Question

1. Which of the following is TRUE?
   1. Hormones are secreted into the blood in pulses by specific stimuli.
   2. Steroid hormones will bind to receptors located on the cell membrane.
   3. An example of a secondary messenger is estrogen, as it is released upon stimulation from a primary messenger, such as LH.
   4. Tyrosine kinase is located in the nucleus and causes new proteins to be created.

Answer 1

Hormones are secreted into the blood in pulses by specific stimuli.

This is true. Hormones are released in small controlled doses as hormones can affect a diverse set of phenotype and hormonal signals are often amplified manyfold before reaching the effector.

Steroid hormones will bind to receptors located on the cell membrane.

Steroid hormones are usually non-polar and are able to cross the cell membrane. Therfore, they typically bind to Cytosolic Receptors.

An example of a secondary messenger is estrogen, as it is released upon stimulation from a primary messenger, such as LH.

Secondary messengers are molecules that carry the signal from the signal receptors to effector and which amplify the signal in the mean time. These are typically small molecules like cAMP. Hormones are not secondary messengers.

Tyrosine kinase is located in the nucleus and causes new proteins to be created.

Tyrosine Kinase Receptors are present on the cell membrane. These molecules do not directly cause new proteins to be made but rather phorphorylate proteins.