BIO111 Principles Of Biology Lecture Notes PDF

BIO111: Principles of Biology Kaunda, S.K.K. Nature Detective: People & Wildlife Senior Lecturer: Ecology and Conservation Department of Biological Sciences University of Botswana Office 247/421 [email protected] The Cell Lecture 2...

BIO111: Principles of Biology Kaunda, S.K.K. Nature Detective: People & Wildlife Senior Lecturer: Ecology and Conservation Department of Biological Sciences University of Botswana Office 247/421 [email protected] The Cell Lecture 25 Biologists study life at different levels ◼ Atoms in elements (done) ◼ Molecules (done) ◼ Cells ◼ Tissues ◼ Organs ◼ Organisms ◼ Populations ◼ Communities ◼ Ecosystems ◼ Biosphere. 8 unifying principles? ◼ Cells ◼ Energy ◼ Metabolism ◼ Reproduction ◼ Heredity ◼ Response to environment ◼ Homeostasis ◼ Interact with the environment Discovery of Cells ◼ 1665- English Scientist, Robert Hooke, discovered cells while looking at a thin slice of cork. ◼ He described the cells as tiny boxes or a honeycomb ◼ He thought that cells only existed in plants and fungi  Anton van Leuwenhoek ◼ 1673- Used a handmade microscope to observe pond scum & discovered single-celled organisms ◼ He called them “animalcules” ◼ He also observed blood cells from fish, birds, frogs, dogs, and humans ◼ Therefore, it was known that cells are found in animals as well as in plants  Development of Cell Theory ◼ 1838- German Botanist, Matthias Schleiden, concluded that all plant parts are made of cells ◼ 1839- German physiologist, Theodor Schwann, stated that all animal tissues are composed of cells.  Development of Cell Theory ◼ 1858- Rudolf Virchow, German physician, concluded that cells must arise from preexisting cells.  The Cell Theory– a core concept The 3 Basic Components of the Cell Theory: 1. All organisms are composed of one or more cells. 2. The cell is the basic unit of life in all living things 3. All cells are produced by the division of preexisting cells.  Modern Cell Theory In addition to the original Cell Theory: ◼ The cell contains hereditary information (DNA) which is passed on from cell to cell during cell division. ◼ All cells are similar in chemical composition and metabolic activities. ◼ All basic chemical & physiological functions occur within cells. ◼ Cell activity depends on the activities of sub-cellular structures within the cell (organelles, nucleus, plasma membrane)  The cell Smallest living unit of an organism Cannot be seen with the naked eye ◼ Grow, Use energy, Respond to the environment, Reproduce, Evolve, and Adapt ◼ A unicellular organism is made up of one cell, ◼ A multicellular organism is made up of many cells. Cell size: What can we see? 12 Cell size: What can we see? 13 Cell size: What can we see? 14 Why are cells so small? ◼ Most cells are between 2µm and 200µm. ◼ A micrometer is one millionth of a meter! ◼ 1/1000 000m ◼ Cells are too small to be seen with a naked eye. ◼ Why can’t cells be bigger? MONSTER cells? 15  Cell size determines diffusion rate ◼ Cells exchange substances with the environment ◼ Raw materials move into the cell ◼ Waste products move out of the cell ◼ The larger the distance, the slower the diffusion. ◼ Efficiency of movement in and out of the cell was achieved through: ◼ Evolution of cells with larger surface area-to-volume ratio (sa/vol or SA:V) ◼ SA:V ratio refers to how much surface area an object has per unit volume 16  Surface area to volume ratio As the size of the cube increases, the volume will increase more rapidly than the surface area, and SA:V ratio will decrease. 17  Cell transport is limited by the SA:V ratio ◼ Cells are usually small. ◼ The surface area and volume determine the cell size ◼ Surface area is the area occupied by the object's surface ◼ The Volume is the amount of space within the object. ◼ The high SA:V ratio of small cells makes them more efficient in transporting substances. ◼ Rate of diffusion is affected by SA:V ratio. ◼ For unicellular organisms exchange of materials through diffusion is easier. ◼ For multicellular organisms, simple diffusion poses a 18 challenge! How do Volume and Surface Area relate to cell biology? ◼ Volume correlates with the amount of chemical activity the cell can perform per unit time ◼ Surface Area correlates with the exchange of nutrients & waste products with its environment ◼ As the cell grows larger, ◼ its rate of waste production increases & ◼ demand for resources increases ◼ The Volume increases faster than Surface Area, through which the cell must obtain resources & excrete waste – a serious challenge! 