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Chapter 12
Water and Major Minerals
Key Terms
1.
ions: Atoms or groups of atoms with an electrical charge resulting from the loss or gain
of one or more electrons.
2.
calmodulin: A calcium-binding protein that regulates a variety of cellular activities, such
as cell division and proliferation.
3.
aldosterone: A hormone secreted from the adrenal glands that acts on the kidneys to
regulate electrolyte and water balance. It raises blood pressure by promoting retention of
sodium (and thus water) and excretion of potassium.
4.
plasma: The fluid portion of the blood that contains blood cells and other components.
5.
oxalate (oxalic acid): An organic acid in some leafy green vegetables, such as spinach,
that binds to calcium to form calcium oxalate, an insoluble compound the body cannot
absorb.
6.
salts: Compounds that result when the hydrogen of an acid is replaced with a metal or a
group that acts like a metal.
7.
insensible water loss: The continual loss of body water by evaporation from the
respiratory tract and diffusion through the skin.
8.
electrolytes: Substances that separate into charged particles (ions) when dissolved in
water or other solvents and thus become capable of conducting an electrical current.
Often used interchangeably with the term ions.
9.
fibrin: A stringy, insoluble protein that is the final product of the blood-clotting process.
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10.
osmosis: The movement of a solvent, such as water, through a semipermeable membrane
from the dilute to the concentrated side until the concentrations on both sides of the
membrane are equal.
11.
phytate (phytic acid): A phosphorus-containing compound in the outer husks of cereal
grains that binds with minerals and inhibits their absorption.
Fill-in-the-Blank
1.
Antidiuretic hormone (ADH) is a hormone secreted by the pituitary gland that increases
blood pressure and prevents fluid excretion by the kidneys.
2.
Anions are ions that carry a negative charge, while cations are ions that carry a positive
charge.
3.
Hydroxyapatite is a crystalline mineral compound of calcium and phosphorus that
makes up bone.
4.
Hypertension is a condition in which resting blood pressure persistently exceeds 140
mm Hg systolic or 90 mm Hg diastolic.
5.
Trace minerals are present in the body and required in the diet in relatively small
amounts compared with major minerals; they are also known as microminerals.
6.
Wavelike motion of small hairlike projections on some cells is called ciliary action.
7.
Osteoclasts are bone cells that break down bone structure and release calcium and
phosphate into the blood.
8.
Major minerals are required in the diet and present in the body in large amounts
compared with trace minerals.
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Fill-in-the-Blank Summaries
Water: The Essential Ingredient for Life
Overall, water makes up 45 to 75 percent of your weight. The body maintains its electrolyte
balance through the intake and excretion of water and the movement of ions. Positively
charged ions are known as cations. Negatively charged ions are known as anions. About
two-thirds (2/3) of body water is in the intracellular fluid, and one-third (1/3) is in
extracellular fluid. The major components of extracellular fluid are interstitial fluid and
blood plasma. To maintain the balance of sodium and potassium, all cell membranes
incorporate sodium-potassium pumps that actively pump sodium out of the cell while
allowing potassium back in. When electrolytes are more concentrated on one side of the
membrane, then water flows to the side of higher concentration. Cells must contain the
right amount of water. Too much and the cell will burst; too little and the cell will shrink.
Too much water in the surrounding spaces causes edema.
Short Answer
1.
What is the most important role of the renin-angiotensin system?
Perhaps the most important role of the renin-angiotensin system is its response to dietary
sodium. It allows a person to consume either very small or very large amounts of sodium
without causing major changes in extracellular fluid volume or blood pressure.
2.
Describe how the kidneys adjust and manipulate urine excretion when water intake is too
low. Describe the kidney’s production when the body has an excess of water.
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When water intake is low, the kidneys conserve water. While continuing to excrete solutes,
they reabsorb water, thus decreasing urine volume and concentrating the urine. When the
body has an excess of water, the kidneys form and excrete a large volume of dilute urine.
3.
Although taste, availability, cultural patterns, and personal habits affect the amount of
fluids we consume, thirst is our most important stimulus for drinking. There are four
major stimuli for making us feel thirsty—what are they?
1) Increased osmolarity of the fluid surrounding the osmoreceptors in the hypothalamus
2) reduced blood volume and blood pressure
3) increased angiotensin II
4) dryness of the mouth and mucous membranes lining the esophagus
4.
Chronic mild dehydration—a fluid deficit of as little as 1 to 2 percent of body weight—
can cause declines in alertness and the ability to concentrate while increasing feelings of
tiredness and headache. Identify two other consequences our body has as a result of
chronic mild dehydration, and give an example of a daily skill this may affect.
Chronic mild dehydration also impairs decision making and reaction times. This may be
important for tasks that involve judgment and skill, such as driving a car.
5.
Plant foods can be excellent sources of several minerals. Explain why the mineral content
of plants can vary dramatically.
The mineral content in plants varies depending on the mineral content in the soil in which
it grows, as well as the maturity of a vegetable, fruit, or grain.
6.
Identify the role(s) of sodium in the body.
Sodium is the major cation in the extracellular fluid; it plays a critical role in regulating
proper water distribution and blood pressure.
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7.
Identify the role(s) of potassium in the body.
Potassium is the major cation in the intracellular fluid. With sodium, it regulates muscle
contractions and nerve impulse transmissions.
8.
Identify the role(s) of chloride in the body.
Chloride is involved in many important metabolic functions. It is used to form the
hydrochloric acid secreted in the stomach, and is important in the generation of nerve
impulses as well as immune function.
9.
Calcium is a major component of bones and teeth. What other body functions require
calcium?
In addition, calcium is required for muscle contraction, nerve impulse transmission, blood
clotting, and regulation of cell metabolism.
10.
Identify the role(s) of phosphorus in the body.
Phosphorus is common in many crucial metabolic systems. It is used to activate and
deactivate enzymes, and is an essential component of ATP, the energy source of the cell.
11.
Identify the role(s) of magnesium in the body.
Magnesium is a cofactor for more than 300 enzymes. Magnesium is required for cardiac
and nerve function, and it helps form ATP.
12.
Identify the role(s) of sulfur in the body.
Sulfur is a component of the amino acids methionine and cysteine, as well as of the vitamins
biotin and thiamin. Sulfur is important in drug detoxification and in maintaining acid–base
balance.
Labeling
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Trace the effects of water deficit by labeling each section of the image.
(top to bottom) Hypothalamus; Osmoreceptors; Pituitary gland
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