Anatomy and Physiology Answer Key

2 membrane surface area is increased by the presence

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Unformatted text preview: e-bound reactions can occur. This facilitates rapid transfers and more "reactive" surface area and therefore increases the speed and efficiency of metabolic reactions. (b) Channel proteins and carrier proteins speed up the rates of diffusion into and out of the cell. Again, this facilitates rapid transfers and efficiency of function. 4. (a) Any of: Golgi apparatus, mitochondria, chloroplasts, endoplasmic reticulum (rough Anatomy and Physiology 1. 3. 4 or smooth), nucleus, vacuoles, lysosomes, peroxisomes. (b) Depends on choice: Generally the membrane’s purpose is to compartmentalize the location of enzymatic reactions, to control the entry and exit of substances that the organelle operates on, and/or to provide a surface for enzyme attachment. Cholesterol lies between the phospholipids and prevents close packing. It thus functions to keep membranes more fluid. The greater the amount of cholesterol in the membrane the greater its fluidity. 6. Anatomy and Physiology 5. (b) Tight junctions bind the membranes of neighboring cells, holding the cells together and making them impermeable to fluid and preventing molecules passing through the spaces between cells. Common in epithelia, e.g. the epithelia of the distal convoluted tubule in the nephron of the kidney, the epithelia of the lung, and the bloodbrain barrier. (c) Desmosomes allow cell to cell adhesion to help resist shearing forces. Common in tissues subjected to mechanical stresses such as the simple and stratified squamous epithelium (e.g. skin cells). 7. 8. Tight junctions are common where it is important that molecules (e.g. large proteins) not leak between cells; materials must actually enter the cells (by diffusion or active transport) in order to pass through the tissue. This pathway provides control over the entry of substances. The importance of tight junctions is illustrated by "leaky gut" syndrome, where failure of tight junctions is implicated in acute and chronic diseases such as inflammatory bowel disease. Labeled diagram: Protein on surface Protein...
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This document was uploaded on 01/28/2014.

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