anymore (the enzyme is denatured)
• All enzymes have an optimum temperature that they work best at
• The pH also affects enzymes - if it's too high or too low, the pH interferes with the bonds holding the enzyme together, changing the shape of the active site and denaturing the enzyme
• All enzymes have an optimum pH that they work best at, often neutral pH but not always
• Investigating the effect of temperature on enzyme activity

  1. Measure how fast a product appears (e.g. oxygen from catalase breaking down hydrogen peroxide)

  2. Measure how fast a substrate disappears (e.g. starch broken down by amylase)
• If the temperature is increased too much, no product will appear because the enzyme is denatured
• Diffusion


  The gradual movement of particles from places where there are a lot of them to places where there are fewer of them
• Diffusion is a passive process that doesn't require energy
• Diffusion happens in both liquids and gases because the particles in these substances are free to move about randomly
• Osmosis


  The net movement of water molecules from an area of higher water concentration (lower solute concentration) to an area of lower water concentration (higher solute concentration) through a partially permeable membrane