Compare and contrast a Chloroplast and a Mitchochondria
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Compare and contrast a Chloroplast and a Mitchochondria Mitochondria Mitochondria are small shaped structures found in the hyaloplasm (clear cytoplasm) of the cell, are responsible for energy production. Mitochondria contain enzymes that help convert food material into adenosine triphosphate (ATP), which can be used directly by the cell as an energy source. Mitochondria are usually near cellular structures that require large inputs of energy, such as the flagellum, which is responsible for movement in sperm cells and single-celled plants and animals. Mitochondria are the powerhouses of the animal cell, where the products of the enzyme breakdown, or metabolism, of nutrients such as glucose are converted into energy in the form of the molecule adenosine triphosphate (ATP). This process uses up oxygen and is called aerobic respiration. Plants possess, in addition to mitochondria, similar organelles called chloroplasts. Each chloroplast contains the green pigment chlorophyll, which is used to convert light energy from the sun into ATP. This process is called photosynthesis. Chloroplast is the structure in the cells of plants and algae where photosynthesis takes place. Chloroplasts are mostly disk-shaped organelles. They occur mostly together in leaf cells, where they can apparently adjust themselves to light.
At the centre of the molecule is a single atom of magnesium surrounded by a nitrogen-containing group of atoms called a porphyrin ring. The structure somewhat resembles that of the active constituent of haemoglobin in the blood. A long chain of carbon and hydrogen atoms proceeds from this central core and attaches the chlorophyll molecule to the inner membrane of the chloroplast, the cell organelle in which photosynthesis takes place. As a molecule of chlorophyll absorbs a photon of light, its electrons become excited and move to higher energy levels. This involves a complex series of chemical reactions in the chloroplast that enables the energy to be stored in chemical bonds. Several kinds of chlorophyll exist. They differ from each other in details of their molecular structure and absorb slightly different wavelengths of light. The most common type is chlorophyll a, making up about 75 percent of the chlorophyll in green plants. It is also found in blue-green algae and in more complex photosynthetic cells. Chlorophyll b is an accessory pigment present in plants and other complex photosynthetic cells; it absorbs light energy of a different wavelength and transfers it to chlorophyll a for ultimate conversion to chemical energy.
The other important functions include 2) Heat generation - especially in brown adipose tissue, which is important in hibernating animals. 3) Calcium regulation - mitchochondria act as a calcium reserved releasing it under the influence of hormones. Calcium is involved in the mobalisation of stored glycogen, muscle contraction and cell motion. 4) Haem synthesis Haem for haemoglobin is synthesised here. A lot of mitchochondria are found in extremely active cells. E.g. Muscle cells - contraction. Neurones - Na/K pump for impulse transmission. Kidney tubule cells - active reabsorbtion. Liver cells - many metabolic processes. Companion cells of phloem - active translocation. Root hair cells - active uptake of minerals. Endodermal cells - active pumping of ions - root pressure. Insect flight muscles. Sperm cells - swimming towards the ovum. Chloroplasts are found in plant palisade and guard cells. A chloroplast will develop from proplastids only if it is exposed to light and they also contain their own DNA and ribosome's. Chloroplasts are the site of the light reactions of photosynthesis. The pigments are located on the thylakoid membranes in structures called quantosomes. The lamellae can angle the thylakoid to absorb maximum light. Chloroplasts are also the site for the dark reaction in the stroma. Hence, the appearance of starch grains and lipid globules - products of photosynthesis.
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