General Biology 1 (BLY 101) PDF

 Outline for Week One and Two 1. Cellular Basis of Life Cell as the basic unit of life 3. Functions of cells and cell organelles Brief history on the discovery of the cell Cell Organelles and their functions Cell Theory Cell Properties (Diversity...

 Outline for Week One and Two 1. Cellular Basis of Life Cell as the basic unit of life 3. Functions of cells and cell organelles Brief history on the discovery of the cell Cell Organelles and their functions Cell Theory Cell Properties (Diversity, Size, Shape and 4. The Microscope Organization) Definition of a Microscope Similarities and Differences between Prokaryotic and Eukaryotic Cell History of Microscope 2. Plant and Animal cells Types of Microscope Similarities between Plant and Animal Parts of a Microscope and its functions cells Parts associated with Microscopes Differences between Plant and Animal Precautions when handling a Microscope cells Structure of Plant and Animal cells 2  1. Cellular Basis of Life Cell as the basic unit of life Later in 1838 a German botanist called Mathias Cells make up the smallest level of a living organism, they Schleiden concluded that all plants were made of cells are found in all plants, animals and bacteria and they while in 1839a German zoologist named Theodor carry out certain basic functions. Cells are therefore the Schwann concluded all animals were made of cells. basic structural and functional units of living organisms In 1858 Rudolf Virchow a German physician, after (life). extensive study of cellular pathology, concluded that Cell Biology is the branch of biology that deals with the cells must arise from pre-existing cells by cell division. study of structure, function and history of a cell. The Cell Theory study of the structure and function of cells continues 1. All living things are composed of one (unicellular) or today, in a branch of biology known as cytology more cells (multicellular) Cell History: The cell was first discovered and named by 2. The cell is the basic unit of life Robert Hooke in 1665 when he observed dead plant tissue using a crude microscope, what he saw looked 3. New cells arise from pre-existing cells (through cell like small boxes and he then called them ‘cells’. The first division) man to witness a live cell under a microscope was Cell Diversity - Not all cells are alike, cells within the Anton van Leeuwenhoek, he used a simple handheld same organism show diversity in size, shape and microscope to view pond water and scrapings from his internal organization as they are specialized to teeth. He observed living cells and called them perform different functions. The basic component of ‘animalcules’.. the cell are common to all biological cell. 3 Types of cell:  Internal organization of cell Plant cell (xylem cell, phloem cell) Unicellular – These are organisms made up of a single cell. Animal cell (nerve cell, blood cell, stem cell) These organisms are capable of independent existence i.e. the single cell carries all the functions of cell, functions like:  Cell size digestion, respiration, reproduction and growth. Unicellular 1μm - 200 mm (A few cells are large enough to be seen by cells are also called acellular organisms example includes: the unaided eye e. g human egg- ovum). Amoeba, Euglena, Paramecium.  Cell Shape Multicellular – These are organisms made up of more than one cell. Here the cells vary in size and shape depending Cells come in variety of shapes depending on the functions. on their functions, they can be spherical, oval, cylindrical and polyhedral in shape examples includes: Plants and Red blood cells – disc shaped Animals. Muscle cells – elongated like a spindle Nerve cells – form branches  Prokaryotic and Eukaryotic cells Kidney tubules – cubed. Prokaryotes  The study of cell is called ‘cytology’ No membrane bound organelles and no true nucleus  Levels of Organization e.g. Bacterial cells Cells contain a variety of internal structures known as Eukaryotes organelles. Well defined membrane bound nucleus and organelles An organelle is a cell component that performs a specific function in the cell, it maintains the life of the cell by carrying e.g. Animal, Plant, Fungi out all life processes. Cell organelles include: Nucleus, Cell membrane, Mitochondria, Chloroplast etc. atom – molecule –organelle – cell – tissue – organ - system - organism 4 Prokaryotic Cell (Bacterium) 5 A Eukaryotic Cell (Plant Cell) 6  2. Plant and Animal cells Similarities between Plant and Differences between Plant and Animal Animal cells cells Structure Animal Cell Plant Cell They both have the following 1. Cell wall Absent Present (formed of cellulose) structures: 2. Vacuole Much smaller than of plant Contains one large central Cytoplasm cells. It contains one of more small vacuoles. vacuole Ribosomes 3. Centrioles Present in animal cells Only in lower plants Mitochondria 4. Chloroplast Absent Present 5. Plastids Absent Present Endoplasmic reticulum (smooth and 6. Cilia Present Most plant cells do not rough) contain cilia Golgi apparatus 7. Shape Round and Irregular in shape Fixed rectangular shapes Microtubules/ Microfilaments 8. Plasma membrane Only cell membrane Cell wall and a cell membrane Flagella 9. Flagella Absent but present in a few Present in some Nucleus 10. Lysosomes Occur cytoplasm Usually not evident 7 Plant Cell 8 Animal Cell 9  3. Functions of cells and cell organelles Cell Organelles and their functions - Some cell 5. Lysosome - Vesicles containing digestive organelles and their Functions: enzymes. Where the digestion of cell 1. Cell membrane - The thin layer of protein nutrients takes place. and fat that surrounds the cell. It is 6. Mitochondrion - The mitochondrion semipermeable, allowing some substances to pass into the cell and blocking others. converts the energy stored in glucose into 2. Cell wall - A thick, rigid membrane that ATP (adenosine triphosphate), a high energy surrounds a plant cell. It gives the cell most molecule, for use by the cell. of its support and structure. 