preview lesson starter objectives carbohydrates lipids chapter 23

Preview

• Lesson Starter• Objectives• Carbohydrates• Lipids

Chapter 23

Lesson Starter

• Why does the can of diet soft drink float and the can of regular soft drink sink?

• The aspartame used to sweeten the diet soft drink is about 200 times as sweet as sucrose.

• The regular soft drink is denser than the diet soft drink, because there is such a large amount of sugar in the regular soft drink, and only a small amount of sweetener in the diet soft drink.

Section 1 Carbohydrates and LipidsChapter 23

Objectives

• Describe the structural characteristics of simple carbohydrates and complex carbohydrates.

• Explain the role of carbohydrates in living systems.

• Describe the structural characteristics of lipid molecules.

• Identify the functions of lipids in living cells.


• Biochemistry is the study of the chemicals and reactions that occur in living things.

• Biochemical compounds are often large and complex organic molecules, but their chemistry is similar to that of the smaller organic molecules


Carbohydrates

• Carbohydrates are molecules that are composed of carbon, hydrogen, and oxygen atoms in a 1:2:1 ratio, and provide nutrients to the cells of living things.

• sugars, starches, and cellulose

• Carbohydrates are produced by plants through a process called photosynthesis.

• Carbohydrates provide nearly all of the energy that is available in most plant-derived food.


Click below to watch the Visual Concept.

Visual Concept

Chapter 23

Carbohydrates

Section 1 Carbohydrates and Lipids

Types of Carbohydrates


Carbohydrates, continuedMonosaccharides

• A monosaccharide is a simple sugar that is the basic subunit of a carbohydrate.

• A single monosaccharide molecule contains three to seven carbon atoms.

• Monosaccharide compounds are

• typically sweet-tasting

• white solids at room temperature

• water soluble


Carbohydrates, continuedMonosaccharides, continued

• The most common monosaccharides are glucose (also called dextrose) and fructose.

• Both have the formula C6(H2O)6.

• Their structural formulas differ.


Structures of Carbohydrates



Visual Concept

Chapter 23

Monosaccharides


Carbohydrates, continuedDisaccharides

• A disaccharide is a sugar that consists of two monosaccharide units that are joined together.

• sucrose, C12H22O11

• A molecule of sucrose forms when a glucose molecule bonds to a fructose molecule.

• lactose • Lactose is made up of a sugar called galactose and

glucose.



Visual Concept

Chapter 23

Disaccharides


Carbohydrates, continuedCarbohydrate Reactions

• Carbohydrates undergo two important kinds of reactions: condensation reactions and hydrolysis reactions.


• A condensation reaction is a reaction in which two molecules or parts of the same molecule combine.

Carbohydrates, continuedCarbohydrate Reactions, continued

• Hydrolysis is a chemical reaction between water and another substance to form two or more new substances.

• Disaccharides and longer-chain polysaccharides can be broken down into smaller sugar units by hydrolysis.



Visual Concept

Chapter 23

Cation Hydrolysis



Visual Concept

Chapter 23

Anion Hydrolysis


Carbohydrates, continuedPolysaccharides

• When many monosaccharides or disaccharides combine in a series of condensation reactions, they form a polysaccharide.

• A polysaccharide is a carbohydrate made up of long chains of simple sugars.

• Cellulose, starch, and glycogen are polymers of glucose.

• Sheets of cellulose make up plant cell walls.• Starch is the storage form of glucose in plants.


Carbohydrates, continuedPolysaccharides, continued

• Glycogen, cellulose, and starch differ in their arrangement of glucose monomers.


Lipids

• A lipid is a type of biochemical that does not dissolve in water, has a high percentage of C and H atoms, and is soluble in nonpolar solvents.

• As a class, lipids are not nearly as similar to each other as carbohydrates are.

• Long-chain fatty acids, phospholipids, steroids, and cholesterol are lipids.



Visual Concept

Chapter 23

Types of Lipids


Lipids, continuedFatty Acids and Triglycerides

• Fatty acids consist of a long, nonpolar hydrocarbon “tail” and a polar carboxylic acid functional group at the “head.”

• They have hydrophilic polar heads, but their hydrocarbon chains make them insoluble in water.

