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Biology 150 : ch5
The Structure and Function of Large Biological Molecules
| Term | Definition |
|---|---|
| All living things are made up of four classes of large biological molecules: | carbohydrates, lipids, proteins, and nucleic acids |
| Macromolecules | are large molecules composed of thousands of covalently connected atoms Molecular structure and function are inseparable |
| Macromolecules are polymers, built from ____ | monomers |
| A polymer is | a long molecule consisting of many similar building blocks – most can’t fit through the cell membrane |
| Three of the four classes of life’s organic molecules are polymers... | Carbohydrates Proteins Nucleic acids |
| monomers | small building-block molecules- are able to fit into the cell, make up polymers |
| A dehydration reaction | occurs when two monomers bond together through the loss of a water molecule |
| hydrolysis | Polymers are disassembled to monomers by hydrolysis, a reaction that is essentially the reverse of the dehydration reaction |
| The Diversity of Polymers | Each cell has thousands of different macromolecules Macromolecules vary among cells of an organism, vary more within a species, and vary even more between species An immense variety of polymers can be built from a small set of monomers |
| Carbohydrates | Carbohydrates include sugars and the polymers of sugars |
| monosaccharides | The simplest carbohydrates are monosaccharides, or single sugars |
| polysaccharides | Carbohydrate macromolecules are polysaccharides, polymers composed of many sugar building blocks |
| Monosaccharides molecular formula | have molecular formulas that are usually multiples of CH2O |
| most common monosaccharide | Glucose (C6H12O6) is the most common monosaccharide |
| how are monosacharides classified | Monosaccharides are classified by 1) The location of the carbonyl group (as aldose or ketose) 2)The number of carbons in the carbon skeleton |
| structure of monosacharides in aqueous solution | Though often drawn as linear skeletons, in aqueous solutions many sugars form rings |
| Monosaccharides serve as a major ... | Monosaccharides serve as a major fuel for cells and as raw material for building molecules |
| A disaccharide is formed when | a dehydration reaction joins two monosaccharides |
| glycosidic linkage | the covalent bond of two monosacharides |
| the polymers of sugars... role? | Polysaccharides, the polymers of sugars, have storage and structural roles |
| The structure and function of a polysaccharide are determined by | its sugar monomers and the positions of glycosidic linkages |
| Starch | Starch, a storage polysaccharide of plants, consists entirely of glucose monomers. Plants store surplus starch as granules within chloroplasts and other plastids |
| amylose | The simplest form of starch is amylose |
| Glycogen | Glycogen is a storage polysaccharide in animals Humans and other vertebrates store glycogen mainly in liver and muscle cells |
| cellulose | The polysaccharide 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 The difference is based on two ring forms for glucose: alpha and beta |
| Polymers with alpha glucose are ____ | Polymers with alpha glucose are helical |
| Polymers with beta glucose are ___ | Polymers with beta glucose are straight |
| In straight structures | In straight structures, H atoms on one strand can bond with OH groups on other strands |
| Parallel cellulose molecules held together this way are grouped into __ | Parallel cellulose molecules held together this way are grouped into microfibrils, which form strong building materials for plants |
| Enzymes that digest starch by hydrolyzing alpha linkage ... | Enzymes that digest starch by hydrolyzing alpha linkages can’t hydrolyze beta linkages in cellulose |
| Cellulose in human food... | Cellulose in human food passes through the digestive tract as insoluble fiber |
| Some microbes use enzymes to digest cellulose | Many herbivores, from cows to termites, have symbiotic relationships with these microbes |
| Chitin | Chitin, another structural polysaccharide, is found in the exoskeleton of arthropods Chitin also provides structural support for the cell walls of many fungi |
| The most biologically important lipids are | fats, phospholipids, and steroids |
| Lipids are hydrophobic because | they consist mostly of hydrocarbons, which form nonpolar covalent bonds |
| Lipids | are the one class of large biological molecules that do not form polymers The unifying feature of lipids is having little or no affinity for water |
| fats | Fats are constructed from two types of smaller molecules: glycerol and fatty acids |
| Glycerol | Glycerol is a three-carbon alcohol with a hydroxyl group attached to each carbon |
| fatty acid | A fatty acid consists of a carboxyl group attached to a long carbon skeleton |
| why are fats hydrophobic | Fats separate from water because water molecules form hydrogen bonds with each other and exclude the fats |
| In a fat, three fatty acids are joined to ... | In a fat, three fatty acids are joined to glycerol by an ester linkage, creating a triacylglycerol, or triglyceride |
| Fatty acids vary in | Fatty acids vary in length (number of carbons) and in the number and locations of double bonds |
| Saturated fatty acids | Saturated fatty acids have the maximum number of hydrogen atoms possible and no double bonds |
| Unsaturated fatty acids | Unsaturated fatty acids have one or more double bonds |
| Fats made from saturated fatty acids are called | Fats made from saturated fatty acids are called saturated fats, and are solid at room temperature. Most animal fats are saturated |
| Fats made from unsaturated fatty acids are called | Fats made from unsaturated fatty acids are called unsaturated fats or oils, and are liquid at room temperature Plant fats and fish fats are usually unsaturated |
| A diet rich in saturated fats may contribute to | cardiovascular disease through plaque deposits |
| Hydrogenation | The process of converting 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 |
| essential fatty acids | Certain unsaturated fatty acids are not synthesized in the human body. These must be supplied in the diet These include the omega-3 fatty acids, required for normal growth, and thought to provide protection against cardiovascular disease |
| 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 |
