* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Cell Structure and Diversity
Survey
Document related concepts
Cytoplasmic streaming wikipedia , lookup
Signal transduction wikipedia , lookup
Cell encapsulation wikipedia , lookup
Programmed cell death wikipedia , lookup
Cellular differentiation wikipedia , lookup
Tissue engineering wikipedia , lookup
Cell membrane wikipedia , lookup
Extracellular matrix wikipedia , lookup
Cell growth wikipedia , lookup
Cell nucleus wikipedia , lookup
Cell culture wikipedia , lookup
Cytokinesis wikipedia , lookup
Organ-on-a-chip wikipedia , lookup
Transcript
Cell Structure and Cell Diversity The Light microscope Eyepiece This lens magnifies (enlarges) the image e.g. x10 Nosepiece Revolves to allow an objective lens to be used Objective lenses Magnify the image. Low power (x4), medium power (x10), high power (x40). Total magnification = Eyepiece (x10) x objective lens (x40) = 10 x 40 = 400. Body tube/barrel Holds the eyepiece at one end and the revolving nosepiece (objective lenses) at the other end. Revolving nosepiece Holds and positions the objective lenses. Coarse focus wheel Used for initial focussing with low and medium power. Fine focus wheel Sharpens the focus after coarse adjustment. Focus the high-power objective with this wheel only. Stage Platform on which slide is placed. Slide is kept in place by clips. Keep dry. Condenser Focuses light onto slide. Diaphragm Controls and adjusts the amount of light passing to the slide. Light source Electric bulb or reflecting mirror. Arm Joins the body tube to the base of the microscope A simple microscope uses one lens to magnify an object e.g. a magnifying glass. A compound microscope uses two or more lenses to magnify an object (multiply the eyepiece and objective lens for total magnification) Electron microscope electrons focussed using magnets onto specimen. As electrons are invisible, image is shown on TV screen, or micrograph. Resolution light waves cannot pass through a space that is smaller than 200nm. Electron microscope can distinguish parts that are only 1nm apart because electrons have a smaller wavelength. It is not possible to observe living material with an electron microscope because the beam of electrons directed onto the specimen consists of minute negatively charged particles which are readily scattered by atmospheric atoms and molecules. It is therefore necessary to place the specimen in a vacuum in which living cells immediately die. Sections of cells and tissues must be extremely thin otherwise electrons will not pass through them Leaving Cert Notes www.leavingcertnotes.ie Page 1 Light Microscope Uses light rays & focuses them with x 2 convex lenses to illuminate an object. Magnifies up to 1400X Low resolution (up to 200 nm) It reveals nucleus, cell organelles, cell walls, vacuoles and chromatin Portable & relatively inexpensive Can examine living tissue (thin) Electron Microscope Uses a beam of electrons & focuses them with electromagnets to illuminate an object. Magnifies up to 500,000 X High resolution (up to 1 nm) – ‘cos beam of electrons has a much smaller wavelength than light. Reveals details of cell organelles & cell structure such as cilia, flagella & membranes Not portable & very expensive Objects dead (in a vacuum) Image = photomicrograph – a grainy black & white picture Transmitting Electron Microscope (TEM) - Sends electrons through objects and reveals the most detail. The TEM uses electromagnets as lenses to focus and magnify the image by bending the paths of the electrons. Scanning Electron Microscope (SEM) – Photographs reflected electrons from surfaces and reveals 3D structures. The surface is usually coated with a thin film of gold. Animal Cell Structure Using a Light Microscope All the living matter of a cell is called protoplasm. The cell is surrounded by an outer cell or plasma membrane. The nucleus is the control center of the cell. The cytoplasm surrounds the nucleus. The cytoplasm is everything within the cell except for the nucleus. There are many small organelles within the cytoplasm. This is where most of the cell’s activities take place. The cytoplasm is composed of 90% water. They cannot be seen using a light microscope. Plant Cell Structure Using a Light Microscope All the living matter of a plant cell is also called protoplasm. The cell is surrounded by a cell or plasma membrane. Unlike the animal cell the plant cell also has a rigid cell wall surrounding it. This is made of cellulose and is very rigid. It supports the plant cell. The nucleus is the control center of the cell. The cytoplasm surrounds the nucleus. The vacuole is a storage area for the plant cell. The vacuole contains cell sap. This is made of sugars, salts, and pigments. The chloroplasts contain chlorophyll. This is where photosynthesis occurs within the cell. Leaving Cert Notes www.leavingcertnotes.ie Page 2 Basic cell structure is revealed by the light microscope (1000x) e.g. nucleus, cell membrane, cytoplasm, cell wall, chloroplast, vacuole. The electron microscope is used to show the ultrastructure of cells. If gives a high level of magnification (500,000x) making the detailed structure of organelles visible. Cell organelles are generally colourless and must be stained to see them Iodine for plant cells Methylene blue for animal cells The Cell All