C C C C C C C C C CC

O

HOH

H

H

H

H

H H

H H

H H

H

H

H H H

H

H

C C C C C C C

H

H

H

H H

H H

H

H

H

H

H

H

H

H

hydrophilic region hydrophobic region


Lipids, continuedFatty Acids and Triglycerides, continued• Triglycerides are formed by condensation reactions in

which three fatty acid molecules bond to one glycerol (a type of alcohol) molecule.

• Fats and oils that are the most common group of lipids in your diet.

• Because they have a large amount of saturated fatty acids, fats are solids at room temperature.

• Oils have more unsaturated fatty acids than fats, and are liquids


• Fat is stored in adipose tissue until it is needed as an energy source.

Lipids, continuedFatty Acids and Triglycerides, continued

• When a fat combines with NaOH, an acid-base reaction called saponification occurs, and a salt and water form.

• This salt is made up of molecules that have long carboxylic acid chains and is called soap.

• Lipids that react with a base to form soap are called saponifiable lipids, which include fats, oils, and fatty acids.


Lipids, continuedOther Important Lipids

• Compound saponifiable lipids play an important role in biochemical processes.

• These lipids are structurally similar to triglycerides in that at least one fatty acid is bonded to the central glycerol or glycerol-like unit.

• These molecules may also have phosphate groups, sugar units, or nitrogen containing groups.

• Phospholipids, are compound saponifiable lipids and are the main structural component of cell membranes.


Lipids, continuedOther Important Lipids, continued

• Phospholipids are arranged in a bilayer, or double layer, at the surface of the cell.


Lipids, continuedOther Important Lipids, continued

• Nonsaponifiable lipids are nonpolar compounds that do not form soap.


• steroids, many vitamins, and bile acids

• Cholesterol is a steroid present in animal cell membranes and is a precursor of many hormones.

Preview

• Lesson Starter• Objectives• Amino Acids• Proteins• Proteins as Enzymes

Chapter 23 Section 2 Amino Acids and Proteins

Lesson Starter

• carboxylic acid

O

R–C–OH

R–N–R˝

R´

N C C

ROH

OH

H

HN C C

ROH

OH

H

H+ N C C

R

OHH

H

N C C

ROH

OHH

+ H2O

Section 2 Amino Acids and ProteinsChapter 23

• condensation reaction to form dipeptide bond

• amine

Objectives

• Describe the basic structure of amino acids and the formation of polypeptides.

• Determine the significance of amino acid side chains to the three-dimensional structure of a protein and the function of a protein.

• Describe the functions of proteins in cells.

• Identify the effects of enzymes on biological molecules.


• Amino acid molecules are the basic building blocks of proteins.

• More than 700 types of amino acids occur in nature.

• Only 20 types of amino acids are found in human proteins.

• The human body can synthesize only 11 of the 20 amino acids as needed.

• The other nine, called the essential amino acids, have to be supplied by the food that we eat.


• Amino acids are organic molecules that contain two functional groups: a basic —NH2 amino group and an acidic —COOH carboxylic acid group.

H2N C COOH

H

R

N C C

ROH

OH

H

H

Amino Acids


• The R-groups of the amino acids present in a protein determine the protein’s biological activity.

or

Structures of Amino Acids



Visual Concept

Chapter 23

Amino Acid

Section 2 Amino Acids and Proteins

• Two amino acids can react with each other in an acid-base reaction.

• The basic amino group of one amino acid reacts with the acidic carboxylic acid group of another amino acid to form a peptide, and a molecule of water is lost.

• This reaction is classified as a condensation reaction

• The bond formed is called a peptide bond.

• The product is a dipeptide.

Amino Acids, continuedAmino Acid Reactions



Visual Concept

Chapter 23

Formation of Dipeptides and Polypeptides


N C C

ROH

OH

H

HN C C

ROH

OH

H

H+

N C C

R

OHH

H

N C C

ROH

OHH

+ H2O

Amino Acids, continuedAmino Acid Reactions, continued


• Longer chains of amino acids are called polypeptides.

• Chains of 50 or more amino acids are called proteins.

• Peptide bonds can be broken, or hydrolyzed, by enzymes called proteases.

