Plant PartsWe all know that plants have roots, stems, leaves, and maybe even flowers. The parts of the plant are specialized to perform different tasks. The roots absorb water and nutrients (like nitrogen) from the soil. The stem transports the water and nutrients to the leaves. And the leaves, thats where the action happens.
The leaves of the plant have specialized cells that all perform jobs to that the plant can do photosynthesis. Photosynthesis is what makes plants different than animals. Plants can make their own food (autotrophs) whereas animals have to eat (heterotrophs) in order to get food. Plants make food by performing photosynthesis. Inside the stem are two types of transport cells, xylem and phloem. Both of these cells make tubes in the stem for transporting different substances. The xylem transports the water and minerals. Phloem transports sugar. Inside the leaves are more specialized cells. The leaf has cells that open and close to allow gases into and out of the leaf. These cells are called guard cells and they open and close the stomata (opening like a mouth in the leaf). When the guard cells are open, carbon dioxide and oxygen can move into and out of the leaf through the stoma. Water vapor can also be lost through the stomata. Also inside the leaf are cells that contain lots of chloroplasts. Chloroplasts are the organelles in plant cells that do photosynthesis. These special cells with lots of chloroplasts are called palisades cells. Chloroplasts contain chlorophyll which is a green pigment that absorbs light from the sun. |
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PhotosynthesisPlants perform photosynthesis in specialized organelles called chloroplasts. The chloroplasts contain chlorophyll, a green pigment that absorbs light from the sun. Inside the chloroplast the light energy is used to make the high energy, carbon-carbon and carbon-hydrogen bonds, in glucose. The atoms needed to make glucose come from the air. Carbon dioxide in the air is used for the carbon in glucose. The oxygen and hydrogen in glucose come from water.
The equation for photosynthesis is: 6CO2 + 6H20 --> C6H12O6 + 6O2 Written out, the equation is: 6 carbon dioxide + 6 water --> glucose + 6 oxygen The energy transformation for photosynthesis is: Light energy --> chemical energy (in glucose) The glucose that is made during photosynthesis can then be used by the plant for energy or for growth. |
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Cellular RespirationCellular respiration in plants is just like cellular respiration in animals. Plant cell, like animal cells, have mitochondria. The mitochondria are organelles that perform cellular respiration. Cellular respiration is the process that living things use to get energy.
The equation for cellular respiration is: C6H12O6 + 6O2 --> 6CO2 + 6H20 Written out, the equation is: glucose + 6 oxygen --> 6 carbon dioxide + 6 water The glucose for cellular respiration in plants comes from photosynthesis. When the plants use the glucose and oxygen they make carbon dioxide and water. The process of photosynthesis is the opposite of the process of cellular respiration. The energy transformation for cellular respiration is: chemical energy (in glucose) --> chemical energy (in ATP) --> heat energy ATP is a molecule that the cell can use to transport energy from the mitochondria to other parts of the cell. If the cell needs energy to perform a task - like transporting salt into the cell - the ATP made in the mitochondria, during cellular respiration, can move to the area of the cell that is transporting salt and the ATP can release the energy for the cell to use. The energy that is stored in ATP is converted into heat energy. |
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BiosynthesisGlucose, made during photosynthesis, can also be used by the plant for growth. Plant cells, like animal cells, are made of proteins, carbohydrates, and lipids. To make these molecules, plants can use glucose in order to build the larger molecules that the plant cell uses to grow and replicate. Turning small molecules (monomers) into large molecules (polymers) is called biosynthesis.
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How do we know?
Plants do photosynthesis - when placed in the light, plants do photosynthesis. We know this because when we put a plant into a container with BTB and leave it in the light the BTB turns blue. This means that carbon dioxide is being pulled out of the air.
Plants do cellular respiration - At night, plants are still performing cell functions that require energy. They get this energy from cellular respiration. We know this because when you put a plant into a container with some BTB overnight the BTB will turn yellow. This means the plant is releasing carbon dioxide. The container will also have a lot of condensation on it. This is because the plant is releasing water as waste during cellular respiration. (Plants also do cellular respiration during the day but because they do more photosynthesis than cellular respiration the BTB will turn blue.)
Plants need light to do photosynthesis - the plant placed in the dark will not cause the BTB to turn blue because the plant cannot do photosynthesis in the dark. Also, when a portion of the leaf is covered, it will not make starch. Starch is made out of glucose and if they leaf cannot make glucose then it cannot make starch. Only the leaves the receive light will make glucose and then starch. This is also how we know that plants can do biosynthesis because starch is made by putting two or more sugar molecules together.
Plants do cellular respiration - At night, plants are still performing cell functions that require energy. They get this energy from cellular respiration. We know this because when you put a plant into a container with some BTB overnight the BTB will turn yellow. This means the plant is releasing carbon dioxide. The container will also have a lot of condensation on it. This is because the plant is releasing water as waste during cellular respiration. (Plants also do cellular respiration during the day but because they do more photosynthesis than cellular respiration the BTB will turn blue.)
Plants need light to do photosynthesis - the plant placed in the dark will not cause the BTB to turn blue because the plant cannot do photosynthesis in the dark. Also, when a portion of the leaf is covered, it will not make starch. Starch is made out of glucose and if they leaf cannot make glucose then it cannot make starch. Only the leaves the receive light will make glucose and then starch. This is also how we know that plants can do biosynthesis because starch is made by putting two or more sugar molecules together.