Biology 1: Chemicals of Life

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Questions and Answers

What percentage of cells is typically composed of water?

20–40%

90–100%

50–70%

70–95% (correct)

What is the primary reason for the polarity of a water molecule?

The arrangement of hydrogen atoms

The electronegativity difference between oxygen and hydrogen (correct)

The linear structure of the molecule

The presence of three hydrogen atoms

Which of the following statements about water is incorrect?

Water is essential for life on Earth.

Water molecules have a net positive charge. (correct)

Water has a unique structure contributing to its properties.

Water is a reactant in many chemical reactions.

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

Hydrogen bonds Signup and view all the answers

Which part of the water molecule carries a partial negative charge?

The oxygen atom Signup and view all the answers

How does the structure of water contribute to life on Earth?

It acts as a solvent and reactant in biological processes. Signup and view all the answers

What is the significance of water's high specific heat?

It stabilizes temperatures in environments. Signup and view all the answers

Which of the following is not a property of water due to its molecular structure?

High density Signup and view all the answers

What role does the high heat of vaporization of water play in the cooling processes of organisms?

It enables water to absorb and carry heat away during evaporation. Signup and view all the answers

How does the density of water compare to most substances when it freezes?

Ice is less dense than liquid water, causing it to float. Signup and view all the answers

What happens to the temperature of water during evaporation?

The temperature of the water decreases as heat energy is absorbed. Signup and view all the answers

What is the significance of water's high heat of vaporization in the environment?

It contributes to the regulation of climate by affecting ocean temperatures. Signup and view all the answers

Why does water reach its highest density at 4ºC?

The arrangement of water molecules is most compact at this temperature. Signup and view all the answers

Which cooling effect is a result of water's high heat of vaporization?

The evaporation of sweat from human skin. Signup and view all the answers

What is a consequence of the lower density of ice compared to liquid water?

Ice floats on water, providing insulation to the aquatic environment. Signup and view all the answers

What quantity of heat must water absorb for 1 g to convert from liquid to gas?

540 cal Signup and view all the answers

Why does ice float on water?

Ice forms a crystalline structure with lower density than water. Signup and view all the answers

What role does water play as a solvent?

It is effective at dissolving polar and ionic substances. Signup and view all the answers

What happens to NaCl when it is dissolved in water?

Water molecules form hydration spheres around the ions. Signup and view all the answers

How does ice insulate water bodies during winter?

Ice floats, creating an insulating layer above the water. Signup and view all the answers

What does the term 'aqueous solution' imply?

A solution where water is the solvent. Signup and view all the answers

Which property of water contributes to its high specific heat?

The strong hydrogen bonds between water molecules. Signup and view all the answers

What is significant about water's cohesion and adhesion properties?

They facilitate the movement of water in plants. Signup and view all the answers

What is a characteristic of an acid in a solution?

It increases the concentration of hydrogen ions. Signup and view all the answers

Which of the following reactions describes a base accepting a hydrogen ion?

NH3 + H+ → NH4+ Signup and view all the answers

What is the primary function of buffers in biological fluids?

To minimize changes in pH. Signup and view all the answers

Which statement describes the role of carbonic acid in the blood buffer system?

It can dissociate to yield both hydrogen ions and bicarbonate ions. Signup and view all the answers

What happens when pH levels rise in the buffer system involving carbonic acid?

Bicarbonate ions convert to carbonic acid. Signup and view all the answers

Which equation represents the dissociation of sodium hydroxide in solution?

NaOH → Na+ + OH− Signup and view all the answers

In the context of acid-base chemistry, what directly combines with hydrogen ions to form water?

Hydroxide ions. Signup and view all the answers

What effect does an acid have on the pH of a solution?

Decreases the pH, making the solution more acidic. Signup and view all the answers

What causes the surface tension of water?

Cohesive forces from hydrogen bonds Signup and view all the answers

What is the significance of lower density of ice compared to liquid water?

It allows ice to float, insulating aquatic life below. Signup and view all the answers

How does water exhibit capillary action?

Through the cohesion between its molecules and adhesion to surfaces. Signup and view all the answers

What is the specific heat capacity of water?

4.2 Joule/1 g/1°C Signup and view all the answers

What allows water to be an effective solvent?

Its polar nature and ability to form hydrogen bonds Signup and view all the answers

What role do hydrogen bonds play in the stability of water?

They allow constant formation and breaking, maintaining stability. Signup and view all the answers

What is the definition of high heat of vaporization?

The amount of heat that must be absorbed for a substance to change from liquid to gas. Signup and view all the answers

What is the effect of cohesion in water?

It contributes to the upward flow of water in plants. Signup and view all the answers

Study Notes

Introduction to Biomolecules

Biomolecules are essential compounds in living organisms, categorized into elements and compounds.
Key types of bonds in biomolecules include ionic, covalent, hydrogen, and van der Waals.

Inorganic Compounds

Water serves as the foundation for life; cells contain 70-95% water.
Acids, bases, and buffers play critical roles in cellular pH regulation.
Mineral salts are vital for various biological functions.

Water: The Essence of Life

Water supports all life forms; its presence preceded terrestrial life by billions of years.
Water consists of one oxygen atom and two hydrogen atoms, forming a polar molecule with uneven charge distribution.

Properties of Water

Cohesion and Adhesion: Water molecules exhibit cohesion (attraction to each other) and adhesion (attraction to polar substances), enabling capillary action.
High Specific Heat: Water can absorb significant heat without drastic temperature changes (4.2 Joules/g/°C), important for temperature regulation in organisms.
High Heat of Vaporization: Requires 540 calories to convert 1g of liquid water to gas; facilitates cooling effects in evaporation (e.g., sweating).
Lower Density of Ice: Ice floats as it reaches maximum density at 4ºC and expands when frozen, insulating water below and protecting aquatic life.
Principal Solvent: Water's polarity allows it to dissolve ionic and polar substances (e.g., NaCl), facilitating chemical reactions and transport within organisms.

Acids, Bases, and Buffers

Acids increase hydrogen ion concentration, e.g., hydrochloric acid dissociates to release H⁺.
Bases reduce H⁺ concentration, either by accepting H⁺ or releasing hydroxide ions (OH⁻).
Buffers stabilize pH in biological fluids by accepting or donating H⁺ ions, ensuring that cellular processes remain unhindered.
An important buffer system in blood involves carbonic acid, which helps maintain a pH range of 7.3 to 7.5 through a dynamic equilibrium with bicarbonate ions.

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Description

This quiz covers the fundamental chemicals of life, focusing on biomolecules and their essential properties. It includes topics such as inorganic compounds, the structure and functions of water, and various types of chemical bonds. Prepare to explore the intricate world of biology through its essential building blocks.