organisms (living things) are made up of tiny units called cells. The cell is the smallest unit of living mater that exhibits the characteristics of life. Cells are three-dimensional structures They are measured in units called micrometres Plant cells Have cell walls. Have chloroplasts Have chlorophyll. Large and more permanent vacuoles. Store carbohydrates as starch. Animal cells No walls. No chloroplasts No chlorophyll Few, if any, small, temporary vacuoles. Store carbohydrate as glycogen. . Cell Structure Using an Electron Microscope Under an electron microscope the ultrastructure of the cell becomes visible: Ribosomes are structures that make protein. They are manufactured in the nucleolus and are composed mainly of RNA. Mitochondria are responsible for cellular respiration. Chloroplasts are the site of photosynthesis in green plants. The green pigment is called chlorophyll and is stored inside the chloroplasts. Leaving Cert Notes www.leavingcertnotes.ie Page 3 There are two cell types: Prokaryotic cells Single celled Do not have a nucleus or membrane-enclosed cell organelles Are usually small Do not have mitochondria or chloroplast Are primitive e.g. bacteria. Eukaryotic cells More developed Have a nucleus and cell organelles, all of which are enclosed by membranes Larger than prokaryotic cells Contain structures like mitochondria or chloroplast which are enclosed by membranes More advanced than prokaryotic cells e.g. plant cell, animal cell, fungi, amoeba. Cell ultra-structure - Cell organelles Biological cell (plasma) membrane (7.5 nm thick) sss The cell membrane is composed of various lipids and proteins arranged in a characteristic pattern. The lipids consist of a double later of phospholipids known as the lipid bilayer, they are embedded in phospholipid bilayer The most acceptable model of the cell membrane is the fluid-mosaic model developed by Singer and Nicolson (1972), which suggests that the lipid bilayer acts as a matrix into which proteins are embedded or into which they are absorbed. Structure: The cell membrane is a fluid phospholipid bilayer coated and embedded with protein. Protein gives elasticity and lipid allows fat-soluble molecules to enter. There are temporary pores throughout the membrane. Function: Holds and retains cell contents - thus giving shape, support (provided by proteins) and protection. Acts as a semi permeable barrier to control entry and exist of molecules ie. can let small molecules e.g. water (by osmosis), oxygen and carbon dioxide (by diffusion) through but not large molecules e.g. salt, sugar, protein. Leaving Cert Notes www.leavingcertnotes.ie Page 4 Some membrane proteins are involved in the immune system, while others act as carrier proteins for transporting materials across the cell membrane. Proteins assist in the active transport of materials across the membrane (energy needed). Thus, the cell can control the amount of water and salt conc. (osmoregulation). Phospholipids affect the fluidity and permeability of membrane. Cytoplast The area of a cell surrounding the nucleus Contains many cell organelles Cytosol is the liquid part of the cytoplasm Structure: This is a watery jelly in which cell organelles are suspended. (Protoplasm = cytoplasm + nucleus) Function: Site of metabolism e.g. glycolysis, protein synthesis. Intercellular transport Storage of water, lipids, amino acids etc. Support of cell organelles. Nucleus (5-10nm diam.) The nucleus is surrounded by the nuclear membrane, which allows molecules to enter and leave the nucleus similar to the plasma membrane. Nuclear pores are the openings through which materials enter and leave the nucleus. The nucleus contains DNA (deoxyribonucleic acid) arranged in groups called chromosomes. The nucleolus is where ribosomes are made from RNA (ribonucleic acid). Genes are located on the chromosomes. These are the structures that control the production of protein and thus determine the characteristics of the organism. The contain a specific number of chromosomes The function of DNA is to code for the production of protein in a cell. Structure: Enclosed by a double membrane. Contains chromatin (genetic material) - becomes arranged into chromosomes during cell division. These are made of protein and DNA. Genes are located along the chromosome. Generally elongated Contains one or more nucleoli. Nuclear pores allow passage of mRNA, rRNA, nucleotides. Nucleoplasm = a liquid in nucleus surrounding nucleolus and chromatin. Leaving Cert Notes www.leavingcertnotes.ie Page 5 Function: Maintains and controls all the activities of the cell. (by making enzymes Contains genetic material. Involved in cell division. Nucleolus Found in nucleus and makes ribosomal RNA. It passes through the pores and makes ribosomes in the cytoplasm. Red blood corpuscles and phloem sieve tube elements do not have nuclei. Mitochondrion (5-10m long) Supply energy for cell respiration Plentiful in active cells e.g. muscle, nerve, liver, brain, kidney, neck region of male sperm, apical meristems (shoot/root tips). Few in inactive cells e.g. fat, bone, skin, cortex in plants. Not found in bacteria. Structure: Surrounded by a double membrane - the inner one is folded into cristae. Lumen is filled with a dense matrix of water, food, enzymes, some ribosomes and small portions of DNA - self-duplicating