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Transcript
Cells Overview Chapter 3 for Anatomy Chapter 7 for Biology Life is Cellular A cluster of neural cells were derived from human embryonic stem cells in the lab. The motor neurons are shown in red; neural fibers appear green and the blue specks indicate DNA in cell nuclei. Microscopes • • • • • • • Mid 1600s 1665 Robert Hooke 1st Compound Microscope After looking at Cork Saw cambers called Cells Anton Van Leeuwenhoek Pond water (animalcules) Cork Cells / Microscopic Animals • Cork Cells at 100X Magnification / Plankton have limited powers of locomotion Scanning Electron Microscope • SEM is a type of electron microscope that images the samples surface by scanning it with a high-energy beam of electrons. Transmission Electron Microscope • TEM uses a beam of highly energetic electrons to examine objects very closely, on a fine scale. A TEM shines a beam of electrons through an object. Scanning Probe Microscope • SPM is a branch of microscopy that forms images of surfaces using a physical probe that scans the specimen. Cell theory • All organisms are comprised of more than one cell • Cell is the basic unit of life • All cells come from preexisting cells What is an organelle? Membrane bound structures with particular functions within eukaryotic cells Types of Organelles • • • • • • • • • • • Nucleus Cell membrane Ribosomes Endoplasmic reticulum Golgi Apparatus Lysosomes Vacuoles Mitochondria Chloroplast – Plants only Cell wall – plants only Cytoskeleton Bacteria cell Cell Wall • The rigid cell wall of plants is made of fibrils of cellulose embedded in a matrix of several other kinds of polymers • Bacteria cell wall is made up of polysaccharides and protein. Chloroplast • Captures light energy in plants and produces ATP and reduce NADP to NADPH through a complex set of processes called photosynthesis. Endoplasmic Reticulum • Synthesis of protein and lipids – Rough ER – protein synthesis – can exsist in cytoplasm – Smooth ER – lipid synthesis Ribosomes • • • • Sites of protein synthesis Scattered throughout cytoplasm Comprised of protein and RNA molecules Provide structural support for RNA during protein synthesis from amino acids Golgi Bodies • Composed of six flattened membranous sacs • Packages and delivers proteins synthesized by ribosomes • Proteins arrive at this spot in vesicles, where glycoproteins are to be received Golgi Bodies • They pass through one end and continue to pass over the sac until the protein is chemically processed • When the altered glycoprotein reaches outermost layer, then bubblelike structures form and move throughout the cell membrane – exocytosis Mitochondria • Elongated fluid filled sacs • Move slowly through cytoplasm and reproduce by dividing • Has inner and outer layers Mitochondria • Inner layer has cristae that control some chemical reactions, through enzymatic processes • Chemical reactions release energy • Major site of ATP production – energy for the cell Lysosome • “garbage men” of the cell • Membranous sacs • Powerful enzymes that breakdown nutrient molecules or foreign particles • In blood cells – can destroy bacteria • In cells in general – can breakdown dead cell parts Microfilaments • Tiny rods of actin protein that form meshwork or bundles • Provide cell mobility • In muscle cells – they aggregate to form myofybrils, which help the cells to contract Microtubules • Long slender tubes with diameter two to three times that of microfilaments • Composed of globular tubulin proteins – 9+2 array (9 outside, 2 inside) Centrosome • Structure near Golgi Apparatus and nucleus • Consists of two hollow cylinders called centrioles • Lie at right angles and distribute chromosomes evenly to new cells during mitosis. Cilia • • • • Motile extensions from certain cells Comprised of microtubules in 9+2 array Tiny hairlike structures Move to and fro, in succession, so that there is a wavelike motion Flagella • • • • Motile extensions from certain cells Comprised of microtubules in 9+2 array A cell will only normally have one flagellum Swim motion Vesicles • Or vacuoles • Membranous sacs formed by part of the cell membrane folding inward and pinching off • Material outside the cell is now inside and in the cytoplasm Cell Nucleus • Houses genetic material • Enclosed in a double layer nuclear envelope – inner and outer lipid bilayer membranes • Protein-lined channels called nuclear pores that allow for certain molecules to exit Nucleolus • Small dense body composed largely of RNA and protein • No surrounding membrane • Forms in specialized regions of certain chromosomes • Ribosomes form in the nucleolus and move through nuclear pores to the cytoplasm Chromatin • Loosely coiled fibers of DNA and proteins = chromosomes • DNA = information for protein synthesis • Beginning of cell division – chromatin coil tightly and individual chromosomes become visible Cell Membrane Structure • A phospholipid consists of a – polar portion, called the head, – two longer fatty acids, called the tail. Cell Membrane Structure http://www.mhhe.com/biosci/esp/2002_general/Esp/default.htm When mixed with water, the heads are attracted to the polar water molecules. The nonpolar tails move as far from water as possible, and a double layer of phospholipids with tails to the interior results. Phospholipid bi-layer of a cell membrane