Amino Acids, continuedAmino Acid Reactions


• Proteins are the most complex and varied class of biochemical molecules.

• A protein is an organic biological polymer that is made up of polypeptide chains of 50 or more amino acids and is an important building block of all cells.

• Proteins are made up of specific sequences of amino acids.

• They have molecular masses that range from 6000 to more than 9 million atomic mass units.

Proteins


• About 9000 different protein molecules are found in cells in the human body.


Visual Concept

Chapter 23

Proteins


• Nitrogen accounts for about 15% of the mass of a protein molecule. Most proteins also contain sulfur. Some contain phosphorus or other elements, such as iron, zinc, and copper.

• Proteins have many important catalytic, structural, regulatory, and antibody defense functions.

• Keratin is the main component of hair and fingernails.

• Enzymes catalyze biochemical reactions.

• Hemoglobin carries oxygen in the blood.

• Insulin regulates glucose levels.

• Antibodies protect the body from foreign substances.

Proteins, continued


• Each peptide, polypeptide, or protein is made up of a special sequence of amino acids.

• A simple set of three-letter abbreviations is used to represent each amino acid in these kinds of molecules.

• The tripeptide made up of valine, asparagine, and histidine would be written as Val–Asp–His.

• Polypeptide and protein function depend not only on the kinds and number of amino acids but also on their order.

Proteins, continuedArrangement of Amino Acids in Peptides and Proteins


• The properties of amino acids—and ultimately polypeptides and proteins—depend on the properties of the side chains present.

• The side chain of glutamic acid is acidic.

• The side chain of histidine is basic.

• The side chains of asparagine and several other amino acids are polar.

• Some amino acid side chains can form ionic or covalent bonds with other side chains.

Proteins, continuedAmino Acid Side-Chain Reactions


• Cysteine is a unique amino acid, because the —SH group in cysteine can form a covalent bond with another cysteine side chain to form a disulfide bridge.

Proteins, continuedAmino Acid Side-Chain Reactions, continued


• The interaction of amino acid side chains determines the shape and structure of proteins.

• These are important to the proteins’ biological functions.

• In a polypeptide chain or protein, the sequence of the amino acids is called the primary (1°) structure.

• The secondary (2°) structure describes how the chain is coiled or otherwise arranged in space.

Proteins, continuedShape and Structure of Protein Molecules


• Secondary structures form because hydrogen bonding occurs between a hydrogen atom attached to the nitrogen atom in one peptide bond and the oxygen atom of another peptide bond farther down the backbone of the protein.

• The alpha (α) helix is a secondary structure that resembles a coiled spring.

• The beta (β) pleated sheet is a secondary structure that has accordion-like folds.

Proteins, continuedShape and Structure of Protein Molecules, continued


• A protein’s characteristic three-dimensional shape is called its tertiary (3°) structure.

• Side-chain interactions at various positions along the protein backbone cause the tertiary structure.

• The side-chain interactions can include

• hydrogen bonding

• salt bridges

• cysteine-cysteine disulfide bonds

• hydrophobic interactions between nonpolar side chains



• Nonpolar side groups tend to be found in the interior of the protein where contact with water is minimal.

• Polar and ionic side chains tend to be on the protein surface, where they are in contact with water.

• In some proteins, different polypeptides, each of which has its own 3° structure, come together.

• In the case of hemoglobin, four different polypeptides make up the quaternary (4°) structure.



Levels of Protein Structure


Proteins, continuedBiological Functions of Proteins


• Fibrous proteins are insoluble in water and are long, thin, and physically strong.

• Fibrous proteins give strength and protection to structures in living things.

• Keratin has a secondary structure is almost entirely alpha helical in shape.

• Collagen is a triple helix of three intertwined alpha helices. It found in bone and tendons.

• Fibrin found in silk has a beta-pleated sheet structure.

• Elastins in blood tissue, fibrins in blood clots, and myosins found in muscle tissue are other kinds of fibrous proteins.

Proteins, continuedBiological Functions of Proteins, continued


• Globular proteins are generally soluble in water and are twisted and folded into a globe-like shape.

• Globular proteins regulate body functions, catalyze reactions, and transport substances.