organelles. Function: Release energy in aerobic respiration – Kreb’s cycle occurs in lumen and electron transport chain occurs in cristae. Ribosomes (14-18nm) Found in large numbers in the liver Make proteins Structure: Small granular structures made of two sub-units. Made of RNA (ribonucleic acid) and protein. Found free in cytoplasm or attached to folded membranes Function: Protein synthesis Free ribosomes make protein used by cell and those on tubes make proteins for export. Cell wall (0.5-1nm thick) Plants only Secreted by cell membrane. Leaving Cert Notes www.leavingcertnotes.ie Page 6 Structure: Made of cellulose. Adjacent cells are stuck together by calcium pectate the middle lamella of pectin Function: Gives strength, support and protection to the cell. Controls cell growth and shape. Prevents osmotic bursting of cell membrane. Fully permeable to allow the free movement of molecules through it Vacuoles Usually one in plants - very large & permanent. Small, temporary and more in animals because they excrete their waste (often called vesicles). Structure: Fluid-filled spaces surrounded by a membrane Function: Temporary storage of food (sugars, amino acids, fats), water, salts (help in osmoregulation), pigments, tannins, gases (O2 & CO2), wastage and excretory products. The cell sap makes the cells turgid. To give shape and structure to the cell. For expansion during cell growth. Chloroplasts (2-5nm) (plant cells only) Both mitochondria and chloroplasts have a double membrane and DNA. Having DNA supports the theory that chloroplasts and mitochondria were once independent prokaryotic organisms that lived symbiotically inside large eukaryotic cells. Structure Double membrane Contain chlorophyll and DNA - self-duplicating. Function Used to make food (carbohydrate) by photosynthesis – light phase in grana and dark phase in stroma. Lysosomes Suicide sacs Found in animal cells Contain acid and enzymes to digest faulty cell parts Destroys faulty cell parts by autolysis Leaving Cert Notes www.leavingcertnotes.ie Page 7 Cell Diversity Cells are not identical – they diversify their structure to suit their function A tissue is a group of similar cells that are adapted to carry out the same function Plant tissues Dermal tissue Surrounds and encloses plants Protection and prevents water loss Found in stem, leaf and roots Contain rectangular cells, with thick, strong walls Has a waterproof layer (the cuticle) Eg. epidermis Ground tissue storage (starch, sugar and salts) Meristematic tissue cell division mitosis (growth) Vascular tissue transports materials around the plant, found in all parts of plant, arranged in vascular bundles water and minerals around the plant food from the leaves to the other parts of the plant Xylem transports Phloem transports Animal Tissues Connective tissue Joins and supports certain parts of the body Consists of cells contained in the matrix (a surrounding substance) (eg. plasma for blood) Eg. cartilage, tendons, ligaments, bones, blood. and adipose tissue Muscle Tissue can contract and relax (movement) Nervous Tissue composed of nerve cells called neurons carry electrical impulses to and from brain Tissue Culture Tissue culture is the growth of cells or tissues, in or on an artificial medium outside an organism The tissue sample is removed from a plant or animal and grown in glassware (in vitro) or in a bioreactor under carefully controlled conditions In vitro – growing inside body Growth is by mitosis (replication) and produces a cluster of identical offspring - a clone Eg. organ transplant Leaving Cert Notes www.leavingcertnotes.ie Page 8 Conditions necessary for Tissue growth Oxygen (for respiration) Nutrients (food for growth) Growth factors and hormones Correct pH Optimum temperature Sterile conditions (in sterile conditions bacteria will multiply at 1 billion / 10 hrs) Freedom from competition Stages in Tissue Culture Skin cells obtained Enzymes added Individual Cells isolated Controlled culture medium Sheets of cells grown Applications of tissue cultures Virus reproduction Hela cells used to grow and investigate viruses Micro propagation of plants Produces exact copies Quickly produces mature plants Doesn’t need pollinators or seeds Producing plants that are disease resistant and virus free Growing human tissue for organ transplants Skin grafts Liver cells Pancreas cells Producing biotechnology products Insulin Interferon Pregnancy testing kits Drug testing kits Cancer testing kits Micropropagation – growth of large numbers of identical plants from pieces of an original plant. A suitable plant is selected, cut into minute pieces (cell size) and grown artificially, then transplanted into soil and grown as normal Advantages – large numbers, quick, genetically identical, cheap Leaving Cert Notes www.leavingcertnotes.ie Page 9 Organs An organ is a structure composed of a number of tissues that work together to carry out one or more functions Plant organs Root Stem Leaf Flower Seeds Fruit Animal organs Heart Stomach Intestine Liver Lungs Skin Organ systems A system consists of a number of organs working together to carry out one or more functions Animal systems Digestive system Endocrine system Nervous system Skeletal system Circulatory system Reproductive system Urinary system Muscular system Leaving Cert Notes www.leavingcertnotes.ie Page 10