cells

• Cells


  • They are the building blocks of life
  • They have all the characteristics of life
  • Many chemical reactions occur in the cell
• • Some medicines are more effective when they target cells
  • Some even target genes
  • Bacteria are cells, cancer is caused by crazy cells
• Microscopes


  • Used to see cells and their parts
  • Cameras can be fitted to take pictures called micrographs
• Micrographs

  • Electron micrograph of fly
  • Electron micrograph of human nose hair with pollen grain
  • Electron micrograph of human tongue
  • Red blood cells in blood vessel
  • Bacterial cells
• Longitudinal section


  Cutting along the long axis of the cell
• Transverse section


  Cutting at right angles to the longitudinal plane
• Cell


  • Living material called protoplasm
  • Made up of cell surface membrane, cytoplasm, and nucleus
• Cell membrane/Plasma membrane


  • The 'outer covering' of the cell
  • Partially permeable - controls what enters and exits the cell
• Cytoplasm


  • The place where most cell activities happen
  • Contains specialised structures called organelles
• Nucleus


  • Surrounded by a nuclear envelope
  • May contain one or more nucleoli and chromatin
  • Controls cell activities like cell division
  • Chromatin is made up of DNA which carries hereditary information
• Cell wall


  • Found in plant cells but absent in animal cells
  • Made of cellulose
  • Protects the cell from injuries and gives the cell shape
  • Fully permeable
• Endoplasmic reticulum (ER)


  • Two types: Rough ER (RER) and Smooth ER (SER)
  • RER transports proteins to the Golgi apparatus
  • SER synthesises substances like fats and steroids, and is involved in detoxification
• Ribosomes


  • Two kinds: free ribosomes and ribosomes on RER
  • Synthesise proteins
• Golgi apparatus


  Modifies substances made by the ER and packages them in vesicles for secretion out of the cell
• Mitochondria


  Perform aerobic respiration to release energy
• Vacuoles


  • Animal cells have many vacuoles containing water and food substances
  • Plant cells have a large central vacuole containing cell sap
• Chloroplasts


  Oval structures containing chlorophyll required for photosynthesis
• Animal cell


  • Organelles: rough ER, nucleus, smooth ER, ribosomes, vesicles, Golgi apparatus, vacuole, mitochondria
• Plant cell


  • Organelles: chloroplast, cell wall, cell membrane, nucleus, cytoplasm
• Differences between animal and plant cells: cell wall present in plant cells, chloroplasts present in plant cells, numerous small vacuoles in animal cells, large central vacuole in plant cells, centrioles present in animal cells
• Protein production


  1. Nucleus contains information for making proteins and passes it to RER

  2. Ribosomes on RER make the proteins

  3. RER transports proteins to Golgi apparatus

  4. Golgi apparatus modifies and packages proteins in secretory vesicles

  5. Secretory vesicles fuse with cell membrane to release proteins outside the cell
• Red blood cells


  • Contains haemoglobin to transport oxygen
  • No nucleus to carry more haemoglobin
  • Biconcave shape to increase surface area to volume ratio
• Root hair cells


  • Long and narrow to increase surface area to volume ratio for faster absorption of water and minerals
• Xylem vessels


  • Long hollow tubes with no cross walls to allow uninterrupted water flow
  • Walls thickened with lignin to prevent collapsing
• Cells


  Specialised for a particular function
• Tissue


  A group of similar cells working together to perform a specific function
• Organ


  Different tissues working together to carry out a specific function
• Organ system


  Several related organs working together to carry out a particular function
• Simple tissues


  • Muscle tissue
• Complex tissues


  • Blood, nerve tissue, phloem tissue
• Organs in humans


  • Brain, heart, kidneys
• Organs in plants


  • Leaves, flowers
• Organ systems in humans

  • Digestive system, respiratory system
• Organ systems in plants

  • Shoot system, root system