Chapter 5: The Structure and Function of Large Biological Molecules

Merged flashcards from Chapter 5 of Pearson's Campbell Biology, Twelfth Edition.

Biological molecules

Macromolecule polymers:

• Carbohydrates (like glucose)

• Proteins (in amino acids)

• Nucleic acids (in DNA)

Non-polymer nor macromolecule:

• Lipids

Macromolecules

Large polymers named for their huge size; cells have thousands and different cells have different varieties

• Many can be built from just a small set of monomers

Polymer

A long molecule consisting of many similar building blocks called monomers

• Includes carbohydrates, proteins, and nucleic acids

Monomer

The repeating units that serve as the building blocks for polymers

Enzymes

Specialized macromolecules that speed up chemical reactions such as those that make or break down polymers

Dehydration reaction

Occurs when two monomers bond together through the loss of a water molecule, thus creating a polymer

Hydrolysis

The disassembly of a polymer to a monomer, creating a reaction that is essentially the reverse of the dehydration reaction

Carbohydrates

Class of macromolecules that consists of sugars and polymers of sugars

Monosaccharides

The simplest forms of carbohydrates that make up the building blocks of polysaccharides (carbohydrate macromolecules)

• Usually have molecular formulas that are multiples of CH₂O, such as in glucose (C₆H₁₂O₆)

• Classified by the location of the carbonyl group or the number of carbons in the carbon skeleton

Polysaccharides

Polymers of monomer monosaccharides, creating complex carbohydrate molecules that serve storage and structural roles

Glucose

The most common monosaccharide with the chemical formula C₆H₁₂O₆

Disaccharides

Formed when a dehydration reaction joins two monosaccharides

Starch

A storage polysaccharide of plants consisting of glucose monomers, such as in potatoes, in granules within chloroplasts and other plastids

Glycogen

A storage polysaccharide in animals, stored mainly in liver and muscle cells for easy utilization and hydrolysis during periods of high demand (like exercise)

Cellulose

A major component of the tough wall of plant cells, it is a polysaccharide

Chitin

Another structural polysaccharide found in the exoskeleton of arthropods as well as the cell walls of many fungi

Lipids

The one class of biological molecules that do not include true polymers, unified by their poor mixture with water

• Consist mostly of hydrocarbon regions

• Biologically important types include fats, phospholipids, and steroids

Fats

Type of lipid constructed from glycerol and fatty acid molecules

Glycerol

A three-carbon alcohol with a hydroxyl group attached to each carbon

Saturated fats

Fats with the maxiumum number of hydrogen atoms and no double bonds

• Solid at room temperature

• Includes most animal fats

• Can cause cardiovascular disease through plaque deposits

Unsaturated fats

Fats with one or more double bonds and fewer hydrogen atoms

• Liquid at room temperature

• Includes plant fats and fish fats

Hydrogenation

The process of converting unsaturated fats to saturated fats by adding hydrogen

• This leads to trans fats with double bonds in vegetable oils that can contribute to cardiovascular disease

Adipose cells

Cells used for storage in humans and other mammals that cushion the body and organs

Phospholipid

Type of lipid with two fatty acids and a phosphate group attached to glycerol

• Fatty acid tails are hydrophobic, phosphate heads are hydrophilic

• In water, they assemble a bilayer with the tails toward the interior as a boundary between cells and their environment

Steroids

Lipids characterized by a carbon skeleton consisting of four fused rings

Cholesterol

A type of steroid from which animal cell membranes and other steroids are synthesized

• High levels of this may contribute to cardiovascular disease

Proteins

Biological molecules that account for more than 50% of the dry mass of most cells, serving in a variety of functions

• Contain one or more polypeptides

• Functions result from their structure of polypeptides twosted, foiled, and coiled to bind to other molecules

Enzymatic proteins

Proteins that selectively accelerate chemical reactions

• Digestive enzymes catalyze the hydrolysis of bonds in food molecules

Defensive proteins

Proteins that protect against disease

• Antibodies activate and help destroy virsues and bacteria

Storage proteins

Proteins that store amino acids

• Casein in milk is the major source of amino acids for baby mammals

• Plants have storage proteins in their seeds

• Ovalbumin is the protein of egg white, used as an amino acid source for the developing embryo

Transport proteins

Proteins that transport substances

• Hemoglobin is the iron-containing protein of vertebrate blood, transporting oxygen from the lungs to other parts of the body

• Transport proteins exist in cell membranes for molecular passage

Hormonal proteins

Proteins that coordinate an organism’s activities

• Insulin (a hormone secreted by the pancreas) causes glucose uptake in cells, regulating blood sugar concentration

Receptor proteins

Proteins that aid cellular responses to chemical stimuli

• Receptors in nerve cell membranes detect signaling molecules released by other nerve cells

Contractile proteins (motor proteins)

Proteins that function in movement

• Motor proteins aid the movement of cilia and flagella

• Actin and myosin proteins are responsible for the contraction of muscles

Structural proteins

Proteins that support cellular structures

• Keratin is the protein of hair, horns, feathers, and other skin appendages

• Insects and spiders use silk fibers to make their cocoons and webs

• Collagen and elastin proteins provide a fibrous framework in animal connective tissues

Amino acids

Organic molecules with amino and carboxyl groups that serve as the monomers in proteins

• Have differing properties due to differing side chains called R groups

Polypeptides

Unbranched polymers built from amino acids joined by peptide bonds

Peptide bonds

Bonds that join amino acids in polypeptides

Primary structure

A protein’s first structure defined by its unique sequence of amino acids

• Like the order of letters in a long word

• Determined by inherited genetic information

Secondary structure

A protein’s second structure defined by its coils and folds in its polypeptide chains

Tertiary structure

A protein’s third structure defined by its interactions among various side chains (R groups)

Quaternary structure

A protein’s fourth and final structure when a protein consists of multiple polypeptide chains to form one macromolecule

• Collagen consists of three polypeptides like a rope

Sickle-cell disease

An inherited blood disorder that results from a single amino acid substitution in the protein hemoglobin, causing an abnormal sickle shape in the red blood cell

Denaturation

The loss of a protein’s native structure caused by physical or chemical conditions

• pH, salt concentration, and temperature are some factors

• Extremely high fevers can be fatal because of this

Gene

A unit of inheritance that consists of DNA to program the amino acid sequences of polypeptides

Dioxyribonucleic acid (DNA)

A nucleic acid that comprises genes through monomers called nucleotides and provides directions for its own replication

Ribonucleic acid (RNA)

Nucleic acid type that is directed by DNA to control protein synthesis through a process called gene expression

• Single-stranded as opposed to double-stranded DNA

• Has the thymine (T) base replaced by uracil (U)

Polynucleotides

The term for nucleic acids as polymers of monomers called nucleotides

Nucleotides

The monomers of polynucleotides, consisting of a nitrogenous base, a pentose sugar, and one or more phosphate groups

Pyrimidines

One of the two families of nitrogenous bases, comprising cytosine (C), thymine (T), and uracil (U)

Purines

One of the two families of nitrogenous basis comprising adenine (A) and guanine (G)

Deoxyribose

The sugar present in DNA

Ribose

The sugar present in RNA

Double helix

The shape of a DNA molecule formed by two polynucleotides in a spiral, running in opposite directions for 5-carbon and 3-carbon sugar strands

Complementary base pairing

The fact that only certain bases pair with each other in DNA, making it possible to generate two identical copies of each DNA molecule in a cell preparing to divide

• Adenine (A) always to thymine (T)

• Guanine (G) always to cytosine (C)