• Insulin is a small protein of 51 amino acids in two polypeptide chains.

• Myoglobin transports oxygen in the muscles.

• Hemoglobin transports oxygen in the blood.

• Casein, found in milk and used for food. It contains phosphorus, which is needed for bone growth.

Proteins, continuedBiological Functions of Proteins, continued


• A single substitution of one amino acid for another can change the shape and function of a protein.

• The genetic disease sickle cell anemia can happen when glutamic acid—is replaced by valine.

Proteins, continuedAmino Acid Substitution



Visual Concept

Chapter 23

Sickle Cell Anemia


Structures and Roles of Several Amino Acids


• An enzyme is a protein that catalyzes a biochemical reaction.

• Enzymes make up the largest and most highly specialized class of proteins.

• Most enzymes are water-soluble, globular proteins.

• The amino acid side chains and the three-dimensional shape of enzymes play a very important role in the enzymatic activity.

Proteins as Enzymes


• An enzyme also does not change the amount of product that is formed in a reaction; it only decreases the time it takes to form the product.

• Enzymes catalyze both decomposition and synthesis reactions.

• Enzymes are very efficient.

• A single molecule of carbonic anhydrase can break down 36 million carbonic acid molecules in 1 minute.

Proteins as Enzymes, continued


• Enzymes are very specific and often catalyze just a single reaction.

• Enzymes act by binding to a specific substrate molecule.

• The shape of the enzyme is such that the substrate can fit into the enzyme at a specific part of the enzyme molecule, called the active site.

Proteins as Enzymes, continuedEnzyme Specificity


• The resulting compound is called the enzyme-substrate complex.

• This model of enzyme action is called the lock and key model.

Proteins as Enzymes, continuedEnzyme Specificity


Enzyme Mechanism



Visual Concept

Chapter 23

Enzyme


• The presence of an enzyme in a chemical reaction can increase the rate of a reaction by a factor of up to 1020.

• Only collisions that have enough energy to overcome the activation energy and have the proper orientation change reactants into products.

• Enzymes lower the activation energy by forming the enzyme-substrate complex, which makes breaking bonds in the reactants and forming new bonds in the products easier.

Proteins as Enzymes, continuedEnzymes and Reaction Rates


Activation Energy With and Without an Enzyme


• Enzymes typically have maximum activity within a relatively narrow range of temperatures.

• Enzymes in the human body work optimally at the normal body temperature of 37°C (98.6°F).

Proteins as Enzymes, continuedTemperature and Enzyme Activity


• High heat can denature, or alter, the shape of a protein, which in turn alters the protein’s function.

• Denaturation is a change in a protein’s characteristic three-dimensional shape due to changes of its secondary, tertiary, and quaternary structure.

• example: cooking an egg

Proteins as Enzymes, continuedTemperature and Enzyme Activity


• The optimal pH for normal cell enzyme functions is almost neutral, about 7.3 to 7.4.

• Changes in pH can cause changes in protein structure and shape.

• Most enzymes become inactivated, or no longer work, because of denaturation when the pH changes.

Proteins as Enzymes, continuedpH and Enzyme Activity


• Pre-enzymes, inactive forms of protein-digesting enzymes, become activated by the stomach’s low pH of 1.5 to 2.0. This prevents the active form of the enzymes from digesting the stomach lining.

Proteins as Enzymes, continuedpH and Enzyme Activity, continued


• Pepsin is a stomach enzyme found in adults.

Preview

• Lesson Starter• Objectives• ATP: Energy for the Cell• Energy Activities• Catabolism• Anabolism

Chapter 23 Section 3 Metabolism

Lesson Starter

• What do you think metabolism is?

• How does your body obtain energy?

• Metabolism consists of all chemical reactions that occur within an organism.

Section 3 MetabolismChapter 23

Objectives

• Describe the role of ATP in cells.

• Explain how energy is released by metabolic reactions.

• Summarize the relationship between anabolism and catabolism.


• Metabolism is the sum of all the chemical processes that occur in an organism.

• Complex molecules are broken down into smaller ones through catabolism.

• Simple molecules are used to build bigger ones through a process called anabolism.

• A metabolic pathway is a series of linked chemical reactions that occur within a cell and result in a specific product.


