b1

• 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
• Mitochondria are responsible for producing energy through cellular respiration.
• The nucleus contains genetic material (DNA) that controls all cell activities.
• Vacuoles store water, nutrients, or waste products inside the cell.
• 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 genetic material consists of a single loop of DNA and small rings of DNA also known as plasmids
• 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
• Axon


  Part of nerve cell that transmits electrical impulses
• Synapses


  Junctions that allow impulses to pass from one nerve cell to another
• Muscle cells


  • Contain protein fibers that can contract and shorten
  • Packed with mitochondria to provide energy for contraction
• Root hair cells


  • Root hair increases surface area to absorb water and dissolved minerals more effectively
  • Do not contain chloroplasts as they are underground and do not need to carry out photosynthesis
• Xylem cells


  • Have thick walls containing lignin to provide support
  • End walls between cells have broken down to form long tubes allowing water and dissolved minerals to flow easily
  • Have no internal structures like nucleus, cytoplasm, vacuole or chloroplasts
• Phloem cells


  • Consist of two types: phloem vessel cells and companion cells
  • Phloem vessel cells have no nucleus and limited cytoplasm, with pores called sieve plates to allow dissolved sugars to move through
  • Companion cells have mitochondria to provide energy to the phloem vessel cells
• Diffusion


  The spreading out of particles resulting in a net movement from an area of higher concentration to an area of lower concentration
• Molecules that move in and out of cells by diffusion


  • Oxygen
  • Carbon dioxide
  • Urea
  • glucose
• Cells need oxygen for respiration


  Oxygen moves into the cell by diffusion
• Urea is a waste product produced inside cells


  Urea diffuses out of the cells into the blood plasma
• Factors affecting the rate of diffusion

  • Difference in concentrations (concentration gradient)
  • Temperature
  • Surface area of the membrane
• Greater concentration gradient


  Faster diffusion
• Higher temperature


  Greater rate of diffusion
• Larger surface area of the cell membrane

  Greater rate of diffusion
• Dilute solution


  • Contains a high concentration of water
  • Contains a low concentration of solute (e.g. sugar)
• Concentrated solution


  • Contains a low concentration of water
  • Contains a high concentration of solute (e.g. sugar)
• Osmosis


  Water diffuses from the dilute solution to the concentrated solution through a partially permeable membrane
• Cell placed in water

  Water moves into the cell by osmosis, causing the cell to expand
• Cell placed in concentrated solution


  Water moves out of the cell by osmosis, causing the cell to shrink
• effects of osmosis on animal cell

  • Cytoplasm is a relatively concentrated solution
  • Cell can burst if too much water enters
• effects of osmosis on plant cell

  • Cell wall prevents the cell from bursting when water enters
  • Cell becomes swollen and turgid when water enters
  • Cell shrinks and becomes flaccid when water leaves
• Distilled water

  Contains no dissolved substances that could affect the weight of osmosis