Biology Chapter 2: Water Functions

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Questions and Answers

What percentage of water is provided by food?

30%

10%

40%

20% (correct)

What happens if we do not replace lost water by drinking regularly?

We will sleep better

We will experience dehydration (correct)

We will gain weight

We will become more energetic

How much of the total body weight is comprised of water for the average 70 kg man?

60% (correct)

50%

80%

70%

What is the percentage of water in the human body?

60% to 70% Signup and view all the answers

Why is water a good choice of drink?

It hydrates without providing energy Signup and view all the answers

What is the function of water in biological reactions?

It is an essential material Signup and view all the answers

How many sources of water does the body have?

Three Signup and view all the answers

How long can humans survive without fluids?

A few days Signup and view all the answers

What is the main reason for water's high melting point, boiling point, and heat of vaporization?

The ability of water to form hydrogen bonds with other molecules Signup and view all the answers

What happens to entropy when crystalline substances dissolve?

Entropy increases as crystalline substances dissolve Signup and view all the answers

What can be measured by the electrical conductivity of water?

The ionization of water Signup and view all the answers

Why are nonpolar gases poorly soluble in water?

Because nonpolar gases are unable to form hydrogen bonds with water molecules Signup and view all the answers

Why are acid-base reactions in aqueous solutions exceptionally fast?

Due to the high ionic mobility of H+ Signup and view all the answers

What is the result of the ionization of water?

The formation of both hydrogen ions and hydroxide ions Signup and view all the answers

What does the equilibrium constant Keq define?

The relationship between reactants and products at equilibrium Signup and view all the answers

What is the effect of nonpolar compounds on the structure of water?

They force energetically unfavorable changes in the structure of water Signup and view all the answers

What is the total hydrogen ion concentration from all sources expressed as?

pH of the solution Signup and view all the answers

What is the purpose of the equilibrium constant in describing the ionization of water?

To describe the extent of ionization of water Signup and view all the answers

What type of acids and bases are completely ionized in dilute aqueous solutions?

Hydrochloric, sulfuric, and nitric acids, and strong bases Signup and view all the answers

What is the result of the dissolution of weak acids in water?

The formation of hydrogen ions Signup and view all the answers

What is of more interest to biochemists?

The behavior of weak acids and bases Signup and view all the answers

What is the term used to describe the bending of the water molecule due to the difference in electronegativity between oxygen and hydrogen atoms?

Partial charge separation Signup and view all the answers

What is the significance of weak acids and bases?

They are ubiquitous in biological systems Signup and view all the answers

What is the relationship between pH and hydrogen ion concentration?

pH is directly proportional to hydrogen ion concentration Signup and view all the answers

What percentage of water is found in milk?

80-88% Signup and view all the answers

What is the main function of water as a carrier of nutrients?

To carry nutrients from intestines to tissues Signup and view all the answers

What is the unique property of water that makes it a 'universal solvent'?

High polarity Signup and view all the answers

Why does ice float on liquid water?

Because ice has a lower density than liquid water Signup and view all the answers

What happens to nonpolar molecules in aqueous solutions?

They cluster together Signup and view all the answers

What is the average number of hydrogen bonds formed by a water molecule in liquid water?

3.4 Signup and view all the answers

Which of the following is NOT a function of water in the human body?

Production of energy Signup and view all the answers

What percentage of water is found in fruits and vegetables?

80-90% Signup and view all the answers

Study Notes

Function of Water

Sources of water: 20% from food (soups, yogurts, fruit, and vegetables), 80% from drinks (water, milk, and juice)
Importance of drinking water regularly to prevent dehydration, which can lead to headaches, irritability, and loss of concentration
Humans can survive for several weeks without food, but only for a short time without fluids

Distribution of Water in the Body

Water makes up 70% or more of the weight of most organisms
Essential material in biological reactions, especially metabolism
60% of the total body weight of an average 70 kg man is comprised of water, equaling 42L
Water balance in healthy adults must be maintained
Sources of water in the body: drinking water, fruits and vegetables (80-90% water), milk (80-88% water), meat (40-75% water), flour, cracks, and bread (5-35% water)

Major Functions of Water

Carrier of food nutrients: carries nutrients from intestines to tissues through blood
Constituent of liquid: major constituent of all body liquids (blood, urine, sweat, lymph)
Regulates body temperature
Provides safety and security to delicate organs (lungs, heart, brain)

Physical and Chemical Properties of Water

"Universal solvent" and most abundant surface on Earth
Water molecules are extremely polar and form hydrogen bonds
Five main properties: high polarity, high specific heat, high heat of vaporization, low solid density, and attraction to other polar molecules
Hydrogen bonds between water molecules provide cohesive forces, making water a liquid at room temperature

Importance of Hydrogen Bonds

Hydrogen bonds between water molecules create a regular crystal lattice structure in ice, making it less dense than liquid water
Hydrogen bonds between water molecules and polar solutes are energetically favorable
Hydrogen bonds between water molecules and nonpolar molecules are inefficient, causing them to cluster together

Ionization of Water, Weak Acids, and Weak Bases

Water can be ionized into hydrogen ions (H+) and hydroxide ions (OH-)
Ionization of water is described by an equilibrium constant
Weak acids contribute H+ by ionizing, while weak bases consume H+ by becoming protonated
pH Scale designates the H+ and OH- concentration, with a pH of 7 being neutral, below 7 being acidic, and above 7 being basic

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Description

This quiz covers the functions of water in the human body, its sources, distribution, and physical and chemical properties. It also touches on ionization of water, weak acids, and weak bases.