Chapter 5 - The Structure and Function of Large Biological Molecules

Question 1

All living things are made up of these four classes of large biological molecules:

Answer 1

• carbohydrates
• lipids
• proteins
• nucleic acids

Question 2

Macromolecules

Answer 2

large molecules composed of thousands of covalently connected atoms.

Question 3

polymer

Answer 3

A long molecule consisting of many similar or identical monomers linked together by covalent bonds.

Question 4

monomer

Answer 4

The subunit that serves as the building block a polymer

Question 5

dehydration reaction

Answer 5

occurs when two monomers bond together through the loss of a water molecule.

Question 6

hydrolysis

Answer 6

Polymers are disassembled to monomers. Hydrolysis adds a water molecule, breaking a bond.

Question 7

Carbohydrates

Answer 7

include sugars and the polymers of sugars. Though often drawn as linear skeletons, inaqueous solutions many sugars form rings.

Question 8

monosaccharides

Answer 8

• The simplest carbohydrates.
• Also known as “single sugars”.
• have molecular formulas that are usually multiples of CH₂O
• Glucose (C₆H₁₂O₆) is the most common monosaccharide
• serve as a major fuel for cells and as raw material for building molecules

Question 9

Monosaccharides are classified by…

Answer 9

• The location of the carbonyl group (as aldose or ketose)
• The number of carbons in the carbon skeleton

Question 10

polysaccharides

Answer 10

• A polymer of many monosaccharides, formed by dehydration reactions.
• The polymers of sugars have storage and structural roles.
  
  • Structure and function determined by its sugar monomers and the positions of glycosidic linkages

Question 11

disaccharide

Answer 11

A double sugar, consisting of two monosaccharides joined by a glycosidic linkage formed by a dehydration reaction.

Question 12

Glycosidic linkage

Answer 12

A covalent bond formed between two monosaccharides by a dehydration reaction.

• Polymers with α glucose are helical
• Polymers with β glucose are straight
  
  • H atoms on one strand can bond with OH groups on other strands

Question 13

Starch

Answer 13

A storage polysaccharide in plants, consisting entirely of glucose monomers joined by α glycosidic linkages.

• Plants store surplus starch as granules within chloroplasts and other plastids
• The simplest form of starch is amylose

Question 14

Glycogen

Answer 14

An extensively branched glucose storage polysaccharide found in the liver and muscle of animals; the animal equivalent of starch.

Question 15

Cellulose

Answer 15

A structural polysaccharide of plant cell walls, consisting of glucose monomers joined by β glycosidic linkages. In these β structures, H atoms on one strand can bond with OH groups on other strands. Parallel cellulose held together this way are grouped into microfibrils, which form strong building materials for plants.

• Cellulose is a major component of the tough wall of plant cells
• Like starch, cellulose is a polymer of glucose, but the glycosidic linkages differ
  
  • Difference is based on two ring forms for glucose: alpha (α) and beta (β)
• Enzymes that digest starch by hydrolyzing α linkages can’t hydrolyze β linkages in cellulose
  
  • Passes through the digestive tract as insoluble fiber, or like in many herbivores, microbes use enzymes to digest the cellulose.

Question 16

Chitin

Answer 16

A structural polysaccharide, consisting of amino sugar monomers, found in many fungal cell walls and in the exoskeletons of all arthropods.

Question 17

Lipids

Answer 17

Any group of large biological molecules, including fats, phospholipids, and steroids, that mix poorly, if at all, with water.

• Do not form polymers
• Lipids are hydrophobic because they consisty mostly of hydrocarbons, which form nonpolar covalent bonds.

Question 18

Fat

Answer 18

A lipid consisting of three fatty acids linked to one glycerol molecule; also called a triacylglycerol or triglyceride.

• Fats separate from water because water molecules form hydrogen bonds with eachother and exclude the fats
• In a fat, three fatty acids are joined to glycerol by an ester linkage, creating a triacylclycerol, or triglyceride.
  
  • Ester linkage: any of a class of compounds produced by reaction between acids and alcohols with the elimination of water. Esters with low molecular weights, such as ethyl acetate, are usually volatile fragrant liquids; fats are solid esters
• The major function of fats is energy storage
  
  • Humans and other mammals store their fat in adipose cells
    
    • Adipose tissue also cushions vital organs and insulates the body

Question 19

Glycerol

Answer 19

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

Question 20

Fatty Acid

Answer 20

A carboxylic acid with a long carbon chain. Fatty acids vary in length and in the number and location of double bonds; three fatty acids linked to a glycerol molecule form a fat molecule, also known as a triacylglycerol or triglyceride.

