Answer:
Hormones
Hormones are any of various internally secreted compounds, as insulin or thyroxine, formed in endocrine glands, that affect the functions of specifically receptive organs or tissues when transported to them by the body fluids.
What are the main types of membrane proteins?
Two types of membrane proteins: peripheral proteins and integral proteins. Peripheral proteins have weaker and temporary connections to the membrane. Some just sit on the surface, anchored with a few ionic bonds while others might have small sections that dip into the hydrophobic section of the bilayer. When you look at the entire membrane, there are more peripheral proteins when compared to the number of integral proteins. Transmembrane proteins are integral proteins that cross the membrane and can act as pathways for ions and molecules. Polytypic transmembrane proteins cross the membrane several times. Some are receptor proteins while others form channels. Ion movement that does not require work is called passive transport while active transport systems use work to move molecules. Active transport is regularly used when membrane proteins pump ions against the concentration gradient.
Okay, but are hormones considered proteins:
Sometimes but not always. There are three main classes of hormones: amino-acid based (amines/peptides/proteins), eicosanoids, and steroids.
Peptide hormones and protein hormones (the former having a shorter amino acid chain) are synthesized from mRNA inside the cell nucleus just like any other protein or peptide. Prohormones are then typically processed in the endoplasmic reticulum to remove the N-terminus and the signal sequence. Sometimes glycosylation (addition of glycans) will be performed. These hormones can then be secreted by the cell in response to stimuli.
Some common and well-known peptide/protein hormones include angiotensin, insulin, and glucagon.
Thanks,
Eddie