Lecture 1 General Introduction to Cell Biology PDF

CELL BIOLOGY COURS Lecture (1) General Introduction to Biology Lecture out line: * Definition of Biology. *Branches of Biology. *Characteristics of living organisms. *Cell Theory. *The Domains of life. What is Biology? Biology is a natural science...

CELL BIOLOGY COURS Lecture (1) General Introduction to Biology Lecture out line: * Definition of Biology. *Branches of Biology. *Characteristics of living organisms. *Cell Theory. *The Domains of life. What is Biology? Biology is a natural science concerned with the study of life and living organisms, including their form, function, growth, origin, evolution, distribution, and classification. Origin of word “biology”: The word Biology (Greek word) is divided into two parts: Bios = life Logos = Study of (science of). Branches of Biology: Zoology (Study of animals). Cytology (Study of cell). Botany (Study of plants). Parasitology (Study of parasites). Human Biology (Study of human). Genetics (Study of heredity). Entomology (Study of insects). Taxonomy (Study of classification). Ecology (Study of environment). Microbiology (Study of small organisms). Histology (Study of tissues). 1 Characteristics of living organisms: The characteristics of living organisms provide great insight into the unique nature of organisms and help us distinguish living things from nonliving things. Living Organisms Characterized by the Following: 1_ Organization: Living organisms are organized. The levels of organization begin with atoms, which are the basic units of matter. Cells are basic units of living organisms. Cellular Organization: Cell Organelle Molecule Atom Atom: Smallest unit of element composed of electrons, protons, and neutrons. Molecule: Union of two or more atoms of the same or different elements. Organelle: Small membranous structure in the cytoplasm having a specific structure and function. Cell: The basic structural, functional and biological unit of all known living organisms. 2 Organismal Level: Organism Organ system Organ Tissue Cell Cell: The basic structural, functional and biological unit of all known living organisms. Tissue: A group of cells with a common structure and function. Organ: Composed of tissues functioning together for a specific task. Organ system: Composed of several organs working together. Organism: An individual; complex individuals contain organ systems. According to the number of cell, living organism are divided into two types: A. Unicellular organisms: The body is composed of only one cell. Bacteria, Paramecium, Amoeba, Euglena. B. Multicellular organisms: The body is composed of more than one cell. Human, Animals, Plants. 2_ Nutrition. Living things cannot maintain their organization or carry on life’s activities without an outside source of nutrients. Food provides nutrients, which are used as building blocks of the body or for energy. According to their source of food, living organisms are divided into: 3 A. Autotrophic organisms: Make their own organic food from inorganic materials and a source of energy. (plants and algae). They possess chlorophyll and carry on photosynthesis: 6CO2+6H2O light energy & chlorophyll C6H12O6+6O2. B. Heterotrophic organisms: Feed on organic molecules made by other organisms. Herbivores: Feed directly on plants or algae. (Insects, antelopes, and bison). Carnivores: Feed on other animals. (Birds, hawks, and lions). Omnivores: Feed on both plants and animals such as (Chickens, raccoons, and humans). 3_ Acquisition of Energy: The ultimate source of energy for nearly all life on Earth is the SUN. Plants capture solar energy and carry on photosynthesis to produce nutrients. All life on Earth acquires energy by metabolizing nutrient molecules made by plants and other autotrophic organisms. 4_ Respiration: Respiration is the sequence of events that results in gas exchange between the body’s cells and the environment. In terrestrial vertebrates, respiration includes these steps: Ventilation (breathing): includes inspiration and expiration. 4 External respiration: gas exchange between the air and the blood within the lungs. Internal respiration: gas exchange between the blood and the body’s cells. In the end, oxygen enters Mitochondria, where cellular respiration takes place. Cellular Respiration is the release of energy from digested food. Cellular Respiration: C6H12O6+6O2 6CO2+6H2O + ATP. 5 5_ Reproduction: Life comes only from life. Every type of living thing can reproduce, or make another organism like itself. Bacteria, protists, and other unicellular organisms simply split in two (Asexual Reproduction). In most multicellular organisms, the reproductive process begins with the pairing of a sperm from one partner and an egg from the other partner (Sexual Reproduction). 