Biology Chapter: Properties of Water

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Questions and Answers

What property of water allows it to support life on Earth?

Its lack of hydrogen bonds

Its high electronegativity

Its ability to freeze quickly

Its polar covalent bonds (correct)

Why can humans only survive about a week without water?

Water helps to regulate body temperature

Water is required for digestion only

Water supports essential cellular reactions (correct)

Water is needed for blood clotting

What defines the polarity of water molecules?

The presence of only hydrogen bonds

Equal sharing of electrons between hydrogen and oxygen

Absence of covalent bonds

Unequal distribution of electrons leading to partial charges (correct)

How does a hydrogen bond form between two water molecules?

Through attraction between opposite charges Signup and view all the answers

What happens to hydrogen bonds in liquid water?

They form and break frequently Signup and view all the answers

How does reduced water intake affect the body?

It activates neuroendocrine defenses and influences metabolism Signup and view all the answers

What is the significance of water's properties for life on Earth?

Water is essential for cellular reactions and environment Signup and view all the answers

What misconception might people have about water's role in living organisms?

Water is only a solvent with no other roles Signup and view all the answers

What term describes substances that have an affinity for water?

Hydrophilic Signup and view all the answers

Which of the following correctly describes a colloid?

A stable suspension of fine particles in a liquid Signup and view all the answers

What type of substances repel water due to being nonpolar?

Hydrophobic Signup and view all the answers

Why is it important to calculate the concentration of solutes in aqueous solutions?

To know how many chemical reactions can occur Signup and view all the answers

What is the molecular mass of glucose (C6H12O6) in Daltons?

180 Da Signup and view all the answers

What is the effect of hydrophobic molecules on cell membranes?

They form a barrier that prevents water from entering Signup and view all the answers

Which of the following compounds primarily provides cells with structure and temperature regulation?

Water Signup and view all the answers

What does the term 'hydrophobic' literally mean?

Water-fearing Signup and view all the answers

What happens when two objects of different temperatures are brought together?

Heat passes from the warmer to the cooler object until they reach the same temperature. Signup and view all the answers

How much heat is required to raise the temperature of 1 g of water by 1 °C?

1 calorie Signup and view all the answers

What is the role of water in the process of dissolving salt?

It acts as a solvent, forming hydration shells around the ions. Signup and view all the answers

What characterizes a solution?

It is a uniform mixture of two or more substances. Signup and view all the answers

What is the function of hydrogen bonds when polar molecules dissolve in water?

They form between water molecules and solute molecules. Signup and view all the answers

Which type of molecules can dissolve in water?

Non-ionic polar molecules and ionic molecules. Signup and view all the answers

What is released when 1 g of water cools by 1 °C?

1 cal Signup and view all the answers

What defines the solvent in a solution?

It is the substance present in the greatest quantity. Signup and view all the answers

What defines the emergent properties of water?

The high structural organization due to hydrogen bonding Signup and view all the answers

What does electronegativity refer to?

The attraction an atom has for electrons in a bond Signup and view all the answers

What would happen if oxygen and hydrogen had equal electronegativity?

Water molecules would no longer be polar Signup and view all the answers

Which statement is true regarding the arrangement of neighboring water molecules?

They are likely to repel each other due to their positive charges Signup and view all the answers

How do hydrogen bonds contribute to the property of cohesion in water?

They allow water molecules to stay closely linked together Signup and view all the answers

What is the role of water as a heat bank?

It can absorb and release large amounts of heat with minimal temperature change Signup and view all the answers

Which factor primarily affects the ability of water to moderate temperature?

The specific heat capacity of water Signup and view all the answers

What property of water helps it travel against gravity?

Cohesion due to hydrogen bonding Signup and view all the answers

What is the role of ammonia in solution?

It reacts with water to form a hydroxide. Signup and view all the answers

What does dynamic equilibrium indicate about a chemical reaction?

The forward and reverse reactions occur at the same rate. Signup and view all the answers

Which statement correctly describes the acid dissociation constant (Ka)?

It is a measure of an acid's strength in solution. Signup and view all the answers

What happens to the pH of a solution when a strong acid is added?

The pH decreases significantly. Signup and view all the answers

At what pH level can human blood be considered extremely hazardous?

7.8 Signup and view all the answers

Why is the pH scale important in biology?

Small changes in pH can affect cellular processes. Signup and view all the answers

When carbonic anhydrase is involved in a reaction, what is the equilibrium position when H2CO3 is added to water?

Very little H2CO3 dissociates. Signup and view all the answers

How does the pH scale change with each unit?

Each unit change represents a 10-fold difference. Signup and view all the answers

What is the process called when water diffuses across a selectively permeable membrane?

Osmosis Signup and view all the answers

What is affected by high solute concentration in a solution?

The concentration of water Signup and view all the answers

During osmosis, where does water move in relation to solute concentration?

From low solute concentration to high Signup and view all the answers

What is a crucial aspect of maintaining water balance in organisms?

