Cells - PDF

What is a cell? CELL ● Cells are the basic structures of all living organisms. ● Cells provide structure for the body, take in nutrients from food and carry out important functions. ● Cells group together to form tissues, which in turn group together to form organs?, such as the heart and brain....

What is a cell? CELL ● Cells are the basic structures of all living organisms. ● Cells provide structure for the body, take in nutrients from food and carry out important functions. ● Cells group together to form tissues, which in turn group together to form organs?, such as the heart and brain. What are organelles? ORGANELLES ● contain a number of functional structures ● they carry out tasks such as making proteins, processing chemicals and generating energy for the cell. Organelles- are specialized structures that perform various jobs inside cells. - The term means “little organs.” the organelles serve specific functions to keep a cell alive. Discovery of cells The cell was first discovered by Robert Hooke in 1665, he uses compound microscope. One observation was from very thin slices of bottle cork. Hooke discovered a multitude of tiny pores that he named "cells". This came from the Latin word Cella, meaning ‘a small room’ Cell Theory, which states that: ● all organisms are made up of one or more cells ● all the life functions of an organism occur within cells ● all cells come from preexisting cells. PROPONENTS OF CELL THEORY 1. THEODOR SCHWANN “Cell is the basic unit of Life” -All organisms are made up of Cells -While looking at cork, Hooke observed box-shaped structures, which he called “cells” as they reminded him of the cells, or rooms, in monasteries. This discovery led to the development of the classical cell theory. The classical cell theory was proposed by Theodor Schwann in 1839 Theodor Schwann (1810-1882) German physiologist who founded modern histology by defining the cell as the basic unit of animal structure. PROPONENTS OF CELL THEORY 2. MATTHIAS JAKOB SCHLEIDEN “All the life functions of an organism occur within cells” *All living organisms are made up of cells Matthias Jakob Schleiden In 1838, Matthias Schleiden, a German botanist, concluded that all plant tissues are composed of cells and that an embryonic plant arose from a single cell. He declared that the cell is the basic building block of all plant matter. This statement of Schleiden was the first generalizations concerning cells. PROPONENTS OF CELL THEORY 3.RUDOLF VIRCHOW Virchow's theory stated that just as animals are unable to arise without previously existing Rudolf Virchow animals, cells are unable to arise without previously existing cells. The idea that new cells arose from pre-existing cells in both diseased and healthy tissue was not original ● all cells come from preexisting cells. ● proposed that omnis cellula e cellula, which translates to each cell comes from another cell, and which became a fundamental concept for cell theory , In 1855, at the age of 34. Cell Division WHAT IS CELL DIVISION? ➔ The process in which the parent cell divides, eventually giving rise to new daughter cells ➔ It is the means used by multicellular organisms in order to grow, replenish (repair), and reproduce Life of a cell • Millions of cells in your body die every minute but are constantly being replaced. • The process is called the cell cycle • Most of the cell cycle process is spent growing. • A small portion of time is taken to divide. What are these? • Humans: • 23 pairs • 46 total • 22 pairs = autosomes • Autosomes control the inheritance of all an organism's characteristics except the sex-linked ones, • 1 pair = sex-determining Autosomes control the inheritance of all an organism's characteristics except the sex-linked ones, Chromosomes • Chromo: visible • Some: body • Passes genetic information from generation to generation. • Chromosomes are copied in the cell cycle. • Each chromosome has two identical “sister” chromatids • Sister chromatids are attached at the centromere • When the cell divides, the chromatids separate • Each new cell gets one chromatid. MITOSIS ❖ Mitosis is a process where a single cell divides into two identical daughter cells (cell division). ❖ The major purpose of mitosis is for growth and to replace worn out cells. MEIOSIS ❖ Meiosis is a process where a single cell divides twice to produce four cells containing half the original amount of genetic information. These cells are our sex cells – sperm in males, eggs in females. ❖ Therefore the purpose of meiosis is to produce gametes, the sperm and eggs, with half of the genetic complement of the parent cells. DEFINITION OF TERMS 1. PROPHASE -the initial stage of mitosis and of the mitotic division of meiosis characterized by the condensation of chromosomes consisting of two chromatids, disappearance of the nucleolus and nuclear membrane, and formation of mitotic spindle. 2. METAPHASE is a stage in the cell cycle where all the genetic material is condensing into chromosomes. These chromosomes then become visible. During this stage, the nucleus disappears and the chromosomes appear in the cytoplasm of the cell. 3. ANAPHASE the stage of mitosis and meiosis in which the chromosomes move toward the poles of the spindle. 4. TELOPHASE is the fifth and final phase of mitosis, the process that separates the duplicated genetic material carried in the nucleus of a parent cell into two identical daughter cells. ... During telophase, a nuclear membrane forms around each set of chromosomes to separate the nuclear DNA from the cytoplasm. 5. CHROMOSOMES a structure found inside the nucleus of a cell. A chromosome is made up of proteins and DNA organized into genes. Each cell normally contains 23 pairs of chromosomes. 6. A CHROMATID is one of two identical halves of a replicated chromosome. During cell division, the chromosomes first replicate so that each daughter cell receives a complete set of chromosomes. Mitosis • PMAT: Four phases of Mitosis • Prophase: • Centrioles separate and move to opposite sides of the nucleus. • Chromosomes become visible • Metaphase: • Chromosomes line up at the Middle of the cell • Spindle fibers connect to the centromere of each chromosome, ready to separate them. • Anaphase: • Sister chromatids separate and move apart. • A-shaped • Telophase: • Chromosomes go to opposite ends of cell and lose their shape • New nuclear envelopes form around chromosomes • Cell pinches at the middle (except if cell wall is present) Cytokinesis • Cytoplasm pinches in half: Furrowing • Each new daughter cell has an identical set of chromosomes. • Identical to parent cell • Cell cycle begins again