• Fatty acids vary in length (number of carbons) and in the number and locations of double bonds.

Question 21

Saturated fatty acid

Answer 21

A fatty acid in which all carbons in the hydrocarbon tail are connected by single bonds, thus maximizing the number of hydrogen atoms that are attached to the carbon skeleton.

• Solid at room temperature
• Most animal fats are saturated
• Diets rich in this may contribute to cardiovascular disease through plaque deposits

Question 22

Unsaturated fatty acids

Answer 22

A fatty acid that has one or more double bonds between carbons in the hydrocarbon tail. Such bonding reduces the number of hydrogen atoms attached to the carbon skeleton.

• Also known as oils because they are liquid at room temperature
• Plant fats and fish fats are usually unsaturated
• Certain unsaturated fatty acids are not synthesized in the human body and must be supplied in the diet
  
  • Omega-3 fatty acids: required for normal growth and thought to provide protection against cardiovascular disease

Question 23

Trans fat

Answer 23

An unsaturated fat, formed artificially during hydrogenation of oils, containing one or more trans double bonds.

• Converts unsaturated fats to saturated fats by adding hydrogen.
• Hydrogenating vegetable oils also creates unsaturated fats with trans double bonds
• These trans fats may contribute more than saturated fats to cardiovascular disease

Question 24

Phospholipid

Answer 24

• A lipid made up of glycerol joined to two fatty acids and a phosphate group.
• The hydrocarbon chains of the fatty acids act as nonpolar, hydrophobic tails, while the rest of the molecule acts as a polar, hydrophilic head.
• Phospholipids form bilayers that function as biological membranes.
  
  • When added to water, they self-assemble into a bilayer, with the hydrophobic tails pointing toward the interior. This results in a bilayer arrangement found in cell membranes
• Phospholipids are the major component of all cell membranes

Question 25

Steroid

Answer 25

A type of lipid characterized by a carbon skeleton consisting of four fused rings with varius chemical groups attached.

Question 26

Cholesterol

Answer 26

A steroid that forms an essential component of animal cell mambranes and acts as a precursor molecule for the synthesis of other biologically important steroids, such as many hormones. High levels of cholesterol in the blood may contribute to cardiovascular disease.

Question 27

Protein

Answer 27

* A biologically functional molecule consisting of one or more polypeptides folded and coiled into a specific three-dimensional structure. * Account for more than 50% of the dry mass of most cells * Functions include structural support, storage, transport, cellular communications, movement, and defense against foreign substances * The sequence of amino acids determines a protein's three-dimensional structure * A protein's structure determines its function

Question 28

Enzymatic Proteins

Answer 28

* A macromolecule serving as a catalyst, a chemical agent that increases the rate of a reaction without being consumed by the reaction. * Can perform their functions repeatedly, functioning as workhorses that carry out the processes of life

Question 29

Storage Proteins

Answer 29

Question 30

Hormonal Proteins

Answer 30

Question 31

Contractile and Motor Proteins

Answer 31

Question 32

Defensive Proteins

Answer 32

Question 33

Transport Proteins

Answer 33

Question 34

Receptor Proteins

Answer 34

Question 35

Structural Proteins

Answer 35

Question 36

Polypeptides

Answer 36

* A polymer of many amino acids linked together by peptide bonds. * Range in length from a few to more than a thousand monomers * Each polypeptide has a unique linear sequence of amino acids, with a carboxyl end (C-terminus) and an amino end (N-terminus)

Question 37

Amino Acid

Answer 37

* An organic molecule possessing both a carboxyl and an amino group. * Serve as the monomers of polypeptides * Differ in their properties due to differing side chains, called R groups * Linked by peptide bonds

Question 38

Peptide Bond

Answer 38

The covalent bond between the carboxyl group on one amino acid and the amino group on another, formed by a dehydration reaction.

Question 39

Functional Protein

Answer 39

Consists of one or more polypeptides precisely twisted, folded, and coiled into a unique shape.

