Cells communicate by several distinct mechanisms. Which of the following is NOT a mechanism in which cells communicate directly:

A.  Cytoplasmic flow between cells

B.  Neurotransmitters

C.  Cell-cell adhesion

D.  A and B

E.  A and C

B. Neurotransmitters

Cells commuicate indirectly by neurotransmitters produced by a nerve cell

True or False

Epinephrine (adrenaline) is a hormone and a neurotransmitter.

True

Epinephrine is secreted by nerve cells and acts as a neurotransmitter; it is also secreted by the adrenal medulla and acts on various organs as a hormone.

Hormones can be classified by their source. Which hormone is accurately paired with its source?

A. Endocrine hormone: secreted by one cell and acts on the same cell

B.  Paracine hormone: secreted into the blood circulation, and typically, acts on distant target cells in other organs

C.  Autocrine hormone: secreted by one cell but acts on a nearby cell

D.  None of the above

D. None of the above

Autocrine hormones are secreted by one cell and act on the same cell.

Paracrine hormones are secreted by one cell but act on a nearby cell.

Endocrine hormones are secreted into the blood circulation and typically act on distant targets cells in other organs.

True or False

All hormones work by binding to receptors.

True or False

Receptors convert the substrate ligand into a product.

False

• Receptors are distinct from enzymes, which convert the substrate ligand into product.
• Receptors recognize and bind certain hormones, and trigger some effect only when the hormone is present.

Some receptors are located on the surface of the cell. Others are inside the cell. Which of the following is a characteristic of a receptor located on the cell surface?

A. Receptors on the cell surface bind hormones that are hydrophilic.

B. Receptors on the cell surface bind hormones that are hydrophobic.

C. They bind mostly steroids.

D. They bind DNA, and transcribe a specific group of genes that encode other proteins.

Binding of the hormone (the first messenger) leads to production of a second messenger inside the cell. This is true for which receptor?

A. Receptors on the cell surface
B. Receptors inside the cell

Hormone receptors can be classified as the following except:

A.  Ligand gated ion channels

B. G protein coupled receptors

C.  Steriod receptors

D. Enzymatic activators

E.  Growth factor receptors

Receptors inside the cell

• Bind hydrophobic hormones
• Bind mostly steroids

True or False

In ligand-gated-channels, the receptor is both the receiver and the direct transmitter of the signal.

G protein coupled receptors

• Binding of hormone to the receptor triggers a change in receptor conformations, or overall shape.

• The conformational shape allow the cytoplasmic portion of the receptor to bind G proteins inside the cell.

Which of the following is not associated with G protein coupled receptors?

A.  Conformational change

B.  2 subunit, and 9 membrane-spanning segments

C.  Release of GDP, binding of GTP

D.  Binding of G proteins

B. 2 subunit, and 9 membrane- spanning segments

G protein coupled receptors have 1 subunit and 7 membrane-spanning segments