General Biology 1 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 Scien...

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 ❖Characteristics of living things ❖Classification of living things 3 Cell structure and organization Learning Objectives At the end of the class, the students should understand: ✓The biological cell, ✓The cell theory ✓Features of cells ✓Cell organelles and their functions 5  Introduction All living things are made up of cells Cells are composed of: ❑genetic material, ❑cytoplasm, ❑ribosomes ❑cell membrane Cell communicates with one another…….. 6 Image source: https://fa.itb.ac.id/wp-content/uploads/sites/56/2016/06/Cell-Communication-2014.pdf  Introduction Robert Hooke (1665) examined thin slices of the bark of plant and he saw ‘pore like’ regular structures – ‘cella’. The cell looks like an empty box surrounded by a wall. Robert Hooke’s cells 7 The cell theory 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. 8  What is a cell? A bag - the chemistry of life, separated from the outer environment by a thin membrane. It is the fundamental unit (i.e. building block) of all living organisms. A cell contains organelles which provide the necessary functions to sustain itself. 9  Two categories a) Prokaryotes b) Eukaryotes Differences – nuclear membrane, genetic material, organelles, ribosomes, and size. Cytology - study of the structure and components of cell. Cells can be study using microscope, such as the light and electron microscopes 10 Edouard Chatton (1937) first distinguished the two cell types: The Prokaryotes – pro (before); karyote (nucleus) Single cell – mainly bacteria and archaea 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 the prokaryotic and eukaryotic cells? 11 Prokaryotes Eukaryotes 1. Do not have true nucleus Possess true nucleus (the chromosomes (chromosomes are not surrounded by a are surrounded with a membrane membrane) 2. The organelles are not membrane The organelles are bounded by membrane bound 3. The cells are usually smaller in size. Cells are usually larger and multicellular 4. Haploid chromosomes are present. Diploid chromosomes are present 5. Have 70S ribosome Have 80 s ribosome 6. Many surrounded by cell wall. Plant cell and fungi has cell wall 7. All genetic information is in a single Genetic materials are enclosed in the thread of DNA nucleus 12 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 (20-30o nm). Image source: https://www.researchgate.net/figure/Basic-structure-of-a-virus-Taylor-2019_fig2_340249925 All are parasitic because they can only reproduce by infecting and taking over living cells 13  Plant cell 14 Image source: https://www.britannica.com/science/plant-cell Animal cell 15 Image source: https://micro.magnet.fsu.edu/cells/bacteriacell.html 16  Bacteria cell 17 Image source: https://micro.magnet.fsu.edu/cells/bacteriacell.html Common features in animal and plant cells ❖Small structures within the cell - organelles: Cell membrane Cytoplasm Nucleus Mitochondria Golgi bodies Vacuole Endoplasmic reticulum Ribosomes Cytoskeletons 18 Differences - animal and plant cells oStructures commonly found in animal cells but ABSENT in plant cells - centriole, microvilli. oPlant cells possess cell walls, large permanent vacuoles and chloroplasts. Cell wall and plasmodesmata Cell wall gives the definite shape. Prevents bursting during osmosis. Plant cells are linked to one another by plasmodesmata (singular: plasmodesma) 19 Vacuoles Plant cells often possess a large, central vacuole, surrounded by a tonoplast. The fluid in the vacuole contain pigments, enzymes, sugars, organic compounds, mineral salts, oxygen and carbon dioxide. Vacuoles - regulate the osmotic pressure within the cell. 20 Chloroplasts Found in the green parts of the plant. Contains the chlorophyll (green pigment which absorbs light during photosynthesis). 21  Structures and functions of organelles  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, which is organized into functional units called genes. Genes control the activities of the cell and inheritance -the nucleus controls all the activities in the cell. 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. Image source: https://www.britannica.com/science/plant-cell 25  ER can be rough ER or smooth ER. Rough ER is covered with many tiny organelles called ribosomes. Ribosomes (about 25 nm) are the sites for protein synthesis. Ribosomes can be found freely in the cytoplasm and on the rough ER. Ribosomes on the ER gives rough appearance of the rough ER. Ribosomes are made of RNA (ribonucleic acid) and protein. 26  Ribosomes – needed for protein synthesis (for growth, development and metabolism). Proteins are essential for all cellular functions. Translate messenger RNA (mRNA) into proteins by assembling amino acids in a sequence dictated by the mRNA’s nucleotide sequence. Made up of two subunits: a small subunit and a large subunit. The small subunit binds to messenger RNA (mRNA), which contains the genetic code for the protein. The large subunit adds amino acids to the growing protein chain. 27 Ribosome Image source: https://www.geeksforgeeks.org/interesting-facts-about-ribosomes/ 28  The human cell may have thousands to millions of ribosomes. Prokaryotic has 70S, while eukaryotic 80S ribosomes. It can disassemble and reassemble to regulate protein synthesis. Dysfunction/mutations in ribosomal proteins or rRNA are associated with some human diseases, certain cancers, and genetic disorders (ribosomopathies). Some antibiotics (e.g. tetracycline, erythromycin, and streptomycin) target bacterial ribosomes, inhibiting protein synthesis and thereby killing or inhibiting their growth 29  Proteins on the rough ER enter the sacs and move through them. Small sacs called vesicles can break off from the ER and these 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. 30 Golgi body (Golgi apparatus/complex) 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 is referred to as 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. 31  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 32  Lysosomes They are spherical sacs, surrounded by a membrane layer (about 0.1– 0.5 μm). Lysosomes breakdown (digestion) unwanted materials (e.g. old organelles). 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 33  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 (adenosine triphosphate); also in 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). 34 ATP is produced in the mitochondria (via Kreb’s cycle). Mitochondrion Image source: https://byjus.com/biology/mitochondria/ 35 Cell membrane A semi-permeable thin layer that surrounds the cytoplasm of a cell. Functions of the cell membrane - 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). 36  Fluid mosaic structure of the membrane 37 Image source: https://www.bing.com/th?id=OIP.QhUXn0t2ZYxH8OXwQRp0bQHaDP&w=299&h=131&c=7&o=5&pid=1.7  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). 38 Microtubules and microtubule organizing 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 determines the cell’s shape. Membrane bound organelles are held in place by the cytoskeleton. The microtubules form part of the structure of centrioles. The MTOCs controls the assembly of microtubules from tubulin 39 molecules  Peroxisome The peroxisome oxidizes and breakdown fatty acids and amino acids. Also help to detoxifies poisons in the cell. 40