Biochemistry Exam 3 Flashcards
What are:
- Soluble in organic solvents (ether, chloroform)
- Serve multiple purposes in the body like storing energy, protecting, insulating internal organs, and act as chemical messengers
- Important feature in cell membranes, fat-soluble vitamins, and steroid hormones
- Lipids
What are esters that can be hydrolyzed to give fatty acids and other molecules?
Lipids such as:
- waxes,
- triacylglycerols,
- glycerophospholipids
- sphingolipids
_______ and ______ contain the alcohol glycerol.
-Triacylglycerols and glycerophospholipids
What contains the amino alcohol sphingosine?
- Sphingolipids
What can not be hydrolyzed and doesn’t contain fatty acids?
- Steriods
What contain a fused four-membered ring system?
- Steriods
What contain long carbon chains and carboxyli groups?
- Fatty acids
______ long, unbranched carbon chains with a carboxylic acid group at the end. Typically 12–18 carbon atoms long and insoluble in water because of the long carbon chain.
- Fatty acids
Fatty acids are _______ when they do not contain C = C double bonds in the carbon chain.
- Saturated ( Has properties similar to an alkane)
Fatty acids are ______ when they contain C = C double bonds in the carbon chain.
- Unsaturated
Fatty acids can be ______, with only one double C = C bond in the carbon chain.
- Monounsaturated ( Has properties similar to an alkene)
Is the carboxylic acid part of the fatty acid hydrophobic or hydrophilic?
- Hydrophilic
What makes fatty acids insoluble in water?
- Long Hydrophobic carbon chain
Fatty acids can be ______, with at least two double C = C bonds in the carbon chain
- Polyunsaturated
What requires a significant amount of energy and high temperatures to separate and melt?
- Saturated Fatty acids, because the contain only single carbon bonds that fit closely together in a regular pattern, with strong dispersion forces between carbon. cahins.
True or False almost all naturally occurring unsaturated fatty acids have one or more cis double bonds?
-True
If interactions between molecules are reduced by irregular molecule shape due to cis bonds, what will happen?
- The reduced interactions in fatty acids with cis bonds reduce the melting point of the molecules.
_______ cannot synthesize sufficient amounts of polyunsaturated fatty acids such as linoleic acid, linolenic acid, and arachidonic acid.
- Humans
What Fatty acids are normally solids at room temperature?
- Saturated Fatty Acids
Fatty acids such as linoleic acid, linolenic acid, and arachidonic acid are knowen as _____.
- Essential Fatty Acids, because they must be obtained from the diet.
______ are also known as eicosanoids, formed from arachidonic acid, a polyunsaturated fatty acid with 20 carbon atoms.
- Prostaglandins
______ have many functions, such as lowering or raising blood pressure and stimulating contraction and relaxation of the smooth muscle of the uterus.
- Prostaglandins
Prostaglandin E (PGE) has a _____ group on carbon 9
- ketone
Prostaglandin F (PGF) has a _____ group on carbon 9
- hydroxyl
When tissues are injured, _______ is converted to prostaglandins that produce inflammation and pain in the area.
- arachidonic acid
_____ are hormone-like substances produced in small amounts in most cells.
- Prostaglandins
What essential fatty acid (EFA) is the precursor of arachidonic acid, the polyunsaturated fatty acid with 20 carbon atoms?
- Linoleic
True or False prostaglandins are broken down quickly?
- True
_____ block production of prostaglandins, decreasing pain and inflammation.
- Nonsteroidal anti-inflammatory drugs (NSAIDs)
____ such as those in vegetable oils and fish are recognized as more beneficial to health than saturated fats.
- Unsaturated fats
______ is an ester of a long-chain fatty acid and a long chain alcohol, each containing from 14 to 30 carbon atoms.
- A wax
How are fatty acids stored in the body?
- As triacylglycerols (triglycerides)
How are triacylglycerols formed and how are they named?
- esters of glycerol, a trihydroxy alcohol, and fatty acids.
- formed when three hydroxyl groups of glycerol react with the carboxyl groups of three fatty acids.
- named by changing glycerol to glyceryl and naming the fatty acids as carboxylates.
True or False: Triacylglycerol may contain different fatty acids, such as the triacylglycerol made from stearic, oleic, and palmitic acids.
- True
______ have low melting points because they have a higher percentage of unsaturated fatty acids than do animal fats.
- Vegetable oils
This happens double bonds in unsaturated fatty acids react with hydrogen gas to produce carbon–carbon single bonds.
- Hydrogenation reaction, hydrogen gas is bubbled through the heated oil typically in the presence of a nickel catalyst.
What process causes:
- the addition of hydrogen is stopped before all the double bonds in a liquid vegetable oil become completely saturated.
- the partial hydrogenation of a liquid vegetable oil changes it to a soft, semisolid fat.
- the more saturated product has a higher melting point.
- Commerical hydrogenation
How are triacylglycerols hydrolyzed (split by water)?
