Most of the phosphate in a body is present as
a) Lipids
b) Plasma membranes
c) DNA
d) Calcium phosphate salt
e) Carbohydrates
d
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Moving a solute or solvent across a membrane against a concentration gradient is a(n) ________ process that requires an expenditure of ATP.
Fill in the blank(s) with the appropriate word(s).
Emphysema results in
A) all of the above. B) loss of alveolar wall elasticity. C) a decrease in the total surface area of the respiratory membrane. D) diminishment in the number of respiratory capillaries.
Which of the following statements concerning the permeability of a typical neuron membrane at rest is TRUE?
A. The permeability to Na+ is much greater than the permeability to K+. B. All of the K+ channels in the membrane are open. C. The voltage-gated Na+ channels are in the inactivated state. D. Most of the voltage-gated Na+ channels are in the closed state. E. There is equal permeability to Na+ and K+.
Which of these does NOT provide a physical or chemical barrier?
a) Macrophages b) Saliva c) Urine d) Mucus e) Stratified squamous epithelium