In nerve cells, the _______ use ATP
a. potassium channels
b. sodium channels
c. sodium-potassium pumps
d. potassium and sodium channels
e. sodium channels and the sodium-potassium pump
C; The sodium-potassium pump uses ATP to power the exchange of sodium and potassium ions and move them against a concentration gradient. The sodium and potassium channels allow ions to leak through them down a concentration gradient, and therefore do not use energy during ion movement.
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Osteocytes are bone cells. Collagen fibers and calcium salts are found in abundance between and among the osteocytes. The collagen and calcium salts are _____
A) components of the plasma membrane of osteocytes B) part of the extracellular matrix C) extensions of the endoplasmic reticulum D) deposited by the circulatory system but not associated with the osteocytes
Protists cause four of the following diseases. Which one is the exception?
a. dysentery b. neurotoxic shellfish poisoning c. malaria d. AIDS e. trichomonas infections of the reproductive tract
All gymnosperms have needle-like leaves and produce some type of resin.
Answer the following statement true (T) or false (F)
Which go these observations gives the most support to the endosymbiotic theory for the origin of eukaryotic cells?
a. the existence of structural and molecular differences between the plasma membranes of prokaryotic and the internal membranes of mitochondria and chloroplasts b. the similarity in size between the cytosolic ribosomes of prokaryotes and the ribosomes within mitochondria and chloroplasts c. the size disparity between most prokaryotic cells and most eukaryotic cells d. the observation that some eukaryotic cells lack mitochondria