Why don't na+ ions move across the plasma membrane of neurons and down their concentration gradient all the time? a. the plasma membrane is not permeable to na+ ions. b. the na+/k+ pump is required and it only operates when atp is plentiful c. a na+ channel is required and it is usually closed. a & c. a, b, & c.

What evidence did mendel find that supported his law of independent assortment? a. some traits are controlled by several different genes. b. a trait can be passed on from a parent to an offspring. c. most traits have a dominant form and a recessive form. d. different traits are passed on independently of each other.

Abody cell has been growing and at synthesis proteins. in the nucleus of this body cell, dna replication is taking place. and a copy of the cells genetic material is copied. which of the following is the best conclusion you can make about the life cycle of this cell ? a) the cell is ready to undergo mitosis. and a chemical signal will send the cell to prophase b)the cell is undergoing meiosis and will cross over the genetic material next c)the cell is in the s phase of interphase and will move next to the g2 phase d) the cell is in the g2 phase of the interphase and is ready to begin diving

Each nephron is made up of capillaries that form the __ sweat glands bladder glomerulus ureter