Biochemistry 1: Importance of Water

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Questions and Answers

What shape does a water molecule resemble?

Flat rectangle

Perfect tetrahedron

Linear and symmetrical

Irregular, slightly skewed tetrahedron (correct)

Which atom is at the center of a water molecule?

Hydrogen

Carbon

Nitrogen

Oxygen (correct)

How does the shape of a water molecule affect its properties?

It makes water a good conductor of electricity.

It allows water to be a solid at room temperature.

It contributes to its ability to form dipoles. (correct)

It enhances water's acidity.

What geometric feature characterizes the structure of a water molecule?

A irregular tetrahedron Signup and view all the answers

What is the significance of the dipole nature of water molecules?

It enables hydrogen bonds to form. Signup and view all the answers

What phenomenon is favored by the hydrogen bonding characteristic of water molecules?

Self-association into ordered arrays Signup and view all the answers

What aspect of water molecules contributes to their ability to self-associate?

Presence of both hydrogen and oxygen atoms Signup and view all the answers

Which characteristic of water molecules is primarily responsible for the formation of ordered arrays?

Hydrogen bonding Signup and view all the answers

What is the result of the self-association of water molecules due to hydrogen bonding?

Formation of ordered arrays Signup and view all the answers

Which factor does NOT contribute to the self-association of water molecules?

Lack of hydrogen bonds Signup and view all the answers

What type of bond is primarily responsible for the unique properties of water?

Hydrogen bonds Signup and view all the answers

Which statement accurately describes the charges within a water molecule?

The hydrogen atoms carry a partial positive charge, while the oxygen atom carries a partial negative charge. Signup and view all the answers

What characteristic of water is attributed to its polar nature?

Solvent properties Signup and view all the answers

Which of the following best explains why water has a high surface tension?

Strong hydrogen bonds between water molecules Signup and view all the answers

What results from the unshared electrons of the oxygen atom in a water molecule?

The development of a partial negative charge on the oxygen atom Signup and view all the answers

What is primarily responsible for buffering physiological fluids in cells?

Ionization of phosphoric acid Signup and view all the answers

Which ions are formed from the ionization of phosphoric acid (H3PO4)?

Phosphate ions Signup and view all the answers

What role do phosphates play in physiological fluids?

They act as buffers Signup and view all the answers

Which physiological condition is affected by the buffering capacity of phosphates?

pH balance in bodily fluids Signup and view all the answers

Why is phosphoric acid considered essential for cellular functions?

It ionizes to form phosphates that aid in buffering. Signup and view all the answers

What is the general format of the Henderson-Hasselbalch equation?

pH = pK + Log {coo}/{cooH} Signup and view all the answers

Which group in drugs is directly predicted by the Henderson-Hasselbalch equation?

The carboxyl group (cooH) Signup and view all the answers

Why is understanding the degree of ionization of drugs important?

It affects the drug's ability to be absorbed through biological membranes. Signup and view all the answers

What does the 'pK' in the Henderson-Hasselbalch equation represent?

The acid dissociation constant of the acid form Signup and view all the answers

In the context of drug absorption, which form of the drug passes through biological membranes more easily?

The unionized form Signup and view all the answers

What role does the CO2 bicarbonate system play in the body?

It prevents acid or base imbalance. Signup and view all the answers

In which bodily fluids is the CO2 bicarbonate system primarily active?

Plasma and interstitial fluid. Signup and view all the answers

Which of the following best describes the function of the CO2 bicarbonate system?

It buffers changes in pH. Signup and view all the answers

What would happen to the body without the CO2 bicarbonate buffering system?

Risk of acid or base imbalance. Signup and view all the answers

Which of the following systems interacts with the CO2 bicarbonate system to manage acid-base balance?

Respiratory system. Signup and view all the answers

Study Notes

Course Information

Course: Biochemistry 1
Department/Semester: Fourth semester, Fall
Lecture: First
Instructor: Uda Talha Khujli Abbas
Academic Year: 2025-2024

Biomedical Importance of Water

Water is the primary chemical component in living organisms.
It dissolves various organic and inorganic molecules due to its dipolar structure and ability to form hydrogen bonds.
Water is a reactant or product in many metabolic reactions.
Water slightly dissociates into hydroxide and proton ions.
Buffers maintain extracellular fluid pH between 7.35 and 7.45.
Acidosis (blood pH < 7.35) results from conditions like diabetic ketosis and lactic acidosis.
Alkalosis (pH > 7.45) can occur due to vomiting of acidic gastric contents.

Water as a Biological Solvent

Water is an ideal biological solvent due to its dipole nature.
Water molecules are slightly skewed tetrahedrons with oxygen at the center.
The oxygen atom is electronegative, pulling electrons away from hydrogen, creating partial positive and negative charges.
This polarity allows water to dissolve many charged compounds like salts.

Water Molecules and Hydrogen Bonds

Water molecules form hydrogen bonds.
Unshielded hydrogen nuclei bonded to electronegative oxygen or nitrogen atoms readily interact with unshared electron pairs in other oxygen or nitrogen atoms, creating hydrogen bonds.
Hydrogen bonding causes self-association of water molecules, influencing properties like viscosity, surface tension, and boiling point.
Water dissolves many organic biomolecules with functional groups that form hydrogen bonds.

Physical Properties of Water

Water is colorless, odorless, and tasteless.
Water molecules have intermolecular bonds that result in unique characteristics.
Liquid water density is 1.00 g/mL
Ice density is 0.92 g/mL

Structure of Liquid Water

Liquid water structure is irregular, with continual breakdown and reformation of hydrogen bonds
Water molecules act as both hydrogen donors and acceptors.

Self-Ionization of Water

Water molecules dissociate into H+ and OH- ions.
This dissociation occurs through the breakage of an -OH bond.
[H+][OH-] = 10⁻¹⁴ mol²/L² (at 25°C).

pH

pH is a measure of hydrogen ion concentration, calculated as -log[H+].
pH below 7 is acidic, above 7 is basic.
The pH in different compartments of the human body varies.

Acids and Bases

Acids release protons (H+) and gain a negative charge (anions).
Bases accept protons and gain a positive charge (cations).
Amino acids contain both acidic (-COOH) and basic (-NH2) groups, which can ionize depending on the pH.

Ionization of Amino Acids

The ionization state of amino acids depends on the pH of the solution.
At a specific pH (isoelectric pH), amino acids have no net charge (zwitterions).

The Henderson-Hasselbalch Equation

Predicts the ionization state of a weak acid or base based on the pK (acid dissociation constant) and pH.
Useful for calculating the degree of ionization of weak acids, such as those in biological molecules.

Buffers

Resist pH changes when acids or bases are added.
The buffering system in cells and body fluids is vital to maintain a stable pH.
Common buffers include phosphates and bicarbonate.

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Description

Explore the critical role of water in biochemistry through this quiz. Understand how water acts as a solvent and its significance in metabolic reactions, pH regulation, and more. Test your knowledge on the biochemical properties of water.