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CELLS STRUCTURE AND FUNCTION Important Characteristics: Chemically and structurally unique Need energy Have a life span Are capable of growth and reproduction Respond to their environment Organisms are organized The substances from which organisms are made are carefully organized. Organization determines the kind of organism. Each new cell contains the same kind of molecules and the same amount of water as the ‘parent’cell. Some cells are very short-lived – only days ◦ Ex. Scavenger white blood cells At any instant only certain genes in a cell are on or expressed giving orders for the function of that cell. The basic unit of life. All living organisms are made up of one or more cells. Cells are the smallest unit that we say is alive. All cells come from the division of preexisting cells. CELL THEORY Tiny Building Blocks Organisms are made of cells The basic structure of life. A microscope is required to see the structure Structural Units Cell – the basic structure of all living things Cell specialization – differences in cells so they can perform unique activities Tissue – groups of cells that are alike in activity and structure Organ – collections of tissues that work together to perform certain functions Organ systems – several organs that work together to perform an acitivity TYPES OF CELLS Prokaryotic Genetic material contained is held within a single molecule Smallest of all cells Bacteria and bluegreen algae Used in biotechnology Eukaryotic Genetic material held within a nucleus Animal and plants are made of these ANIMAL CELLS Animal Cell Structure Animal cells are typical of the eukaryotic cell, enclosed by a plasma membrane and containing a membrane-bound nucleus and organelles. Unlike the eukaryotic cells of plants and fungi, animal cells do not have a cell wall. Most cells, both animal and plant, range in size between 1 and 100 micrometers and are thus visible only with the aid of a microscope. The lack of a rigid cell wall allowed animals to develop a greater diversity of cell types, tissues, and organs. Specialized cells that formed nerves and muscles gave these organisms mobility. The ability to move about by the use of specialized muscle tissues is a hallmark of the animal world, though a few animals, primarily sponges, do not possess differentiated tissues. Notably, protozoans locomote, but it is only via nonmuscular means, in effect, using cilia, flagella, and pseudopodia. The animal kingdom is unique among eukaryotic organisms because most animal tissues are bound together in an extracellular matrix by a triple helix of protein known as collagen. Plant and fungal cells are bound together in tissues or aggregations by other molecules, such as pectin. Structure 3 COMPONENTS Cell membrane Cytoplasm Organelles Structure CELL MEMBRANE CELL MEMBRANE All living cells have a plasma membrane that encloses their contents. In prokaryotes, the membrane is the inner layer of protection surrounded by a rigid cell wall. Eukaryotic animal cells have only the membrane to contain and protect their contents. Contains protein receptors that control the flow of substances into and out of the cell. Structure CYTOPLASM CYTOPLASM A jellylike substance of which 90 percent is water. Found within the cell membrane and surrounds the nucleus. Structure ORGANELLES NUCLEUS Highly specialized organelle that serves as the information processing and administrative center of the cell. This organelle has two major functions: ◦ it stores the cell's hereditary material, or DNA, and ◦ it coordinates the cell's activities, which include growth, intermediary metabolism, protein synthesis, and reproduction (cell division). The nucleus is a two-layered membrane with pores. Nucleolus an organelle within the nucleus - it is where ribosomal RNA is produced. Some cells have more than one nucleolus. CENTRIOLES Located near the center of the cell are two cylinders Self-replicating organelles Each is made of nine pairs of hollow tubules. Important role in cell division. MITOCHONDRIA The cell’s powerhouse Site of both respiration, (exchange of oxygen and carbon dioxide), and the breakdown of fats and sugars to convert oxygen and nutrients into energy. Mitochondria Oblong shaped organelles that are found in the cytoplasm of every eukaryotic cell. Inner folds contain enzymes that produce adenosine triphosphate (ATP) ◦ Provides energy needed for many cell functions. ENDOPLASMIC RETICULUM Network of tubules and thin, curved sacs - manufactures, processes, and transports chemical compounds for use inside and outside of the cell. 2 types: ◦ Rough – is covered with ribosomes that give it a rough appearance. Play a role in