bio ch. 5

Which of the following pairs of base sequences could form a short stretch of a normal double helix of DNA?

5′-ATGC-3′ with 5′-GCAT-3′

Hydrolysis

A chemical process that splits a molecule by adding water.

Purines

Adenine and Guanine

What do Alzheimer's, Parkinson's, and mad cow disease have in common? (Concept 5.4)

All are associated with the buildup of misfolded proteins in cells.

Generally, animals cannot digest (hydrolyze) the glycosidic linkages between the glucose molecules in cellulose. How then do cows get enough nutrients from eating grass?(Concept 5.2)

Microorganisms in their digestive tracts hydrolyze the cellulose to individual glucose units. right answer feedback:Correct. Cows have digestive chambers populated by microorganisms that can produce certain hydrolytic enzymes that cows cannot. The enzymes hydrolyze (digest) the cellulose polymer into glucose monomers.

alpha glucose

OH on bottom

beta glucose

OH on top

Monosaccharides

Single sugar molecules - ch2o - serve as major fuel for cells + raw material for building molecules

peptide bond

The chemical bond that forms between the carboxyl group of one amino acid and the amino group of another amino acid

Amylase is an enzyme that breaks down starch. Why cannot the same enzyme break down cellulose? (Concept 5.2)

The monosaccharide monomers in cellulose are bonded together differently than those in starch. right answer feedback:Correct. The glucose monomers in cellulose are bonded in a β glycosidic linkage, whereas those in starch have an α glycosidic linkage. The enzyme amylase is specific for the α glycosidic linkage.

Which of the following statements concerning unsaturated fats is true?

They have double bonds in the carbon chains of their fatty acids.

triaglycerol

Three fatty acids linked to one glycerol molecule; also called a fat or a triglyceride.

Lipids differ from other large biological molecules in that they __________. (Concept 5.3)

are not truly polymers right answer feedback:Correct. Lipids are not all made of the same type of monomer. Their association as a group (fats, phospholipids, and steroids) is related to their solubility behavior.

Pyrimides

cytosine, thymine, uracil

fats

glycerol and fatty acids

Nucleotide

monomer of nucleic acids made up of a 5-carbon sugar, a phosphate group, and a nitrogenous base

The structural level of a protein least affected by a disruption in hydrogen bonding is the

primary level.

Chaperonins

protein molecules that assist the proper folding of other proteins

Gene

sequence of DNA that codes for a protein and thus determines a trait

In what polysaccharide form do plants store glucose to be available later as an energy source?(Concept 5.2)

starch

Which of the following lists ranks these molecules in the correct order by size from smallest to largest? (Concept 5.4)

water, glucose, sucrose, protein

dehydration reaction

A chemical reaction in which two molecules become covalently bonded to each other with the removal of a water molecule.

Chitin

A chemical that provides both toughness and flexibility

glycosidic linkage

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

Disaccharide

A double sugar, consisting of two monosaccharides joined by dehydration synthesis.

unsaturated fatty acid

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. - liquid at room temperature

Cholesterol

A lipid that forms an essential component of animal cell membranes and acts as a precursor molecule for the synthesis of other biologically important steroids.

Polymer

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

Phospholipids

A molecule that is a constituent of the inner bilayer of biological membranes, having a polar, hydrophilic head and a nonpolar, hydrophobic tail.

quaternary structure of a protein

A number of polypeptide chains linked together, and sometimes associated with non-protein groups to form a protein.

Polypeptide

A polymer (chain) of many amino acids linked together by peptide bonds.

polynucleotide

A polymer consisting of many nucleotide monomers in a chain; nucleotides can be those of DNA or RNA.

Monomer

A simple compound whose molecules can join together to form polymers

Starch

A storage polysaccharide in plants consisting entirely of glucose.

Cellulose

A substance (made of sugars) that is common in the cell walls of many organisms

protein

A three dimensional polymer made of monomers of amino acids.

Which of the following is true regarding complementary base pairing in DNA and RNA molecules? (Concept 5.5)

Although the base pairing between two strands of DNA in a DNA molecule can be thousands to millions of base pairs long, base pairing in an RNA molecule is limited to short stretches of nucleotides in the same molecule or between two RNA molecules.