- In the presence of strong acids such as HCl or H2SO4, or digestive enzymes called lipases.
_____ is the reaction of a fat with a strong base such as NaOH in the presence of heat.
- Saponification (forming soaps “salts of fatty acids”)
_____ are a family of lipids similar in structure to triacylglycerols; they include glycerophospholipids
and sphingomyelin.
- Phospholipids
What contains two fatty acids that form ester bonds with the first and second hydroxyl groups of glycerol and
a hydroxyl group that forms an ester with phosphoric acid, which forms another phosphoester bond with an amino alcohol?
- Glycerophospholipids
What contains sphingosine instead of glycerol and a fatty acid, phosphate, and an amino alcohol.
- Sphingomyelin
What amino alcohols are found in glycerophospholipids?
- choline, serine, and ethanolamine and they are ionized at physiological pH of 7.4.
What are two types of glycerophospholipids that are
abundant in brain and nerve tissues and found in egg yolk, wheat germ, and yeast?
- Lecithin and Cephalin
What contains both polar and nonpolar regions that allow them to interact with polar and nonpolar substances. They have a polar head containing the ionized amino alcohol and phosphate portion, which is strongly attracted to water. They also have a nonpolar hydrocarbon tail portion soluble only in nonpolar substances such as lipids.
- Glycerphospholipids
What are abundant in the white matter of the myelin sheath?
- Sphingomyelin
What is found in sphingolipids and sphingomyelin?
- Sphingosine
True or false sphingosine is along chain of amino alcohol?
- True
- sphingosine, a long-chain amino alcohol that replaces glycerol.
- an amide bond formed by the amine group on sphingosine to a fatty acid.
- a hydroxyl group that forms an ester bond with phosphate, which forms another phosphoester bond to choline or ethanolamine.
- Sphingomyelin
In multiple sclerosis what is lost from the myelin sheath, which protects the neurons in the brain and spinal cord?
- Sphingomyelins
_____, the 16-carbon saturated fatty acid, is the most common fatty acid found along with the ionized amino alcohol choline in the sphingomyelin of eggs.
- Palmitic acid
All steroids contain a _____, which consists of
three cyclohexane rings and one cylopentane ring, fused together.
- rings designated as A, B, C, and D.
- numbered carbon atoms beginning in ring A.
- two methyl groups at positions 18 and 19.
- steroid nucleus
Where is cholesterol obtained from?
- meats, milk, and eggs
Where is cholesterol synthesized at?
- liver
_______ is needed for cell membranes, brain and nerve tissue, steroid hormones, and vitamin D.
- Cholesterol
What helps with the absorption of cholesterol?
- Bile salts
Where are bile salts synthesized and stored?
- Synthesized in the liver and stored in the gallbladder
What happens when large amounts of cholesterol accumulate in the gallbladder?
- Gallstones are formed
Lipids are nonpolar and are made more soluble by combining them with glycerophospholipids and proteins to form water-soluble complexes called _______.
- Lipoproteins
______ differ in density, composition, and function.
- Lipoproteins (HDL / LDL)
_____ are chemical messengers that serve as a communication system for the body and are produced from cholesterol.
- Steroid hormones
What do mineralocorticoids help balance?
What do glucocorticoids help regulate?
- Electrolyte balance
- Regulation of glucose level
Where are adrenal corticosteroids produced?
- are produced by the adrenal glands located on the top of each kidney.
What adrenal corticosteroid helps regulate electrolytes and water balance by the kidneys?
- aldosterone
What adrenal corticosteroid helps
- glucocorticoid, which increases blood glucose level and stimulates the synthesis of glycogen in the liver.
Why is cholesterol a sterol?
- because is contains an oxygen atom as a hydroxyl group on carbon 3.
How are lipids made more soluble, allowing them to be transported through the bloodstream to the tissues?
- They are combined with phospholipids and proteins forming lipoproteins.
True or False: Most lipids are nonpolar and insoluble in the aqueous environment of blood?
- True
How are Cholesteryl ester formed?
- Esterification of the hydroxyl group in cholesterol with a fatty acid.
Where does LDL (bad) carry cholesterol?
- Deposits cholesterol in the arteries (plaque)
Where does HDL (good) carry cholesterol?
- Liver where it is converted to bile salts
What are derivatives of ammonia, NH3, in which one or more hydrogen atoms are replaced with alkyl or aromatic groups and contain N attached to one or more alkyl or aromatic groups?
- Amines
In the IUPAC names for amines, the e in the corresponding alkane name is replaced with ____.
- amine
_____ with a chain of three or more carbon atoms are numbered to show the position of the —NH2 group and any other substituents.
- Amines
If there is an alkyl group attached to the nitrogen atom, the prefix N and the alkyl name are placed in front of the amine name.
If there are two alkyl groups bonded to the N atom, the prefix N is used for each, and they are listed alphabetically.
- Naming Amines
Common names are often used when alkyl groups are not branched.
- List the names of the alkyl groups bonded to the N atom in alphabetical order in front of amine.
