Chapter 1

• Cells


  The basic building blocks of life
• Cells


  • Take in raw materials
  • Carry out chemical reactions to convert raw materials to new molecules
  • Use the new molecules to fulfil different functions
  • Like chemical factories that carry out different functions to keep us alive
• Cell


  A mass of living matter called protoplasm
• Protoplasm


  • Made up of cell membrane, cytoplasm, and nucleus
• Cell membrane


  Surrounds the cytoplasm, made of lipids and proteins, partially permeable
• Cell wall


  Surrounds the cell membrane in plant cells, made of cellulose, fully permeable
• Cytoplasm


  Found between the cell membrane and the nucleus, site of cellular activities, contains organelles
• Nucleus


  Controls cell activities, essential for cell division, contains chromosomes and nuclear membrane
• Chromosomes


  • Long thread-like structures made of DNA, condense into thick rod-shaped structures during cell division
• Nuclear membrane


  Separates the contents of the nucleus from the rest of the cytoplasm
• Organelles in the cytoplasm

  • Endoplasmic reticulum (rough and smooth)
  • Ribosomes
  • Golgi body
  • Mitochondria
  • Chloroplasts
  • Vacuole (large and central in plant cells, small and numerous in animal cells)
• Rough endoplasmic reticulum (RER)


  Network of flattened spaces lined with a membrane, surface studded with ribosomes, transports proteins made by the ribosomes to the Golgi apparatus
• Ribosomes


  Responsible for protein synthesis, small round structures either attached to RER or lie freely in cytoplasm
• Smooth endoplasmic reticulum (SER)

  More tubular than RER, does not have ribosomes attached, synthesises substances such as fats and steroids, involved in detoxification
• Golgi body (Golgi apparatus)


  Consists of flattened spaces surrounded by membranes, chemically modifies substances from the ER, stores and packages the substances in vesicles for secretion out of the cell
• Golgi body function


  1. Vesicles containing substances made by the ER pinch off from the ER

  2. Vesicles fuse with the Golgi body releasing the substances made by the ER which may be modified

  3. Secretory vesicles containing modified substances pinch off from the Golgi body and move towards the cell membrane

  4. Secretory vesicles fuse with the cell membrane and their contents exit the cell
• Mitochondria


  Oval or sausage-shaped organelles, site of aerobic respiration
• Vacuole


  Fluid filled space enclosed by a partially permeable membrane, large and central in plant cells, small and numerous in animal cells
• Robert Hooke first coined the term 'cells' in 1667
• Most cells are too small to be seen, light and electron microscopes can be used to see cells and their parts

  
• Inventors of microscopes: Robert Hooke and Anton van Leeuwenhoek
• Cameras can be fitted to the microscope to take pictures called micrographs

  
• Cutting cells along the length and across the length provides different perspectives
• Looking at cells from different perspectives is important
• Vesicle formation and secretion

  1. Vesicles containing substances made by the ER pinch off from the ER

  2. Vesicles fuse with the Golgi body releasing the substances made by the ER which may be modified

  3. Secretory vesicles containing modified substances pinch off from the Golgi body and move towards the cell membrane

  4. Secretory vesicles fuse with the cell membrane and their contents exit the cell
• Golgi body


  • Stores and packages the substances in vesicles for secretion out of the cell
• Mitochondria


  • Oval or sausage-shaped organelles
  • Site of aerobic respiration, a process where glucose is oxidized/broken down in the presence of oxygen to release energy for cellular activities
• Vacuole


  • Fluid filled space enclosed by a partially permeable membrane
  • Stores substances within the cell
  • In a plant cell: usually has one large central vacuole that consists of substances such as sugars, mineral salts and amino acids
  • In an animal cell: usually has numerous small vacuoles that store water and food substances, exist temporarily
• Chloroplasts


  • Oval structures found in plant cells
  • Contains a green pigment called chlorophyll, which absorbs light energy for photosynthesis to occur
• Plant cells have a cell wall, a large central vacuole, and chloroplasts, while animal cells do not have a cell wall, have numerous small vacuoles, and no chloroplasts
• Complete Worksheet 1A on Cell Structures as homework
• Explain how the structures of specialised cells are adapted to their functions
• When we think of basketballers, we tend to associate them with being very tall. Why?
• In biology, always think about structure to function relationships
• Differentiation


  The process by which a cell becomes specialised for a specific function
• Red blood cell


  • Contains haemoglobin
  • Circular biconcave shape increases surface area-to-volume ratio for increased rate of oxygen uptake
  • Absence of nucleus allows packing of more haemoglobin for transport of oxygen
  • Flexible to easily squeeze through capillaries
• Root hair cell


  • Long and narrow extension increases surface area-to-volume ratio for increased rate of absorption of water and mineral salts
  • Maintains a lower water potential in vacuole to allow water to enter the root hair cell via osmosis
• Muscle cell


  • Contain many mitochondria to provide energy for contraction
  • Has contractile protein fibres to contract and relax to bring about movement
  • Has many nuclei to allow for cell division
• Stem cells can develop into other specialised cells
• Scientists can grow cells of different organs in the laboratory and transplant them into humans