Question 40

Primary Protein Structure

Answer 40

* A protein's unique senquence of amino acids. * Like the order of letters in a long word * Determined by inherited genetic information * A slight change in primary structure can affect a protein's structure and ability to function * Sickle-cell disease, an inherited blood disorder, results from a single amino acid substitution in the protein hemoglobin

Question 41

Secondary Protein Structure

Answer 41

* Found in most proteins * Consists of coils and folds in the polypeptide chain * These coils and colds of secondary structure result from hydrogen bonds between repeating constituents of the polypeptide backbone * Typical secondary structures are a coil called an α helix and a folded structure called a β pleated sheat

Question 42

Tertiary Protein Structure

Answer 42

* Determined by interactions among various side chains (R groups), rather than interactions between backbone constituents * These interactions between R groups include hydrogen bonds, ionic bonds, hydrophobic interactions, and van der Waals interactions

Question 43

Quaternary Protein Structure

Answer 43

Results when a protein consists of myltiple polypeptide chains * Collagen is a fibrous protein consisting of three polypeptides coiled like a rope * Hemoglobin is a glubular protein consisting of four polypeptides: two alpha and two beta chains

Question 44

Disulfide Bridge

Answer 44

A strong covalent bond formed when the sulfur of one cysteine monomer bonds to the sulfur of another cysteine monomer. * May reinforce a protein's structure

Question 45

Denaturation

Answer 45

* In proteins, a process in which a protein loses its native shape due to the disruption of weak chemical bonds and interactions, thereby becoming biologically inactive * In DNA, the separation of the two strands of the double helix * Occurs under extreme conditions of pH, salt concentration, or temperature * A denatured protein is biologically inactive

Question 46

Chaperonins

Answer 46

* Protein molecules that assist the proper folding of other proteins * Diseases such as Alzheimer's, Parkinson's, and mad cow diease are associated with misfolded proteins

Question 47

X-Ray Crystallography

Answer 47

A technique used to study the three-dimensional structure of molecules. It depends on the diffraction of an X-ray beam by the individual atoms of a crystallized molecule.

Question 48

Gene

Answer 48

* A discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA or RNA * The amino acid sequence of a polypeptide is programmed by genes

Question 49

Nucleic Acid

Answer 49

* A polymer (polynucleotide) consisting of many nucleotide monomers * Serves as a blueprint for proteins and, through the actions of proteins, for all cellular activities * The two types are DNA and RNA

Question 50

Deoxyribonucleic Acid (DNA)

Answer 50

* A nucleic acid molecule, usually a double-stranded helix, in which each polynucleotide strand consists of nucleotide monomers with a deoxyribose sugar and the nitrogenous bases **adenine** (A), **cytosine** (C), **guanine** (G), and **thymine** (T) * The nitrogenous bases in DNA pair up and form hydrogen bonds. Called complementary base pairing. * Adenine is always with thymine * Guanine is always with cytosine * Capable of being replicated and determining the inherited structure of a cell's proteins. * Directs synthesis of messenger RNA (mRNA) and, through mRNA, controls protein synthesis * Protein synthesis occurs on ribosomes * In the DNA double helix, the two backbones run in opposite 5' to 3' directions from each other, an arrangement referred to as antiparallel * One DNA molecule includes many genes.

Question 51

Ribonucleic Acid (RNA)

Answer 51

* A type of nucleic acid consisting of a polynucleotide made up of nucleotide monomers with a ribose sugar and the nitrogenous bases **adenine** (A), **cytosine** (C), **guanine** (G), and **uracil** (U) * Single polypeptide chain * functions in protein synthesis, gene regulation, and as the genome of some viruses * Complementary pairing is similar to DNA * Thymine is replaced by uracil so adenine and uracil pair

Question 52

Polynucleotide

Answer 52

* A polymer consisting of many nucleotide monomers in a chain. The nucleotides can be those of DNA or RNA. * Adjacent nucleotides are joined by covalent bonds that form between the -OH group on the 3' carbon of one nucleotide and the phosphate on the 5' carbon on the next * These links create a backbone of sugar-phosphate units with nitrogenous bases as appendages

Question 53

Nucleotide

Answer 53

* The building block of a nucleic acid, consisting of a five-carbon sugar covalently bonded to a nitrogenous base and one or more phosphate groups * Nucleotide = Nucleoside + phosphate group * The portion of a nucleotide without the phosphate group is called a nucleoside * Nucleoside = Nitrogenous base + sugar

Question 54

Pyrimidine

Answer 54

* One of the two types of nitrogenous bases found in nucleotides, characterized by a six-membered ring. * Cyosine (C), thymine (T), and uracil (U) are pyrimidines

Question 55

Purine

Answer 55

* One of the two types of nitrogenous bases found in nucleotides, characterized by a six-membered ring fused to a five-membered ring. * Adenine (A) and guanine (G) are purines.