cell biology

• Eukaryotic cells


  Cells that contain their genetic material enclosed in a nucleus
• Eukaryotic cells

  • Contain a nucleus
  • Contain a cell membrane
  • Contain cytoplasm
• Prokaryotic cells


  Cells where the genetic material is not enclosed in a nucleus
• Prokaryotic cells


  • Do not have a nucleus
  • Have a cell membrane
  • Have a cell wall
  • Contain cytoplasm
  • May have plasmids
• Prokaryotic cells


  Are much smaller than eukaryotic cells
• Bacterial cells are an example of prokaryotic cells
• Centimeter (cm)


  One hundredth of a meter
• Milli


  One thousandth
• Millimeter (mm)


  One thousandth of a meter
• Micrometer (μm)


  One millionth of a meter
• Size of objects


  • Typical human cell is 10-20 micrometers in size
• Nanometer (nm)


  One billionth of a meter
• Size of objects


  • Hemoglobin molecule is around 5 nanometers in diameter
• Smaller units like micrometers and nanometers are used to measure the size of cells and their components
• Order of magnitude


  A way to compare the approximate size of different objects
• Pineapple is around 10 times larger than a lemon


  Pineapple is one order of magnitude larger than the lemon
• Dog is around 100 times longer than a woodlouse


  Dog is two orders of magnitude longer than the woodlouse
• Order of magnitude


  Every order of magnitude is 10 times greater than the one before
• The number of zeros tells you the order of magnitude
• Calculating order of magnitude


  1. Find how many times larger one object is than another

  2. Count the number of zeros to determine the order of magnitude
• Eukaryotes


  Organisms whose genetic material is enclosed in a nucleus
• Nucleus


  Encloses the genetic material
• Cytoplasm


  Watery solution where chemical reactions take place
• Cell membrane


  Controls the molecules that can enter and leave the cell
• Mitochondria


  Where aerobic respiration takes place
• Ribosomes


  Sites of protein synthesis
• Ribosomes are too small to be seen using a light microscope, an electron microscope is required
• Proteins carry out many functions, such as enzymes
• Plant cells


  • Have a regular shape, unlike animal cells which can easily change their shape
  • Are packed full of green structures (chloroplasts)
• Chloroplasts


  Contain chlorophyll and are the sites of photosynthesis
• Structures common to both plant and animal cells


  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Mitochondria
  • Ribosomes
• Plant cells


  • Have a cell wall made from cellulose, which strengthens the cell
  • Contain a large permanent vacuole filled with cell sap, which helps give the cell its shape
• Plants can use light to carry out photosynthesis, unlike animals
• Algae are very simple forms of plant life and also have a cellulose cell wall
• Specialized animal cells


  Cells that have adaptations which help them to carry out a particular function
• Differentiation


  When cells become specialized
• Sperm cells


  • Long tail to swim to ovum
  • Packed with mitochondria to provide energy for swimming
  • Contain enzymes to digest outer layer of ovum
• Fertilization


  The process where the genetic information of the ovum and sperm combine
• Nerve cells


  • Long axon to transmit electrical impulses
  • Axon covered in myelin to insulate and speed up transmission
  • Dendrites to increase surface area for connections
• Muscle cells


  • Contain protein fibers that can contract to shorten the cell
  • Packed with mitochondria to provide energy for contraction