2.1 cell structure

• Nucleus is surrounded by a double membrane called the envelope containing pores which enable molecules to enter and leave the nucleus. The nucleus also contains chromatin and a nucleolus which is the site of ribosome production
• • Rough endoplasmic reticulum which is a series of flattened sacs enclosed by a membrane with ribosomes on the surface. RER folds and processes proteins made on the ribosomes.
• • Smooth endoplasmic reticulum is a system of membrane bound sacs. SER produces and processes lipids.
• • Golgi apparatus is a series of fluid filled, flattened & curved sacs with vesicles surrounding the edges. Golgi apparatus processes and packages proteins and lipids. It also produces lysosomes.
• • Mitochondria are usually oval shaped, bound by a double membrane called the envelope. The inner membrane is folded to form projections called cristae with matrix on the inside containing all the enzymes needed for respiration.
• • Centrioles are hollow cylinders containing a ring of microtubules arranged at right angles to each other. Centrioles are involved in cell division.
• • Ribosomes are composed of two sub units and are the site of protein production
• • Lysosome is a vesicle containing digestive enzymes bound by a single membrane
• • The cytoskeleton of the cell plays an important role in providing mechanical strength as well as aiding transport within cells and enabling cell movement.
• (prokaryote) Cell wall –Rigid outer covering made of peptidoglycan
• • (prokaryote) Capsule – Protective slimy layer which helps the cell to retain moisture and adhere to surfaces
• •(prokaryote) Plasmid –Circular piece of DNA
• •(prokaryote) Flagellum- a tail like structure which rotates to move the cell
• • (prokaryote) Pili- Hair-like structures which attach to other bacterial cells
• •(prokaryote) Ribosomes- Site of protein production
• Protein transport:

  • Proteins are produced on the ribosomes

  • Proteins which are produced on the surface on RER are folded and processed in the RER

  • The proteins are then transported from the RER to the Golgi apparatus in vesicles

  • They are then modified in the Golgi apparatus

  • Golgi apparatus packages proteins into vesicles to be transported around the cells to where they’re required. Some of the proteins such as extracellular enzymes leave the cell by exocytosis.