2. Basic Components of Living Systems

• Plasma membrane.

  The membrane found on the surface of animal cells and just inside the cell wall of plant cells and prokaryotic cells. It's made phospholipids and proteins.
• The function of the plasma membrane.

  Regulating the movement of substances into and out of the cell. it also has receptor molecules on it, which allow it to respond to chemicals like hormones.
• Cell wall.

  A rigid structure that surrounds plants cells. It is made mainly of cellulose.
• The function of the Cell wall.

  Supports plant cells.
• Nucleus

  A large organelles surrounded by a nuclear envelope (double membrane), which contains many pores. The nucleus contains chromatin and a structure called the nucleolus.
• The function of the nucleus.

  the nucleus controls the cell's activities by controlling transcription of DNA. DNA contains instructions to make proteins. The pores allow substances to move between the nucleus and the cytoplasm. The nucleolus makes ribosomes.
• Lysosomes.

  Round organelles surrounded by a membrane, with no clear internal structure.
• Ribosomes.

  Very small organelles that either float free in the cytoplasm or is attached to the rough endoplasmic reticulum. Made up of proteins and RNA. Not surrounded by a membrane.
• Rough Endoplasmic Reticulum.

  A system of membranes enclosing a fluid-filled space. The surface is covered with ribosomes.
• The function of the RER

  Folds an processes proteins that have been made at the ribosomes.
• Smooth endoplasmic reticulum


  Similar to the RER, but with no ribosomes.
• Function of SER

  Synthesises and processes lipids.
• Vesicles. 


  Small fluid-filled sac in the cytoplasm, surrounded by a membrane.
• Function of vesicles. 


  Transports substances in and out of the cell via the plasma membrane and between organelles. Some are formed by the Golgi apparatus or the endoplasmic reticulum, while others are formed at the cell surfaces.
• Golgi apparatus


  A group of fluid-filled, membrane-bound, flattened sacs. Vesicles are often seen at the edges of the sacs.
• Function of Golgi apparatus


  Processes and packages new lipids and proteins. It also makes lysosomes.
• Mitochondrion

  Oval shaped organelles with a double membrane - the inner one is folded to form structures called cristae. Inside is the matrix, which contains enzymes involved in respiration.
• Function of mitochondria

  The site of aerobic respiration, where ATP is produced. They're found in large numbers in cells that are very active and require a lot of energy.
• Chloroplasts


  A small, flattened structure found in plant cells, surrounded by a double membrane, and also has membranes inside called thylakoid membranes. These membranes are stacked up in some parts of the chloroplast to form grana. Grana are linked together by lamellae - thin, flat pieces of thylakoid membrane.
• Centrioles


  Small, hollow cylinders, made of microtubules (tiny protein cylinders). Found in animal cells, but only some plant cells.
• Function of chloroplasts


  The site where photosynthesis takes place. Some parts of photosynthesis happen in the grana, and other parts happen in the stroma (a thick fluid found in chloroplasts).
• Function of centrioles


  Involves with the separation of chromosomes during cell division.
• Cilia


  Small, hair-like structures found on the surface membrane of some animal cells. In cross-section, they have an outer membrane and a ring of nine pairs of protein microtubules inside, with two microtubules in the middle.
• The function of cilia


  The microtubules allow the cilia to move. This movement is used by the cell to move substances along the cell surfaces.
• Flagellum

  Flagellum on eukaryotic cells are like cilia but longer. They stick out from the cell surface and are surrounded by the plasma membrane. Inside they're like in the centre and nine pairs around the edge.
• The function of the flagellum


  The microtubules contract to make the flagellum move.
• The cytoskeleton has four main functions: 


  1. The microtubules and microfilaments support the cell's organelles, keeping them in position.
  2. Helps to strengthen the cell and maintain shape.
  3. Responsible for the movement of materials with in the cell.
  4. The proteins of the cytoskeleton can cause the cell to move.
• Proteins are made at the ribosomes
• The ribosomes on the rough endoplasmic reticulum make proteins that are excreted or attached to the cell membrane. The free ribosomes in the cytoplasm make proteins that stay in the cytoplasm.
• New proteins produced at the RER are folded and processed in the rough ER. Then, they're transported from the ER to the golgi apparatus in vesicles.
• At the Golgi apparatus, the proteins may undergo further processing. The proteins enter more vesicles to be transported around the cell.
• Prokaryotes have extremely small cells, and eukaryotes are larger.
• Prokaryotic DNA is circular, eukaryotic DNA is linear.
• Prokaryotes have no nucleus.
• Prokaryotic cell walls are made of a polysaccharide, but no cellulose or chitin.
• Eukaryotic animal cells have no cell wall, plant cell walls are made of cellulose, and fungi cell walls are made of chitin.
• Prokaryotic cells have few organelles and no membrane-bound organelles, like no mitochondria, and eukaryotic cells have many organelles and membrane-bound organelles, like mitochondria.
• Prokaryotic cells have small ribosomes, eukaryotic cells have larger ribosomes.
• Prokaryotes like bacteria are roughly a tenth the size of eukaryotes, so normal microscopes are not powerful enough to look at their internal structure.
• Magnification formula

  Magnification = image size / object size