Which cell type is the most metabolically active among the following: TABLE 3.1 Composition of Selected Membranes Membrane Protein Lipid Carbohydrate Red blood cell membrane 49% 43% 8% Myelin membrane around nerve cells 18% 79% 3% Inner mitochondrial membrane 76% 24% 0% O Myelin surrounding nerve cells O These membranes are metabolically equal O Inner mitochondrial membrane

[#142] How many cells are you? How many cells in a human? Assume that cells have a typical size of about 10 um (1um = 10-6 m) in all directions. And that we are the same density as water, and are made completely of cells (both exaggerations, of course, but fine for an order of magnitude estimate). Hints: What is the volume of a cell? What is the volume of a human? How can these quantities be related to give the number of cells in your body? The shape of the cell is not important in this rough estimate: for instance, the difference in volume fraction between say cubes and close packed spheres is only 26%. Format: When you enter your answer, enter it as a power of 10. For example: for 100000, enter "10^5". We'll use this notation later, too.

would substances be able to pass through the plasma membrane if the phospholipi tails of the plasma membrane were oth satueated fatty acids? why or why not, explain?

Ammonia (NH3) is a weak base that under acidic conditions becomes protonated to the ammonium ion in the  following reaction: NH3   +  H+   →   NH+4 NH3 freely permeates biological membranes, including those of lysosomes. The lysosome is a subcellular organelle with a pH of about 4.5–5.0; the pH of cytoplasm is about 7.0. What is the effect on the pH of the fluid content of lyso- somes when cells are exposed to ammonia? Note: Ammo- nium (NH4+) does not diffuse freely across membranes.