• Cells require energy to make the proteins, carbohydrates, lipids, and nucleic acids that are necessary for life.

• The original source for almost all of the energy needed by living systems is the sun.

• Autotrophs, such as plants and photosynthetic bacteria, use sunlight, water, and CO2 to make carbon-containing biomolecules.

• This process is called photosynthesis.

ATP: Energy for the Cell



Visual Concept

Chapter 23

Photosynthesis

Section 3 Metabolism

• Photosynthesis occurs in the cells of plants and algae, within structures called chloroplasts.

• Chloroplasts contain chlorophyll, an organic molecule that absorbs solar energy.

• This energy is captured immediately in the bonds of two compounds, one of which is adenosine triphosphate (ATP).

ATP: Energy for the Cell, continued



Visual Concept

Chapter 23

Chlorophyll a and b


• ATP is a high-energy molecule that plant cells use to make carbohydrates.

• The other compound, known as NADPH, is also used in carbohydrate-forming reactions.

• Living things, including most microorganisms, which depend on plants or other animals for food, are called heterotrophs.

• Heterotrophs use the energy obtained in the breakdown of complex molecules to drive chemical reactions in cells.

ATP: Energy for the Cell, continued



Visual Concept

Chapter 23

Linking Photosynthesis and Respiration


ATP/ADP Cycle


• The cycle between ATP and ADP, adenosine diphosphate, is the primary energy exchange mechanism in the body.

• ATP is the molecule that serves to carry energy from energy-storing molecules, carbohydrates, lipids, and proteins to specific energy-requiring processes in cells.

• When ATP is hydrolyzed to ADP, energy is released to power the cell’s activities.

Energy Activities



Chapter 23

Comparing ADP and ATP


Hydrolysis of ATP


• The energy that your body needs to maintain its temperature and drive its biochemical reactions is provided through catabolic processes.

• Catabolism is the part of metabolism in which complex compounds break down into simpler ones and is accompanied by the release of energy.

• First, enzymes break down the complex compounds in food—carbohydrates, fats, and proteins—into simpler molecules.

Catabolism


Catabolic Pathways


• Carbohydrate digestion begins in the mouth, where the enzyme amylase in saliva begins to break down polysaccharides.

• Carbohydrates are broken down intoglucose and other monosaccharides.

• Digestion of fats occurs only in the small intestine.

• Fats are broken down into fatty acids and glycerol.

• Protein digestion begins in the stomach and is completed in the small intestine.

• Proteins are broken down into amino acids.

Catabolism, continued


• Once in the cells, glucose and other monosaccharides, fatty acids, some amino acids, and glycerol enter the mitochondria and feed into a complex series of reactions called the citric acid cycle, or Krebs cycle.

• The citric acid cycle produces carbon dioxide and other molecules, such as NADH and ATP.

• This NADH and ATP then move through another set of reactions to produce more ATP and water.

Catabolism, continued



Visual Concept

Chapter 23

Energy Yield in Aerobic Respiration


• Cells use the simple molecules that result from the breakdown of food to make larger, more complex molecules.

• Anabolic processes are the energy-consuming pathways by which cells produce the molecules that they need for sustaining life and for growth and repair.

• The conversion of small biomolecules into larger ones is called anabolism.

Anabolism


• In an anabolic pathway, small precursor molecules are converted into complex molecules, including lipids, polysaccharides, proteins, and nucleic acids.

• Energy from ATP and NADH is necessary for these biosynthesis reactions to occur.

• Catabolism and anabolism occur simultaneously.

• ATP and NADH serve as chemical “links” between the two processes.

Anabolism, continued


• One important anabolic pathway that is common to animals, plants, fungi, and microorganisms is gluconeogenesis.

• Glucose is synthesized in this pathway from non-carbohydrate substances.

• In mammals, glucose from the blood is a fuel source.

Anabolism, continued



Chapter 23

Cellular Respiration


Preview

• Lesson Starter• Objectives• Nucleic Acid Structure• DNA: Deoxyribonucleic Acid• RNA: Ribonucleic Acid• Technology and Genetic Engineering

Chapter 23 Section 4 Nucleic Acids

Lesson Starter

• To understand how DNA replicates itself and passes genetic information to RNA to make proteins, it is important to understand hydrogen bonding.

