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Cells and Cell Parts Grade 8 Science Parkland Junior High 2012-2013 The game of life so far… Cell Theory: Formulated by Schleiden, Schwan, and Virchow in the 19th century States that: all living things are composed of one or more cells The cell is the basic unit of life All cells come from already existing cells The Cell as a City http://www.youtube.com/watch?v=o1G QyciJaTA&feature=related A cell is The smallest unit that can perform the functions of life A cell is like a small city where every structure has a purpose to keep the city running smoothly. Every cell must carry out certain activities that keep it alive. Cell Structure All cells have similar basic structures in common even though the shape, size, colour may vary. These basic structures carry out the functions of the cell. These structures are known as organelles. Organelle means “little organ” Each organelle has a role to play in the activities necessary for life. Organelles found in Plant and Animal Cells Plant and animal cells share similar structures and have organelles that perform the same functions. Cell Membrane The cell membrane is like the skin covering your body or the shell surrounding an egg. This membrane is not only for protection but also allows and controls the movement of substances in and out of the cell. In our “city cell”, the cell membrane would be like the city boundaries. Cytoplasm Much of the inside of the cell is made up of cytoplasm. Cytoplasm is constantly moving inside your cell and it distributes materials such as oxygen and food to different parts of the cell. In our “city cell”, the cytoplasm would be similar to all the parks and greenspace in town because it fills all the space where other organelles are not found. Golgi Apparatus The Organelle of Many Names Many Names… This organelle has many different names: The Golgi Apparatus The Golgi Body The Golgi Complex Nice ‘stache, dude! It was identified in 1897 by the Italian physician Camillo Golgi and named after him. What does it do? The organelle’s main job is to package big molecules (like protein and fat) after they are made (or used up) by other parts of the cell. These packages are called vesicles. What does it look like? A series of stacked membranes. Unlike the twisty Endoplasmic Reticulum, the Golgi Body is stacked – kind of like a stack of pancakes. Small vesicles that look like bubbles are found inside the Golgi Body, as well as around it. Role in the “Cell City” The golgi works like a post office. The post office sorts packages by destination (domestic and international). It boxes and labels the packages and then distributes them to their final destination Miss Golgi? Endoplasmic Reticulum Here are our highway and road system in our city. Goods are manufactured and shipped to needed areas via this road system. The ER is a folded membrane that forms a system of canals within the cytoplasm. Materials are transported through these canals to different parts of the cell or to the outside of the cell. Rough Endoplasmic Reticulum The rough endoplasmic reticulum is studded with ribosomes giving it a rough appearance. It is continuous with the nuclear membrane. This means it extends out directly from the nuclear membrane into the cytoplasm. The ribosomes on the rough endoplasmic reticulum make proteins that are exported from the cell. Smooth Endoplasmic Reticulum The smooth endoplasmic reticulum (SER) is not studded with ribosomes giving it a smooth appearance. The membranes of the SER extend from the RER in the cytoplasm. The SER has two functions; it synthesizes lipids and detoxifies harmful substances. It also helps in the packaging of materials inside the cell. Ribosomes Ribosomes assemble protein according to the cells specific genetic instructions and are found on the RER and “free” within the cytoplasm. Ribosomes help in protein synthesis. The RER “pinches” off the ribosomes so they can move throughout the cell. Nucleus The nucleus is the most easily seen organelle in the cell. It would be the mayor of our city cell. The nucleus controls the cells functions and activities. The nucleus houses the majority of genetic material of a cell. The nucleus is the brain of the cell and controls all activity within the cell, using DNA as a blueprint (like the blueprints of a city) Nucleus continued… Inside the nucleus you will find chromosomes. These structures are made of genetic material that direct a cell’s growth and reproduction. The nucleus is also surrounded by a nuclear membrane which controls what enters and leaves the nucleus. Think of this as security surrounding the mayor of our city and city hall. Chromosomes A chromosome is a threadlike structure in the nucleus of a cell. The chromosomes carry the genetic material (DNA) for the cell. There are 46 chromosomes in every human. Cell Wall So if our city cell was a plant cell, we wouldn’t have just a boundary or a border, we would have a fortified wall surrounding our city. Cell walls are much more rigid and thicker than the cell membranes found in animal cells. The cell wall provides support for the cell. Cell walls are much thicker and more rigid than cell membranes and are made mostly of a tough material called cellulose. Cell Wall The cell wall occurs only in plants, fungi, and some unicellular organisms. Chloroplasts Chloroplasts are the solar energy plants in the city cell. Like a solar energy plant they use sunlight to create energy for the city. Chloroplasts are the site of photosynthesis a process in which the plant uses carbon dioxide, water and sunlight to create energy in the form of glucose for the plant cell as well as the organisms that consume the plant. Folded membranes inside each chloroplast contain the green pigment chlorophyll which absorbs sunlight. Chloroplasts Chloroplasts are found only inside cells in green plants and in some unicellular organisms. They are not found in animal cells. Energy for Cells Cells need energy for all life processes. Energy is stored in food called glucose (a type of sugar) To release energy cells must carry out cellular respiration. Here the energy is converted to another form of energy. Takes place in the mitochondrion. Mitochondria Welcome to our energy plant!! Because cells do work, they need energy. Their energy is produced by oval-shaped organelles called mitochondria. Inside the mitochondria, tiny food particles are broken down to release their chemical energy for the cell’s activities. Some cell’s such as muscle cells have more mitochondria than others because they need more energy to function. • Most energy is released as heat. • Oxygen is necessary for cellular respiration. • Carbon dioxide and water vapour are waste gases produced. These are removed from the cell. Dividing Cells Necessary for growth and reproduction Will replace cells that are dead or in need of repair How does this happen? Mitosis Occurs in body cells (somatic cells) not in gamete cells. Cell Parts and Cell Size Part 2 Plant vs. Animal Parkland Junior High Mrs. Friesen PLANT ANIMAL Cell membrane Cytoplasm Cell wall Brick shape Round shape Nucleus Vacuole Mitochondrion Chloroplast Large & few Small & many Plant Vs. Animal Cells Now that you know some important cell organelles, we need to identify those that distinguish plant cells from animal cells. There are three organelles that are found only in plants and not in animals. 1) cell wall (versus a cell membrane in animal cells) 2) central vacuole (regular vacuoles are found in animal cells) 3) chloroplasts (animals do not perform photosynthesis and therefore do not have chloroplasts). Comparing Plants and Animal Cells Plant and animal cells are very similar but there are some important differences that we need to remember: Plant cells have chloroplasts because they make their own food. As well, plant cells have a cell wall. Animal cells do not either. Plant cells have a single large vacuole. Animal cells have many small vacuoles. Plants use photosynthesis. Animal cells do not. Plant cells have a regular shape (usually rectangular). Animal cells are circular or irregular in shape. Plant vs. Animal Cells Vacuole Here are some pictures of real cells. Can you pick out some of the major organelles?