Question

Plant cells are different from animal cells in several ways. All plant cells have a cell wall during their entire existence. The cell wall has many different functions in different cell types.

Compare and contrast between the two types of plant cell walls as to their chemical make up, shape, when they are formed, and morphological properties. Include all chemical components in the cell wall we discussed during lecture.

Draw two figures showing how each of these cell walls are formed in a cell. Show and label the various organelles and structures involved.

Answer 1

Ans: Animal cells do not have a cell wall, while plant cells do. Animal cells are circular and plant cells are rectangular. All animal cells have centrioles while they are only present in low plant forms. Animal cells do not have chloroplasts, plant cells do. Both have cytoplasm, ribosomes, mitochondria and a nucleus

Parenchyma cells are the most common type of plant cell are variable in size, shape and function and are found throughout a plant. It has thin walls and large water filled vacuoles in the middle. Parenchyma cells carry huge amounts of chloroplasts, ribosomes, ER, and Golgi bodies. Depending on what type, they may carry starch, proteins, fats, pigments, and even crystals. The thin cell walls of parenchyma cells are composed of cellulose, hemicellulose, and calcium pectate. The plasmodesmata and the middle lamella are also commonly present. The sugars present in these thick walls become the nutrients for the germinating embryo. Some parenchyma cells may also develop lignified or secondary walls and may even be indistinguishable from sclerenchyma cells. Photosynthesis occurs in green chloroplasts within parenchyma cells in leaves. Both chloroplasts and colorless plastids in parenchyma cells within roots and stems store starch. The flesh of many fruits we eat is also made of parenchyma cells. They have the ability to divide throughout their entire lives so they are important in healing wounds to the plant and regenerating parts. For example parenchyma cells allow us to place stem cuttings of many types of plants in water to grow into a complete, new plant and have thin and flexible cell walls that can change shape. They are the site of general metabolism i.e., chemical reactions take place and their functions includes storage, photosynthesis and they also store starch, oils and water and are capable of dedifferentiation or rededifferentiation

Collunchyma cells are found in the shoot system (stems and leaves) in regions that require stretchable support. Collenchyma cells has cell walls that range from thin to thick, providing support while still allowing the plant to grow. These cells are most common in the younger tissues of leaves and shoots. They often form into strands. (celery strings). They are flexible. Cell walls does not contain lignin, so they are stretchy and can change size. As a young leaf grows, collenchyma cells can elongate and still give the leaf structure.