ANSWERS

1. What do the cells of the body together form?
   Tissues.
2. What are the main differences between eukaryotic and prokaryotic cells?
   • Eukaryotic - have a nucleus and nuclear membrane (covers most living organisms).
   • Prokaryotic - have no distinct nucleus and nuclear membrane (found primarily in bacteria, and occasionally fungi).
3. What is a macrophage?
   A large cell with a phagocytic role, serving to engulf and remove foreign material from the body. There are 3 main types:
   • Monocytes - present in the blood.
   • Histiocytes - present in connective tissue.
   • Buffer cells - present in the liver.
4. What is phagocytosis?
   The ingestion of solid substances required by the cell.
5. What is pinocytosis?
   The ingestion of liquid substances required by the cell.
6. What is a mast cell?
   A leukocyte with agranular cytoplasm which produces histamine and promotes inflammation. It is active in immune response.
7. What structures are common to most cells?
   • Chromosomes.
   • Endoplasmic reticulum.
   • Mitochondria.
   • Ribosomes.
8. What is the average size of most animal cells?
   10-100um (one-hundredth to one tenth of a millimetre); prokaryotic cells are smaller at 1-10 um.
9. What type of microscope provides the most effective visualisation of cells?
   An electron microscope.
10. Is it the number of cells or the size of the cells that determines the actual size of an animal?
    The number of cells (although over-nutrition of a growing animal will mean that cell size will increase and that animal will be predisposed to obesity throughout the rest of its life).
11. What is the material of which cells are made called?
    Protoplasm.
12. What are the 2 main components of a cell?
    • Nucleus.
    • Cytoplasm.
13. What are organelles?
    Organised units of living material within the cytoplasm of the cell with important specific functions. Examples include mitochondria and ribosomes.
14. What is the name given to accumulations of cell products often of a temporary nature, such as lipids, pigments and secretory droplets?
    Cytoplasmic inclusions.
15. Name 2 pigments that may be found within the cytoplasm.
    • Haemosiderin - a golden brown pigment associated with haemoglobin breakdown.
    • Melanin - brown or black granules associated with pigmented areas of the body.
16. What is the cell membrane made of?
    Phospholipids.
17. The cell membrane is described as selectively permeable. What is the significance of this?
    The cell membrane acts as a diffusion barrier and selectively allows certain substances in and out of the cell by osmosis (the passage of fluid from a low concentration to one of a higher concentration through a semi-permeable membrane).
18. What is the purpose of microvilli?
    Microvilli are finger-like projections which increase the surface area of the cell membrane.
19. What is the function of mitochondria?
    Mitochondria are the "power packs" of the cell. They contain enzymes responsible for the release of energy and various synthetic pathways. They are involved in protein metabolism.
20. What organelle has a secretory function?
    The Golgi apparatus (or Golgi body); this is particularly common in glandular cells.
21. What is the function of ribosomes?
    Ribosomes contain RNA responsible for the production of protein to be used within the cell.
22. Where within the cell are the ribosomes produced?
    The nucleolus.
23. What is the name of the membranous compartments within the cell that contain enzymes which serve to breakdown organic compounds?
    Lysosomes.
24. What is the term that describes the death of a cell?
    Lysis.
25. What is the name given to the dense area of cytoplasm close to the nucleus which contains the centrioles?
    The centrosome (or centrosphere).
26. With what role are the centrioles associated?
    Reproduction.
27. What part of the cell is its control centre?
    The nucleus; this contains DNA which governs the activities of the cytoplasm - particularly reproduction, and controls heredity.
28. What are vacuoles?
    Spaces within the cytoplasm. They are a product of phagocytosis or secretion and are the hole that is left following digestion.
29. The endoplasmic reticulum is a fluid filled network of membranous tubular structures. What is the difference between rough and smooth endoplasmic reticulum?
    • Rough - carries ribosomes.
    • Smooth - associated with the transport of newly synthesised proteins.
30. What is the name given to sites for fluid collection that can be found along the cell membrane?
    Pinocytic vessels.

NB. Cell division is not covered in this module since it may be found in Book One - Chapter 5 - Genetics & Animal Breeding. Please refer to Module 2 - Cell Replication.