Essential Chemistry for Biology

Essential Chemistry for Biology

• PowerPoint® Lectures created by Edward J. Zalisko for Campbell Essential Biology, Seventh Edition, and Campbell Essential Biology with Physiology, Sixth Edition.
• Created by Eric J. Simon, Jean L. Dickey, and Jane B. Reece.
• Copyright 2019 Pearson Education, Inc.

Matter: Elements and Compounds

• Biological systems can be broken down to the chemical level.
• Matter is anything that occupies space and has mass.
• Mass measures the amount of material in an object.
• An element is a substance that cannot be broken down into other substances by chemical reactions.
• All matter is composed of chemical elements.

Abbreviated Periodic Table of the Elements

• The periodic table shows elements and their properties.
• Elements display different properties, atomic numbers and atomic masses are shown.

Matter: Elements and Compounds (continued)

• Of the 92 naturally occurring elements, 25 are essential to humans.
• Four elements (carbon, hydrogen, oxygen, and nitrogen) make up about 96% of the human body's weight.
• Trace elements are necessary for life in small amounts.
• Elements combine to form compounds, substances containing two or more elements in a fixed ratio.

Chemical Composition of the Human Body

• The human body is largely composed of oxygen, carbon, hydrogen, and nitrogen.
• Other elements like calcium, phosphorus, potassium and sulfur.
• Trace elements like boron, chromium, cobalt, copper, fluorine, iodine, iron, manganese, molybdenum, selenium, silicon, tin, vanadium, and zinc.

Atoms

• Each element is composed of one kind of atom.
• An atom is the smallest unit of matter that retains the properties of an element.
• Atoms are comprised of protons, neutrons, and electrons.
• Protons are positively charged.
• Neutrons have no charge.
• Electrons are negatively charged.

A Simplified Model of a Helium Atom

• Atoms have a nucleus containing protons and neutrons and they have electrons in a cloud around the nucleus.

Atoms (continued)

• All atoms of a particular element have the same unique number of protons (atomic number).
• An atom's mass number is the sum of its protons and neutrons.
• Isotopes are atoms of the same element with varying numbers of neutrons.
• Radioactive isotopes have unstable nuclei which decay spontaneously.

Isotopes of Carbon (Table 2.1)

• Carbon-12, Carbon-13, and Carbon-14 are isotopes of carbon.
• They have different numbers of neutrons but the same number of protons.

Chemical Bonding and Molecules

• Only electrons are involved directly in chemical reactions.
• The number of electrons in an atom determines the atom's chemical properties.
• Chemical reactions enable atoms to transfer or share electrons/form bonds
• These interactions keep atoms together. These attractions are called chemical bonds.

Ionic Bonds

• Ions are atoms or molecules with an electrical charge (charged as a result of gaining or losing electrons).
• Ionic bonds form between oppositely charged ions.
• Compounds such as table salt (NaCl) are ionic compounds because their structure is held together by ionic bonds.

Electron Transfer and Ionic Bonding

• Electrons moving from one atom to another form ions.
• Attraction between opposite charges holds the ions together to form ionic compounds.

Covalent Bonds

• A covalent bond is formed when atoms share pairs of electrons.
• Covalent bonds are the strongest of the chemical bonds.
• They hold atoms together in a molecule.

Hydrogen Bonds

• Water (H₂O) molecules are formed from covalent bonds between oxygen and hydrogen atoms.
• Electrons are not evenly shared between the oxygen and hydrogen atoms.
• This unequal sharing of electrons results in water being a polar molecule with a partially positive and partially negative charge.
• Water molecules are held together by weak electrical attractions called hydrogen bonds.

Water and Life

• Life on Earth originated in water and evolved there.
• Modern life relies on water.
• Organisms are largely made of water (70-95%).
• The abundance of water allows Earth to support life.
• Water's properties (polarity and hydrogen bonding) are critical for life-supporting functions.

The Cohesion of Water

• Hydrogen bonds cause water molecules to stick together, a property called cohesion.
• Cohesion is stronger in water than in most other liquids.
• Cohesion is crucial for water transport in plants (e.g., trees).
• Surface tension is a measure of the difficulty to stretch or break the surface of a liquid.
• Hydrogen bonding gives water a high surface tension.

Cohesion and Water Transport in Plants

• Illustrations demonstrating water movement in plants, highlighting cohesion and hydrogen bonding.

A Raft Spider Walking on Water

• An image of a spider walking on water, showcasing the high surface tension of water.

How Water Moderates Temperature

• Hydrogen bonds allow water to resist changes from its temperature easier than other materials.
• Water absorbs and stores a lot of heat without drastically changing temperature.
• This property is important for regulating temperature in organisms and the environment. -Evaporative cooling happens when substances evaporate, cooling the remaining liquid behind.

The Biological Significance of Ice

• When water freezes, its molecules move apart and form ice.
• Ice is less dense than liquid water, allowing it to float.
• Floating ice insulates liquid water, protecting life forms in aquatic environments that might get too cold.
• If ice sank, bodies of water would freeze solid.

Why Ice Floats

• Hydrogen bonds in ice hold the molecules farther apart than in liquid water.
• This creates a less dense structure.
• Ice floats on the surface of water.

Water as the Solvent of Life

• A solution is a liquid with a homogeneous mixture of two or more substances.
• The dissolving agent is called the solvent.
• The dissolved substance is called the substance.
• Solutions where water is the solvent are called aqueous solutions.

A Crystal of Table Salt Dissolving in Water

• Visualization of sodium chloride dissolving in water, due to the attraction between water molecules and the positive and negative ions in the salt.

Acids, Bases, and pH

• Acids release hydrogen ions (H⁺) in a solution.
• Bases accept hydrogen ions (H⁺) in a solution.
• The pH scale measures hydrogen ion concentration (H⁺) in a solution.
• Buffers minimize changes in pH.

The pH Scale

• The pH scale ranges from 0 to 14.
• 7 is neutral.
• Below 7 is acidic.
• Above 7 is basic.
• The scale represents a logarithmic increase or decrease in H+ concentration. Different substances with ranges of pH.

Ocean Acidification by Atmospheric CO₂

• Carbon dioxide(CO₂) from the atmosphere dissolves in seawater.
• It reacts with water to form carbonic acid (H₂CO₃), lowering ocean pH.

Evolution Connection: Radioactivity as an Evolutionary Clock

• Radioactive decay provides evidence of the evolutionary history of life on earth.
• Fossils can be dated using radioactive isotopes to track the amount of half-life reductions.
• Scientists use techniques to estimate the fossils' age and place them in the fossil record.

Radiometric Dating

• Graphs illustrating radioactive decay, particularly involving Carbon-14, to determine time elapses from the fossil record.

Explore the key concepts of matter, elements, and compounds as they relate to biological systems. This quiz delves into the definitions and properties of elements, as well as the importance of the periodic table. Understand how chemical principles underpin biological functions.