Cell Theory PDF

CELL THEORY Cell- primary building blocks of life. They come in all shapes and sizes. Discovery of Cells  Robert Hooke (1665) – cells were first recorded.  Improving the design of microscope when he observed a piece of cork.  He saw box-like structures (cell wall) The Cell Theory...

CELL THEORY Cell- primary building blocks of life. They come in all shapes and sizes. Discovery of Cells  Robert Hooke (1665) – cells were first recorded.  Improving the design of microscope when he observed a piece of cork.  He saw box-like structures (cell wall) The Cell Theory  German scientists: Theodor Schwann, Matthias Schleiden, Rudolph Virchow. 3 Postulates of Cell Theory 1. All living things are composed of one or more cells. 2. Cells are the basic unit of life. 3. All cells come from preexisting cells. Cell Theory Timeline  Robert Hooke (1665) – he coined the term “cellulae” which was shortened to “cell” when he observed the cork.  Antoine van Leeuwenhoek – (1660) observed protists (single-celled organisms) that he called animacules from pond water; (1670) observed the bacteria from his teeth (dental scrapings).  Matthias Schleiden (1838) – concluded that plants are made of cells.  Theodor Schwann (1839) – animal consists of cells and cell products (basic unit of animal structure).  Robert Remak (1842) – three layers of the early embryo: ectoderm, mesoderm, endoderm.  Rudolph Virchow (1855) – concluded “omnis cellula e cellula” which means “all cells develop only from preexisting cells.” PLANT & ANIMAL CELLS (ORGANELLES & STRUCTURES)  Organelles – different structures inside a cell that each have different jobs or functions to complete within the cell. TYPES OF ORGANELLES  Cell Membrane (plants/animals) – helps keep fluid and other organelles inside the cell. Acts as a “security guard.”  Cell Wall (plant) – helps keep everything inside the cell protected. It keeps anything harmful outside of the cell.  Cytoplasm (plants/animals) – fluid that fills a cell. Made up of many dissolved molecules, can be used for other processes throughout the cell.  Nucleus (plants/animals) – controls growth and reproduction. Located near the center of the cell. Contains all chromosomes.  Nucleolus (plants/animals) – found inside the nucleus. Made of RNA and protein. Looks like a nucleus inside of a nucleus.  Chloroplast (plant) – converts light energy of the sun into sugars. Photosynthesis takes place.  Mitochondria (plants/animals) – performs cellular respiration. Nutrients are broken down and turned into the energy the cell can use. “Powerhouse” of the cell.  Golgi Apparatus (plants/animals) – combinations of molecules into new and more complex molecules then sends them out of the cell or stores them. Functions in secretion. Exports proteins, carrying them from the ribosomes to the membrane.  Smooth ER (plants/animals) – attached to the nucleus that’s important in the creation and storage of lipids.  Rough ER (plants/animals) – attached to the nucleus, works with ribosomes to help with the synthesis and packing of proteins.   Vacuole (plants/animals) – a storage bubble that stores food and nutrients the cell needs to survive. Larger in plant.  Ribosomes (plants/animals) – build long chains of amino acids for the cell known as the “protein builders” of the cell which the cell makes new parts and reproduces itself.  Peroxisome (plants/animals) – digests nutrient and helps break down toxic materials. Have digestive enzymes in their membrane to digest nutrients like amino acids, cholesterol, and fatty acids.  Lysosome (animal) – helps digest and break down food in the cell with the help of enzymes that are stored here.  Microtubules (animal) – provide structure to the cell. Helps with the cell division.  Centrioles (animal) – helps the cell divide during mitosis and meiosis. Made up of microtubules. THE DIFFERENCES BETWEEN CELLS PLANT CELLS ANIMAL CELLS Have cell walls Don’t have cell wall – Have larger vacuoles only a cell membrane Have centrioles CELLS  Some organisms are composed of just one cell.  