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Transcript
The Study of the cell Cell: the smallest unit that can carry on all of life’s processes CELL THEORY A theory resulting from many scientists’ observations & conclusions CELL THEORY 2. All living things are made of 1 or more cells. Matthias Schleiden (botanist studying plants) Theodore Schwann (zoologist studying animals) stated that all living things were made of cells Schwann Schleiden CELL THEORY 3. All cells divide & come from old cells. (Virchow) Virchow Ocular Lens Body Tube Nose Piece Arm Objective Lenses Stage Clips Diaphragm Stage Coarse Adj. Fine Adjustment Light Source Base Skip to Magnification Section Magnification To determine your magnification…you just multiply the ocular lens by the objective lens Ocular 10x Objective 40x:10 x 40 = 400 So the object is 400 times “larger” Objective Lens have their magnification written on them. Ocular lenses usually magnifies by 10x TOTAL MAGNIFICATION Powers of the eyepiece (10X) multiplied by objective lenses determine total magnification. Using a Microscope Start on the lowest magnification Don’t use the coarse adjustment knob on high magnification…you’ll break the slide!!! Place slide on stage and lock clips Adjust light source (if it’s a mirror…don’t stand in front of it!) Use fine adjustment to focus FROM CELL TO ORGANISM Cell The basic unit of life Tissue Group of cells working together Organ Group of tissues working together Organ System Group of organs working together Organism Any living thing made of 1 or more cells Eukaryotic Cell http://www-class.unl.edu/bios201a/spring97/group6/eukcell.jpg Parts of Eukaryotic Cells Endoplasmic Reticulum Nucleolus Cytoplasm DNA Mitochondria Vesicles Golgi Complex Ribosomes Nucleus Cell Membrane - Parts of Eukaryotic Cells CELL MEMBRANE (Plasma membrane) Outer covering, protective layer around ALL cells Allows food, oxygen, & water into the cell & waste products out of the cell. CELL MEMBRANE (Plasma membrane) The boundary of the cell…separates inside from outside of cell Is Semipermeable Membrane: allows some substances into cell and keeps others out of cell. CELL MEMBRANE (Plasma membrane) Has a phospholipid bilayer. The lipid molecules are fluid and can move past one another in a fluid manner…also allows proteins to move and change in this layer thus scientist explain cell membrane and call it a Fluid Mosaic Model Cell Membrane are made of a phospholipid bilayer A Phospholipid Bilayer Phospholipids can form: BILAYERS -2 layers of phospholipids with hydrophobic tails protected inside by the hydrophilic heads. The PHOSPHOLIPID BILAYER is the basic structure of membranes. NUCLEUS Directs all cell activities Contains instructions for everything the cell does These instructions are found on a hereditary material called DNA Usually the largest organelle Parts of the nucleus Nuclear envelope Nuceolus Nucleoplasm chromosomes Actual Cell Nucleus NUCLEOLUS Aka “little nucleus” Found in the nucleus Contains RNA and proteins for ribosome synthesis CHROMATIN contains genetic code that controls cell made of DNA & proteins Condenses to form chromosomes during cell division Made of DNA and proteins Parts include: 2 sister chromatids held together by the centrally located centromere Cytoplasm gelatin-like inside cell membrane constantly flows aka protoplasm It contains the various organelles of the cell Contains the various organelles Internal Organization: Organelles = perform specific functions. - function like tiny organs, analogous to organs of a multicellular body. Centrioles Short cylinder near nuclear envelope There generally are 2 at right angles to each other They control cell division ENDOPLASMIC RETICULUM A series of folded membranes that move materials (proteins) around in a cell like a conveyor belt Smooth ER – ribosomes not attached to ER, functions in lipid synthesis Rough ER – ribosomes attached to ER, functions in producing proteins RIBOSOMES Make proteins Float freely or attached to the endoplasmic reticulum (ER) Ribosomes are made in the nucleolus and are small particles of RNA GOLGI BODIES (GAWL jee) Stacked flattened membranes Sort and package proteins LYSOSOMES (LI suh sohmz) The word "lysosome" is Latin for "kill body." The purpose of the lysosome is to digest things. They might be used to digest food or break down the cell when it dies. Break down food molecules, cell wastes & worn out cell parts MITOCHONDRIA Organelles that release energy from food (power house of cell) This energy is released by breaking down food into carbon dioxide the powerhouse b/c they release energy (ATP) from food Folds of mitochodria are called: VACUOLES Temporary storage spaces Store food, water, waste CYTOSKELETON scaffolding-like structure in cytoplasm that gives cell its shape helps the cell maintain or change its shape made of protein microfilaments and microtubules Microfilaments Built from actin, a globular protein and function in support of cytoskeleton and localized contraction of cell Microtubules Found in cytoplasm of all eukaryotic cells and function in cell support Microbodies Various membrane bound organelles that contain specialized teams of enzymes for specific metabolic pathways important types: 1. peroxisomes: break down H2O2 and detoxify alcohol Intermediate filaments Size intermediate to microtubules and microfilaments. Function in reinforcing cell shape Cilia Short hair like projections from the cell that by beating produce organized movement. Found in the trachea Flagella Long whiplike organelle whose action produces movement. Extracellular material Found outside cell Material secreted by cell into the cell matrix, ranging from saliva, to gastric juices, ext… Transport through cell membranes There are 5 basic mechanisms: 1. DIFFUSION 2. OSMOSIS 3. ACTIVE TRANSPORT 4. FILTRATION 5. ENDOCYTOSIS Diffusion is the net movement of molecules (or ions) from a region of their high concentration to a region of their lower concentration. The molecules move down a concentration gradient. Ex oxygen diffuses from RBC to cells body Osmosis = Water diffusion, moving “down” the gradient The net direction of osmosis depends on the solute concentrations on both sides. Hypotonic = lower solute concentration Hypertonic = higher solute concentration Isotonic = equal concentrations on both sides of the membrane Osmosis in Red Blood Cells Active Transport requires energy use to move materials up their concentration Moves from an area of low concentration to an area of high concentration Example: sodium-potassium pump Ex nerve cells transport sodium ions to extracellular environment Ion Pump for Na+ and K + process by which cells ingest external fluid, macromolecules, and large particles, including other cells Two Types of Endocytosis - Pinocytosis = Cell drinking - Phagocytosis = Cell eating Exocytosis of Vesicle Contents Filtration Molecules pass through a membrane by physical force during filtration Ex blood pressure forces substances to leave circulation The process by which cells reproduce themselves. Two types (Mitosis and Meiosis) I. Mitosis = produces body cells with identical genetic material as the original. II. Meiosis = reduces the chromosome number by half in the sex cells. (haploid) Chromosomes – composed of 2 sister chromatids connected by centromere During cell division in eukarotic cells the DNA is coiled into very compact chromosomes, made of both DNA and proteins. Chromatid – each chromosome consists of two identical halves called chromatids (= copies Chromatin - Before cell division, the DNA is not tightly coiled, but loosely arranged, and its codes can then be read by the cell to direct the cell’s activities. chromosome centromere chromatids Homologues or homologous chromosomes The cycle = repeating set of events composing the life of a cell. * There are two periods: Interphase and Cell Division * Interphase is the time between divisions, and is divided into three phases. 