Ap Biology Essay 1

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  • Topic: Cell membrane, Cholesterol, Phospholipid
  • Pages : 3 (707 words )
  • Download(s) : 586
  • Published : February 25, 2012
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2007 AP Question 1
A) Three macromolecules that are very important components of the Cell Membrane of Eukaryotic organisms include molecules such as phospholipids, cholesterol and Glycoproteins all of which contribute to the continued functioning of the cell membrane. Phospholipids

Structure: form the majority of the cell membrane, two layers of phospholipids combine to form the phospholipid bilayer, the phospholipids are made of two fatty acid tails attached to a phosphate head, the phosphate heads are hydrophilic (Polar) while the fatty acid tails are hydrophobic (Non-Polar) because of this the fatty acid tails are sandwiched between the phosphate heads in the phospholipid bilayer. Function: the phospholipid bilayer is selectively permeable and plays an important role in determining what molecules can enter or exit the cell, it also makes the membrane very fluid (fluid mosaic model) which is of use when the cell moves by cytoplasmic streaming or when ingesting a particle by endocytosis (or secreting wastes by exocytosis). It also plays a role in protecting the cell from the outer environment as it is a physical barrier. Cholesterol

Structure: Cholesterol is the basis for many steroids, it consists of a ring structure of 3 hexagonal compound attached to a pentagonal compound, cholesterol is amphipathic and has a very small polar part that is soluble in water, however most of it is insoluble and non-polar, because of this Cholesterol is embedded inside the phospholipid Bilayer. Function: Cholesterol is very important in regulating the fluidity and rigidity of the membrane, in high temperatures it prevents the membrane from becoming too fluid and in low temperatures it stops the membrane from becoming too rigid. It maintains the stability of the Phospholipid bilayer. Glycoproteins

Structure: Glycoproteins are carbohydrate chains attached to proteins; these proteins are attached to the “Head” of the carbohydrates and sticks out of the phospholipid...
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