CJC Organelles & Cellular Structures Lecture Notes

1 CATHOLIC JUNIOR COLLEGE 9744 H2 Biology CORE IDEA: 1] THE CELL AND BIOMOLECULES OF LIFE 1.1 ORGANELLES AND CELLULAR STRUCTURES Narrative: Cellular structures provide the means to drive cellular processes Knowing how cellular structures facilitate specific cellular processes is fundamental to explaining how life ‘works’. The cell theory states that the cell is the smallest and most basic unit of life and th at cells grow only from existing cells. Understanding the role of cellular organelles (such as nucleus, ribosome, chloroplast and mitochondrion) and cellular structures (for example, the cytoskeleton) is crucial to understanding how organisms and life at large work . One key concept often explored in this chapter is “how are the structures of the organelles adapted for their functions?” There are significant differences between cells of prokaryotes and eukaryotes. Using bacteria as a model, the nucleoid is not enclosed by any membrane. Plasmid may be present as extra -chromosomal DNA. Membrane-bound organelles, such as mitochondria and endoplasmic reticulum, are absent. Prokaryotic ribosomes are different from eukaryotic ribosomes. Some bacterial cells have cell walls that comprise peptidoglycan rather than cellulose. Within the eukarya domain, the cell model of plants is also different from that of animals. Unlike unicellular organisms which merely undergo cellular division, cells of multicellular organisms undergo both division and differentiation to allow them to carry out their specific functions. Guiding Questions: ● Why is a cell the basic unit of life and how does it promote continuity of life? ● How is the basic unit crucial in understanding what constitutes life? ● What are the differences between cells of prokaryotes and eukaryotes, between cells of plants and animals, and between cells of unicellular and multicellular organisms? ● In what ways do viruses not fit the cell model? LEARNING OUTCOMES Candidates should be able to: Subtopic Learning Outcomes Pg. Cell Theory (a) Outline the cell theory with the understanding that cells are the smallest unit of life, all cells come from pre-existing cells; and living organisms are composed of cells. 3 Eukaryotes (b) Interpret and recognise drawings, photomicrographs and electronmicrographs of the following membrane systems and organelles: rough and smooth endoplasmic reticulum, Golgi body, mitochondria, ribosomes, lysosomes, chloroplasts, cell surface membrane, nucle ar envelope, centrioles, nucleus and nucleolus. (c) Outline the functions of the membrane systems and organelles listed in (b). 3-22 Prokaryotes (Bacteria) (d) Describe the structure of a typical bacterial cell (small and unicellular, peptidoglycan cell wall, circular DNA, 70S ribosomes and lack of membrane - bound organelles). 23-27 Viruses (e) Describe the structural components of viruses, including enveloped viruses and bacteriophages, and interpret drawings and photographs of them. (f) Discuss how viruses challenge the cell theory and concepts of what is considered living. [not in student lecture notes, but discussed in tutorials] 28-32 33 REFERENCES 1. Campbell, Neil A and Reece, J B (2015) Biology: A Global Approach (10Th edition) (Pearson global edition) 2. Campbell, Neil A and Reece, J B (2011) Biology (Ninth edition) (Addison Wesley-Benjamin Cummings, www.aw-bc.com) 3. Campbell, Neil A and Reece, J B (2005) Biology: Concepts and Connections (Fourth edition) (Benjamin Cummings) 4. Taylor, D J, Green, N P O, Stout, G W and Soper R (1997) Biological Science 1 (Third edition) ( CUP, www.cambridge.org) ISBN 0521561787 5. Longman A-Level Course in Biology (Core Syllabus) by Hoh Y. K. 6. Biology of Microorganisms (Seventh Edition) by Brock Madigan Martinko Parker

