When would a cell be able to use the krebs cycle and etc?

What type of lipids are found in all biological membranes?

Johnny rode his bike to a friend's house 4 blocks down the street in his neighborhood. he immediately rode back home once he realized his friend was not able to play. what was his displacement for the total bike ride? how did you determine this? what could we use as a reference point to determine he was in motion during his bike ride? why can you use it as a reference point

Explain how sequences of amino acids in proteins can be used to reveal relationships among organisms.