Other organisms (like plant, animals, humans) are composed of trillions of cells. 2 MAJOR TYPES OF CELLS  Prokaryotes  Eukaryotes SIMILARITIES  Have DNA  Have a cell membrane  Have carbohydrates, proteins, nucleic acids, minerals, fats, vitamins. DIFFERENCES  PROKARYOTES ARE OLD (3.5 billion years). Eukaryotes have been around 1.5 billion years.  Eukaryotes are much bigger. (10X bigger that prokaryotes). PROKARYOTES EUKARYOTES No membrane bound Has membrane bound organelle. organelle. No nucleus. Has nucleus. CELL CYCLE  Three major stages: Interphase, Mitosis, and Cytokinesis. 1. Interphase – G1 (Growth 1) phase, S (DNA Synthesis), G2 (Growth 2) phase. 2. Mitosis – prophase, metaphase, anaphase, and telophase. 3. Cytokinesis – cytoplasm divides.  Cell Division – process of reproducing cells. Occurs during growth, repair, and development of tissues.  Cell Cycle – repeating sequence of cellular growth and division throughout the life of an organism. A. G1 1. Cell grows rapidly and carries out routine functions. 2. Phase takes most of the cell’s life. 3. Muscle and nerve cells never divide, so they remain in G1. B. SYNTHESIS (S) 1. Cell’s DNA is copied.  2. At the end of the stage, each chromosome consists of 2 chromatids attached at a centromere. C. G2 1. Hollow microtubules are assembled. 2. Microtubules are used to move chromosomes during mitosis. D. MITOSIS 1. Nucleus is divided into 2 nuclei 2. Each nucleus ends up with the same number of chromosomes as the original cell. 3. Includes prophase, metaphase, anaphase and telophase. E. CYTOKINESIS 1. During this final stage, the cytoplasm divides. CONTROL OF THE CELL CYCLE There are three checkpoints: 1) G1 Checkpoint a. Decides when a cell can divide based on environmental conditions, health and cell size b. Favorable conditions begin S phase (If not favorable, a resting period begins) 2) G2 Checkpoint a. DNA repairs enzymes and checks DNA replication b. Once this checkpoint is passed, then mitosis begins 3) Mitosis Checkpoint a. Signals end of mitosis and G1 begins again What happens when checkpoints fail? 1. Cancer can occur. (Cancer is the uncontrolled growth of cells.) 2. Mutation missed by checkpoint can cause overproduction of growth hormone. 3. Damage done to a cell by environmental factors can cause cells to constantly repair. MEIOSIS Meiosis – type of cell division where a single cell divides twice and produces four daughter cells with half the amount of genetic material (sex cells). Importance – makes sure that all organisms produced via sexual reproduction contain the correct number of chromosomes - half from each parent. STAGES Prophase 1 – The chromosomes condense and the nucleolus breaks down. As chromosomes move around, crossing over happens - this means genetic material can be exchanged. Metaphase 1 – The chromosomes align in pairs in the centre of the cell. Random assortment occurs - this means that chromosome pairs line up randomly. Anaphase 1 – Chromosome pairs separate and move to opposite ends of the cell. This ensures each cell contains half the number of chromosomes (haploid). Telophase 1 – Two new nuclei form around each set of chromosomes. The cytoplasm splits and two (haploid) daughter cells are formed. Prophase 2 – Phase 2 happens to allow 4 haploid sex cells (sperm and egg cells) to be created. The chromosomes condense and the nucleolus breaks in both cells. Metaphase 2 – The chromosomes align single file in the centre of the cell. This occurs to ensure sister chromatids separate in the next stage. Anaphase 2 – Sister chromatids separate and move to opposite ends of the cell. This ensures the daughter cells remain haploid - that means they have half the genetic material of the original parent cell. Telophase 2 – Four new nuclei form around each set of chromosomes. The cytoplasm split and four (haploid) daughter cells are formed.