- Use prefixes di and tri to identify duplicate alkyl substituents.
- Common names for Amines
The amine of benzene is named ____ by IUPAC.
- Aniline
A _____ amine has one carbon group bonded to the nitrogen atom.
- primary (1°)
A _____ amine has two carbon groups bonded to the nitrogen atom
- secondary (2°)
A _____ amine has three carbon groups bonded to the nitrogen atom.
- tertiary (3°)
____ contain polar N—H bonds, which allow primary and secondary amines to form hydrogen bonds with each other, while all amines can form hydrogen bonds with water.
- Amines
_______ can only form hydrogen bonds with water molecules.
- Tertiary amines
______ is not as electronegative as oxygen, so hydrogen bonds in amines are weaker than the hydrogen bonds in alcohols.
- Nitrogen
_____ have boiling points that are higher than those of alkanes but lower than those of alcohols.
- Amines
_____ amines can form more hydrogen bonds and have higher boiling points than secondary (2°) amines of the same mass.
- Primary (1°)
amines cannot form hydrogen bonds with each other and have lower boiling points than primary or secondary amines of the same mass.
- Tertiary (3°)
Amines with _____ carbon atoms, including tertiary amines, are soluble in water.
- one to six
As the number of _____ in an amine increases in the nonpolar alkyl portions, the effect of hydrogen bonding is diminished.
- carbon atoms
In a neutralization reaction,
- an amine acts as a base and reacts with an ____ to form an ammonium salt.
- the lone pair of electrons on the_____ accepts H+ from an acid to give an ammonium salt; no water is formed.
- acid
- nitrogen atom
An ______ is named by using its alkylammonium ion name followed by the name of the negative ion.
- ammonium salt
In a quaternary ammonium salt,
- a nitrogen atom is bonded to _____, which classifies it as a quaternary (4°) amine.
- the nitrogen atom has a ______ and is not bonded to an H atom.
- four carbon groups
- positive charge
What are ionic compounds with strong attractions between the positively charged ammonium ion and an anion, usually chloride?
- solids at room temperature, odorless, and soluble in water and body fluids.
- Ammonium Salts
A ______ is a cyclic organic compound that consists of a ring of five or six atoms, of which one or two are nitrogen atoms. `
- heterocyclic amine
_____ is a five-atom ring with one nitrogen atom and two double bonds
- Pyrrole
____ which is a ring of four carbon atoms and one nitrogen atom, all with single bonds.
- pyrrolidine
____ is a five-atom ring that contains two nitrogen atoms.
- imidazole
_____ responsible for the pungent aroma and taste of black pepper, is a six-atom heterocyclic ring with a nitrogen atom.
- piperidine
_______ are physiologically active compounds produced by plants that contain heterocyclic amines and are used in anesthetics, in antidepressants, and as stimulants, and many are habit forming.
- Alkaloids
Morphine and codeine are?
- alkaloids obtained from the oriental poppy plant.
- used as painkillers and in cough syrups.
Within a nerve cell, _____ are synthesized and stored in vesicles at the end of the axon terminal.
- neurotransmitters
A _____ is a chemical compound that transmits an impulse from a nerve cell to a target cell. Target cells may be another nerve cell, a muscle cell, or a gland cell.
- neurotransmitter
Neurotransmitters can be removed from the receptors in different ways:
- The neurotransmitter diffuses away from the synapse.
- Enzymes in the receptors break down the neurotransmitter.
- Reuptake returns the neurotransmitter to the vesicles, where it is stored.
_____ contain nitrogen atoms as amines and alkylammonium ions
- they are synthesized from compounds such as amino acids obtained from our diets.
- their amino groups are usually ionized, forming ammonium cations and carboxylate anions.
- Neurotransmitters
_______ communicates between the nervous system and the muscle.
- regulates muscle activation as well as learning and short-term memory.
- is synthesized by forming an ester between choline and acetate and is stored in the vesicles.
- is released into the synapse, where it binds to receptors on the muscle cells and causes the muscles to contract.
- Acetylcholine
The loss of the ______ at the receptors causes muscle cells to relax.
- acetylcholine
- dopamine, norepinephrine, and epinephrine.
closely related in structure. - synthesized from the amino acid tyrosine found in meats, nuts, eggs, and cheese.
- The most important catecholamine neurotransmitters
What are synthetic central nervous system stimulants that increase excitatory catecholamine neurotransmitters, particularly dopamine and norepinephrine?
- Amphetamine and methamphetamine
The neurotransmitters dopamine, norepinephrine, and epinephrine are synthesized from what?
- the amino acid tyrosine after it is converted to L-dopa.
_____ is used to increase dopamine levels in the brain. Parkinson’s disease causes the midbrain nerve cells to lose their ability to produce dopamine.
- L-Dopa
______ is synthesized from the amino acid tryptophan, which can cross the blood-brain barrier.
- Serotonin
what is synthesized in nerve cells in the hypothalamus from the amino acid histidine and produced by the immune system in response to pathogens and invaders or injury?