protein synthesis and transport. ◦ Smooth – site of calcium storage and fat production. Rough ER Smooth ER RIBOSOMES All living cells contain ribosomes Small, granular structures function in the assembly of proteins. Tiny organelles composed of approximately 60 percent RNA and 40 percent protein. In eukaryotes, ribosomes are made of four strands of RNA. In prokaryotes, they consist of three strands of RNA. GOLGI APPARATUS (also called the Golgi body or Golgi complex) Stacks of flattened sacs receive and process small vesicles of protein from the rough reticulum. The proteins are modified and repackaged into larger vesicles and released at the cell membrane for body functions The distribution and shipping department for the cell's chemical products LYSOSOME The main function of these microbodies is digestion. This organelle produces powerful enzymes that degrade dangerous materials taken into the cell. Break down cellular waste products and debris from outside the cell into simple compounds, which are transferred to the cytoplasm as new cell-building materials. Dispose of any unwanted substances or worn out organelles. Lysosomes are about 1 μm in diameter, are surrounded by a single membrane, and have a densely staining, featureless interior. There may be dozens of lysosomes in a cell, depending on its needs. http://highered.mcgrawhill.com/sites/0072495855/student_view0/ chapter2/animation__lysosomes.html Peroxisome A membrane-bound organelle that contains specific enzymes imported from the cytoplasm (cytosol). CHROMATIN A granular material composed of DNA. (the cell’s genetic material) VACUOLE Storage Bins to the Cells Sac stores and transports water, ingested materials and waste products. MICROVILLI Some cells have projections that increase their surface area to aid absorption. ◦ Lining of the small intestine Flagella and cillia http://programs.northlandcollege.edu/biol ogy/Biology1111/animations/flagellum.htm l CYTOSKELETON The internal framework of the cell has 2 main types of structure. ◦ Actin Filaments – provide support and contraction ◦ Microtubules – hollow tubes that aid movement of substances through the cell’s cytoplasm ◦ Structural strength all eukaryotic cells (prokaryotes don't have them) There are many different types of cells. Each cell has a shape, and size adapted for its function. Types of Cells SIZE Major difference in cells occurs between plant cells and animal cells. While both plant and animal cells contain the structures discussed before plant cells have some additional specialized structures. PLANT CELL Cell Wall Many animals have skeletons to give their body structure and support. Plants do not have a skeleton for support and yet plants don't just flop over in a big spongy mess. cell wall This is because of a unique cellular structure called the cell wall. The cell wall is a rigid structure outside of the cell membrane composed mainly of the polysaccharide cellulose. They become thicker with age. Vacuoles One or a few very large ones are found in each cell. As the cells mature the vacuoles tend to get larger and fuse into a single vacuole that is up to 90% of the cell’s volume. Contain large quantities of water and dissolved substance. storing foods (e.g., proteins in seeds) storing wastes storing malic acid in CAM plants storing various ions (e.g., calcium, sodium, iron) which, among other functions, helps to Water flows in and creates osmotic pressure which is responsible for the rigidity (“turgor”) of plants When water is in short supply the vacuoles lose their osmotic pressure and the plant wilts. Holds solid crystals of substances that color flowers. PLASTIDS Can color a plant They are usually disk-shaped and about 5-8 µm in diameter and 2-4 µm thick. A typical plant cell has 20-40 of them. The chloroplast allow plants to harvest energy from sunlight. Specialized pigments in the chloroplast (including the common green pigment chlorophyll) absorb sunlight and use this energy to complete the chemical reaction: 6 CO2 + 6 H2O + energy (from sunlight) C6H12O6 + 6 O2 In this way, plant cells manufacture glucose and other carbohydrates that they can store for later use. Chloroplast Membrane-bound organelle and the site of photosynthesis and ATP production Leucoplasts are whitish in color and store starch, lipid or protein. Chromoplasts produce and store other pigment, the carotenoids which give color to particular parts of a plant. http://www.biology.ualberta.ca/facilities/m ultimedia/uploads/cell_biology/plantcell_D D.html An Overview of Photosynthesis Photosynthesis converts light energy into the chemical energy of sugars and other organic compounds. This process consists of a series of chemical reactions that require