Chemical Composition of Organisms

Water unique property

Exists naturally as a solid liquid and gas on Earth and supports life in all three states

Ice density

Solid water is less dense than liquid water which allows ice to float on liquid water

Importance of floating ice

Floating ice insulates water below and allows aquatic organisms to survive in cold environments

Adhesion

Attraction between water molecules and other substances allowing water to stick to surfaces

Cohesion

Attraction between water molecules causing them to stick together and form droplets

Surface tension

Resistance of water surface to breaking due to cohesive hydrogen bonding between molecules

Cause of water properties

Hydrogen bonds between polar water molecules create cohesion adhesion and surface tension

Universal solvent

Water dissolves many substances due to its polarity and ability to surround charged particles

High specific heat

Water requires a large amount of energy to change temperature helping stabilize environments

Evaporative cooling

Water absorbs heat during evaporation which cools surfaces such as skin during sweating

Acids

Substances that increase hydrogen ion concentration in a solution

Bases

Substances that decrease hydrogen ion concentration in a solution

pH scale

Measures hydrogen ion concentration ranging from acidic to basic

Neutral pH

A pH value of seven where hydrogen ion concentration is balanced

Low pH

Indicates high hydrogen ion concentration and strong acidity

High pH

Indicates low hydrogen ion concentration and strong basicity

Buffers

Substances that resist changes in pH by neutralizing added acids or bases

Strong acid plus strong base

Reaction that can produce a neutral solution and water

Matter

Anything that has mass and occupies space including solids liquids and gases

Element

Pure substance made of only one type of atom that cannot be broken down chemically

Atom

Smallest unit of an element that retains its chemical properties

Protons

Positively charged particles located in the nucleus of an atom

Neutrons

Neutral particles located in the nucleus that contribute to atomic mass

Electrons

Negatively charged particles that move in shells around the nucleus

Molecule

Two or more atoms chemically bonded together forming a stable unit

Compound

Substance made of two or more different elements chemically combined in fixed ratios

Molecule vs compound

All compounds are molecules but molecules can contain the same or different elements

Valence electrons

Electrons in the outermost shell that determine how atoms interact and bond

Reactive atoms

Atoms with incomplete valence shells that tend to form bonds to become stable

Chemical bond

Force of attraction that holds atoms together in molecules or compounds

Covalent bond

Bond formed by sharing pairs of electrons between atoms

Nonpolar covalent bond

Equal sharing of electrons resulting in no charge difference

Polar covalent bond

Unequal sharing of electrons creating partial positive and negative regions

Ionic bond

Bond formed when one atom transfers electrons to another creating charged ions

Anion

Negatively charged ion formed when an atom gains electrons

Cation

Positively charged ion formed when an atom loses electrons

Hydrogen bond

Weak attraction between slightly positive hydrogen and slightly negative atoms in nearby molecules

Chemical reaction

Process in which chemical bonds are broken and new bonds are formed

Reactants

Starting substances that undergo change during a chemical reaction

Products

Substances formed as a result of a chemical reaction

Reversible reaction

Reaction that can proceed in both forward and reverse directions

First Law of Thermodynamics

Energy cannot be created or destroyed only transferred or transformed

Second Law of Thermodynamics

Energy transformations increase disorder and reduce usable energy

Endothermic reaction

Chemical reaction that absorbs energy from the surroundings

Exothermic reaction

Chemical reaction that releases energy into the surroundings

Organic molecule

Molecule containing carbon and often hydrogen oxygen or nitrogen

Monomer

Small single molecular unit that can join with others to form a polymer

Polymer

Large molecule composed of many repeating monomer units

Four macromolecules

Carbohydrates lipids proteins and nucleic acids that are essential for life

Carbohydrates

Organic molecules made of carbon hydrogen and oxygen used for energy and structure

Monosaccharide

Simple sugar that serves as the monomer of carbohydrates

Glucose

Common monosaccharide used by cells as a primary energy source

Polysaccharide

Complex carbohydrate made of many monosaccharides linked together

Starch

Plant storage polysaccharide used to store energy

Lipids

Hydrophobic organic molecules that do not mix with water and store energy

Lipid functions

Include long term energy storage forming cell membranes and providing waterproofing

Waxes

Lipids that create protective water resistant coatings

Fats

Lipids used for long term energy storage in organisms

Phospholipids

Lipids that form the structure of cell membranes with hydrophilic and hydrophobic regions

Steroids

Lipids that function as hormones and signaling molecules

Proteins

Complex organic molecules that perform many structural and functional roles in cells

Amino acids

Monomers of proteins each containing an amino group and carboxyl group

Polypeptide

Chain of amino acids linked together forming a protein

Peptide bond

Covalent bond that connects amino acids in a polypeptide chain

Protein functions

Include catalyzing reactions providing structure transporting substances and defending the body

Nucleic acids

Organic molecules that store and transmit genetic information

Nucleotide

Monomer of nucleic acids consisting of a base sugar and phosphate group

DNA

Molecule that stores genetic instructions using deoxyribose sugar

RNA

Molecule involved in protein synthesis using ribose sugar

Nucleotide parts

Nitrogenous base sugar and phosphate group that make up each nucleotide

Deoxyribose

Sugar found in DNA lacking one oxygen atom

Ribose

Sugar found in RNA with an extra oxygen atom

Nitrogen bases

Molecules that encode genetic information including adenine thymine uracil cytosine and guanine

Thymine

Nitrogen base found only in DNA that pairs with adenine

Uracil

Nitrogen base found only in RNA that pairs with adenine

Base pairing

Specific matching of bases where adenine pairs with thymine or uracil and cytosine pairs with guanine

DNA structure

Double helix formed by two complementary strands twisted together

DNA bonds

Hydrogen bonds between nitrogen bases hold the two strands together

Sugar phosphate backbone

Alternating sugar and phosphate groups that form the sides of the DNA ladder

Complementary strands

Each DNA strand can serve as a template to build the other due to base pairing rules

Origin of life

Life began approximately three point five billion years ago based on fossil evidence

First organisms

Simple single celled organisms such as bacteria and archaea

Possible origins

Life may have originated in deep sea vents hot springs or tidal pools

First step of life

Formation of simple organic molecules from nonliving components

Self replication

Ability of molecules to copy themselves which allowed evolution to begin

Membranes

Structures that formed around molecules creating early cell like compartments

Cell division

Process by which early cells reproduced to pass on genetic material

Metabolism

Chemical processes that convert energy and matter to sustain life

Evidence of common ancestry

Shared DNA metabolic pathways cell structures and fossil records among organisms

Glycolysis

Universal metabolic pathway used by all organisms to produce energy from glucose