Cell biology

• • Eukaryotic cells include plants & animal cells
  • Prokaryotic include bacterial cells
• Animal & cell structure

  cell membrane - controls what substances can pass in & out of the cell

  Nucleus - holds, genetic material

  cytoplasm - where chemical reactions take place

  Mitochondria - Provide the cell with energy in order for the cell to function

  Ribosomes - is where protein is made
• plant cells structure

  • also contain chloroplast in which photosynthesis happens
  • Also contains a permanent vacuole containing the cell sap
• Specialise cells in animals

  • Sperm cell
  • nerve cells
  • muscle cells
• Specialise cells in plants

  • Root hair cells
  • Xylem cells
  • phloem cells
• Cell differentiation is important as it allows us to specialise and perform specific functions in an organism
• Plant cells - Differentiation happens throughout life
• Animal cells - differentiation happens at early stage of life
• Explain how electron microscopy has increased understanding of sub cellular structures

  Electron microscopy have a higher magnification, then light microscopy & so you can see final details. this has enabled biologist to see an understand subcellular structures
• Magnification = size of image / size of real object
• A nucleus of a cell contains chromosomes made up of DNA molecules. Each chromosome carries a large number of genes
• stages of cell cycle

  • Growth
  • DNA replication & mitosis
  • Division (cytokinesis)
• Cell cycle

  • Firstly, the cell grows in which increases the number of sub cellular structures e.g ribosomes & mitochondria
  • Then the DNA duplicates forming two sets of chromosomes
  • In which mitosis takes place & chromosomes it’s pulled to each side of the cell
  • The nucleus divides
  • Cytoplasm & cell membrane also divides causing two identical cells
• Cells in animals

  • Sperm cell is reproduction in which is to get the male DNA to a female dna
  • Muscle cells function is to contract quickly
  • Nerve cells function is to carry electrical signals
• Cells in plants

  • Root hair cells absorb, water and minerals
  • Xylem & Phloem transport substances such as food and water
• Cell division in mitosis is important in growth and development of multicellular organisms
• Stem cells - cells that can divide to produce more cells of the same type.
• Stem cells can come from early human embryos, in which can be cloned, and made a differentiate into most different types of human cells
• Stem cells from adults in bone marrow, can form many types of cell, including blood cells E.G red blood cells & white blood cells
• Meristem can differentiate into many types of plant cells throughout the life of a plant
• Pros of stem cells

  • Species can be cloned to prevent extinction
  • Stem cells produce clones in plants which is quicker & cheaper
  • Cure diseases such as paralysis & diabetes
  • Grow crops with special features, such as disease resistance
• Cons of stem cells

  • virus transmission
  • Embryos have potential for human life
  • Tumor development
  • Destroying of embryos
• Diffusion - substances move in and out of the cell through the cell membrane
• Diffusion moves from a higher concentration to a lower concentration
• A single cell organism has a relatively large surface area of volume ratio. This allows sufficient transport of molecules in and out of the cell to meet the needs of the organism.
• Explain how the small intestines & lungs in mammals, gills in fish & the roots are leaves and plants are adapted for exchange materials

  Multicellular organisms, surfaces & Organ systems are specialised for exchange and materials. This allows sufficient transport of molecules in out of the cell to meet the needs of the organisms.
• The effectiveness of an exchange surface is increased by

  • Having a large surface area
  • A membrane that is to provide a short diffusion path
• Osmosis the diffusion of water from a dilute solution to a concentrate solution through a partially permeable membrane
• Percentage change = (new value - old value) / old value x 100
• Active transport is the movement of molecules from an area of low concentration to an area of high concentration against a concentration gradient
• Differences in osmosis, diffusion & active, transport

  -Diffusion & osmosis is from a high to lower concentration

  -osmosis only takes place with water

  -Active transport requires additional energy from respiration
• osmosis practical

  • cut up your potatoes into 5 pieces making sure they’re all the same size
  • measure the length & mass of each cylinder
  • place each cylinder into a test tube in which one test tube will be a sugar solution
  • the rest will be pure water
  • leave for 24 hours
  • take the cylinders out pat dry
  • measure length & mass again
  • work out percentage change
• specialised cells - cells that have specific structures & functions in the body