Cells and Cell Specialisation

• 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 contain structures that animal cells do not, including chloroplasts, cell walls, and large permanent vacuoles
• Plant cells


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


  Contain chlorophyll and are the sites of photosynthesis
• Cell wall


  Made from cellulose, strengthens the cell
• Vacuole


  Large permanent structure filled with cell sap, helps give the plant cell its shape
• Structures common to both plant and animal cells

  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Mitochondria
  • Ribosomes
• Plants are eukaryotes, like animals
• Nucleus contains genetic material
• Cytoplasm is where chemical reactions take place
• Cell membrane controls what molecules enter and leave the cell
• Mitochondria carry out aerobic respiration
• Ribosomes are the site of protein synthesis
• 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
• Sperm cells only contain half the genetic information of a normal adult cell
• 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
• Muscle cells work together to form muscle tissue
• Root hair cells


  • Root hair increases surface area for water and mineral absorption
  • No chloroplasts as they are underground and do not require photosynthesis
• Xylem cells


  • Thick walls containing lignin for support
  • Broken down end walls forming long tubes for easy flow of water and dissolved minerals
  • No internal structures like nucleus, cytoplasm, vacuole or chloroplasts
• Phloem cells


  • Phloem vessel cells have no nucleus and limited cytoplasm
  • Phloem vessel cells have porous sieve plates to allow flow of dissolved sugars
  • Companion cells connected to phloem vessel cells provide energy through mitochondria
• Specialized plant cells include root hair cells, xylem cells, and phloem cells
• Specialization of plant cells is called differentiation
• Key plant cell structures are chloroplasts, cellulose cell wall, and permanent vacuole