EJC CELL STRUCTURE AND FUNCTION

EJC H2 Biology T2W3 Cell Structure and Function 1 Cell Structure and Function 1. Overview of Topic The study of cells is known as cytology. This branch of biology studies the different structures and functions of the cell and is based on the concept of the cell as the basic unit of life. Knowledge of cell biology helps to explain the relationship between structure and function of cell organelles, their physiological properties, metabolic processes, signalling pathways, life cycle and interactions with the environment. This study can be done both on a microscopic and level, involving prokaryotic and eukaryotic cells. Viruses, which are considered as non -living and non-cellular, have long challenged the cell concept. Yet, understandi ng viruses is necessary as they have had and will continue to exert a far reaching impact on our lives, especially when it comes to infection and diseases. T opics related to cell structure are: Biomolecules of Life topic in Core Idea 1, Core Idea 2: Genetics and Inheritance, Core Idea 3: Energy and Equilibrium and Extension Topics A: Infectious Diseases and B: Impact of Climate Change on Animals and Plants. 2. Learning Outcomes 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 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, nuclear envelope, centrioles, nucleus and nucleolus (for practical assessment, candidates may be required to operate a light microscope, mount slides and use a graticule) c) outline the functions of the membrane systems and organelles listed in (b) 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) 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

EJC H2 Biology T2W3 Cell Structure and Function 2 3. References Alberts, B., Johnson, A., Lewis, J., Morgan, D., Raff, M., Roberts, K. and Walter, P. (2014) Molecular Biology of the Cell (Fifth Edition) (Garland Science) ISBN 0815344643 Raven, P. H., Johnson, G. B., Mason, K. A., Losos, J. and Singer S. (2013) Biology (Tenth Edition) (McGraw-Hill) ISBN 007338307 Reece, J. B., Urry, L. A., Cain, M. L., Wasserman, S. A., Minorsky, P. V. and Jackson, R. B. (2011) Campbell Biology (Ninth Edition) (Pearson Higher Education) ISBN 0321739752 Microbiology – An Introduction, 9th Edition by Tortora, Funke and Case. (2007). Benjamin-Cummings Publishing Co. ISBN-13: 9781269357999 ISBN-10: 1269357999 Biological Science Vol 1 and 2, 3 rd edition, Green N.P.O, Stout G.W and Taylor .J, (2004) Cambridge ISBN-13: 9780521561785 ISBN-10: 0521561787 Biology, 9th Edition, Mader, Sylvia S (2007), McGraw -Hill ISBN-13: 9780073309811 ISBN-10: 0073309818

EJC H2 Biology T2W3 Cell Structure and Function 3 Contents 1. Overview of Topic ................................ ................................ ....................... 1 2. Learning Outcomes ................................ ................................ .................... 1 3. References ................................ ................................ ................................ . 2 4. The Cell Concept ................................ ................................ ........................ 4 5. Overview of Eukaryotic Cell Structure ................................ ......................... 4 6. Nucleus (with Nucleolus) and Ribosomes ................................ ................... 9 A Nucleus…………………………………………………………………………….. 9 B Ribosomes……………………………………………………………………….. 12 7. The Endomembrane System ................................ ................................ .....13 A Nuclear Envelope……………………………………………………………….. 14 B Endoplasmic Reticulum………………………………………………………… 14 C Golgi Apparatus…………………………………………………………………. 17 D Lysosomes………………………………………………………………………. 18 E Cell surface membrane ………………………………………………………... 19 8. Other Organelles and Structures ................................ ............................... 20 A Mitochondrion……………………………………………………………………. 20 B Chloroplast……………………………………………………………………….. 21 C Vacuole…………………………………………………………………………... 22 D Centrioles………………………………………………………………………... 23 E Microtubules…………………………………………………………………….. 24 9. Bacterial Cells (Prokaryotic Cells) .............................................................................. 26 A Morphology……………………………………………………………………… 27 B General Bacterial Structure (Ultrastructure)……………………………….… 27 C Characteristics of Bacteria……………………………………………………. 30 D Comparing General Structure of Prokaryotic and Eukaryotic Cells …….. 31 10. Viruses ................................ ................................ ................................ ......33 A Are viruses living or non-living?................................................................... 33 B Morphology………………………………………………………………………. 34 C Structure of Viruses (Ultrastructure)………………………………………….. 35 D Structural Components of Viruses……………………………………………. 36

EJC H2 Biology T2W3 Cell Structure and Function 4 4. The Cell Concept According to the cell theory or cell doctrine credited to Schleiden and Schwann in 1938 with contributions from discoveries by other scientists: a. Cells are the basic building unit of life b. All living things or organisms are made of cells c. New cells are created by old cells dividing into two 5. Overview of Eukaryotic Cell Structure Eukaryotic cells (Greek: eu – true; karyon – kernel) contain internal membrane structures that partition the cell into specialised compartments so that cellular processes can occur with optimal activity e.g. chloroplasts and mitochondria. The endomembrane system, consisting of the rough and smooth endoplasm ic reticulum and Golgi apparatus, is responsible for protein processing and vesicular transport within the cell. A typical eukaryotic cell consists of the following: 1. Plasma membrane or cell surface membrane (ref to cell membrane notes) This structure defines the boundary of a cell and retains its contents. It acts as a barrier which controls the movement of various substances in and out of the cell. 2. Nucleus It contains the hereditary material that directs cellular activities – DNA. 3. Cytoplasm This consists of:  Cytosol  semi-fluid jelly like substance. Contains ions & organic compounds e.g. sugars, amino acids, proteins  Organelles  means ‘little organs’; discrete subcellular structures with a specific function. Include: ribosomes, endoplasmic reticulu m, Golgi body, lysosome, mitochondrion, chloroplast, centriole  Cytoskeleton  a framework of protein filaments, such as microtubules, microfilaments and intermediate filaments that give eukaryotic cells their shape 4. Cell wall This is p resent in plant cells (and in bacterial cells but not in animal cells), external to the plasma membrane Compared to the light microscope, subcellular contents are seen in greater detail under the electron microscope. The term cell ultrastructure refers to a cell’s anatomy revealed under an electron microscope. Notes to Self:

EJC H2 Biology T2W3 Cell Structure and Function 5 An animal and plant cell as seen under the light microscope. Animal and Plant Cells

EJC H2 Bio