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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,
(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
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.
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This document was uploaded on 01/28/2014.
- Winter '13