2 CONTENT PAGE CONTENT Pg. 1 Cell Theory 3 2 Eukaryotes 3-22 Introduction to Eukaryotes 3 Concept Map for Organelles 7 2.1] Cell Surface Membrane 8 Non-membrane bound organelles 2.2] Ribosomes 9 2.3] Centrioles 10 Single membrane bound organelles 2.4] Endoplasmic Reticulum 2.4.1] Rough Endoplasmic Reticulum 2.4.2] Smooth Endoplasmic Reticulum 11 2.5] Golgi Body 13 2.6] Lysosomes 14 Double membrane bound organelles 2.7] Nucleus 15 2.8] Mitochondrion 18 2.9] Chloroplast 19 2.10] Endomembrane system 20 3 Prokaryotes (Bacteria) 23-26 Introduction to Prokaryotes 23 3.1] Cell Wall 24 3.2] Genome 25 3.3] Ribosome 26 4 Comparison between Eukaryotes and Prokaryotes 26-27 Concept Map of Eukaryotes and Prokaryotes 26 Table of Comparison 27 5 Viruses 28-36 5.1] Structural Components of Viruses 28 5.2] Examples of Viruses 29 5.3] Structure of Bacteriophages 5.3.1] T4 Phage 5.3.2] Lambda Phage 30 5.4] Structure of Animal Viruses 5.4.1] Structure of Influenza Virus 5.4.2] Structure of Human Immunodeficiency Virus (HIV) 31 32 5.5] Viruses challenge the cell theory 33 6 Experimental Skills and Miscellaneous 34-38 6.1] Units of Measurement 34 6.2] Microscopy 35 6.3] Calculating Magnification 36 6.4] Cell Fractionation 37 6.5] Endosymbiotic Theory 38

3 1] CELL THEORY Cell Theory LO (a) Outline the cell theory with the understanding that cells are the smallest unit of life, all cells come from pre-existing cells; and living organisms are composed of cells. Cell Theory arose in the mid-nineteenth century as a result of work by three German biologists, Schleiden, Schwann and later, Virchow. The Cell Theory states that: i) The cell is the smallest, most basic unit of life, in terms of structural, functional and organisation of an organism. ii) All living organisms are composed of cells. Organism could be unicellular or multicellular. iii) All cells arise from pre-existing cells by cell division, through mitosis and meiosis in eukaryotic cells and binary fission in prokaryotes. 2] EUKARYOTES EUKARYOTES are organisms made of cells that have a true, membrane bound nucleus. They also possess membrane bound organelles. Examples of eukaryotic organisms are animals (Fig. 3), plants (Fig. 4), fungi and protoctists. A typical eukaryotic cell consists of the following: (a) Cell surface membrane This defines the boundary of a cell and retains its contents. (b) Nucleus This contains the genetic material that directs cellular activities. (c) Cytoplasm This consists of the following: o Cytosol This is the aqueous solution of ions and organic compound s (e.g. sugars, amino acids and proteins). o Organelles These include the organic cellular structures, usually enveloped by a membrane, such as the ribosome, endoplasmic reticulum, Golgi body, lysosome, mitochondrion, vacuole and centriole. o Cytoskeleton This consists of a network of microtubules, intermediate filaments and microfilaments made of protein.

4 FIG. 3: ANIMAL CELL Fig. 3a 3-dimensional model of an Animal Cell Fig.3b An illustration of an Animal Cell Fig. 3c An illustration of a generalised animal cell as seen with the Electron Microscope chromatin Chromatin vesicle chromatin

5 FIG. 4: PLANT CELL Fig. 4a 3-dimensional model of a Plant cell Fig.4b An illustration of a plant cell as seen under a Light Microscope Fig. 4c An illustration of a generalised plant cell as seen with the Electron Microscope vesicle chromatin chromatin chromatin

6 COMPARISON BETWEEN PLANT CELL AND ANIMAL CELL: Basis of Comparison (Features) Plant cell Animal cell Cell wall Tough, slightly elastic cellulose cell wall present (in addition to the cell membrane) Cell wall absent – only a membrane surrounds the cell Pits and plasmodesmata Pits and plasmodesmata present in the cell wall No cell wall and therefore no pits or plasmodesmata Plastids Plastids, e.g. chloroplasts and leucopla