• DNA does not duplicate itself by making an identical DNA molecule.

• It replicates by unfolding its two strands, which then pair up with complementary nucleotides.

• Each DNA molecule has one “new” strand and one “original” strand that are complementary.

Section 4 Nucleic AcidsChapter 23

Objectives

• Describe the role of ATP in cells.

• Explain how energy is released by metabolic reactions.

• Summarize the relationship between anabolism and catabolism.


• Nucleic acids contain all of the genetic information of an organism.

• They are the means by which a living organism stores and conveys instructional information for all of its activities.

• The two nucleic acids found in organisms are • deoxyribonucleic acid (DNA)

• ribonucleic acid (RNA)


• A nucleic acid is an organic compound, either RNA or DNA, whose molecules carry genetic information and is made up of one or two chains of monomer units called nucleotides.

• A nucleotide molecule is composed of a five-carbon sugar unit that is bonded to both a phosphate group and a cyclic organic base containing nitrogen.

phosphate–sugar–phosphate–sugar

base base

Nucleic Acid Structure



Visual Concept

Chapter 23

Nucleic Acid

Section 4 Nucleic Acids

• The sugar unit in DNA is deoxyribose.

• The sugar unit in RNA is ribose.

• The five nitrogenous bases found in nucleic acids are adenine (A), guanine (G), cytosine (C), thymine (T), and uracil (U)

• Adenine (A), guanine (G), and cytosine (C) are found in both DNA and RNA.

• Thymine (T) is found only in DNA.

• Uracil (U) is found only in RNA.

Nucleic Acid Structure



Visual Concept


Examples of Nucleotides

Nitrogenous Bases of Nucleic Acids


• Every single instruction for all of the traits that you have inherited and all of the life processes that occur in your cells is contained in your DNA.

• Human cells contain 46 relatively large DNA molecules.

• Each human cell contains about 2 m of DNA, which is divided and packed into the cell’s 46 chromosomes.

DNA: Deoxyribonucleic Acid




DNA Overview

• DNA is a double helix. In this structure, two strands of the sugar-phosphate backbone are wound around each other, and the nitrogenous bases point inward.

• The sequence of these nitrogenous bases along the phosphate-sugar backbone in DNA forms the code responsible for transferring genetic information.

• Hydrogen bonding between pairs of A—T (adenine-thymine) or G—C (guanine-cytosine) bases makes the double helix stable.

DNA: Deoxyribonucleic Acid, continued


Structure of DNA


• In the DNA double helix, base pairing exists only between A—T and between C—G.

• The interaction between base pairs accounts for the ability of DNA to replicate itself.

• Combinations of the four-letter alphabet of A,T,G, and C form the genes that define our heredity.

• Each gene is a section of DNA that contains a specific sequence of four bases (A,G,T, and C) and typically contains about 1000 to 2000 base pairs.

DNA: Deoxyribonucleic Acid, continuedNitrogenous Base Pairs


Hydrogen Bonding in DNA



Visual Concept

Chapter 23

Gene


• The two strands of the double helix of DNA are not identical.

• A base on one strand is paired through hydrogen bonding to its complementary base on the other strand.

• Each time a cell divides, an exact copy of the DNA of the parent cell is reproduced for the daughter cells.

• The process by which an identical copy of the original DNA is formed is called DNA replication.

DNA: Deoxyribonucleic Acid, continuedDNA Replication



Chapter 23

DNA Replication


DNA Replication




Ribonucleic Acid (RNA)

• Molecules of RNA make up about 5% to 10% of the mass of a cell.

• RNA molecules are responsible for the synthesis of proteins.

• RNA differs from DNA in four basic ways:

1. the sugar unit in the backbone of RNA is ribose rather than deoxyribose

2. RNA contains the base uracil, U, instead of thymine, which occurs in DNA

RNA: Ribonucleic Acid


3. RNA is a single-stranded molecule rather than a double-stranded helix like DNA

4. RNA molecules typically consist of 75 to a few thousand nucleotide units rather than the millions that exist in DNA.

• It is not uncommon for up to 50% of an RNA molecule to have a double-helix structure.

