Topic. 1 - cell biology

• Eukaryotic cells


  A type of cell found in animals and plants that contain a nucleus
• Genetic material


  A chemical called DNA that forms structures called chromosomes contained within the nucleus
• Organisms with eukaryotic cells

  • Animals
  • Plants
  • Fungi
  • Protista
• Prokaryotic cells


  A type of single-celled organism found in bacteria that does not contain a nucleus, much smaller in comparison to eukaryotic cells
• Prokaryotic cells


  • 0.2-2.0 µm in length
  • 1-2 orders of magnitude smaller than eukaryotes
• Organelle


  A specialised structure found inside a cell
• Specialised cell


  Cells that are adapted to perform a specific function
• Stem cell


  An undifferentiated cell that can divide to produce many specialised cells of the same type
• Cell membrane


  A partially permeable barrier that surrounds the cell
• Cell wall


  An outer layer made of cellulose that strengthens plant cells
• Chloroplasts


  An organelle which is the site of photosynthesis
• Mitochondria


  An organelle which is the site of respiration
• Nucleus


  An organelle found in most eukaryotic cells that contains the genetic material of the cell and controls the activities of the cell
• Plasmid


  Loops of DNA found in the cytoplasm of prokaryotic cells
• Vacuole


  An organelle that stores cell sap
• Cytoplasm


  Gel-like substance which contains enzymes
• Ribosomes


  Where proteins are made
• Functions of parts of cells

  • Nucleus controls activities of cell
  • Cytoplasm location of many chemical reactions
  • Mitochondria location where aerobic respiration occurs and most of the cell's ATP is produced
  • Ribosomes location where amino acids are connected together to produce proteins
  • Cell membrane controls which substances can enter and leave the cell
  • Cell wall supports and strengthens cell
  • Vacuole water storage and maintenance of turgor within the cell
  • Chloroplast location where photosynthesis occurs and sugar is produced
  • Plasmids contain genes that help cells to function, eg genes for antibiotic resistance
  • Slime capsule can protect the bacteria from some toxic chemicals
• These differences in cells are controlled by genes in the nucleus
• Functions of specialised cells

  • Nerve cell - carry nerve impulses around the body
  • Sperm cell - carry the father's genetic information (DNA) when fertilising the egg
  • Ciliated cell - designed to stop lung damage, the hairs sweep mucus with dust back up the throat to be swallowed
  • Egg cell - carries the mothers DNA and supports the growing embryo
  • Red Blood cell - carries oxygen from the lungs to the body
  • Palisade cell - to carry out photosynthesis
  • Root Hair cell - absorb minerals and water from soil
  • Xylem - transport dissolved sugars and amino acids up and down the stem
  • Phloem - they support the plant
  • Muscle cells - function to contract quickly
• Cell differentiation


  The process by which a cell changes to become specialised for its job
• As cells change, they develop different subcellular structures and turn into different types of cells
• Most differentiation occurs as an organism develops. In most animal cells, the ability to differentiate is then lost at an early stage, after they become specialised. However, lots of plant cells don't ever lose this ability
• The cells that differentiate in mature animals are mainly used for repairing and replacing cells, such as skin or blood cells
• Stem cells


  Undifferentiated cells that can divide to produce many specialised cells of the same type
• Chromosomes


  Coiled up lengths of DNA molecules that contain genes which control our characteristics
• Body cells normally have two copies of each chromosome - one from the organisms 'father' and one from the 'mother'
• Gene


  A combination of two alleles that codes for a specific protein
• Mitosis


  When a cell reproduces itself by splitting two from to identical offspring with the same number of chromosomes
• Cell cycle


  1. Growth and replication

  2. Mitosis
• Uses of mitosis in multicellular organisms

  • Growth
  • Repair
  • Asexual reproduction
• What happens during the cell cycle

  1. Growth and replication

  2. Mitosis
• Stem cells


  Undifferentiated cells of an organism which are capable of dividing and giving rise to many more cells of the same type
• Stem cells: Animals vs Plants

  • Embryonic stem cells in animals help form all tissues and organs
  • Adult stem cells in animals replace damaged cells
  • Meristem cells in plants can differentiate into any plant cell type
• It is possible to grow human embryos in the lab and to extract embryonic stem cells from them
• Scientists and doctors could use stem cell technology to repair damaged organs by growing new tissue from stem cells produced by embryos created using genetic information from the patient
• Therapeutic cloning


  Producing an embryo with the same genes as the patient to obtain stem cells that will not be rejected by the patient's body
• Evaluating stem cells in medicine

  • Ethical issues
  • Potential to cure diseases
  • Availability of plant stem cells without ethical objection
• Light microscope


  Uses light and lenses to form an image of a specimen and magnify it
• Electron microscope


  Uses electrons instead of light to get an image, has a much larger magnification and resolving power than light microscopes