Cell Specialization & Differentiation 6th period

Please write your full name and your Biology period number in the space below. Let's Get StartedLet’s explore a fundamental characteristic of multicellular organisms—cell differentiation and specialization. Essential QuestionsWhat is cell differentiation and why is it important?What role do stem cells play in cell differentiation?How is gene expression related to cell differentiation and specialization?What type of factors can influence cell differentiation and specialization?How are plant and animal cellsspecialized?VocabularyMulticellularUnicellularCell DifferentiationDNAStem CellsChromosomesRNAGene Expression Differentiation and Gene ExpressionMulticellular organisms begin as just one single cell—a fertilized egg. Growing from one single cell to trillions of specialized cells that perform different functions is a process that happens with the regulation of DNA and RNA. Directions: Watch Differentiation and Gene Expression for an introduction to cell differentiation and gene expression. _ is the process by which cells become specialized in order to perform different functions. Gene Expression Cell Differentiation Specialized bodies DNA Expression Roles of DNA and RNA in Cell Differentiation Dexoyribonucleic Acid, or DNA, controls the way cells function. It also determines what type of specialized cells will be made. Stem cells are cells that have the ability to become any type of specialized cell in the body. After an egg cell and sperm cell unite to begin forming a new organism, all of the DNA in each cell of that organism will be virtually identical. If every part of the DNA in each cell is the same, then how do cells become different types of cells? Let’s look more closely at DNA to find out. What are stem cells? Cells that only exist during embryonic development Cells that come from the stem of a plant Cells that have the ability to become any type of specialized cell in the body Cells that are specialized in function DNA is wound tightly intochromosomes. Different regions of the chromosome code for every different function and cell type. Not all sections of a chromosome are turned on, or expressed, at the same time. Only the regions that are needed to perform a specific function are expressed in each cell. These regions are often depicted as bands or stripes on a drawing of a chromosome. These bands are called genes, and whether or not a gene is expressed determines what type of cell will be created. For example, genes that are expressed (turned on) in a nerve cell are different from the genes that are expressed in a muscle cell. Both cells have the same DNA, but expressing different genes generates different cell types.This process by which information from a gene is used to make the structures of a cell is called gene expression. Since RNA translates and transcribes the DNA code into proteins (the structures of a cell), it also plays a role in cell differentiation. If the DNA in each body cell is the same, how do cells become differentiated? One chromosome cannot code for every different function and cell type Gene expression ensures that each cell reads all its genes simultaneously Only the genes that are needed to perform a specific function are expressed in each cell Different genes can generate the same cell type Environmental Factors Influence Gene Expression Environmental factors can also influence gene expression and cell differentiation. For example, available nutrients, salinity, and temperature are all factors that can influence gene expression in organisms. In Himalayan rabbits, genes that code for fur color are turned on and off depending on temperature. In warm parts of the rabbit's body (anything warmer than 35°C), gene expression is turned off, and the fur color is white. Cooler parts of the rabbits body (anything cooler than 35°C) turn on the gene, creating black fur. The Himalayan rabbit shown below lost black fur on her ears due to an infection. When new fur grew back in, it was white, showing that this new round of gene expression occurred at temperatures greater than 35°C. Another example of environmental factors influencing gene expression is metamorphosis. Metamorphosis is regulated by external and internal factors, including temperature, available resources, and hormones. For example, a tadpole in a pond will go through many physical changes as it responds to the environment. Environmental conditions trigger hormone release that allows the tadpole to create new specialized cells so that it can survive in its environment.Look at the pictures below. Tadpole A will spend about 16 weeks of its life undergoing metamorphosis before becoming an adult frog. Tadpole B is living in an area of drought, and in response to its environment, it will release hormones to speed up the process of metamorphosis. Tadpole B will spend about 10 weeks of its life undergoing metamorphosis before becoming an adult frog. Both tadpoles will survive to become adult frogs, but their cell differentiation is controlled at different rates. How can an environmental factor like temperature influence gene expression? Himalayan rabbits grow white fur on the warmer parts of its body and black fur on the cooler parts of its body Himalayan rabbits grow black fur on the warmer parts of its body and black fur on the cooler parts of its body Himalayan rabbits grow black fur when it's warm outside The genes of Himalayan rabbits are not affected by temperature at all Specialized Plant CellsNow that you know how living organisms transition from one