CELLS

• what is a eukaryotic cell?

  cell with a nucleus
• what is a prokaryotic cell?

  cell without a nucleus
• what sub-cellular structures do animal cells contain?

  - nucleus

  - cytoplasm

  - cell membrane

  - mitochondria

  - ribosomes
• what sub-cellular structures do plant cells contain that animal cells don't?


  - vacuole

  - cell wall

  - chloroplasts
• what sub-cellular structures do bacterial cells contain?

  - cytoplasm

  - cell membrane

  - nucleoid

  - cell wall

  - plasmids
• what is the equation for magnification?

  magnification = image size / real size
• what is differentiation?


  the process by which a cell changes to become specialized
• what for and how are sperm cells specialized for?

  for reproduction; stream-lined heads, long tails, lots of mitochondria, enzymes
• what for and how are muscle cells specialized for?

  contraction; long, lots of mitochondria
• what for and how are nerve cells specialized for?

  rapid signalling; long, branched connections
• what for and how are root hair cells specialized for?

  absorption; large surface area
• what for and how are xylem and phloem cells specialized for?

  transport; joined end to end, hollow, few sub-cellular structures
• what are chromosomes?


  coiled up lengths of DNA molecules
• how many chromosomes are there in a human cell?

  23 pairs
• why do cells divide?


  growth, repair, reproduction
• what are the stages of the cell cycle?

  - growth and DNA replication

  - mitosis

  - cytoplasm and membrane divide
• what happens during the growth and DNA replication stage of the cell cycle?

  - the cell grows and increases the number of sub-cellular structures

  - DNA replicates to form two copies
• what happens during mitosis?


  one set of chromosomes is pulled to each end of the cell and the nucleus divides
• what can bacteria be grown in?


  - a nutrient broth

  - colonies on an agar gel plate
• what is a stem cell?

  an undifferentiated cell
• where can stem cells be found in humans?

  embryos and bone marrow
• where can stem cells be found in plants?

  meristem
• what are the advantages of stem cells in humans?

  they can be used to cure disease such as diabetes and paralysis
• what are the disadvantages of stem cells in humans?

  ethical and religious contradictions, viruses
• what is therapeutic cloning?


  an embryo is produced with the same genes as the patient; stem cells aren't rejected and they may be used for treatment
• what are contradictions against therapeutic cloning?


  - each embryo could be a potential life

  - usually the embryo is unwanted

  - scientists should concentrate on finding other sources

  - banned in some countries
• what is diffusion?

  the spreading out of particles from a region of high concentration to a region of lower concentration
• what is osmosis?

  the movement of water particles from a region of higher water concentration to a region of lower water concentration through a partially permeable membrane
• what is active transport?

  the movement of particles from a region of low concentration to a region of higher concentration across the concentration gradient
• what are factors affecting diffusion?


  - temperature

  - concentration gradient

  - surface area
• what is the effectiveness of an exchange surface increased by?

  - thin membrane

  - large surface area

  - efficient blood supply

  - ventilation
• how is the small intestine adapted for absorption?

  - villi and microvilli provide a very large SA

  - single layer of cells

  - very good blood supply
• how are the lungs adapted for absorption?

  - very large surface area (alveoli)

  - moist lining

  - very thin walls

  - good blood supply
• how are gills adapted for absorption?


  - gill filaments gave a very high SA as well as lamelae

  - good blood supply

  - thin surface layer

  - large concentration gradient
• Ribosomes are responsible for protein synthesis.
• Mitochondria produce energy through respiration.
• The nucleus is the control centre of the cell, containing DNA which controls all activities within the cell.
• 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