19 Some substances exchanged between animal cells and the environment ◼ Animal cells need ◼ Oxygen for aerobic respiration and ◼ Nutrients for body building ◼ Animal cells must excrete waste products such as ◼ Carbon dioxide, ◼ Urea, and ◼ Water ◼ Heat must be exchanged to maintain constant body temperature 20  Cell diversity ◼ Appear in different shapes and sizes ◼ There are different unicellular organisms ◼ Perform different functions (specialization) in multicellular organism 21 Cells come in various types, various shapes, and specialisation 22  Cell classification ◼ Cells are divided and classified in many ways ◼ One common classification method is the presence or absence of a nucleus ◼ Absence of true nucleus and membrane-enclosed organelles - prokaryotic cell ◼ Presence of membrane-enclosed nucleus and membrane-enclosed organelles - eukaryotic cell Prokaryotic Cell “Why is what where when?” Lecture 26  Prokaryotic Cell ◼ Organisms with prokaryotic cells are called prokaryotes ◼ Greek (pro-) "before" + (karyon) "nut or kernel" ◼ Examples: Bacteria, blue-green algae (Cyanobacteria) 26  Prokaryotic cell ◼ No true nucleus ◼ Unicellular ◼ DNA is not contained within a membrane; not separated from the rest of the cell; but is coiled up in a region of the cytoplasm called the nucleoid. ◼ No other membrane-bound organelles (sub-cellular structures)  Features of Prokaryotes Capsule ◼ Layer of slime outside the cell wall ◼ Found in some bacterial cells ◼ Composed mainly of polysaccharides or polypeptides. ◼ Protects the cell when it is engulfed by other organisms ◼ Protects the cell from immune cells and from desiccation ◼ Helps in adherence to surfaces.  Features of prokaryotes Cell Wall - Outer covering, provides shape, support, and protection to the cell. ◼ Found in most bacteria and archaea ◼ Composition and structure vary between bacteria and archaea ◼ Composition differs even between different species within each group, ◼ Plays a vital role in maintaining the cell's integrity, especially in challenging environments. 29  Features of prokaryotes Specific Functions of the Cell wall ◼ Protection: The cell wall protects the cell from ◼ Mechanical damage, ◼ Osmotic stress (swelling or bursting in hypotonic environments), and ◼ Harmful substances. ◼ Maintains Shape: It gives the prokaryotic cell its specific shape (spherical, rod-shaped, spiral, etc.). ◼ Prevents Lysis: The cell wall helps prevent the cell from lysing (bursting) due to the high internal osmotic pressure caused by the concentration of solutes inside the cell. 30 Features of prokaryotes Cytoplasm - A gel-like substance composed mainly of; ◼ Cytosol - fluid component of the cytoplasm, consisting primarily of water, ions, nutrients, and enzymes, and various organic molecules. ◼ Medium in which biochemical reactions occur. ◼ Cell components such as nucleoid region, ribosomes, plasmids, storage granules etc. 31 Features of prokaryotes General functions of Cytoplasm ◼ Metabolism and Biochemical Reactions: catabolism and anabolism ◼ Protein Synthesis: Ribosomes produce proteins ◼ Nutrient Storage: The cytoplasm houses inclusion bodies that store excess nutrients for later use ◼ Cell Division: plays a role in binary fission ◼ Transport and Distribution: allows diffusion of molecules 32 Features of prokaryotic cells ◼ Cell or Plasma Membrane - regulates the flow of substances in and out ◼ Pili - Hair-like structures on the surface of the cell – for adherence ◼ Flagella - Long, whip-like protrusion that aids in locomotion. ◼ Ribosomes - Cell structures responsible for protein production.  Features of Prokaryotic cells ◼ Plasmids - Gene carrying, double stranded, circular DNA structures that are not essential for normal survival and reproduction ◼ Found in bacteria, some archaea, and some eukaryotes. ◼ Replicate independently of host cell's main replication machinery of chromosomal DNA ◼ Carry additional genes that can provide advantageous traits to the host organism, such as ◼ Antibiotic resistance, ◼ Metal resistance, ◼ Nitrogen fixation, and 34 ◼ Toxin production.  