carbon dioxide (CO2) and water (H2O) and store chemical energy in the form of sugar. Light energy from light drives the reactions. Oxygen (O2) is a byproduct of photosynthesis and is released into the atmosphere. The following equation summarizes photosynthesis: 6 CO2 + 6 H2O → 6(CH2O) + 6 O2 sugar http://www.stolaf.edu/people/giannini/flash animat/metabolism/photosynthesis.swf Calvin cycle These 3-carbon molecules serve as the starting material for the synthesis of glucose and other food molecules. The process is called the Calvin cycle and the pathway is called the C3 pathway. The graphic shows the steps in the fixation of carbon dioxide during photosynthesis. http://highered.mcgrawhill.com/sites/0070960526/student_view0/ chapter5/animation_quiz_1.html Transports molecules in and out of the cell MEMBRANE TRANSPORT SYSTEMS 2 Types PASSIVE TRANSPORT Diffusion It is diffusion that causes a smell (expensive perfume or smelly socks) in one part of the room to gradually move through the room so it can be smelt on the other side. Diffusion occurs in the air and in liquids. In the animal’s body diffusion is important for moving oxygen and carbon dioxide between the lungs and the blood, for moving CO2 digested food molecules from the gut into the blood and for the removal of waste products from the cell. O2 Diffusion through a Liquid In the body, diffusion causes molecules that are in a high concentration on one side of the cell membrane to move across the membrane until they are present in equal concentrations on both sides. It takes place because all molecules have an in-built vibration that causes them to move and collide until they are evenly distributed. Small molecules like oxygen, carbon dioxide, water and ammonia as well as fats, diffuse directly through the double fat layer of the membrane. The small molecules named above as well as a variety of charged particles (ions) also diffuse through the protein-lined channels. Larger molecules like glucose attach to a carrier molecule that aids their diffusion through the membrane.This is called facilitated diffusion. Diffusion http://www.northland.cc.mn.us/biology/Bi ology1111/animations/transport1.html Osmosis Osmosis is the diffusion of water across a membrane that allows water across but not larger molecules. This kind of membrane is called a semipermeable membrane. Osmosis The movement of water molecules from an area of high concentration to an area of low concentration. It is osmosis that plumps out dried fruit when you soak it before making a fruit cake or makes that wizened old carrot look almost like new when you soak it in water. Osmosis http://www.stolaf.edu/people/giannini/flash animat/transport/osmosis.swf Active transport When a substance is transported from a low concentration to a high concentration i.e. uphill against the concentration gradient, energy has to be used. This is called active transport. Active transport is important in maintaining different concentrations of the ions sodium and potassium on either side of the nerve cell membrane. It is also important for removing valuable molecules such as glucose, amino acids and sodium ions from the urine. http://highered.mcgrawhill.com/sites/0072495855/student_view0/ chapter2/animation__how_facilitated_diff usion_works.html Phagocytosis Phagocytosis is sometimes called “cell eating”. It is a process that requires energy and is used by cells to move solid particles like bacteria across the plasma membrane. Finger-like projections from the plasma membrane surround the bacteria and engulf them as shown in diagram 3.10. Once within the cell, enzymes produced by the lysosomes of the cell (described later) destroy the bacteria. The destruction of bacteria and other foreign substance by white blood cells by the process of phagocytosis is a vital part of the defense mechanisms of the body. http://highered.mcgrawhill.com/sites/0072495855/student_view0/ chapter2/animation__phagocytosis.html To make the function of the parts of the cell easier to understand and remember you can compare them to a factory. THE CELL AS A FACTORY The nucleus (1) is the managing director of the factory consulting the blueprint (the chromosomes) (2); The mitochondria (3) supply the power The ribosomes (4) make the products; The chloroplasts of plant cells (5) supply the fuel (food) The Golgi apparatus (6) packages the products ready for dispatch; The ER (7) modifies, stores and transports the products around the factory; The plasma membrane is the factory wall and the gates (8); The lysosomes dispose of the waste and worn-out machinery. http://www.wisconline.com/objects/index_tj.asp?objID=A P11403 http://www.wisconline.com/objects/index_tj.asp?objID=A P11604