- Histamine
What is the most abundant neurotransmitter in the nervous system and is used to stimulate over 90% of the synapses?
- Glutamate
When glutamate binds to its receptor cells, it stimulates the synthesis of ______, also a neurotransmitter in the brain.
- nitrogen oxide (NO)
_____ and NO are thought to be involved in learning and memory.
- Glutamate
In Lou Gehrig’s disease (ALS), production of an excessive amount of _____ causes the degeneration of nerve cells in the spinal cord
- glutamate
What is produced from glutamate and is the most common inhibitory neurotransmitter in the brain?
It reduces anxiety by inhibiting the ability of nerve cells to send electrical signals to nearby nerve cells and is involved in the regulation of muscle tone, sleep, and anxiety.
- Gamma(γ)-aminobutyric acid (GABA)
Alcohol, sedatives, and tranquilizers increase the inhibitory effects of GABA. ____ decreases the GABA levels in the synapses, leading to conditions of anxiety and sleep problems.
- Caffeine
What are derivatives of carboxylic acids in which a nitrogen group (—NH2) of a primary or secondary amine replaces the hydroxyl (—OH) group of carboxylic acids?
- Amides
What is produced in a reaction called amidation or condensation?
This happens when a carboxylic acid reacts with ammonia or a primary or secondary amine and heat.
- Amides
Amide production is accompanied by the production of water.
In both the common and IUPAC names, amides are named by dropping _________ from the carboxylic acid name and adding the suffix amide.
- the oic acid (IUPAC) or ic acid (common)
Alkyl groups attached to the nitrogen of an amide are named with the prefix N followed by the ______.
- alkyl name
Only ______ is a liquid at room temperature, while other amides are solids.
- methanamide
_____ amides have the highest melting points because the —NH2 group can form the most hydrogen bonds.
- primary (1°)
What can form hydrogen bonds with the –NH2 group of other amides?
What form hydrogen bonds with water molecules making them soluble in water as long as they have less than five carbons?
- Primary (1°) amides
What have lower melting points than primay amides because they form fewer hydrogen bonds with other amides?
What forms hydrogen bonds with water molecules, making them soluble in water as long as they have fewer than five carbons?
- Secondary (2°) amides
What have the lowest melting points out of the amides because they form the fewest hydrogen bonds and can only form one hydrogen bond with H2O?
- Tertiary (3°) amides
What is the simplest natural amide and is the end product of protein metabolism in the body?
- excreted in the urine.
- Urea
What in the body are polymers made from 20 different amino acids, differ in characteristics and functions, form structural components such as cartilage, muscles, hair, and nails?
- Proteins
What molecular building blocks of proteins, have a central carbon atom called the α carbon, bonded to
two functional groups: an ammonium group (—NH3+) and a carboxylate group (—COO−) and a hydrogen atom with an R group or side chain in addition to the carboxylate and ammonium groups?
- Amino acids
What amino acids have hydrogen, alkyl, or aromatic R groups?
- nonpolar (hydrophobic)
What amino acids have R groups that interact with water, which makes them hydrophilic?
- polar
What amino acids contain hydroxyl (—OH), thiol (—SH), or amide (—CONH2) R groups?
- polar neutral
What amino acids contain a carboxylate (—COO−) R group?
- polar acidic
What amino acids contain an ammonium (—NH3+) R group?
- polar basic
An amino acid is _____ when the R group is H, alkyl, or aromatic.
- nonpolar
An amino acid is ______ when the R group is an alcohol, a thiol, or an amide.
- polar
An amino acid is ____ when the R group is a carboxylate (—COO−) group.
- polar acidic
An amino acid is _____ when the R group is an ammonium (—NH3+) group.
- polar basic
A _____ is an amide bond that forms when the —COO− group of one amino acid reacts with the —NH3+ group of the next amino acid.
- peptide bond
What is characterized by a high concentration of cystine in the urine?
- Cystinuira
______ is an amide bond that forms between the —COO− group of one amino acid and the —NH3+ group of the next amino acid.
- Peptide bond
______ begins with the name of the N-terminal amino acid residue.
- gives all the following amino acid residues up to the C-terminal amino acid in which the ine or ate endings are replaced with yl.
- retains the complete name of the C-terminal amino acid.
A tripeptide consisting of alanine, glycine, and serine residues is named as alanylglycylserine
- Naming a Peptide
A _______ is a polypeptide of 50 or more amino acids with biological activity.
The primary structure of a ____ is the particular sequence of amino acids held together by peptide bonds.
- protein
______ such as eggs, milk, meat, and fish contain all of the essential amino acids.
- Complete proteins
_____ from plants such as grains, beans, and nuts are deficient in one or more essential amino acids.
- Incomplete proteins
The ______ of a protein describes the structure that forms when amino acids form hydrogen bonds between the atoms in the backbone and atoms on the same or another peptide chain.
- secondary structure
Two common types include alpha helix and beta-pleated sheet.
