Which of the following describe the role a biochemical pump plays in active transport? a, it move materials across the membrane against the concentration gradient. b, it large molecules that do not normally cross the cell membrane to enter or exit cells. c, it a cell accumulate a relatively high concentration of a molecule. d, it move water more quickly across the membrane.

Molecules always tend to move downhill i.e, from higher concentration to lower concentration, but if a molecule has to move uphill i.e towards higher concentration then energy has to be spent.  

Active transport requires energy in the form of ATP i.e. ATP must break down for the movement of molecule against its concentration gradient. (ans is A)

the menstrual cycle – higher tier. negative feedback mechanisms affect the production of hormones in the menstrual cycle. oestrogen also stimulates the release of lh (luteinising hormone) from the pituitary gland, which in turn controls the production of progesterone.