1. G1 phase – offspring cells grow to mature size (= Gap after division and before DNA replication) 2. S phase – The DNA is copied 3. G2 phase – Gap after DNA synthesis & before division. (The cell is preparing for division.) * Cells can exit the G1cell cycle at G1 and enter a state called Go phase. (In G0 , nerve cells for example stop dividing.) Chromosomes duplicate Chromosomes are not visible Nucleus has clearly defined nucleus LOOKS SPAGHETTI LIKE, longest phase The DNA which was copied in S phase, now supercoils. Nucleolus and nuclear membrane break down. Centrosomes with centrioles move to poles. (Plants have no centrioles.) Spindle fibers (microtubules) radiate from them. Mitotic spindle is this array of fibers. Metaphase – CHROMOSOMES line up in a straight line in the center ( equatorial plane) of the cell . Centromere of each pair of chromatids attaches to a separate spindle fiber. Anaphase – centromeres & chromatids separate. (Each new chromosome moves slowly to opposite poles Shortest phase Looks like they have wiped out waters skiing Plant Anaphase 3-D Telophase – spindle fibers disassemble, chromatin forms, nucleus reappears. (new nuclear envelope forms for each set of chromosomes Cell plate forms in plant cell Cleavage furrows appear in animal cells Mitosis Telophase Metaphase Prophase Anaphase Cell Division Puzzle: Mitosis Unscramble it by labeling & numbering the stages. Metaphase (second) Telophase (fourth) Cytokinesis (fifth) Interphase (sixth) Prophase (first) Anaphase (third) Meiosis is a process in which gonad cells divide twice to produce haploid cells. * Gonads are sex organs (ovaries and testicles). * Gametes (sex cells – sperm and eggs) are the resulting haploid cells. * Cells preparing for meiosis first undergo the G1, S, and G2 phases of interphase. Meiosis I and Meiosis II are the names for the two divisions of Meiosis. There are some important differences in the stages compared to mitosis. Exploring Meiosis Meiosis I – Has four stages, plus Cytokinesis (Prophase I, Metaphase I, Anaphase I, Telophase I) * Similar to mitotic prophase except for Synapsis. Synapsis is where the homologues pair up & twist around one another. Tetrads is the term for these paired homologues (4 chromatids). Crossing-Over then occurs where parts of the chromatids exchange genes. Genetic Recombination is the result, which increases variation. tetrads line up randomly at the mid- line of cell - Spindle fibers from one pole attach to one centromere of one homologue. - Spindle fibers from the other pole attach to the other homologue’s centromere. * the spindle fibers randomly pull the homologues to separate poles. - Independent Assortment is the term for the random separation. - Note that the centromeres do not split the chromatids at this point. - The homologous chromosome (consisting of two chromatids) stays intact. Telophase I – is the final phase of Meiosis I, and the chromosomes reach the poles. Cytokinesis then begins to separate the cytoplasm into TWO new cells. At this point, the TWO new cells contain a Haploid number of chromosomes, yet each has two sister chromatids (copies) attached by a centromere. Meiosis II - the DNA is NOT duplicated in meiosis II. * Prophase II – spindle fibers form and begin moving chromosomes to midline. * Metaphase II – chromosomes are at the midline, facing the poles. * Anaphase II – chromatids separate at the centromeres and move to opposite poles. * Telophase II & Cytokinesis results in four haploid cells, each with a single chromatid. Formation of Gametes* Spermatogenesis = male testes cell produces four gametes called spermatids. * Oogenesis = female ovaries produce eggs (ova), but only one ova (not four) is produced from the meiotic divisions of each ovary cell. - The other three “donate” most of their cytoplasm to the one mature ova, so that it has plenty of energy reserves to grow once it is fertilized by a sperm. Cell Growth and Reproduction DNA transcription to RNA Translation to protein DNA contains the genetic info for making proteins Cells make protein by translating the genetic codes into protein So DNA controls life by controlling protein synthesis Replication: DNA copies itself Transcription: DNA copies to mRNA Translation: mRNA copies to tRNA to protein 3 Types of RNA: mRNA: found in the cytoplasm and specifies the exact sequence of amino acid tRNA: acts as an interpreter molecule which recognize specific amino acids and nucleotide base sequences rRNA: forms part of the protein synthesis site in the cytoplasm Synthetase enzymes: attach the correct amino acids to its transfer RNA