7. Nuclear membrane - The membrane that 3. Chloroplast - An elongated or disc-shaped surrounds the nucleus. organelle containing chlorophyll. Photosynthesis (in which energy from 8. Nucleus – It’s a spherical body surrounded sunlight is converted into chemical energy - by the nuclear membrane. It contains food) takes place in the chloroplasts. mostly DNA in chromosomes. The nucleus 4. Chlorophyll - chlorophyll is a molecule that can use light energy from sunlight to turn controls many of the functions of the cell water and carbon dioxide gas into glucose (by controlling protein synthesis). The and oxygen (i.e. photosynthesis). nucleolus is found within the nucleus. Chlorophyll is green. 9. Ribosome - Small organelles composed of RNA. Are sites of protein synthesis. 10 Microscope 4. The Microscope In 1609, Galileo (an Italian) improved on the A microscope is a high precision optical instrument that uses a lens or a combination principle of lenses and added a focusing device to of lenses to produce highly magnified images improve upon what the Janssen’s had done. These of small specimens or objects too small to be rudimentary instruments didn’t change much until seen by the naked eye. the early 1670s. The use of a microscope for investigation or A Dutchman, Anton van Leeuwenhoek, is observation is called ‘Microscopy’ considered the father of microscopes because of History of the microscope the advances he made in microscope design and 1. Zacharias Janssen and Hans use. He worked as an apprentice in a dry goods Janssen(about 1590) store where magnifying lenses were used to count 2. Galileo Galilei (1609) the threads in cloth. 3. Antony Van Leeuwenhoek (1674) Anton was inspired by these glasses and he taught About 1590 two Dutch spectacle makers, himself new methods for grinding and polishing Zacharias Janssen and his son Hans, small lenses which magnified up to 270x. This led experimented with a crude concept of a to the first practical microscopes. In 1674, Anton microscope that enlarged objects 10x to was the first to see and describe bacteria, yeast, about 30x. plants, and life in a drop of water. 11  Not many improvements were made until the 1850’s  Parts of a Microscope and its functions when several inventors in Europe and America made vast 1. Eye piece (ocular): to observe object under study (usually improvements. with a magnification of x 10) In the early 1930’s the first electron beam microscopes 2. Objective lens: the lens closest to the specimen that were developed which were a breakthrough in magnifies the object under view. technology as they increased the magnification from about 1000x or so up to 250,000x or more. These 3. Nose piece (turret): for rotation of lens while viewing an microscopes use electrons rather than light to examine object. objects. 4. Iris Diaphragm: Controls the amount of light that reaches  Types of Microscope the specimen. Optical microscope(Light microscope)- It relies on light to 5. Focus knob: observe the magnified image/specimen, the types of light microscope are: a. Coarse focus knob – 1. Compound microscope (High power microscope) b. Fine focus knob - fine tunes the focus and increases the detail of the specimen. 2. Stereo or Dissecting microscope (Low power microscope) 6. Aperture: The hole in the middle of the stage that allows Electron microscope: Scanning electron microscope light from the illuminator to reach the specimen. (SEM) and Transmission electron microscope (TEM) 7. Mechanical stage: for placing slides for observation. Fluorescence microscope 8. Safety rack stop: for focusing and moving the mechanical stage Scanning probe microscope 9. Condenser: for focusing light on the specimen under others observation. 10. Arm: supports and connects the tube of the microscope to its base. 11. Base: gives support to the microscope. 12 A Monocular Light Microscope 13 A binocular Light Microscope 14  4X, 10X 40X and 100X objective lenses Objective lenses of a compound microscope Objectives mounted The Objective lenses gathers the light passing through the specimen and magnifies it by the respective power of the lenses. 15 Microscope accessories Precautions when handling a microscope Blank and prepared slides Always support the microscope with two hands Filters when carrying (one hand at the arm and the other at the base of the microscope). Cover slip etc. When viewing an object/image through the Terms associated with Microscopes microscope, focus the eye by looking into the respective eye piece (left eye-left eye piece and Magnification – Enlargement of an object i.e. right eye-right eye piece). the number of times the image is larger than the object, it is determined by multiplying the If immersion oil was used, wipe it from the lens power of the eye piece by the power of the with lens paper at the end of each session of objective lens being used e.g. use. Mg = 40 objective lens X 10 eyepiece = 400(the Only the 100x objective can be used for specimen was magnified 400 times) viewing under immersion oil. All other Field of View – It is the diameter of the cycle lenses are to be used without immersion oil; of light that is seen when looking into a keep them dry and avoid applying oil or any microscope and it is measured in millimeters. liquid to them. Turn of the light of the microscope after use. Cover the microscope with the microscope bag/cover when not in use to prevent dust and other particles that can cause damage to the microscope. 16 Suggested Books for further reading: 1. Taylor, D.J., Green, N.P.O and Stout, G.W. (2010) Biological Sciences. Cambridge University Press, 10th Edition, South Africa. 2. “The Microscope and how to use it” by George Stehli 3. Anatomy, Histology and Cell biology Pre-Test Self- Assessment and Review, Third Edition by Robert M. Klein 17