Do Now—Answer in your spiral What is the difference between complete and incomplete proteins? In which foods can you find each?

Why Is Water Essential to Life? Water is the most abundant substance in the body. An average healthy adult is 45 to 75 percent water. Distribution depends on: Age Percent of water declines with age. Gender Males have more body water than females. Composition of fat and muscle Muscle is ~65 percent water. Fat is 10 to 40 percent water. © 2014 Pearson Education, Inc.

The Composition of the Body © 2014 Pearson Education, Inc.

The Functions of Water in the Body © 2014 Pearson Education, Inc. Water is a polar molecule. Neutral electrical charge Maintains acid-base balance

Functions of Water in the Body (Cont'd) Universal solvent: liquid in which substances dissolve Polarity attracts charged particles into a solution that dissolves proteins, glucose, and some minerals. Important to digestion Helps transport dissolved nutrients and other substances throughout the body Transports oxygen, nutrients, and hormones to cells Transports waste products away from cells for excretion in urine and stool © 2014 Pearson Education, Inc.

Water Is a Universal Solvent © 2014 Pearson Education, Inc.

Functions of Water in the Body (Cont'd) Maintains body temperature Absorbs and releases heat generated by the body Lubricant for: Joints, sensitive eye tissues, mouth, and intestinal tract Provides a protective cushion Bathes certain organs with fluid During pregnancy the fetus is surrounded by watery amniotic fluid. Provides structure to cells © 2014 Pearson Education, Inc.

Functions of Water in the Body (Cont'd) Participates in hydrolysis and condensation reactions During digestion water hydrolyzes the bonds of: Carbohydrate molecules Protein molecules Fat molecules Water is formed and released when smaller molecules join together during condensation. Plays a role in acid-base balance Water is used to reduce or increase pH levels. Breaks down or forms carbonic acid © 2014 Pearson Education, Inc.

How Is Water Balance Maintained? Fluid balance (homeostasis) Is necessary for normal reactions within the cells Body adapts to changes in water intake and losses Water balance Water consumed = water excreted © 2014 Pearson Education, Inc.

Sources of Body Water Include Beverages and Food Beverages are the largest source. All foods contain some water. Fruits and vegetables contain the most. Grains contain the least. Metabolism Water generated during metabolism is metabolic water. These sources contribute to an average daily intake of 2,550 ml (about 2 quarts). © 2014 Pearson Education, Inc.

Water Is Excreted through the Kidneys, Large Intestine, Lungs, and Skin Majority of fluid is excreted through the kidneys as urine Urine production is dependent on water intake. Water is lost through intestinal fluids in the stool. Plant fibers can reduce excretion. Diarrhea and vomiting can increase excretion. Evaporated through exhalation and through the skin Insensible water loss © 2014 Pearson Education, Inc.

Water Is Excreted through the Kidneys, Large Intestine, Lungs, and Skin (Cont'd) Losses through sweat Varies based on Environmental factors Temperature Humidity Wind Sun's intensity Clothing worn Amount of physical activity © 2014 Pearson Education, Inc.

Water Is Balanced between Fluid Compartments Body fluid is located In intracellular fluid (ICF) – within the cells Contains potassium, proteins, various acids In extracellular fluid (ECF) – outside the cells Contains sodium chloride and sodium bicarbonate solutions Two types of ECF Interstitial fluids: bathe the outside of cells Intravascular fluids: in blood and lymph Fluids move between ECF and ICF easily. © 2014 Pearson Education, Inc.

The Intracellular and Extracellular Fluid Compartments © 2014 Pearson Education, Inc.

Electrolytes Participate in Fluid Balance Electrolytes maintain water balance between compartments. Sodium has the greatest effect on fluid balance. Osmosis Affects the movement of water between cells, not the solutes Water moves from a diluted concentration to a high concentration of electrolytes. Osmotic pressure controls the directional flow of water. Based on osmolality or the concentration of particles in a solution (number of solutes) © 2014 Pearson Education, Inc.

Osmosis

Think-Pair-Share How might your life be different if water didn’t behave the way it does?

How Much Water Do You Need and What Are the Best Sources? Water needs depend on Physical activity Environmental factors Diet Recommendations 80 percent intake from beverages and 20 percent from food Adult women: approximately 9 cups of fluid per day Adult men: approximately 13 cups of fluid per day People who are very active have higher water requirements. © 2014 Pearson Education, Inc.

Daily Beverage Recommendations

Water Content of Foods © 2014 Pearson Education, Inc.

How Much Water Do You Need and What Are the Best Sources? Drink bottled or tap water, milk, and juices throughout the day. Most foods can also contribute to meeting daily water needs. Fruits and vegetables can be 70 percent or more water by weight. Dry grain products provide some water. © 2014 Pearson Education, Inc.

Do Diuretics Like Caffeine and Alcohol Affect Water Balance? Alcoholic drinks, regular coffee, and tea contribute to total water intake. Alcohol and caffeine are considered diuretics. Contribute to water loss Overconsumption can upset fluid balance. © 2014 Pearson Education, Inc.

Caffeine Does Not Cause Significant Loss of Body Water Mild diuretic that blocks the action of ADH in the kidneys Does not result in dehydration Caffeine doesn't cause a significant loss of body water over the course of the day compared with noncaffeinated beverages. Tolerance to diuretic effects develops over time Does not negatively affect hydration status © 2014 Pearson Education, Inc.

Alcohol Can Be Dehydrating Interferes with water balance by inhibiting ADH Can induce urination as quickly as 20 minutes after consumption Is dehydrating Affects electrolyte concentration, especially potassium Older drinkers are less affected than younger drinkers. To prevent dehydration Reduce alcohol consumption. Drink water after consuming alcohol. © 2014 Pearson Education, Inc.

Consuming Too Much Water Can Cause Hyponatremia Water intoxication Rare in healthy individuals who consume a balanced diet, as more urine will be produced Drinking fluid too fast without adequate sodium replacement depletes sodium and increases the rate of urine production. Results in hyponatremia Can cause swelling in the brain Symptoms include fatigue, confusion, and disorientation. © 2014 Pearson Education, Inc.

Consuming Too Little Water Is a Common Problem Dehydration can be caused by: Inadequate water intake Losing excessive amounts of water due to diarrhea, vomiting, high fever, or use of diuretics As little as a 2 percent loss of body water can trigger: Loss of short-term and long-term memory Lower attention span and cognition Reduced ability to maintain core temperature Increased risk of urinary tract infections and fatigue © 2014 Pearson Education, Inc.

Consuming Too Little Water Is a Common Problem (Cont'd) Consequences of dehydration can be severe for children, elderly, and athletes. Elderly: misdiagnosed as dementia Athletes: impairs performance © 2014 Pearson Education, Inc.

Consuming Too Little Water Is a Common Problem Thirst is often the first physical sign of dehydration. Water is lost from the body. Reduced blood volume Reduced blood pressure Hypotension if severe enough Reduced cardiac output Impaired digestion Fainting or blackout During dehydration Water is depleted from ECF and ICF © 2014 Pearson Education, Inc.

Dehydration © 2014 Pearson Education, Inc. Look at urine color to assess hydration.

DOL—answer on your DOL worksheet 1.What would be the best source of water? a)Fruit loops (dry) b)Orange juice c)Slice of cheddar cheese 2.List two functions of water in your body. 3.What are the effects of dehydration on your body/life? 4.What is one way you can tell you are dehydrated? 5.Why is it important that water is a universal solvent?