In the secondary structure of a ______, hydrogen bonds form between the carbonyl oxygen atoms and hydrogen atoms in the amide groups bending the polypeptide chain into a sheet.
- beta-pleated sheet (β-pleated sheet)
In the secondary structure of a ______,
three polypeptide chains are woven together.
hydrogen bonds hold the chains together, giving the polypeptide the added strength typical of collagen, connective tissue, skin, tendons, and cartilage.
- triple helix
- hydrogen bonds form between the oxygen of the C O groups and the hydrogen of N—H groups of the amide bonds in the next turn of the α helix.
- the formation of many hydrogen bonds along the polypeptide chain gives the helical shape of a spiral staircase.
- In the secondary structure of an alpha helix
In patients with____ , beta-amyloid proteins change from (a) a normal alpha-helical shape to (b) beta-pleated sheets that stick together and form plaques in the brain.
- Alzheimer’s disease
The _____ of a protein is an overall three-dimensional shape formed by the interactions and repulsions of amino acid residues in different parts of the chain.
- tertiary structure
_____ occur between two amino acids that have nonpolar R groups, forming a nonpolar center at the interior of the protein. The amino acids with nonpolar Rgroups are pushed away from the aqueous environment to form a hydrophobic center at the interior of the protein molecule.
- Hydrophobic interactions
_______ interactions occur between the external aqueous environment and the R groups of polar amino acid residues that are pulled to the outer surface of most proteins.
- Hydrophilic
_____ are ionic attractions between ionized Rgroups of polar basic and polar acidic amino acids.
- Salt bridges
_______ form between the H of a polar Rgroup and the O or N of another polar amino acid.
- Hydrogen bonds
_______ are covalent bonds that form between the —SH groups of cysteine residues in a polypeptide chain.
- Disulfide bonds (—S—S—)
Biologically active proteins with ______ chains or subunits have a quaternary structure.
- two or more polypeptide
Peptide bonds are broken through ____ reactions.
- Hydrolysis
_______ occurs in the stomach when enzymes catalyze the hydrolysis of proteins to give amino acids.
- breaks up the primary structure by breaking the covalent peptide bonds that link the amino acids.
- Hydrolysis
occurs when a change _____ disrupts the interactions among residues that stabilize the secondary, tertiary, or quaternary structures and
does not affect the amide bonds among amino acids.
- Denaturation of a protein
The loss of secondary and tertiary structures in a protein occurs when conditions change, such as
- increasing the temperature.
- making the pH very acidic or basic.
- adding certain organic compounds or heavy metal ions.
- adding mechanical agitation.
When the interactions among the residues are disrupted, a globular protein unfolds. the tertiary structure is disrupted and the protein is no longer biologically active.
Proteins are denatured when heated above ____. The heat disrupts the hydrogen bonds and hydrophobic interactions among nonpolar residues.
It does not change the nutritional value of proteins but make them more digestible.
- 50°C
Proteins can be denatured by changing the _____ , which
breaks hydrogen bonds and disrupts ionic bonds and salt bridges.
- pH
_______ such as ethanol and isopropyl alcohol act as disinfectants by
exchanging the bacterial protein’s hydrogen bonds to water with their own.
disrupting the side chain intramolecular hydrogen bonding.
- Organic compounds
Heavy metal ions such as Ag+, Pb2+, and Hg2+ _____ by forming bonds with ionic residues or reacting with disulfide —S—S— bonds.
- denature proteins
______ are biological catalysts that
increase the rate of a reaction by changing the way a reaction takes place.
- are not changed in the process of the reaction.
- lower the activation energy of the reaction.
- Enzymes
_____ are globular proteins with a unique three-dimensional shape that recognizes and binds a small group of reacting molecules, called substrates.
- Nearly all enzymes
_______ have a tertiary structure that includes a region called the active site where one or more small groups of substrates bind to create a chemical reaction.
- Nearly all enzymes
_____ have specific amino acid residues within the active site that interact with functional groups of the substrate to form hydrogen bonds, salt bridges, and hydrophobic interactions.
- Nearly all enzymes
The __ provides an alternative pathway for the reaction with lower activation energy.
- Enzyme - substrate (ES) complex
Within the active site, amino acid R groups catalyze the reaction to form an _____.
- enzyme–product (EP) complex
A ____ model has a rigid substrate binding to a rigid enzyme, much like a key fitting into a lock.
- lock-and-key
The _____, a more dynamic model of enzyme action, states that the active site is flexible enough to adapt to the shape of the substrate.
- induced-fit model
The induced-fit model has the substrate and enzyme working together to acquire a geometrical arrangement that lowers the activation energy.
- usually ends in ase.
- identifies the reacting substance; for example, sucrase catalyzes the reaction of sucrose.
- describes the function of the enzyme; for example, oxidases catalyze oxidation.
- can be a common name, particularly for the digestive enzymes, such as pepsin and trypsin.
- The name of an enzyme
- are most active at an optimum temperature (usually 37°C in humans).
