General Biology 1 Notes PDF

GENERAL BIOLOGY 1 Course code: BIO 101 Credit units: 2 Instructor: Olukemi Aromolaran (Ph.D.) Office: COAES Building, Room 36 Office hours: 8 am – 5 pm  Recommended text Taylor, D.J., Green, N.P.O and Stout, G.W. (2010). Biological Sciences....

GENERAL BIOLOGY 1 Course code: BIO 101 Credit units: 2 Instructor: Olukemi Aromolaran (Ph.D.) Office: COAES Building, Room 36 Office hours: 8 am – 5 pm  Recommended text Taylor, D.J., Green, N.P.O and Stout, G.W. (2010). Biological Sciences. Cambridge University Press, 10th Edition, South Africa. Jones, M., Fosbery, R., Gregory, J. and Taylor, D. (2014). Cambridge International AS and A Level Biology. Cambridge University Press, 4th Edition, United Kingdom 2  Course Outline Cell structure and organization What is a cell? The cell theory The plant cell, animal cell, bacterial cell and their features Similarities and differences between the animal and plant cells Cell structure Organelles in the cell Functions of the organelles Characteristics of living things Classification of living things 3 Cell structure and organization Learning Objectives At the end of the class the students should be able to: Describe a biological cell, The cell theory Features of the animal, plant and bacterial cells Structures within the cell and their functions 5  Introduction Robert Hooke (1665) examined thin slices of plant material and he saw ‘pore like’ regular structures - cells. The cell looks like an empty box surrounded by a wall. It is the fundamental unit of all living things. Robert Hooke’s cells 6  Matthias Schleiden and Theodor Schwann found the cell theory (1838): 1. All organisms are made up of cell. 2. Cell is the basic unit of structure and function of all living organisms. Rudolf Virchow (1855) proposed the third theory: 3. All cells arise from pre-existing cells by cell division. 7  What is a cell? A bag containing the chemistry of life, separated from the outer environment by a thin membrane. It is the building block of all living organisms. A cell is the basic, structural and functional unit of all living organisms. A cell contains organelles which provide the necessary functions to sustain itself. Averagely, the human body has > 30 trillion of cells Cytology is the study of the structure and components of cell. Cells can be study using microscope, such as the light and electron microscopes 8 Edouard Chatton (1937) first distinguished the two cell types: The Prokaryote - pro (before); karyote (nucleus) Single cell - mainly bacteria and archea The Eukaryote – eu (true); karyote (nucleus) The animal, plant, fungi and protists Later adopted by Roger Stanier and Van Niel in 1962. What are the common features between prokaryotic and eukaryotic cells? Prokaryotes Eukaryotes 1. Do not have a true nucleus 1. Possess true nucleus (the (the nucleus are not nucleus is surrounded by a surrounded by a membrane membrane e.g. Protist, Plants, e.g. Bacteria Animals, and Fungi 2. The organelles are not 2. The organelles are bounded membrane bound. by membrane. 3. The cells are usually smaller 3. Cells are larger and may be in size. multicellular. 4. Haploid chromosomes are 4. Diploid chromosomes are present. present. 5. Have 70S ribosome. 5. Have 80S ribosome. 6. Plant cells have cell wall. 6. Many surrounded by cell wall. 7. Genetic materials are 7. All genetic information is in a single thread of DNA – enclosed in the nucleus. bacterial chromosome. Virus? No cell structure -no membrane containing cytoplasm with ribosomes. Many contain genetic material (DNA or RNA) and a protective coat of protein molecule (capsid). Viruses range in size (20–300 nm). Image source: https://blog.addgene.org/viral-vectors-101-what-is-a-virus-and-a-viral-vector All are parasitic because they can only reproduce by infecting and taking over living cells.  