single cell to many differentiated cells, let’s discuss some of the specialized cells that are made as a result of this process. In plants, cells are specialized for the roles they play in the plant’s survival. Three of the many specialized cell types in plants include the cells of the roots, stems, and leaves. Root CellsRoot cells are specialized plant cells that absorb dissolved minerals and water from the ground. Root cells grow in long lengths called root hairs in order to increase the surface area of the root system. This also helps anchor the plant. Since root cells grow underground, you would not expect to find chloroplasts in these cells since the purpose of chloroplasts is to absorb energy from the sun.The tip of the root also has specialized cells in an area called the root cap. These cells discharge a slippery substance that helps them burrow down into the soil more easily.Cells of Plant StemsNot to be confused with the type of embryonic stem cells that can differentiate, the stem cells of plants are specialized cells that transport water, nutrients, and the products of photosynthesis throughout the plant. They connect the photosynthesis factories in the leaves with the storage site in the roots.Xylem cells transport water from the roots in the upward direction. Phloem cells transport nutrients in both directions to reach all parts of the plant. Some plants have specialized stem cells that form the wood to support the plant as it grows upward and outward.Leaf CellsThe cells found in the leaves of plants are highly specialized, and there are many different types. Column-shaped palisade cells are found near the surface of the leaf. They are full of chloroplasts ready to capture energy from the sun and turn it into chemical energy.Along the bottom of the leaf, guard cells open and close to allow the transfer of gases with the atmosphere as well as the transpiration of water. These cells can help protect the plant from drying out. Match the following plant cells with their specialized functions. Root Cells The root cap discharges a slippery substance that helps these cells burrow down into the soil more easily. Cells of Plant Stems Xylem cells transport water from the roots in the upward direction. Phloem cells transport nutrients in both directions to reach all parts of the plant. Leaf Cells Guard cells open and close to allow the transfer of gases with the atmosphere as well as the transpiration of water. This prevents the plant from drying out. Specialized Animal CellsAnimals also require many different specialized cells in order to function. Some cells must be able to move (like sperm cells), while other cells need to contract (like muscle cells). Three of the many specialized cell types in animals include red blood cells, muscle cells, and skin cells. Red Blood CellsRed blood cells are specialized cells found in animals that transport oxygen throughout the body. Since transport is their primary function, they do not need a nucleus. The lack of a nucleus leaves more space in the cell for hemoglobin, the protein that binds to oxygen. This also gives red blood cells their unique shape. Unlike most cells red blood cells do not reproduce through mitosis. They are created in the marrow found in the bones.Muscle CellsMuscle cells are long, fibrous cells that have the ability to contract. They allow animals to move and allow their organs to function in circulation as well as digestion. Muscle cells are made up of two special types of proteins called actin and myosin. Because of actin and myosin, muscle strands are able to slide past each other. This sliding action allows muscle cells to contract. Since a lot of energy is needed in your muscle cells, you will find more mitochondria in them than is found in most cells.Epithelial CellsEpithelial cells are the cells that line the outside, as well as the inside, of your body. They are the cells that make up your skin. Skin epithelium is actually located just below the surface of your skin. The epithelial cells are responsible for making new cells. They also produce the pigment, melanin, which protects us from the sun’s harmful rays. Epithelium also lines the inside of your digestive tract and your respiratory system. Epithelial cells come in many shapes and sizes, depending on their function. Match the following animal cells with their specialized functions. Red Blood Cells These cells lack a nucleus to have more space for hemoglobin, the protein that binds to oxygen. Muscle Cells These cells contain more mitochrondria than most other cells, due to the need for more energy. Epithelial Cells These cells produce the pigment melanin, which protects us from the sun's harmful rays. Match each of these vocabulary terms to its correct definition. Multicellular Made of more than one cell, such as plants Unicellular Made of a single cell, such as bacteria Cell Differentiation The process by which cells become specialized in order to perform different functions DNA (Deoxyribonucleic acid) Nucleic acid that controls the way cells function, and determines what type of specialized cells will be made RNA (Ribonucleic Acid) Nucleic Acid that translates and transcribes the DNA code into proteins Stem Cells Cells that have the ability to become any type of specialized cell in the body Chromosomes Contains tightly wound DNA; different regions code for every different function and cell type Gene Expression The process by which information from a gene is used to make the structures of a cell Gene A segment of DNA, looks like a band or stripe on a chromosome