EXTRA

• This video is for paper one of GCSE biology and combined science
• You can get extra help with this exam by downloading my revision workbooks and my maps from Emma DT ChiCom the link is in the description below
• I really hope you find this video useful
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• GCSE these are tough but the fact that you're watching this means that you care and are putting effort in and that always pays off good luck for your exams and thanks again for watching
• Our first topic is cell biology and we're starting with number one microscopy
• Light microscope


  It was first developed in the mid 17th century and it uses light to form an image
• Light microscope


  • It can be used to view live specimens
  • It's pretty cheap and easy to use
  • The best ones can magnify up to 2,000 times
• Resolution


  The ability to see two things as separate objects
• Light microscope


  • It has a low resolution with a resolving fire of around 200 nanometers
• Electron microscope


  It was developed by scientists in the 1930s and it uses electrons to form an image
• Electron microscope


  • The specimens must be dead first so it can't be used to view living specimens
  • It's a very expensive microscope and it has a lot of conditions so that needs to be capped on
  • The magnification can be up to two million times
  • It has a high resolution of just 0.2 nanometers
• The electron microscope is much better than the light microscope in terms of magnification and resolution
• This allows scientists to see and understand lots more about the subcellular structures of cells
• We'll look at these in more detail in the next video
• Number 2 animal and plant cells
• Organelles in an animal cell

  • Nucleus
  • Cell membrane
  • Cytoplasm
  • Mitochondrion
  • Ribosome
• Nucleus


  Controls the cell's activities and contains genetic material (DNA)
• Cell membrane


  Responsible for controlling the passage of substances in and out of the cell
• Cytoplasm


  Liquid gel that fills up the entire cell and where chemical reactions occur
• Mitochondrion


  Where aerobic respiration occurs and releases energy for the cell
• Ribosome


  Where protein synthesis occurs
• Organelles in a plant cell

  • Nucleus
  • Ribosomes
  • Mitochondrion
  • Cytoplasm
  • Cell membrane
  • Chloroplast
  • Permanent vacuole
  • Cell wall
• Chloroplast


  Contains chlorophyll and is important for photosynthesis
• Permanent vacuole


  Filled with cell sap and helps keep the cell rigid
• Cell wall


  Made of cellulose, strengthens and supports the plant cell
• Animal and plant cells are both eukaryotic cells
• Prokaryotic cells, such as bacteria, are different from eukaryotic cells
• Features of prokaryotic cells

  • Cell membrane
  • Cytoplasm
  • Ribosomes
  • Cell wall (not made of cellulose)
  • Genetic material not enclosed in a nucleus
  • May have plasmids
  • May have a slime layer
  • May have flagella
• Prokaryotic cells do not have chloroplasts or mitochondria
• As an organism develops, its cells differentiate and become specialized
• Specialized animal cells


  • Sperm cell
  • Muscle cell
  • Nerve cell
• Sperm cell


  • Has a tail to help it swim
  • Has many mitochondria in the mid-piece to provide energy
  • Has an acrosome to break down the egg cell
• Muscle cell


  • Has many mitochondria to release energy for contraction
  • Has special proteins that cause contraction by sliding across each other
  • Can store glycogen for respiration
• Nerve cell


  • Has a long axon to carry electrical impulses
  • Has dendrites to connect to other nerve cells
  • Has nerve endings that release chemical messengers
• Specialized plant cells


  • Root hair cell
  • Xylem cell
  • Phloem cell
• Root hair cell


  • Has a large surface area for absorption of water and minerals
  • Has a large permanent vacuole to speed up osmosis
  • Has many mitochondria for active transport of minerals
• Xylem cell


  • Forms long hollow tubes for easy movement of water and minerals
  • Has spirals of lignin to strengthen the cell and support the plant
• Phloem cell


  • Has sieve plates with holes to allow easy movement of dissolved food
  • Has companion cells with many mitochondria to provide energy for food transport
• Diffusion is the spreading out of particles in a solution or gas, resulting in a net movement from an area of higher concentration to an area of lower concentration