6_ Adaptation. The process by which a species becomes fitted to its environment; it is the result of natural selection's acting upon heritable variation over several generations All organisms need to adapt to their habitat to be able to survive 6 7_ Homeostasis: Homeostasis, from the Greek words for "same" and "steady," refers to any process that living things use to actively maintain fairly stable conditions necessary for survival. The term was coined in 1930 by the physician Walter Cannon A state of balance among all the body systems needed for the body to survive and function correctly. Three examples of homeostasis are: Body temperature regulation. Blood pressure regulation. Blood sugar regulation 8_ Locomotion: Locomotion is the ability to move and the act of moving from one place to another. Locomotion and movement are two important terms in the study of motion and the most important features in all living beings. All living organisms excluding plants move from one place to another in search of food, shelter, to escape predators and for a variety of reasons. 9_ Growth & Development: Increase in size, weight, complexity and may be accompanied with differentiation and organization. Growth refers to the increase in mass and size of a body or organs. It typically occurs through the multiplication of cells and an increase in intracellular substance. Development refers to the physiological and functional maturation of the organism 7 10_ Respond to Stimuli: Response to stimuli is any action made by a biological system after a variation in its homeostatic balance is detected through stimuli. Responses are often corrective actions that counteract change restoring balance in the case of the homeostatic negative feedback loops. The cell was first discovered and named by Robert Hooke in 1665. He remarked that it looked strangely similar to cellula or small rooms which monks inhabited, thus deriving the name. However what Hooke actually saw was the dead cell walls of plant cell (cork) as it appeared under the microscope. * The Dutch shopkeeper Antoni van Leeuwenhoek (1632–1723) may have been the first person to see living cells by the use of the microscope. In this way, Antoni van Leeuwenhoek reported seeing the parasite Giardia lamblia in his feces. Giardia lamblia 8 Cell Theory: The cell theory is based upon the work of Schleiden, Schwann, Virchow and many other scientists. 1. Schleiden (1838): All plants are made of cells! 2. Schwann (1839): All animals are made of cells! 3. Virchow (1850s): All cells come from pre-existing cells! The Cell Theory states: The cell theory is based upon the work of Schleiden, Schwann, and Virchow. It states that: 1. All organisms are composed of cells. 2. Cells are the basic units of structure and function in organisms. 3. Cells come only from preexisting cells because cells are self- reproducing. There are two different types of cells exist: 1- Prokaryotic cells: Which lack a membrane-bounded nucleus and the DNA (deoxyribonucleic acid) is located in a region called a nucleoid. They are present in great numbers in the air, in bodies of water, in the soil, and they also live in and on other organisms. Although they are structurally less complicated. E.g. Domain Bacteria and Domain Archaea. They are an extremely successful group of organisms whose evolutionary history dates back to the first cells on the earth. 9  Bacterial cell 2- Eukaryotic cells are defined as cells containing organized nucleus and organelles which are enveloped by membrane-bound organelles. Examples of eukaryotic cells: Animal cells, plant cells, fungi and protists. The Domains of Life: Because life is so diverse, it is helpful to group organisms into categories. Taxonomy is the discipline of identifying and grouping organisms according to certain rules. 10 Several of the basic classification categories, or taxa, going from least inclusive to most inclusive, are species, genus, family, order, class, phylum, kingdom, and domain. Organisms in Life are Classified into Three Domains: 11 1. Domain: Bacteria Kingdom: Eubacteria 2. Domain: Archaea Kingdom: Archaebacteria 3. Eukarya Domain: 1. Kingdom: Protista 2. Kingdom: Fungi 3. Kingdom: Plantae 4. Kingdom: Animalia 12