- show little activity at low temperatures.
- lose activity at high temperatures as denaturation occurs.
- Enzymes
- are most active at optimum pH, where proper tertiary structure of the protein is maintained.
- contain amino acid R groups with proper charges at optimum pH.
- lose activity in low or high pH as tertiary structure is disrupted.
- Enzymes
- increases the rate of reaction (at constant substrate concentration).
binds more substrate with enzyme.
- An increase in enzyme concentration
- increases the rate of reaction (at constant enzyme concentration).
- eventually saturates an enzyme with substrate to give maximum activity.
- An increase in substrate
concentration
______ is a type of covalent modification that activates or deactivates an enzyme.
- Phosphorylation
Enzyme activity can be regulated by ______, feedback control, and covalent modifications.
- allosteric enzymes
- change the shape of the enzyme, which causes a change in the shape of the active site.
- can be a positive regulator that changes the shape of the active site to allow the substrate to bind more effectively.
- can be a negative regulator that changes the shape of the active site to prevent the proper binding of the substrate, which decreases the rate of the catalyzed reaction.
- Allosteric enzymes
In feedback control, when the end product level is high?
- the end product of a series of reactions acts as a negative regulator and binds to the allosteric site.
- the substrate cannot bind to the active site, and production of all of the intermediate compounds in the subsequent reaction sequence stops.
Is covalent modification reversible?
- Yes
____ such as the proteases trypsinogen and chymotrypsinogen are stored in the pancreas until after food is ingested.
- are released when triggered by hormones from the pancreas.
- Zymogens
Once a ______ is formed, it is transported to where the active form is needed.
- converted to its active form by a covalent modification.
- zymogen
- digestive enzymes; protein hormones, such as insulin; and blood clotting enzymes.
- proteases, or digestive enzymes that hydrolyze protein, produced as larger, inactive forms.
- Zymogens include
_____ is a type of covalent modification through which an enzyme is deactivated or activated.
- Phosphorylation
Enzyme activity is modified by ____ to a group on the polypeptide chain that are formed or broken.
- covalent bonds
Covalent modification is another way in which enzymes are modified.
_____ are different forms of an enzyme that catalyze the same reaction in different cells or tissues of the body.
- Isoenzymes
- are molecules that – cause a loss of catalytic activity.
- prevent substrates from fitting into the active sites.
- can be classified as either reversible inhibitors or irreversible inhibitors.
- Inhibitors
- cause a loss of enzyme activity that can be restored.
- can act in different ways but do not form covalent bonds with the enzyme.
- Reversible Inhibitors
Reversible inhibition can be competitive or noncompetitive.
- has a chemical structure and polarity similar to the substrate.
- competes with the substrate for the active site.
- has its effect reversed by increasing substrate concentration.
- A competitive inhibitor
Some bacterial infections are treated with competitive inhibitors called _____-.
- antimetabolites
Sulfanilamide competes with p-aminobenzoic acid (PABA), an essential metabolite in the growth cycle of bacteria.
- has a structure that is much different from that of the substrate.
- does not compete for the active site.
- distorts the shape of the enzyme, which prevents the binding of the substrate at the active site.
- cannot have its effect reversed by adding more substrate.
- A noncompetitive inhibito
In irreversible inhibition, enzyme activity is destroyed when
- the inhibitor covalently bonds with R groups of an amino acid that may be near the active site.
- the inhibitor changes the shape of the enzyme, which prevents the substrate from entering the active site.
A _____ is an active enzyme that consists only of protein.
- simple enzyme
Many enzymes are active only when they combine with _____ such as metal ions or small molecules.
- cofactors
A _____ is a cofactor that is a small organic molecule such as a vitamin.
- coenzyme
- are soluble in aqueous solutions and cannot be stored in the body.
- are cofactors for many enzymes.
are excreted in urine each day. - are easily destroyed by heat, oxygen, and ultraviolet light, so care must be taken in food preparation.
- Water-soluble vitamins must come from our food each day; they
Many of the ____ are precursors of cofactors required by many enzymes to carry out certain aspects of catalytic action.
- water-soluble vitamins
_______ is necessary to avoid beriberi, whose symptoms are fatigue, poor appetite, and weight loss.
- Thiamine,
associated with coenzyme thiamine pyrophosphate (TPP),
is found in the liver, yeast, whole grain bread, cereals, and milk.
has an RDA of 1.2 mg.
_____ is necessary to avoid dermatitis; dry skin; red, sore tongue; and cataracts.
-Riboflavin,
associated with coenzymes flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN), is found in the liver, beef, chicken, eggs, green leafy vegetables, dairy foods, peanuts, and whole grains.
has an RDA of 1.2–1.8 mg.
______ is necessary to avoid pellagra: dermatitis, muscle fatigue, loss of appetite, diarrhea, and mouth sores
- Niacin,
associated with coenzymes nicotinamide adenine dinucleotide (NAD2+) and nicotinamide adenine dinucleotide phosphate (NADP2+), is found in brewer’s yeast, chicken, beef, fish, liver, brown rice, and whole grains.
has an RDA of 14–18 mg.
