What process allows Na+ and K+ to move in and out of the cell simultaneously? ANSWERS:

A. Simple Diffusion
B. Facilitated Diffusion
C. Active Transport
D. Osmosis

The correct answer is: C. Active Transport.

Explanation:

Because Na+ and K+ are ions, which makes them charged molecules, they can only diffuse through the cell membrane when using specialized protein channels. This is called facilitated diffusion and is a form of passive transport because sodium and potassium move following their gradients, which are made of the difference in concentration between the inside of the cell and the outside of the cell. For example, potassium is highly concentrated inside the cell and poorly concentrated outside the cell, so potassium diffuses from the inside to the outside to even the concentrations.

But the question asks in which process Na+ and K+ move in and out of the cell SIMULTANEOUSLY, so the answer is actually active transport. Active transport is the opposite of passive transport. While passive transport occurs naturally and doesn't need ATP (energy) to happen, active transport needs ATP because it moves molecules AGAINST their gradient. One of the most famous and important structures involved in active transport is the Na+/K+ pump, which consists of a specialized protein using energy to enter 2 potassium ions and take out 3 sodium ions at the same time. This Na+/K+ is fundamental to maintain the gradients, which are important for the correct functioning of many cells.

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interphase

the period of cell growth when the cell synthesizes new molecules and organelles. the cell is not dividing and it constitutes the majority of the time spent in the cell cycle

prophase

changes occur in the nucleus and cytoplasm. the chromatin condenses to form structures (sister chromatids) visible with a light microscope and the mitotic spindle begins to form, but the nucleus is still in tact

prometaphase

the nuclear envelope fragments and the spindle microtubules attach to the kinetochores of the sister chromatids

metaphase

all the cell's duplicated chromosomes are lined up at an imaginary plane equidistant between the poles of the mitotic spindle

anaphase

begins when sister chromatids separate from each other and ending when a complete set of daughter chromosomes arrives at each of the two poles of the cell

telophase

the daughter nuclei form at the two poles of a cell

cytokinesis

the division of a cytoplasm to form two separate daughter cells. usually occurs during telophase during mitosis. this and mitosis make up to mitotic (m) phase of the cell cycle