Back To CourseGED Science: Tutoring Solution
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Joanne has taught middle school and high school science and health for more than ten years and has a master's degree in education.
Your body is a complex organism. You have many different parts, organs and systems all working together to keep you alive and well. Your stomach lets you digest that delicious birthday cake. Your skin reacts to touch while acting as a barrier to things like bacteria and disease. Your legs keep you moving while you are running around the track or running to catch the bus. Your heart pumps blood so that all parts of your body can get the water, oxygen and nutrients that they need. Your brain is the command center, making sure that all your many parts are doing what they are supposed to do.
Just like your body, eukaryotic cells are complex and require organization to keep everything running smoothly. A eukaryotic cell is a cell whose intracellular components are organized into membrane-bound organelles. Organelle literally means 'little organ', and like organs, organelles perform specific functions for the cell. Like your brain, the nucleus is the command center, providing the information and instructions for cellular activities. Like your skin, the cell membrane separates the inside of the cell from the outer environment and controls what can enter and leave the cell.
Eukaryotic plant cells have all of the organelles that other eukaryotic cells have. However, they also contain specialized organelles that identify them as members of the Plant Kingdom. The Plant Kingdom is comprised of multicellular organisms, supported by cell walls constructed of cellulose, that obtain energy from sunlight.
It can be difficult to remember the functions of all the different eukaryotic organelles. One of the most common memorization techniques to do this is to write a silly rhyme using the organelle's name and job. There are suggestions written for each organelle, but, of course, you can always write your own.
The large, central vacuole is filled with water, and helps the plant cell maintain its shape through turgor pressure. Turgor pressure is the pushing of the cell membrane against the cell wall. When you forget to water your plant and it starts to wilt, you are witnessing a loss of turgor pressure as the vacuole sends its stored water out to help with more important cellular processes. In addition to storing water, the vacuole stores useful molecules for the cell and, similar to your excretory system, it breaks down waste materials and exports them from the cell. A silly rhyme for remembering this is: To recall the role of the vacuole, think of him as the storage dude! He holds water, molecules and food.
The cell wall, located on the outside of the cell membrane, is a rigid structure composed of the carbohydrates cellulose and pectin. It provides protection and flexible support for the plant cell. Similar to our skeleton, the cell wall provides structure and shape for the plant. Dissimilar to our skeleton, the cell wall is on the outside of the cell, as opposed to the inside. Also, it is more elastic than our skeleton.
Cell walls bend before they break, allowing plants to respond to changes in water (wilting and then regaining shape) and sunlight (curving towards a light source). Pores in the cell wall, called plasmodesmada, allow water and nutrients to flow freely from cell to cell. Use this silly rhyme to recall the role of the cell wall: Remember that the plasmodesmata move the wattah (think water in a Boston accent), and the cell wall protects it all.
Chloroplasts contain the pigment chlorophyll, which captures energy from sunlight during the process of photosynthesis. Then, using the reactants carbon dioxide and water, the chloroplasts store this energy in carbohydrates such as glucose. We do not have any equivalent of this organelle! By definition, members of the Animal Kingdom cannot capture and store energy. We must acquire our energy and nutrients by consuming other organisms. Here is a silly rhyme for remembering their function: Those chloroplasts absorb light fast!
There are three types of plant cells, sclerenchyma cells, collenchyma cells and parenchyma cells. All big words, but it is not hard to remember the difference.
Sclerenchyma is from the Greek word skleros, meaning 'hard'. Sclerenchyma cells form the primary support system for the plant. These are cells with an extremely thick cell wall, and often die upon maturity (think of the bark of a tree).
Collenchyma is from the Greek word kolla, meaning 'glue'. Collenchyma cells also have thickened cell walls and provide structural support. Unlike, sclerenchyma cells, however, collenchyma cells do not die upon maturity, therefore they are a good support system for new growth in plants. These cells help the new growth 'stick' to the mature plant.
Parenchyma is from the Greek word para, meaning 'beside'. When you think of a plant cell, you are usually thinking of a parenchyma cell. These thin-walled cells are versatile, unspecialized and make up most of the volume of plants including the stems, leaves, flowers, fruits and roots. They are 'beside' the supporting cells.
Let's review. Plant cells are eukaryotic cells with organelles specialized for organisms in the Plant Kingdom. These include the vacuole, which stores water and small molecules; the cell wall, which provides structure and support for the plant cell; and chloroplasts, which are essential for the energy-converting process of photosynthesis.
There are three primary types of plant cells, sclerenchyma, collenchyma and parenchyma cells. Sclerenchyma and collenchyma cells both provide support for the plant. Sclerenchyma cells are primarily found in mature sections of the plant, while collenchyma cells provide support for new growth. Parenchyma cells provide a variety of functions for the plant depending on their location. This is the most common type of plant cell, making up most of plants' stems, leaves, flowers, fruit and roots.
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Back To CourseGED Science: Tutoring Solution
34 chapters | 724 lessons