The movement of water across cell membranes Signup and view all the answers

What role do buffers play in biological fluids?

They resist changes in pH Signup and view all the answers

What is the result when water dissociates?

Creation of H3O+ and OH- Signup and view all the answers

Which of the following statements about diffusion is incorrect?

Active transport increases diffusion rates. Signup and view all the answers

Which water molecules are unable to cross a selectively permeable membrane during osmosis?

Those heavily clustered around solute molecules Signup and view all the answers

Study Notes

Nutritional Biochemistry: Principles of Chemistry: Water

Matter is composed of elements, and compounds are combinations of elements.
Key elements for life include carbon, oxygen, hydrogen, and nitrogen (96% of living organisms).
Atomic number represents the number of protons in an atom.
Isotopes of an element have different numbers of neutrons.
Electrons exist in energy levels within atoms.
Strong bonds include covalent bonds (sharing electrons) and ionic bonds (donating electrons).
Weak bonds include van der Waals interactions and hydrogen bonds.
Biology is understood using chemical principles.

Last Time - Quiz

Trace elements differ from other elements in their abundance and role in biological processes.
Atomic number is the number of protons, while atomic mass is the total number of protons and neutrons in an atom.
Major elements (carbon, hydrogen, oxygen, nitrogen) have atomic values; the atomic masses and numbers for each should be known.
Isotopes of an element have similar numbers of protons but different numbers of neutrons, hence differing atomic masses. Values for the five isotopes of zinc are provided.
Covalent bonds involve electron sharing, while ionic bonds involve electron transfer.
Weak bonds (van der Waals interactions, hydrogen bonds), have significance in biological molecules.
Macromolecular structures utilize the different types of bonds

Learning Outcomes

Understand the relationship of polarity and hydrogen bonding to water's properties.
Describe the properties of water, including its polarity, hydrogen bonding, and other chemical interactions that relate to biological function.
Detail how acid-base conditions are regulated in blood and cells.
Explain the importance of diffusion in water movement (osmosis).

The Molecule That Supports Life: Water

Water on other planets is important for supporting life as we know it on Earth.
All organisms primarily consist of water.
Life on Earth originated and evolved in water before spreading to land.

The Molecule That Supports Life: Water (2)

Humans can survive weeks without food, but only a short time without water.
Water is essential to many biological reactions.
Biological cells are primarily composed of water.

Clinical Relevance

Water requirements vary among different demographics.
Proper water intake is vital for general bodily functions, including neuroendocrine regulation and metabolism.
Prolonged inadequate water intake can impact various bodily processes, leading to chronic health issues.

The Polarity of Water Molecules

Water (H₂O) has a more electronegative oxygen atom, drawing electrons in the covalent bonds towards it.
This unequal electron distribution creates polar covalent bonds within the water molecules.
The resulting polarity causes the molecules to possess distinct negative and positive poles.

Water and Hydrogen Bonds

Water molecules are attracted to each other due to hydrogen bonding between a slightly positive hydrogen atom of one molecule to a slightly negative oxygen atom of a nearby molecule.
Hydrogen bonds are relatively weak compared to covalent bonds.
The properties of water stem from the hydrogen bonding between its molecules.

Activity

Students need to draw water molecules showing covalent bonding and hydrogen bonding with appropriate partial charge labels.
Electronegativity affects intermolecular interactions in water.
Water molecule arrangements are unlikely in a particular way that doesn't follow the rules of their attraction.
Water properties depend on the unequal sharing of electrons between oxygen and hydrogen.

Answers

Water molecules cannot form hydrogen bonds without sufficient electronegativity difference.

Properties of Water: Cohesion

Water molecules are attracted to each other due to hydrogen bonding, creating cohesion.
This cohesion provides water with structure, allowing it to travel against gravity.

Properties of Water: Moderation of Temperature

Water absorbs and releases heat effectively, moderating temperature changes.
The ability to absorb heat with minimal temperature changes makes water important to living organisms, particularly in regulating body temperature.

Properties of Water: Temperature Continued

A calorie is the amount of energy needed to raise the temperature of 1 gram of water by 1°C.
A kilocalorie (kcal) is the amount of energy needed to raise the temperature of 1 kilogram of water by 1°C.
Measurements on food packaging use these units to indicate the caloric content of food.

Properties of Water: Solvent

Water's polarity allows it to dissolve many substances.
Solutions are homogeneous mixtures of two or more substances, where water is the solvent in many biological reactions.
Water's ability to dissolve substances is very important to living organisms.

Properties of Water: Solvent 2

Water's polarity is crucial for dissolving ions and polar molecules.
Water molecules surround and separate ions in a solution, which is termed hydration shell.

Properties of Water: Solvent 3

Water surrounds and shields ions within a solution.
This process is critical for dissolving various substances in aqueous solutions.

Properties of Water: Solvent 4

Water's polarity can dissolve many types of compounds, including non-ionic polar molecules.
This is crucial as it permits biological fluids that contain a range of compounds to function properly.

