Chapter5

The signals that bind to receptors on nearby cells are known as

Paracrine signals

A benefit of the many steps involved in a protein kinase cascade is that they allow for

activation or inhibition of many enzymes; amplification of the signal; distribution of the signal throughout the inside of the cell; variation in the response.

Cholesterol molecules

alter the fluidity of the membrane.

The signals that bind to receptors of the same cell that made them are known as

autocrine signals

When a severely dehydrated patient is brought to the hospital, an IV of normal saline is started immediately. Distilled water is not used because

it would cause the patient's blood cells to swell and eventually burst.

Biological membranes are composed of

lipids, proteins, and carbohydrates.

The compounds in biological membranes that form a barrier to the movement of hydrophilic materials across the membrane are

lipids.

Osmosis moves water from a region of _______ to a region of _______.

low; high

Contact with ice numbs a person's fingers because at lower temperatures

membrane fluidity is reduced in nerve cells.

In hibernating animals during the winter,

membrane lipid composition changes: saturated fatty acids are replaced with unsaturated fatty acids

Functions of membrane proteins

Allowing movement of molecules that otherwise would be excluded by the lipid components of the membrane; Transferring signals from outside the cell to inside the cell; Facilitating the movement of water across the membrane; Facilitating the transport of macromolecules across the membrane

A molecule that binds to the particular three-dimensional structure of another molecule's receptor site is known as a(n)

Ligand

For a G protein to play its part in moving events forward in a signal pathway,

GDP must be released, and a GTP must occupy the nucleotide-binding site.

Which function is a recognition signal for interactions between cells?

Glycolipid

Signals that travel to distant cells through the circulatory system are known as

Hormones

A protein that forms an ion channel through a membrane is most likely

a transmembrane protein.

After the GTP-bound subunit of the G protein separates from the rest of the G protein, it travels until it encounters

an effector protein.

The rate at which a substance diffuses is affected by the

diameter of the molecules or ions; temperature of the solution; concentration gradient in the system.

Houseplants adapted to indoor temperatures may die if they are left outdoors, because in a cold environment their

membranes lack adequate fluidity.

When placed in water, wilted plants lose their limpness because of

osmosis of water into the plant cells

The difference between osmosis and diffusion is that

osmosis refers specifically to the movement of water, whereas diffusion refers to the movement of any type of molecules.

When placed in a hypertonic solution, animal cells

shrink

If a red blood cell is placed in an isotonic solution, it will

take up and release water at equal rates.

The existence of a concentration gradient of glucose across a membrane means that

the glucose molecules are more crowded on one side of the membrane than on the other

Protein-linked receptors are

transmembrane proteins

What bind(s) strongly to the acetylcholine receptor?

Acetylcholine

In what way do ligand-receptor interactions differ from enzyme-substrate reactions?

The ligand signal is not usually metabolized into useful products.

In biological membranes, the phospholipids are arranged in a _______, with the _______.

bilayer; fatty acids pointing toward each other

Acetylcholine

binds to a sodium channel receptor; acts as a neurotransmitter; When bound to its receptor, allows sodium to diffuse down its concentration gradient; binds to receptors on skeletal muscle cells.