Biology Chapter 2: Water as Life's Medium

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What primary role does bicarbonate play in the renal system?

It primarily excretes hydrogen ions.

It stores carbonic acid.

It increases water retention.

It acts as a main buffer in the body. (correct)

Which enzyme is crucial for the regeneration of bicarbonate in renal tubular cells?

Aldose reductase

Dehydrogenase

Carbonic acid synthase

Carbonate dehydratase (correct)

What is the consequence of not regenerating bicarbonate in the body?

Decreased acid production

Increased osmolarity in the plasma

Increased bicarbonate excretion

Depletion of the buffering capacity (correct)

During the renal response to acidosis, which process occurs first?

Reabsorption of filtered HCO3− Signup and view all the answers

What happens to CO2 and water within renal tubular cells during bicarbonate regeneration?

They combine to form carbonic acid. Signup and view all the answers

What is the approximate amount of bicarbonate filtered in the kidneys over 24 hours?

4300 mmol Signup and view all the answers

What role do hydrogen ions play in the bicarbonate buffering process?

They are secreted into urine to regenerate bicarbonate. Signup and view all the answers

What effect do solutes have on the local structure of water molecules?

They decrease the freezing point of water. Signup and view all the answers

Which of the following is NOT a colligative property of a solution?

Molarity concentration changes Signup and view all the answers

How does the presence of amphiphilic molecules affect water structure?

They result in the formation of micelles. Signup and view all the answers

What is the consequence of increased solute concentration in terms of vapor pressure?

It results in vapor pressure lowering. Signup and view all the answers

Which statement accurately describes osmotic pressure in relation to solute concentration?

Osmotic pressure is lower when solutes are polymerized. Signup and view all the answers

What is the primary driver behind the attraction between nonpolar solutes in water?

A net decrease in local order of water molecules. Signup and view all the answers

Which of the following best describes the relationship between solutes and the boiling point of water?

Solutes increase the boiling point of water. Signup and view all the answers

What role does vapor pressure play in the transition of water from liquid to gas?

It determines the equilibrium point for liquid and gas phases. Signup and view all the answers

Which species acts as a Brønsted-Lowry base in the reaction between HCl and H2O?

H2O Signup and view all the answers

What defines a substance as an Arrhenius acid?

It produces H+ ions when dissolved in water. Signup and view all the answers

In the Brønsted-Lowry definition, how is a base characterized?

As any substance that accepts a proton. Signup and view all the answers

What does the term 'conjugate base' refer to in a Brønsted-Lowry acid-base reaction?

The original acid after donating a proton. Signup and view all the answers

Which statement correctly describes a Brønsted-Lowry acid?

It must contain hydrogen and donate a proton. Signup and view all the answers

What is the product of the reaction of NH3 with H2O according to the Brønsted-Lowry definition?

NH4+ and OH− Signup and view all the answers

Which describes the equilibrium position of the reaction HCl + H2O ⇌ Cl− + H3O+?

Equilibrium lies mostly to the right. Signup and view all the answers

In a given equilibrium reaction, if Cl− acts as a base, what is H3O+ classified as?

Conjugate acid Signup and view all the answers

What is a key limitation of the Arrhenius definition of acids and bases?

It includes only water as a solvent. Signup and view all the answers

Which of the following statements about Brønsted-Lowry acids and bases is correct?

Their formulas differ by exactly one proton. Signup and view all the answers

Why do weak acids require a double arrow in their ionization reactions?

They establish an equilibrium with their ions. Signup and view all the answers

What is the pH of a 0.15 M solution of hydrochloric acid?

3.00 Signup and view all the answers

Which chemical species is produced when H2SO4 reacts with H2O?

HSO4− Signup and view all the answers

What is the molarity of hydrogen ions in a solution with a pH of 8.5?

$3.16 imes 10^{-9}$ M Signup and view all the answers

Which of the following is a characteristic of strong acids?

They completely dissociate in solutions of 1.0 M or less. Signup and view all the answers

What does pOH equal when pH is 3.17?

10.83 Signup and view all the answers

How does the concentration of strong bases compare to weak bases in solution?

Strong bases completely dissociate while weak bases do not. Signup and view all the answers

If aspirin has a hydronium ion concentration of $1.7 imes 10^{-3}$ M, what is the pH of the solution?

2.77 Signup and view all the answers

What is the optimal pH range for the phosphate buffer to function effectively in intracellular fluid?

6.8 Signup and view all the answers

Which chemical reaction represents the neutralization of a base by the protein buffer system?

-NH3+ + OH- → -NH2 + H2O Signup and view all the answers

Which of the following statements correctly describes the role of hemoglobin as a buffer system?

