Carbon dioxide and oxygen are molecules that can move freely across a semipermeable membrane of cells. what determines the direction that carbon dioxide and oxygen molecules move?
a. orientation of cholesterol in the plasmamembrane
b. location of receptors
c. concentration gradient across the cell membrane
d. configuration of phospholipids in the cell membrane

This is a typical grassland food web. it is also a small picture of an important cycle on earth: the carbon cycle. describe how the carbon gets into this food web. a) bacteria and fungi, the decomposers, recycle carbon from dead organisms. b) carbon is found in the grass and is passed from one level to the next in this food web. eliminate c) all living things give off carbon dioxide as a by-product of respiration and it is released into the atmosphere. d) plants use carbon dioxide as a reactant in photosynthesis, to make usable chemical energy in the form of a sugar.

What is the main fuel source for the work of the cell

Why does the earth spin slowly, not faster? is it possible to prove it scientifically? can you prove it with math?