Properties of Water: Summary

Water plays a critical role in maintaining the structure, regulating temperature, and delivering essential molecules within cells.

Solute Concentration in Aqueous Solutions

Solutes dissolved in water are involved in numerous biological reactions.
To understand these reactions, calculating the concentration is crucial.
Molecular mass, the sum of atomic masses of constituent atoms, is needed for calculating solute concentration.

Glucose - Molecular Mass

Calculate the molecular mass of glucose using its chemical formula (C₆H₁₂O₆).
Daltons are units of mass, roughly corresponding to atomic masses, although measurements are in moles.

Calculating Glucose

One mole (mol) of any substance contains Avogadro's number of molecules (6.02 × 10²³).
Grams in one mole of substance equals the molecular mass

Why use Moles?

The mole is a convenient unit to measure large quantities of substances, where quantities of atoms are equal irrespective of the substance.
Molarity is used to denote the composition of solutions.
Blood sodium concentration values are provided as an example.

Summary 1

Water's polarity gives rise to several crucial properties.
Properties of water, including cohesion, temperature moderation, and dissolving elements, are essential to maintaining life.

10 Minute Break

Acids and Bases

Acid-base reactions are crucial for determining pH using titration methods.
Acids (e.g., HCl) dissociate into H+ and correspondingly charged negatively-charged ions.
Bases (e.g., NaOH) dissociate into Na+ and OH- correspondingly charged.

Clinical Relevance?

Acid-base balance is critical to bodily functions.
Lungs and kidneys are vital organs in regulating these conditions.

Acid and Base: Water

Water molecules can exchange protons (H+) to form hydronium ions (H₃O⁺) and hydroxide ions (OH⁻).

Acid and Base: Equilibrium

Acid and base reactions are reversible.
An equilibrium state occurs when the rate of acid and base reactions are essentially the same.

Acid and Base: Reversible

In pure water, the dissociation of water molecules to form H⁺ and OH⁻ is reversible.
This equilibrium is critical for life's chemical processes.

Acid and Base Conditions

Changes in H⁺ and OH⁻ concentrations significantly affect biological systems (e.g., proteins).
Biologists utilize the pH scale to determine the acidity or basicity of a substance.

Acids

Acids release H⁺ ions when dissolved in water.
Hydrochloric acid (HCl) is an example of an acid found in the stomach.

Bases

Bases accept H⁺ ions when dissolved in water.
Ammonia (NH₃) and sodium hydroxide (NaOH) are examples of bases.

One Direction versus Dynamic

HCl and NaOH reactions proceed to completion, whereas other acid-base reactions result in dynamic equilibrium.

Dynamic Equilibrium

In dynamic equilibrium, forward and reverse reactions are balanced, with the rates being equal.
The concentrations of products and reactants don't change with time in such a system.

Acid Dissociation Constant

The acid dissociation constant (Ka) measures the strength of an acid.
A higher Ka value indicates a stronger acid.

The pH Scale

The pH scale measures the H⁺ concentration in a solution.
Neutral solutions have an equal concentration of H⁺ and OH⁻.

pH in the Body

The internal pH of most cells is close to 7.4 (slightly basic).
Significant changes in pH can adversely affect biological processes and may lead to significant damage.

Buffers

Buffers help to maintain the pH of solutions by minimizing changes in H⁺ and OH⁻ concentrations.

Carbonic Anhydrase

Carbonic anhydrase catalyzes the conversion of carbon dioxide and water into carbonic acid (H₂CO₃).
This reaction and its reverse are important in regulating pH.

Diffusion: Molecular Energy

Diffusion is the process through which molecules move from a region of higher concentration to a region of lower concentration.
Thermal energy of molecules drives this movement.

Diffusion: Semi Permeable Membrane

Molecules can diffuse across the membrane when the concentration of the substance is higher on one side of the membrane.
Semi permeable membrane allows diffusion of molecules into the side where concentration is lower

Diffusion Down a Gradient

Diffusion occurs spontaneously.
Substances move from higher to lower concentration.

Water Diffusion: Osmosis

Water diffusion across a selectively permeable membrane is called osmosis.

Effects of Osmosis on water Balance

The effect of osmosis relates to the differences in the concentrations of solutes.
Osmosis is important for processes at the cellular level across cell membranes.

Summary 2

Water molecules can transfer H+, resulting in the formation of hydronium and hydroxide ions.
Buffers are critical for maintaining pH in biological systems.
Diffusion and osmosis are fundamental to water movement and maintaining balance.

Questions

What does polarity in water mean?
What are the three important properties of water?
Calculations of sucrose concentration are required.
Water dissociation details and products are outlined.
Reversible chemical reactions are defined and explained.
Details about water molecule movement during osmosis.

Before Next Time

It is essential to review the topic to be prepared for the next class.
Further learning material for the next session is suggested.

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Description

Explore the crucial properties of water that enable life on Earth with this quiz. We will cover topics such as hydrogen bonding, polarity, and the significance of water's characteristics for living organisms. Test your knowledge on water's role and its effects on cellular functions.