| phospholipid | two fatty acids and a phosphate group are attached to glycerol The two fatty acid tails are hydrophobic, but the phosphate group and its attachments form a hydrophilic head |
| Phospholipids are the major component of all | Phospholipids are the major component of all cell membranes |
| When phospholipids are added to water, | they self-assemble into a bilayer, with the hydrophobic tails pointing toward the interior The structure of phospholipids results in a bilayer arrangement found in cell membranes |
| Steroids | Steroids are lipids characterized by a carbon skeleton consisting of four fused rings |
| Cholesterol | Cholesterol, an important steroid, is a component in animal cell membranes Although cholesterol is essential in animals, high levels in the blood may contribute to cardiovascular disease |
| Proteins account for more than ... | 50% of the dry mass of most cells |
| Protein functions include | structural support, storage, transport, cellular communications, movement, and defense against foreign substances |
| Amino acids | Amino acids are linked by peptide bonds A polypeptide is a polymer of amino acids |
| Polypeptides | Polypeptides 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) |
| A functional protein | A functional protein consists of one or more polypeptides precisely twisted, folded, and coiled into a unique shape |
| The sequence of amino acids... | The sequence of amino acids determines a protein’s three-dimensional structure A protein’s structure determines its function |
| The primary structure of a protein | The primary structure of a protein is its unique sequence of amino acids |
| Secondary structure of a protein | Secondary structure, found in most proteins, consists of coils and folds in the polypeptide chain |
| Tertiary structure of a protein | Tertiary structure is determined by interactions among various side chains (R groups) |
| Quaternary structure of a protein | Quaternary structure results when a protein consists of multiple polypeptide chains |
| Primary structure, the sequence of amino acids in a protein, | is like the order of letters in a long word Primary structure is determined by inherited genetic information |
| The coils and folds of secondary structure result from | hydrogen bonds between repeating constituents of the polypeptide backbone Typical secondary structures are a coil called an alpha helix and a folded structure called a beta pleated sheet |
| Tertiary structure is determined by | interactions between 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 and disulfide bridges. |
| disulfide bridges | Strong covalent bonds called disulfide bridges may reinforce the protein’s structure |
| Quaternary structure results when | two or more polypeptide chains form one macromolecule Collagen is a fibrous protein consisting of three polypeptides coiled like a rope Hemoglobin is a globular protein consisting of four polypeptides: two alpha and two beta chains |
| 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 |
| What else can determine protein structure | In addition to primary structure, physical and chemical conditions can affect structure Alterations in pH, salt concentration, temperature, or other environmental factors can cause a protein to unravel |
| denaturation | This loss of a protein’s native structure is called denaturation A denatured protein is biologically inactive |
| Renaturation | sometimes the protein can begin to reform the structure before the damage, but this is only sometimes if the damage is not too extensive |
| Nucleic acids roles: | Nucleic acids store, transmit, and help express hereditary information |
| gene | The amino acid sequence of a polypeptide is programmed by a unit of inheritance called a gene. Genes are made of DNA, a nucleic acid made of monomers called nucleotides |
| There are two types of nucleic acids | There are two types of nucleic acids Deoxyribonucleic acid (DNA) Ribonucleic acid (RNA) |
| DNA provides ... | DNA provides directions for its own replication DNA directs synthesis of messenger RNA (mRNA) and, through mRNA, controls protein synthesis Protein synthesis occurs on ribosomes |
| polynucleotides | Nucleic acids are polymers called polynucleotides |
| nucleotides | Each polynucleotide is made of monomers called nucleotides |
| Each nucleotide consists of | Each nucleotide consists of a nitrogenous base, a pentose sugar, and one or more phosphate groups |
| nucleoside | The portion of a nucleotide without the phosphate group is called a nucleoside Nucleoside = nitrogenous base + sugar |
| 2 families of nitrogenous bases | There are two families of nitrogenous bases Pyrimidines (cytosine, thymine, and uracil) have a single six-membered ring Purines (adenine and guanine) have a six-membered ring fused to a five-membered ring |
| DNA vs RNA sugar | In DNA, the sugar is deoxyribose; in RNA, the sugar is ribose Nucleotide = nucleoside + phosphate group |
| Nucleotide Polymers | Nucleotide polymers are linked together to build a polynucleotide 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 |
| nucleotide polymer links | These links create a backbone of sugar-phosphate units with nitrogenous bases as appendages The sequence of bases along a DNA or mRNA polymer is unique for each gene |
| double helix | DNA molecules have two polynucleotides spiraling around an imaginary axis, forming a double helix |
| RNA molecules usually exist as | single polypeptide chains |
| antiparallel | In the DNA double helix, the two backbones run in opposite 5→ 3 directions from each other, an arrangement referred to as antiparallel One DNA molecule includes many genes |
| Called complementary base pairing | The nitrogenous bases in DNA pair up and form hydrogen bonds: adenine (A) always with thymine (T), and guanine (G) always with cytosine (C) |
| RNA complementary base pairing | Complementary pairing can also occur between two RNA molecules or between parts of the same molecule In RNA, thymine is replaced by uracil (U) so A and U pair |
| The linear sequences of nucleotides in DNA molecules are ... | passed from parents to offspring Two closely related species are more similar in DNA than are more distantly related species Molecular biology can be used to assess evolutionary kinship |
Created by:
catalin1993
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