• The base sequences along the helical regions of the RNA strand are complementary.

RNA: Ribonucleic Acid, continued



Visual Concept

Chapter 23

Comparing DNA and RNA


• RNA is synthesized in the nucleus of the cell

• DNA and protein molecules actually help synthesize specific RNA molecules.

• As RNA is synthesized, the information contained in the DNA is transferred to the RNA molecules.

• The genetic information of RNA is carried in its nucleotide sequence.

RNA: Ribonucleic Acid, continuedSynthesis of RNA


• One type of RNA molecule is called messenger RNA (mRNA) because it carries the instructions for making proteins out into the cytosol, where proteins are produced on ribosomes.

• A ribosome is a cell organelle that is composed of RNA and protein. Ribosomes are the main site of protein production in cells.

RNA: Ribonucleic Acid, continuedSynthesis of RNA, continued


• The DNA template is also used to make two other types of RNA molecules: ribosomal RNA (rRNA) and transfer RNA (tRNA).

• Both of these types of RNA also leave the nucleus and come together in the ribosome where they help synthesize proteins.

• Ribosomal RNA becomes part of the structure of the ribosome.

• Transfer RNA is used to transfer amino acids into the ribosome.

• Only mRNA carries the coded genetic information that is translated into proteins.




Visual Concept

Chapter 23

Types of RNA


• The portion of DNA that holds the specific genetic code for a single, specific mRNA molecule is a gene.

• Each gene is typically a section of the DNA chain that contains about 1000 to 2000 nucleotides.

• A gene has the information necessary in this sequence to direct RNA to produce several proteins that have specific functions.



• At a gene, a portion of DNA unwinds and RNA is assembled using the same complementary base pairs as DNA except that uracil replaces the thymine

• As in DNA replication, the RNA sequence that forms has the complementary base pairs of the DNA gene.

DNA strand: C C C C A C C C T A C G G T G

RNA strand: G G G G U G G G A U G C C A C

RNA: Ribonucleic Acid, continuedRNA and Protein Synthesis


• A sequence of three bases in mRNA codes for a specific amino acid.

• The sequence CAG codes for glutamic acid.

• The sequence GUC codes for valine.

• There are 64 (43) unique combinations of three-base sequences made from four bases.

• Because only 20 amino acids require codes, some of the amino acids have more than one code.



• The genetic code is universal.

• The “stop” signal in the gene is also a three-base code: UAG, UAA, or UGA.




Chapter 23

Genetic Code


Using the Genetic Code


• Scientists in the field of genetic engineering study how manipulation of an organism’s genetic material can modify the proteins that are produced and the changes that result in the organism.

• Today genetic engineering refers to recombinant DNA technology that is used for cloning and the creation of new forms of life.

Technology and Genetic Engineering



Visual Concept

Chapter 23

Genetic Engineering


• DNA is unique to an individual except for identical twins.

• This technology is used in criminal investigations, paternity testing, and victim identification.

• The technique of the polymerase chain reaction (PCR) may be used to copy a DNA sample to supply sufficient DNA for identification.

Technology and Genetic Engineering, continuedDNA Fingerprinting



Visual Concept

Chapter 23

DNA Fingerprint



Visual Concept

Chapter 23

Making a DNA Fingerprint



Visual Concept

Chapter 23

Polymerase Chain Reaction


• Cloning is the process of making an exact copy of an organism.

• Artificial cloning, using stem cells from animals or meristem cells from plants, can produce identical replicas of the parent cells or, under specialized conditions, a complete organism that is identical to the original organism.

Technology and Genetic Engineering, continuedCloning



Visual Concept

Chapter 23

Cloning


• Recombinant DNA technology has been used to insert DNA from one organism into another.

• The technique splices a gene from one organism’s DNA into a molecule of DNA from another organism.

• When the spliced DNA is inserted into a cell, the cell is able to make the protein that is coded by the spliced gene.

Technology and Genetic Engineering, continuedRecombinant DNA Technology



Visual Concept

Chapter 23

Using Plasmids to Produce Insulin


End of Chapter 23 Show

preview lesson starter objectives carbohydrates lipids chapter 23

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