CELL THEORY Postulate: Demand and Claim To assume or claim as true, existent, Orr necessary: depend upon or start from the postulate of. A cell is the smallest unit that is capable of building organisms. History of Cell Biology 1595 – Zacharias Janssen credited first compound microscope 1626 – Francisco Redi postulated that living things do not arise from spontaneous generation 1655 – Robert Hooke describe cells in cork 1674 – Anton Van Leeuwenhoek discovered protozoa. He saw bacteria some 9years later. 1833 - Robert Brown described the cell nucleus in the cell of the orchid. 1838 Matthias Jakob Schleiden and Theodore Schwann, cell theory 1858 – Rudolph Virchow - (Physician, pathologist, and anthropologist) expounds his famous conclusion: omnis cellula e cellula that is cells develop only from existing cells (cells come from pre-existing cells). 1898 – Golgi describes the Golgi apparatus 1953 – Crick, Wilkins and Watson proposed structure of DNA double-helix Cell Organelles: ORGANELLES ● Cellular Machinery - Derived from membranes - Bacteria-like organelles ● "Little organs" ● Found in eukaryotic cells ● All the stuff in between the Organelles is cytosol. ● Everything in a cell except the nucleus is cytoplasm. Cell membrane ● Boundary of the cell ● Made of phospholipid bilayer Nucleus ● Control center of the cell ● Contains DNA ● Surrounded by a double membrane ● Usually the easiest organelle to see under a microscope ● Usually one per cell Cytoskeleton ● Acts as skeleton and muscle ● Provides shape and structure ● Help move organelles move around the cell ● Made of three filaments: Microtubules, Actin Filaments, Intermediate Filaments Endoplasmic reticulum E.R.: ● Connected to nuclear membrane ● Highway of the cell ● Rough ER, Soft ER Ribosome ● Site of the protein synthesis ● Found attached to rough ER or floating free in Cytosol ● Produced in a part of the nucleus called the Nucleolus Golgi apparatus ● Looks like a stack of plates ● Stores, modifies and packages proteins. ● Molecules transported to and from the Golgi by means of Vesicles Lysosomes: ● Garbage disposal of the cell ● Contain digestive enzymes break down wastes that Mitochondria ● Powerhouse of the cell ● Cellular respiration occurs here to release energy for the cell to use ● Bound by a double membrane 2 ● Has its own strand of DNA Chloroplast ● Found only in plant cells ● Contain green pigment called chlorophyll ● Site of food (glucose) production ● Photosynthesis Cell wall ● Found in plant and bacterial cells ● Rigid, protective barriers ● Made of Cellulose (fiber) Vacuole ● Large central vacuole usually in plant cells ● Many smaller vacuoles in animal cells ● Storage container for water, food, enzymes, wastes, pigments, etc. Centrioles ● Aids in cell division ● Usually found only in animal cells ● Made of Microtubules Prokaryotic cells vs eukaryotic cells Difference between prokaryotes and eukaryotes: ● Prokaryotic cells were here first for billions of years and wherein the only form of life on earth. All prokaryotic organisms are unicellular. ● Eukaryotic cells appeared on earth long after prokaryotic cells but they are much more advanced. Eukaryotic organisms unlike prokaryotic can be unicellular or multicellular. Characteristics of prokaryotes ● Prokaryotes are the simplest type of cell ● Oldest type of cell appeared about four billion years ago ● Prokaryotes are the largest group of organisms ● Prokaryotes unicellular organisms that are found in all environment Ringworms are fungus carried by pets or soil. Anti-fungal cream. Antibiotics target bacterias, reproduction destruction, cell walls. Organism itself, describing it Both have DNA, ribosomes, cytoplasm, cell membrane - maintains cell membrane Difference of Pro vs Euk DNA; in nucleoid region - membrane bound nucleus Size: usually smaller - usually larger Organization: usually one celled - often multicellular Metabolism: may not need oxygen - usually need oxygen to exist Organelles: no membrane bound organelles - membrane bound organelles Major divisions of the eukaryotic cell: Nucleus, other organelles, cytosol, cytoskeleton, plasma membrane Types of Cells Stem Cells – unique in that they originate unspecialized cells and have the ability to develop into specialized cells that can be used to build specific organs tissues. Bone cells – type of mineralized connective tissue that comprise a major component of the skeletal system. Bones are made up of a matrix of collagen and calcium phosphate minerals. 3 Blood Cells – from transporting oxygen throughout the body to fighting infection, blood cell activity is vital to life. projections called flagella. Female sex cells or ova are non-motile and relatively large in comparison to male gametes. Muscle Cells – form muscle tissue which enables all bodily movement. Three types: skeletal, cardiac and smooth Pancreas Cells – functions as both an exocrine and endocrine organ, meaning that it discharges hormones both through ducts and directly into other organs. Pancreatic cells are important for regulating blood glucose concentration levels as well as for the digestion of proteins, carbohydrates, and fats. Fat Cells – also called adipocytes, are a major cell component of adipose tissue, Adipocytes contain droplets of stored fat (triglycerides) that can be used for energy. Skin Cells – is composed of a layer of epithelial tissue (epidermis) that is supported by a layer of connective tissue (dermis) and an underlying subcutaneous layer. The outermost layer of the skin is composed of flat, squamous epithelial cells that are closely packed together. Nerve cells – neurons are the most basic unit of the nervous system. Nerves send signals between the brain, spinal cord, and other body organs via nerve impulses. Structurally, a neuron consists of a cell body and nerve processes. The central cell body contains the neuron's nucleus, associated cytoplasm, and organelles. Endothelial cells – form the inner lining of the cardiovascular system and lymphatic system structures. They make up the inner layer of blood vessels, lymphatic vessels, and organs including the brain, lungs, skin, and heart. Endothelial cells are responsible for angiogenesis or the creation of new blood vessels. Sex cells or gametes are reproductive cells created in male and female gonads that bring new life into existence. Male sex cells or sperm are motile and have long, tail-like Cancer Cells – work to destroy the body. Cancer results from the development of abnormal cell properties that cause cells to divide uncontrollably and spread to other locations. Cancer cell development can originate from mutations stemming from exposure to chemicals, radiation, and ultraviolet light. Cancer can also have genetic origins such as chromosome replication errors and cancer-causing viruses of the DNA. Cell Division Cell becomes two daughter cells 2 types: ● Mitosis/asexual reproduction division of body cells/somatic cells ● Meiosis division of sex cells/reproductive cells 3 reason why cells reproduce by asexual reproduction. - Growth, Repair, Replacement Cell Cycle – entire life of a cell. G1 (first gap) – daughter cell starts to grow S – Synthesis G2 – Second Gap 4 Mitosis Cycle ● Interphase – cell prepares for division ● Prophase – the cells prepares for nuclear division animal and plant cells both packages DNA into chromosomes ● Metaphase – The cell prepares chromosomes for division animal and plant cell both have chromosomes line up to the center of the cell, Spindle fibers attach from daughter cells to chromosomes at the centromere. ● Anaphase – the chromosomes divide animal and plant cells both have spindle fibers pull chromosomes apart ½ of each chromosomes (called chromatid) moves to each daughter cell. ● Telophase – the cytoplasm divides animal cells DNA spreads out 2 nuclei form, Cell wall pinches in to form the 2 new daughter cells while the plant cell DNA spreads out 2 nuclei form, NEW cell wall forms between to nuclei to form the 2 new daughter cells. ● Cytokinesis – Cell membrane moves inward to create two daughter cells – each with its own nucleus with identical chromosomes.
