Cells

• Cells are the building blocks of life.
• many chemical reactions occur continuously inside the cells eg. photosynthesis & aerobic respiration
• cell consists of living material called protoplasm
• protoplasm is a jelly like substance and Carries out many chemical activities that allow the cell to survive and grow
• Cell surface membrane

  • made up of lipids and proteins
  • partially permeable membrane (allows only some substances to pass through)
  • controls the movement of substances in and out of the cell
• Cellulose cell wall

  • fully permeable
  • protects the cell from injuries and prevents the cell from bursting
  • supports and gives a regular shape
• Cytoplasm

  • Most cell activities occur here
  • contains organelles (cellular structures that perform a specific job within a cell) such as mitochondria, endoplasmic reticulum, Golgi body, ribosomes
  • only visible under electron microscope
• Parts of cytoplasm

  • nucleus
  • RER
  • SER
  • ribosomes
  • golgi body
  • mitochondrion
  • chloroplasts
  • vacuole
• Nucleus

  • surrounded by the nuclear membrane
  • contains genetic info. in form of chromosomes (made up of proteins & DNA)
  • (Function) controls cell activities eg. Cell division, protein synthesis & essential for cell division
• During cell division, chromatin threads coil, condense and shorten to form chromosomes, which can only be seen when the cell is actively dividing
• RER

  • appears rough when viewed under the electron microscope due to the ribosomes attached to its outer surface.
  • Outer surface is attached to the nuclear membrane
  • (function) transports proteins made by ribosomes to the Golgi body for secretion out of the cell
• SER

  • tubular, connected to the RER & does not have ribosomes attached
  • (Function) synthesises substances such as fats and steroids(sex hormones, testosterone) & converts harmful substances into harmless substances through a process known as detoxification done in the liver mainly
• Ribosomes

  • small round structures attached to the RER or lie freely in the cytoplasm
  • (function) synthesis proteins
  • the ones attached to the RER synthesise proteins that are transported out of the cell
  • the ones lying freely synthesise proteins that are used within the cytoplasm of the cell
• Golgi body

  • (function) chemically modifies substances made by ER & stores and packages the substances in vesicles(tiny spherical spaces enclosed by a membrane, transports substncaes within the cell) for secretion out of the cell
  • vesicles can be seen fusing with one side of the Golgi body & pinching off from the opposite side
• process of secretion of cell (golgi body)

  1. substances made by the ER are pinched off from the ER through small vesicles
  2. vesicles fuse with the Golgi body & release their contents into the Golgi body
  3. substances made by the ER may be modified in the golgi body
  4. secretory vesicles containing the modified substances are pinched off from the golgi body
  5. vesicles move to the cell surface membrane and fuse and their contents are released
  6. substances are released out of the cell
• What are the types of organelles in the cytoplasm

  Mitochondria, endoplasmic reticulum, nucleus, Golgi body,
• Mitochondria

  • aerobic respiration occurs here
  • small oval and sausage shaped & has a double membrane
  • (function) oxidises glucose to release a large amount of energy during aerobic respiration. Energy released is used for many cellular activities such as active transport, cell division, muscle contraction
• Chloroplasts

  • site for photosynthesis
  • contains a green pigment called chlorophyll(absorbs light energy to be converted into CPE stored in glucose during photosynthesis)
• Vacuoles

  • fluid filled space enclosed by a partially permeable cell surface membrane
  • (function) maintain water potential for absorption of water & exert turgor pressure to keep plant cells turgid
  • stores substances within a cell
  • animals cells have many temporary, small vacuoles containing water & dissolved food molecules(eg. Glucose, amino acids)
  • plant cells have a singular, large central vacuole containing cell sap(contains dissolved substances eg. sugars, mineral salts, amino acids)
• differentiation is the process by which a cell becomes specialised for a specific function
• RBC and its adaptations

  • (function) transports oxygen from lungs to all body cells
  • lacks a nucleus - enables the cell to store more haemoglobin to transport more oxygen to all body cells
  • contains haemoglobin - haemoglobin binds with oxygen to form oxyhemoglobin and transports oxygen from lungs to all body cells
  • circular and biconcave shape - increases surface area to volume ratio so that more oxygen can diffuse in and out of the RBC at a faster rate
  • elastic (flexible) - allows the RBC to squeeze through blood vessels smaller than itself easier
• Root hair cells and its adaptations

  • (function) absorption of water & dissolved mineral salts from the soil
  • has a long and narrow protrusion which increases the surface area to volume ratio to absorb water and dissolved mineral salts from the soil at a faster rate
• Muscle cells

  • contains many mitochondria
  • a large amount of energy is released through aerobic respiration in the mitochondria to provide energy for muscle cells to contract & relax
• Why does the RBC lack a nucleus

  To store more haemoglobin to transport more oxygen from lungs to body cells