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
• Eukaryotic cells include animal and plant cells
• Prokaryotic cells include bacterial cells
• You will find plenty of questions on eukaryotic and prokaryotic cells in the revision workbook
• Meter

  The base unit of measurement in science
• Sizes in biology

  • Often much smaller than a meter
• Centi

  One hundredth
• Centimeter (cm)


  One hundredth of a meter
• Size of objects


  • Width of little finger is around 1 cm
• Milli


  One thousandth
• Millimeter (mm)


  One thousandth of a meter
• Size of objects

  • Tip of a ballpoint pen is around 1 mm
• Micro


  One millionth
• Micrometer (μm)

  One millionth of a meter
• Size of objects

  • Typical human cell is 10-20 μm in size
• Nano


  One billionth
• Nanometer (nm)


  One billionth of a meter
• Size of objects


  • Hemoglobin molecule is around 5 nm in diameter
• 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 with a light microscope, an electron microscope is required
• Proteins carry out many functions, such as enzymes
• In the exam, you could be asked to identify cell structures from a diagram
• You can find plenty of questions on the structure of animal cells in the revision workbook
• Active transport


  Moves substances from a more dilute solution to a more concentrated solution, against the concentration gradient, requiring energy from respiration
• Diffusion


  Particles move down the concentration gradient, does not require energy from respiration
• Active transport


  Particles are moved against the concentration gradient, requires energy from respiration
• Active transport in animals

  • Cells lining the human small intestine transport sugars like glucose from the lumen (lower concentration) into the cell (higher concentration)
• Cells lining the human small intestine

  • Have many mitochondria to provide the energy for active transport
• Active transport in plants

  • Root hair cells transport ions like magnesium from the soil (lower concentration) into the cell (higher concentration)
• Root hair cells


  • Have many mitochondria to provide the energy for active transport
• Plants need magnesium to make chlorophyll in the leaves