Features of prokaryotic cells Plasmid genes confer important functions: ◼ Antibiotic resistance: Carry genes that allow bacteria to resist antibiotics, which is a major concern in medical treatment. ◼ Virulence factors: Contain genes that enhance a bacterium's ability to cause disease. ◼ Metabolic functions: Provide the ability to metabolize unusual substances, giving the host an advantage in specific environments. 35 Features of prokaryotic cells Nucleiod Region - A region within the cytoplasm where the genetic material is concentrated and compacted ◼ Contains the cell’s chromosomal DNA, typically a single, circular molecule of double-stranded DNA. ◼ Not membrane-bound: It is not a distinct, membrane-bound structure like the nucleus in eukaryotes. ◼ Controls cellular activities, such as growth, metabolism, and reproduction 36  Prokaryotes Prokaryotes are in the domains Bacteria and Archaea All are unicellular Most are important positively (N-fixation) or negatively (diseases)  Microorganisms 1: Bacteria Lecture 27 Bacteria  Microorganisms 1: Bacteria Micro-organisms (microbes) play a very important role in our lives. ◼ Some cause disease ◼ Majority are completely harmless ◼ We couldn’t live without them, but they could live without us  What are they? ◼ Very small living organisms, so small that most of them are invisible to the naked eye ◼ Can only be seen with a microscope ◼ Make up more than 60% of the Earth’s living matter ◼ Estimated that 2-3 billion microbial species share the planet with us  Classification Occur in a wide variety of shapes and sizes, and fall into the following five groups: ◼ Bacteria (in Kingdom Monera) ◼ Protists (in Kingdom Protista) ◼ Algae (in Kingdom Protista or Plantae, depending on taxonomy) ◼ Fungi (in Kingdom Fungi) ◼ Viruses  NOTE WELL ◼ Only members of the Kingdom Animalia and most Plantae are not considered microbes. ◼ Viruses are also considered microbes. ◼ Viruses are not cells. ◼ Each Kingdom has its own associated viruses.  Bacteria Commonly known as “germs,” invisible creatures that can invade our bodies and make us sick. ◼ Size of a typical cell compared to a typical bacterium: ◼ A typical animal or plant cell is 10 to 100 micrometres, whereas ◼ A bacterium is less than 2 micrometres in diameter  Morphology Bacteria occur in different shapes: ◼ Rods or bacilli (singular bacillus) ◼ Spheres or cocci (singular coccus) Spherical ◼ Spiral forms or spirilla (singular spirillum) Coils ◼ Filamentous forms - grow in branching filamentous network ◼ Pleiomorphic - lack distinct shape  Bacterial Nomenclature ◼ Uses the Linnaean system: Genus and species Escherichia coli is named after Theodor Escherich, who discovered this organism in 1885. Bacillus megaterium is a large rod shaped organism, a member of the genus Bacillus. ◼ The name often reveals some characteristic feature.  NOTE WELL: the usage of terms e.g. Bacillus (one genus of bacteria, italicized) bacilli (general term for rods, not italicized)  Importance of Microbes ◼ Disease agents: most infectious diseases controlled by proper sanitation, preventive medicine, and chemotherapy ◼ Agriculture: microbes are vital in processing materials in soil, e.g. fixing gases as is the case in nitrogen fixation  Importance of Microbes (cont’d) ◼ Food and drink: Microbial fermentations in production of alcoholic beverages, breads, pickles, cheeses ◼ Chemical products: Used to produce acetone and other commercial solvents, pharmaceuticals, antibiotics, preservatives  Importance of Microbes (cont’d) ◼ Basic research: Microbes grow fast, produce enormous number of offspring. Easy to scale up. Crucial to modern biology ◼ Biotechnology: e.g. genetic engineering, ability to move genes freely from one organism to another. Bacteria are natural candidates for such activities. ◼ Bioremediation - breaking down sewage and other toxic wastes into safe matter  Importance… Microscopic organisms play a key role ◼ maintaining life on earth ◼ fixing gases ◼ breaking down dead plant and animal matter ◼ biotechnologists exploit the activities of microbes to benefit humans