Anatomy and Physiology I Test 2

The structural functional unit of all living organisms is the

• ribosome.

• cell.

• organ.

• organelle.

• plasma membrane.

The plasma membrane

• separates the nucleus from the rest of the cell.

• is a rigid protein membrane.

• allows water soluble molecules to move freely across the membrane.

• has a single layer of phospholipids.

• regulates movement of materials into and out of the cell.

The environment outside the plasma membrane is most appropriately referred to as

• intracellular.

• extracellular.

• multicellular.

• centrocellular.

• none of the above.

Plasma membrane phospholipids

• have polar (charged) tails.

• are arranged in a single layer.

• have tails that face the exterior of the membrane.

• are 95% cholesterol.

• have a hydrophilic (likes water) head and hydrophobic (hates water) tails.

In general, water-soluble molecules diffuse through the ____ ____; and lipid-soluble molecules diffuse through the ____ ____.

• protein channels; protein channels

• protein channels; phospholipid bilayer

• bilipid layer; protein channels

• bilipid layer; bilipid layer

• none of the above

Cell membrane phospholipids

• have lipid tails.

• form a bilayer.

• have phosphate heads.

• create a selectively permeable barrier.

• all of the above.

When a sperm cell comes into contact with an egg cell, there is a change in the electrical charge across the plasma membrane and various channel proteins close. These channels would be called

• open-gated channels

• voltage-gated channels

• ligand-gated channels

• nongated ion channels.

Channel proteins

• are binding sites for other molecules

• utilize the G protein complex to function.

• are found only on endoplasmic reticulum.

• allow cells to recognize one another.

• provide a “door” through which extracellular molecules can enter the cell.

The plasma membrane is selectively permeable. This means

• only gasses and water can pass through it

• substances need permission to pass through it.

• only certain substances can pass through it.

• substances need carrier molecules to pass through it.

• ATP is always needed to move molecules across the plasma membrane.

Vitamin A, a fat-soluble vitamin, would move across the plasma membrane into the cell

• in vesicles.

• through vitamin membrane channels.

• by simple diffusion through the phospholipid bilayer.

• by transport with carrier molecules.

• by active transport.