Plant cell 12 Image source: https://www.britannica.com/science/plant-cell  Plant cell Image source: https://biologydictionary.net/animal-cell/ 13  Bacterial cell Image source: https://courses.lumenlearning.com/suny-wmopen-biology1/chapter/prokaryotes-and-eukaryotes/ 14 Common features in animal and plant cells Many small structures (small organs) seen within the cell are known as organelles: Cell membrane Cytoplasm Nucleus Mitochondria Golgi bodies Vacuole Endoplasmic reticulum Ribosomes Cytoskeletons 15 Differences between animal and plant cells o The structures commonly found in animal cells and not in plant cells - Centrosome, microvilli. o Plant cells also differ from animal cells in possessing cell walls, large permanent vacuoles and plastids (chloroplasts, chromoplasts, and leucoplasts). 16  Structures and functions of organelles Cell wall and plasmodesmata The cell wall gives the cell a definite shape. It prevents the cell from bursting during osmosis. Plant cells are linked to neighbouring cells by means of the plasmodesmata (singular: plasmodesma)  Bacterial cell wall - peptidoglycan.  Fungal cell wall - chitin, glucans, and proteins  Plant cell wall consist - cellulose, glucose, and polymer. 18 Functions of Cell Wall Support: Gives mechanical support to the cell. Defense: Serves as a mechanical barrier. Cell gateway: Allow some molecules in and disallow some. Cell division: Signals for cell division. Communication: The plasmodesmata allow cells to communicate with one another. Storage: For storing some saps/materials. 19 Vacuoles Plant cells often possess a large, central vacuole, surrounded by a tonoplast. Image source: https://microbenotes.com/plant-cell-vacuole/ The fluid in the vacuole contain pigments, enzymes, sugars and other organic compounds (including some waste products), mineral salts, oxygen and carbon dioxide. Vacuoles help to regulate the osmotic pressure within the cell. 20 Plastids Plastids are found in plant cells and Euglenoids. Usually double-membrane bound organelles with their own DNA and ribosomes. Mainly for manufacture and storage of food. They provide plants with unique pigments - chloroplasts, chromoplasts, and leucoplasts. Chloroplasts - contain chlorophyll, the green pigment which absorbs light during the process of photosynthesis. Chromoplasts - contain carotene, xanthophylls, and other fat-soluble carotenoid pigments. Leucoplasts - nutrient-storing, colourless plastids (Amyloplasts - store carbohydrates, Elaioplasts - store oils and fats, and Aleuroplasts - store proteins). 21  Chloroplasts (about 3 - 10 μm) Found in the green parts of the plant. Image source: lifeofplant.blogspot.com/2011/05/chloroplasts-and-other-plastids.html The space limited by inner membrane is called stroma. Thylakoids are in stacks like the piles of coins called grana. Thylakoids contain the pigment - chlorophyll. Stroma contains enzymes for synthesis of protein and carbohydrates. 22  Nucleus The largest cell organelle surrounded by two membranes (nuclear envelope). The outer membrane of the nuclear envelope is continuous with the endoplasmic reticulum. The nuclear envelope has many small pores called nuclear pores for exchange of materials between the nucleus and the cytoplasm (mRNA, ribosomes, nucleotides, ATP, thyroid hormone T3). Chromosomes are loosely coiled (chromatin) within the nucleus. Chromosomes contain DNA, organized into functional units - genes. Genes control the activities of the cell and inheritance. 23  The nucleus divide first prior cell division. The nucleolus use the information in its own DNA to make ribosomes. Nucleus 24 Image source: https://micro.magnet.fsu.edu/cells/nucleus/nucleus.html Endoplasmic reticulum and ribosomes The endoplasmic reticulum (ER) is a tubular network of membranes that extends through the cytoplasm. Interconnected to form the reticulum. The ER is continuous with the outer membrane of the nuclear envelope. ER can be rough ER or smooth ER. Image source: https://www.britannica.com/science/plant-cell Rough ER is covered with many tiny organelles called ribosomes. Ribosomes (about 25 nm) are the sites for protein synthesis. 25  Ribosomes are found freely in the cytoplasm as well as on the rough ER. They are made of RNA (ribonucleic acid) and protein. Small sacs called vesicles can break off from the ER. Proteins on the rough ER enter the sacs and move through them. The vesicles can join together to form the Golgi body. Smooth ER do not have ribosomes attached to it. The ER serves for storage, synthesis of protein and metabolism of lipids. 