B1 - Cell biology

• Eukaryotic cells

  Complex cells that include all animal and plant cells
• Prokaryotic cells


  Smaller and simpler cells, e.g. bacteria
• Prokaryote

  A single celled organism
• Animal cell

  • Nucleus- contains genetic material & controls activities of cell
  • Cytoplasm- gel like substance where chemical reactions happen
  • Cell membrane- controls what goes in and out
  • Mitochondria- reactions where aerobic respiration take place
  • Ribosomes- protein is made
• Plant cell

  • Rigid cell wall- made of cellulose, supports cell & strengthens it
  • Permanent vacuole- contains cell wall
  • Chloroplasts- where photosynthesis occurs, contains green substance called chlorophyll (needs light needed for photosynthesis)
• Cells differentiate to become specialised for their function.

  Differentiation - cell changes to become specialised for its job

  Some cells are undifferentiated - stem cells
• Sperm cells:

  • specialised for reproduction.
  • long tail
  • streamlined head to help swim to egg
  • a lot of mitochondria needed to provide energy
  • carries enzymes
• Nerve cells:

  • specialised for rapid signalling
  • carry electrical signals
• Muscle cells:

  • contracts quickly
  • contains lots of mitochondria to generate energy needed for contraction.
• Root hair cells:

  • specialised for absorbing water & minerals
  • gives plant large surface area to absorb water & mineral ions from soil
• Phloem & Xylem:

  • transport substances (food & water) around plants
  • Xylem cells are hollow In centre
  • Phloem cells have very few sub cellular structures
• Chromosomes:

  • contain genetic Information
  • coiled up in lengths of DNA molecules
  • different genes control different characteristics
  • body cells have two copies of each chromosome
• Cell cycle:

  • body cells in multicellular organisms divide to produce new cells
  • cell division is called mitosis
  • multicellular organisms use mitosis to grow or replace cells that have been damaged
• Diffusion:

  • spreading out of particles from high concentration to low concentration
• Diffusion:

  • bigger the concentration gradient, faster diffusion rate
  • higher temperature gives faster diffusion rate, particles have more energy
• Cell membranes:

  • only small molecules diffuse through cell membranes (oxygen, glucode, amino acids, water)
  • Big molecules (starch, proteins) can’t fit through membrane
• Osmosis:

  • movement of water molecules across a partially permeable membrane from high concentration to low concentration
• Active transport:

  • substances absorbed from a low concentration to a high concentration
• Gas exchange:

  • happens in lungs
  • job of lungs (transfer oxygen to blood & remove waste carbon dioxide
• Alveoli:

  • specialised to maximise diffusion of oxygen & carbon
  • large surface area
  • moist lining to dissolve gases
  • thin walls
  • good blood supply
• Villi:

  • provides big big surface area
  • millions of villi covers small intestine
  • single layer of surface cells
  • very good blood supply
  • increase surface area to absorb digested food into blood