Nutrition Science and Everyday Application - beta v 0.1

PROTEIN FUNCTIONS 325
the pancreas releases the hormone insulin. Insulin tells the cells of the body that glucose is
available and to take it up from the blood and store it or use it for making energy or building
macromolecules. A major function of hormones is to turn enzymes on and off, so some
proteins can even regulate the actions of other proteins. While not all hormones are made
from proteins, many of them are.
FLUID AND ACID-BASE BALANCE
Adequate protein intake enables the basic biological processes of the body to maintain
homeostasis (constant or stable conditions) in a changing environment. One aspect of this is
fluid balance, keeping water distributed properly in the different compartments of the body.
If too much water suddenly moves from the blood into a tissue, the results are swelling and,
potentially, cell death. Water always flows from an area of high concentration to an area of
low concentration. As a result, water moves toward areas that have higher concentrations of
other solutes, such as proteins and glucose. To keep the water evenly distributed between
blood and cells, proteins continuously circulate at high concentrations in the blood. The most
abundant protein in blood is the butterfly-shaped protein known as albumin. The presence
of albumin in the blood makes the protein concentration in the blood similar to that in cells.
Therefore, fluid exchange between the blood and cells is not in the extreme, but rather is
minimized to preserve homeostasis.
Figure 6.12. The butterfly-shaped protein, albumin, has many functions in the body including
maintaining fluid and acid-base balance and transporting molecules.
Protein is also essential in maintaining proper pH balance (the measure of how acidic or
basic a substance is) in the blood. Blood pH is maintained between 7.35 and 7.45, which
is slightly basic. Even a slight change in blood pH can affect body functions. The body
has several systems that hold the blood pH within the normal range to prevent this from
happening. One of these is the circulating albumin. Albumin is slightly acidic, and because