______ is necessary to avoid fatigue, retarded growth, muscle cramps, and anemia.
Pantothenic acid, associated with coenzyme A,
is found in salmon, beef, liver, eggs, brewer’s yeast, whole grains, and fresh vegetables.
has an RDA of 5 mg.
_____ is necessary to avoid dermatitis, fatigue, anemia, and retarded growth.
Pyridoxine, associated with pyridoxal phosphate (PLP),
is found in meat, liver, fish, nuts, whole grains, and spinach.
has an RDA of 1.3–2.0 mg.
____ is necessary to avoid abnormal red blood cells, anemia, intestinal tract disturbances, loss of hair, growth impairment, and depression.
Folic acid, associated with tetrahydrofolate (THF),
is found in green leafy vegetables, beans, meat, seafood, yeast, asparagus, and whole grains enriched with folic acid.
has an RDA of 400 mcg.
_____ is necessary to avoid pernicious anemia, malformed red blood cells, and nerve damage.
Cobalamin, associated with methylcobalamin,
is found in liver, beef, kidney, chicken, fish, and milk products.
has an RDA of 2.0–2.6 mcg.
_____ is necessary to avoid scurvy: bleeding gums, weakened connective tissues, slow-healing wounds, and anemia.
Ascorbic acid
is found in blueberries, citrus fruits, strawberries, cantaloupe, tomatoes, peppers, broccoli, cabbage, and spinach.
has an RDA of 75–90 mg.
_____ is necessary to avoid dermatitis, loss of hair, fatigue, anemia, and depression.
Biotin, associated with biocytin,
is found in liver, yeast, nuts, and eggs.
has an RDA of 30 mcg.
- include A, D, E, and K and are not involved as coenzymes in catalytic reactions.
- are soluble in lipids but not in aqueous solutions.
are stored in the body and not eliminated in urine. - are important in vision, bone formation, antioxidants, and blood clotting.
- Fat-soluble vitamins
___ is needed for retinol (vision) and synthesis of RNA.
has an RDA of 800 g.
is necessary to avoid night blindness, immune system repression, and slowed growth.
- Vitamin A, an antioxidant
_____ is synthesized in skin exposed to sunlight.
regulates the absorption of phosphorus and calcium during bone growth.
has an RDA of 5–10 μg.
is necessary to avoid weakened bones.
- Vitamin D (D3)
_____ is an antioxidant in cells.
is found in whole grains and vegetables.
has an RDA of 15 mg.
is necessary to avoid hemolysis and anemia.
- Vitamin E
_____ is needed for the synthesis of zymogens for blood clotting.
has an RDA of 90–120 mcg.
is necessary to avoid prolonged bleeding time and bruising.
- Vitamin K
Each nucleotide has three components:
- a base that contains nitrogen.
- a five-carbon sugar.
- a phosphate group.
- derivatives of the heterocyclic amines pyrimidine or purine.
- pyrimidines with a single ring containing two nitrogen atoms.
- purines with two rings, each containing two nitrogen atoms.
H+ acceptors at the nitrogen atoms in each base.
- The bases in DNA and RNA are
In DNA,
the purine bases with double rings are adenine _____.
the pyrimidine bases with single rings are cytosine _______.
- (A) and guanine (G).
- (C) and thymine (T)
In RNA,
the purine bases with double rings are adenine (A) and guanine (G).
the pyrimidine bases with single rings are cytosine _______.
- (C) and uracil (U)
____ is composed of a nitrogen-containing base and a sugar, either ribose or deoxyribose.
____ has a base linked by a β-N-glycosidic bond to C1′ of a sugar (ribose or deoxyribose).
- A nucleoside
The addition of a phosphate to a nucleoside forms a _____.
- nucleotide
The name of a nucleoside that contains a purine ends with _____.
The name of a nucleoside that contains a pyrimidine ends with _____ .
The names of DNA nucleosides add ___ to the beginning of their names.
The corresponding nucleotides in RNA and DNA are named by adding monophosphate to the end of the nucleoside name.
- osine
- idine
- deoxy
-
- the nucleotides are joined by phosphodiester bonds.
- the 3ʹ —OH group of the sugar in one nucleotide bonds to the phosphate group on the 5ʹ carbon atom in the sugar of the next nucleotide.
- In the primary structure of nucleic acids
In the primary structure of RNA, A, C, G, and U are connected by _____.
- 3ʹ,5ʹ phosphodiester linkages
DNA contains complementary base pairs in which adenine is always linked by ______ to thymine (AT).
- two hydrogen bonds
DNA contains complementary base pairs in which guanine is always linked by _____ to cytosine (GC).
- three hydrogen bonds
The function of DNA in the cells is to
- preserve genetic information.
- transfer genetic information to new cells as the strands of DNA are copied.