26 Golgi body (Golgi apparatus/complex) Camillo Golgi (1898) observed the Golgi body near the nucleus. The Golgi body is a stack of flattened sacs, may be more than one in a cell. The stack is formed at one end from vesicles which bud off from the ER. The stack of sacs together with the associated vesicles forms the Golgi apparatus or Golgi complex. The Golgi body collects (e.g. protein) from the rough ER and transport it via the Golgi vesicles to other parts of the cell or out of the cell (secretion). - For example, Golgi body add sugars to protein to make – glycoprotein; removes the amino acid methionine from newly formed proteins to make a functioning protein. 27  For the synthesis of glycoproteins and glycolipids. In plants, enzymes in the Golgi body convert sugars into cell wall components. Golgi vesicles are also used to make lysosomes Golgi apparatus Image source: https://www.britannica.com/science/plant-cell 28  Lysosomes (about 0.1– 0.5 μm). They are spherical sacs, surrounded by a membrane layer. Lysosomes breakdown unwanted materials (e.g. old organelles). Contain hydrolytic enzymes - lipase, protease, carbohydrases and acidic PH Forms phagolysosome in white blood cells to digest pathogens. Also, sperm cell contain acrosome (a kind of lysosome),for digesting a path to the ovum. Lysosome https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcROU-WVXKUgbKoy_BRJW-HY6LPiHjhzeLtpXrxBICHVGJ371LiwXN1rxFDeIvHrm7J4-VQ&usqp=CAU 29  Mitochondria The mitochondria (0.75 – 3 µm) often appear as oval-shaped, surrounded by two membranes. It is the power houses of the cell. It generate the energy currency of the cell (ATP); signaling between cells and cell death (apoptosis). The inner membrane is folded to form finger-like cristae and an interspace between the two membranes. The number of mitochondria in a cell is dependent on the energy demand (liver - >2,000; RBC - none). 30 ATP is produced in the mitochondria (via Kreb’s cycle). Mitochondrion Image source: https://byjus.com/biology/mitochondria/ 31 Cell membrane A semi-permeable thin layer that surrounds the cytoplasm of a cell. - Mechanical barrier (protects the contents of the cell). - Selectively permeable (controls the movement of substances). - Transportation of materials (transportation of nutrients and waste products). - Signaling and receptor site (cell to cell communication). - Some metabolic activity (e.g. respiration, secretion, absorption). 32  Fluid mosaic structure of the membrane Image source: https://www.bing.com/th?id=OIP.QhUXn0t2ZYxH8OXwQRp0bQHaDP&w=299&h=131&c=7&o=5&pid=1.7 33 Microtubules and microtubule organising centres (MTOCs) Microtubules - long, rigid, hollow tubes (25 nm). Microtubules are made of a protein called tubulin. Microtubules + actin filaments + intermediate filaments = cytoskeleton. The cytoskeleton aids movement and give rigidity to the cell’s shape. The microtubules form part of the structure of centrioles.* Microtubule organising centres (MTOCs) controls the assembly of microtubules from the tubulin molecules. 34  Peroxisome The peroxisome oxidizes and breakdown fatty acids and amino acids. Also help to detoxifies poisons in the cell. 35  Microvilli (only in animal cell) Microvilli (singular: microvillus) - finger-like extensions of the cell surface membrane. To increase the surface area of the cell surface membrane (absorption in the gut; reabsorption in the proximal convoluted tubules of the kidney). Microvilli Image source: https://microbenotes.com/microvilli-structure-and-functions/ 36  Centrosome An organelle having two centrioles, which lies perpendicularly to one another. The centrioles forms the spindle fibers when animal cells divides. Image source: microbenotes.com/centrosome 37 Let’s discuss 1. Ten structural differences between an animal cell and a bacterium. 2. Three organelles lacking a membrane. 3. Three organelles surrounded by a single membrane. 4. Three organelles bounded by two membranes. Organelles Cells Tissues Organs Systems Organisms Population Communities Ecosystems Biosphere Organization of Life 39