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Chapter 2 of Biology Today and Tomorrow for Biology 114 at Heartland Community College


Form of an element that differs in the number of neutrons in the nucleus


Atom that carries a charge because it has an unequal number of protons and electrons

Covalent Bond

Chemical bond in which the two atoms share a pair of electrons

Ionic Bond

Chemical bond in which atoms of opposite charge are attracted to each other

Hydrogen Bond

Attraction between a covalently bonded hydrogen atom and another atom in a separate covalent bond


Substance that easily dissolves in water


Substance that resits dissolving in water


Molecule that consists primarily of carbon, hydrogen, and oxygen in a 1:2:1 ratio


Tough, insoluble carbohydrate that is the major structural material in plants


Organic molecule that speeds up a reaction without being changed by it


Lipid that consists of a glycerol molecule with one, two, or three fatty acid tails

Fatty Acid

Organic compound that consists of a chain of carbon atoms with an acidic carboxyl group at one end

Lipid Bilayer

Double layer of lipids arranged tail-to-tail that makes up cell membranes


A lipid with a phosphate in its hydrophilic head, and two non polar fatty acid tails. Makes up the lipid bilayer

Saturated Fat

Fat that consists mainly of triglycerides with three saturated fatty acid tails


Type of lipid with four carbon rings and no fatty acid tails


A fat that has three fatty acid tails

Amino Acid

Small organic compound that is a subunit of proteins.


To become so altered in shape that some or all function is lost


Organic compound that consists of one or more chains of amino acids


What cells use for energy, is made in mitochondria

Polarity of Water

Slightly negative at the oxygen end, slightly positive at the two hydrogen ends

Special Properties of Water

1. Sticky 2. Surrounds and dissolves molecules 3. Temperature stable, hard to make jiggle 4. Ice floats


Glucose, fructose and others


Sucrose or table sugar


Starch, glycogen, and cellulose


Polysaccharide that plants use to store fuel


Polysaccharide that animals use to store fuel

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