Changes configuration to transport CO2 and H+. Signup and view all the answers

What physiological system is primarily responsible for the rapid adjustment of blood pH through CO2 regulation?

Respiratory system Signup and view all the answers

What occurs during hyperventilation in relation to blood pH?

Removal of CO2 drives pH higher. Signup and view all the answers

Which component can be conserved and produced by the kidneys to help regulate pH?

HCO3- ions Signup and view all the answers

Which of the following best describes the effect of hypoventilation on blood pH?

Accumulation of H+ ions lowers pH. Signup and view all the answers

Which substance is involved in the bicarbonate buffering system in the body?

Bicarbonate (HCO3-) Signup and view all the answers

Which statement about fixed acids is accurate?

Only the kidneys can eliminate them. Signup and view all the answers

What is the primary consequence of renal failure on pH balance?

Inability to rid body of metabolic acids. Signup and view all the answers

Study Notes

Chapter 2: Water: The Medium of Life

Life originated, evolved, and thrives in the seas.
Water and its ionization products (hydrogen ions and hydroxide ions) are critical determinants of the structure and function of many biomolecules, including amino acids, proteins, nucleotides, nucleic acids, and even phospholipids and membranes.
A difference in hydrogen ion concentration on opposite sides of a membrane represents an energized condition essential to biological mechanisms of energy transformation.
Water has a substantially higher boiling point, melting point, heat of vaporization, and surface tension (anomalously high for a substance of this molecular weight that is neither metallic nor ionic); intermolecular forces of attraction between H₂O molecules are high.
Water's maximum density is found in the liquid (not the solid) state, and it has a negative volume of melting (that is, the solid form, ice, occupies more space than does the liquid form, water).
Permanent dipoles occur when two atoms in a molecule have substantially different electronegativity: One atom attracts electrons more than another, becoming more negative, while the other atom becomes more positive.
Hydrogen bonding in water is key to its properties. The solvent properties of water derive from its polar nature.
The solvent properties of water derive from its polar nature.

2.1 What are the properties of water?

Water has a high dielectric constant. Water's ability to surround ions in dipole interactions and diminish their attraction for each other is a measure of its dielectric constant (D). The attractions between the water molecules interacting with, or hydrating, ions are much greater than the tendency of oppositely charged ions to attract one another.
Water forms H bonds with polar solutes. Water's excellent solvent properties stem from its ability to readily form hydrogen bonds with the polar functional groups on these compounds, such as hydroxyls (-OH), amines (-NH₂), and carbonyls (-C=O).
Hydrophobic interactions—apparent affinity of nonpolar structures for one another. Because nonpolar solutes must occupy space, the random H-bonded network of water must reorganize to accommodate them. The water molecules participate in as many H-bonded interactions with one another as the temperature permits. Consequently, the H-bonded water network rearranges toward formation of a local cagelike (clathrate) structure surrounding each insoluble solute molecule.
The dispersion of lipids in H₂O- Each lipid molecule forces surrounding H₂O molecules to become highly ordered.
Interaction with amphiphilic molecules (compounds containing both strongly polar and strongly nonpolar groups).
Colligative Properties—The presence of dissolved substances disturbs the structure of liquid water, changing its properties, including freezing point depression, boiling point elevation, vapor pressure lowering, and osmotic pressure effects.

2.2 What is pH?

We define an aqueous solution as being neutral when [H+] = [OH-], acidic when [H+] > [OH-], and basic when [H+] < [OH-].
pH = -log [H+].
Kw = [H+][OH-]. Kw is called the ionization constant of water and is very small.
pH scales & relationships
For pure water [OH−] = [H+].

2.3 What are buffers and what do they do?

The lungs and kidneys are primary organs regulating the pH of body fluids.
Major changes in body fluid pH can severely affect biological activities within the cells.
Buffers are present to prevent large fluctuations in pH.
Buffers are present to prevent large fluctuations in pH.

Acids and bases

In the early days of chemistry chemists were organizing physical and chemical properties of substances. They discovered that many substances could be placed in two different property categories.
Arrhenius definition of acids and bases. (Acids are substances that dissociate in water to produce H+ ions & Bases are substances that dissociate in water to produce OH− ions)
Brønsted-Lowry definition of acids and bases. (An acid is a hydrogen-containing species that donates a proton & A base is any substance that accepts a proton)
Conjugate pairs
Strong and weak acids. The ionization of strong acids (HCl) is represented by a single arrow whereas weak acids have a reversible reaction (HF).
Common strong acids and bases.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Explore the essential role of water in biological processes with this quiz based on Chapter 2. Learn about water's unique properties, its importance for biomolecules, and how it influences life on Earth. Test your understanding of the fundamental principles outlined in this chapter.