🏥 Chapter 1 - Cell Structure

• Protoplasm

  It is living material consisting of the nucleus, cytoplasm and cell (surface) membrane. This is present in both plant and animal cells.

  
• cell membrane

  A partially permeable structure that controls movement of substances in and out of a cell. It is made of lipids and proteins. This is present in both plant and animal cells.

  
• cell wall

  It is a fully permeable structure, thus not controlling movement of substances. This structure protects cell from injury and gives it a rigid, fixed shape. It is made of cellulose, and this structure is ONLY found in plant cells

  
• cytoplasm

  It is a gel-like fluid in the cell where numerous chemical reactions occur, as well as containing organelles. This is present in both animal and plant cells

  
• organelles

  These are cellular structures that perform specific functions within the cell. This is present in both animal and plant cells

  
• nucleus

  It is an organelle surrounded by nucleus membrane, and this organelle controls all activities in the cell including cell growth and repair, is responsible for cell division, and also contains hereditary information in the form of chromosomes made of protein and deoxyribonucleic acid (DNA). This is present in both animal and plant cells

  
• vacuole


  (For Animal Cell) This organelle is small and numerous and is present in the cell to store water and food substances. It is partially permeable

  
  

  (For Plant Cell) This organelle is large and central, and contains cell sap, that contains dissolved substances such as mineral salts, sugars and amino acids

  
• Mitochondrion (plural: Mitochondria)

  It is a oval shaped organelle that carries out aerobic respiration to release energy from food. Energy released is then used for cell activities such as cell growth and repair. This is present in both animal and plant cells.

  
• Chloroplast


  They are green-colored organelle that contain chlorophyll to trap light for photosynthesis. They are ONLY found in plant cells

  
• ribosomes


  These are small round structures that synthesise proteins, and are either:

  (Attached to RER) Synthesise proteins to be transported OUT of the cell or to other organelles

  or:

  (Floating freely in the cytoplasm) Synthesise proteins to be used WITHIN the cytoplasm of the cell

  
  

  This is present in both animal and plant cells

  
• rough endoplasmic reticulum (RER)


  The RER membrane is continuous with the nucleus membrane and has a rough texture because ribosomes are attached to its surface. Their function is to assemble and transport proteins synthesised by the ribosomes to the Golgi Apparatus for secretion out of the cell. This is present in both animal and plant cells

  
• Smooth Endoplasmic Reticulum (SER)

  They do not have ribosomes attached to it hence the smooth texture. Their functions is to synthesise fat and steroids, as well as undergoing detoxification, which converts harmful substances, such as drugs and toxins, into harmless substances

  
• Golgi Body (Apparatus)

  It is flattened membrane-bound sacs that look like a disc. Its function is to chemically modify substances made by the ER. It stores and packages the modified substances into vesicles for secretion out of the cell.

  
• Vesicles


  They transport substances within a cell

  
• How does ER and the Golgi apparatus work together to move substances made by the ER out of the cell?

  1) Substances made by the ER are packaged into vesicles and pinch off from the ER

  
  

  2) The vesicles ae transported to the Golgi apparatus

  
  

  3) The vesicles fuse with the membrane of the Golgi Apparatus to release the substances inside it

  
  

  4) Once the substances are further modified by the Golgi apparatus, they are packaged into secretory vesicles and pinch off the Golgi Apparatus.

  
  

  5) The secretory vesicles are transported to the cell membrane, where the fuse with the cell membrane to release its contents out of the cell

  
• Differentiation


  process where by the cell becomes specialised to perform a specific function.

  
• Examples of differentiation


  1) Red Blood Cells- They contain haemoglobin to transport O2 more efficiently, have no nucleus to store more haemoglobin, and have a biconcave shape to increase surface area -to- volume ratio to allow for faster diffusion of O2

  
  

  2) Muscle cell - they contain mitochondria to release energy for muscle cell contraction

  
  

  3) Root hair cell- Has an elongated structure to increase surface area -to- volume ratio to allow substances such as mineral salt and water to be absorbed faster

  
• magnification of drawing 


  X(drawing size / specimen actual size)