During DNA replication,
____ unwinds the parent DNA at several sections.
- helicase
During DNA replication,
_____ catalyzes the replication process at each of the open DNA sections called replication forks.
- DNA polymerase
During DNA replication,
the polymerase moves in the 3′–5′direction, catalyzing the formation of new _____.
- phosphodiester linkages
During DNA replication,
the lagging strand (growing in the ____ direction) is synthesized in short sections called Okazaki fragments.
- 5′–3′
During DNA replication,
____ joins the Okazaki fragments.
- DNA ligase
- makes up most of the nucleic acid found in the cell.
- transmits genetic information from DNA to operate the cell.
- RNA
How does RNA differ from DNA?
- The sugar in RNA is ribose; the sugar in DNA is deoxyribose.
- The base uracil replaces thymine.
- RNA molecules are single stranded; DNA molecules are double stranded.
- RNA molecules are much smaller than DNA molecules.
5% of RNA is _____ , which carries genetic information from DNA to the ribosomes.
- messenger RNA (mRNA)
15% of RNA is _____, which translates the genetic information in mRNA into the amino acid sequence for the protein.
- transfer RNA (tRNA)
80% of RNA is _____, which is the most abundant type of RNA; it is combined with proteins to form ribosomes.
- ribosomal RNA (rRNA)
______ contains an anticodon, which is a series of three bases that complements three bases on mRNA.
- A typical tRNA molecule
DNA undergoes ____ when RNA polymerase makes a complementary copy of a gene using the 3′ to 5′ DNA template strand.
- transcription
- DNA contains exons that code for proteins and introns that do not code for proteins.
- a pre-RNA is formed that includes the noncoding introns.
- the noncoding introns are removed.
- the exons are joined to form mRNA, which goes to the ribosomes with the information for the synthesis of protein.
- In eukaryotes
_____ at the promoter region bind RNA polymerase to DNA, which activates the transcription of a gene.
- Transcription factors
The genetic code consists of sets of three nucleotides (triplets) in mRNA called _____ that specify the amino acids and their sequence in the protein.
- codons
The genetic code
has stop signals, UGA, UAA, and UAG, that signal the termination of protein synthesis.
has a start codon, AUG, that signals the start of ______.
- protein synthesis
A ______ is the replacement of one base in the template strand of DNA with another; this may cause a different amino acid to be inserted into the polypeptide.
- point mutation
A ____ occurs when a point mutation does not change the amino acid.
- silent mutation
In a ______, a base is deleted from the normal order of bases in the template strand of DNA. All the codons that follow are changed, producing a different sequence of amino acids from that point.
- deletion mutation
In an ______, a base is inserted into the normal order of bases in the template strand of DNA. All the codons that follow are changed, producing a different sequence of amino acids from that point.
- insertion mutation
____ result from a defective enzyme caused by mutation in its genetic code.
- Genetic diseases
____ is formed by placing a gene from another organism in a plasmid DNA of a bacterium. This causes the bacterium to produce a nonbacterial protein.
- Recombinant DNA
- made it possible to produce multiple copies of a DNA in a short time.
- separates the sample DNA strands by heating.
- mixes the separated strands with enzymes and nucleotides to form complementary strands.
- is repeated many times to produce a large sample of the DNA.
- polymerase chain reaction (PCR)
- allows screening for defective genes.
- can be used to screen for genes associated with breast cancer.
- Polymerase chain reaction (PCR)
Genetic Testing
- restriction enzymes cut a DNA sample into smaller fragments.
- the sample is placed on a gel and separated using electrophoresis
- DNA fingerprinting
___ are small particles of RNA and DNA containing 3–200 genes that cannot replicate without a host cell.
- Viruses
a ____ processes proteins to produce a protein coat encasing the new viral RNA or DNA; and the new virus particles are released from the cell, ready to infect more cells.
- protease
- a retrovirus, which contains viral RNA but no viral DNA, enters a cell.
- the viral RNA uses reverse transcriptase to produce a viral DNA strand.
- the viral DNA strand forms a complementary DNA strand.
- the new DNA uses the nucleotides and enzymes in the host cell to synthesize new virus particles.
- In reverse transcription
- is a retrovirus that infects and destroys T4 lymphocyte cells.
- leaves the immune system unable to destroy harmful organisms.
is associated with an increased chance of
developing pneumonia and skin cancer associated with AIDS.
- The HIV virus
After a _____ injects its viral RNA into a cell, it forms a DNA strand by reverse transcription.
The single-stranded DNA forms a double-stranded DNA called a provirus, which is incorporated into the host cell DNA.
When the cell replicates, the provirus produces the viral RNA needed to produce more virus particles.
- retrovirus
Treatment for AIDS is based on
- attacking the HIV at different points in its life cycle.
- developing nucleoside analogs that mimic the structures of the nucleosides used for DNA synthesis.
Current treatment for HIV and AIDS involves a combination of drugs that include
- entry inhibitors.
- reverse transcriptase inhibitors.
- protease inhibitors.