Glycogen

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

trans fat

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

Carbohydrates

Broken down to simple sugars

The molecular formula for glucose is C6H12O6. What would be the molecular formula for a polymer made by linking ten glucose molecules together by dehydration reactions?

C60H102O51

Which of the following molecules is a monosaccharide? (Concept 5.2)

C6H12O6 right answer feedback:Correct. Monosaccharides have molecular formulas that are multiples of CH2O.

Polysaccharides

Carbohydrates that are made up of more than two monosaccharides

Enzymes

Catalysts for chemical reactions in living things

High cholesterol levels are considered a major risk factor for heart disease. If it is so bad for humans, why does the body make cholesterol in the first place? (Concept 5.3)

Cholesterol is the precursor for many important molecules such as sex hormones. right answer feedback:Correct. Cholesterol is the basis for many steroid molecules, including sex hormones.

The type of bond that forms to join monomers (such as sugars and amino acids) into polymers (such as starch and proteins) is a(n) __________ bond. (Concept 5.1)

Covalent right answer feedback:Correct. Monomers are joined together by a dehydration reaction in which two molecules are covalently bonded to each other through the loss of a water molecule.

A shortage of phosphorus in the soil would make it especially difficult for a plant to manufacture __________. (Concept 5.5)

DNA

When a protein is denatured, why does it lose its functionality? (Concept 5.4)

Denaturation breaks the intramolecular bonds, such as hydrogen bonds and van der Waals interactions, that hold the protein in its three-dimensional shape. Without the proper shape, the protein cannot function.

lipids

Energy-rich organic compounds, such as fats, oils, and waxes, that are made of carbon, hydrogen, and oxygen. - dont form polymers - no affinity for water

Nutritionally, saturated triacylglycerols are considered to be less healthful than unsaturated triacylglycerols. What is the difference between them? (Concept 5.3)

For carbon skeletons of equal length, saturated triacylglycerols have more hydrogen atoms than unsaturated triacylglycerols do. right answer feedback:Correct. Saturated triacylglycerols are saturated with hydrogen atoms.

Which of the following is a true statement comparing phospholipids and triacylglycerols (fats and oils)? (Concept 5.3)

Phospholipid molecules have a distinctly polar "head" and a distinctly nonpolar "tail," whereas triacylglycerols are predominantly nonpolar. right answer feedback:Correct. Triacylglycerols consist of three (nonpolar) fatty acid tails attached to a glycerol molecule. Phospholipids have two fatty acid tails and a hydrophilic head containing a negatively charged phosphate group.

Which of the following describes a difference between DNA and RNA? (Concept 5.5)

RNA molecules generally consist of a single polynucleotide chain, whereas DNA molecules generally consist of two polynucleotide chains organized into a double helix., Both molecules contain adenine, guanine and cytosine, but DNA also contains thymine and RNA also contains uracil., They contain different sugars.

Enzymes that break down DNA catalyze the hydrolysis of the covalent bonds that join nucleotides together. What would happen to DNA molecules treated with these enzymes?

The phosphodiester linkages of the polynucleotide backbone would be broken.

Hydrogenation

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

Enzyme molecules require a specific shape to perform their catalytic function. Which of the following might alter the shape of an enzymatic protein? (Concept 5.4)

a change in salt concentrations or pH, heating the protein, treating the protein with a chemical that breaks hydrogen bonds, denaturing the protein

If a small droplet of triacylglycerol molecules is suspended in water, the fat molecules form a "ball of spaghetti" with no particular orientation. But if a droplet of phospholipid molecules is put in water, all the molecules point outward, toward the water. Phospholipids are forced into this orientation because phospholipids have __________. (Concept 5.3)

a charged or polar end and an uncharged or nonpolar end right answer feedback:Correct. The nonpolar hydrocarbon tails of phospholipids are hydrophobic—that is, they are excluded from water. The negatively charged phosphate group and its attachments form a hydrophilic head that is attracted to water.

The peptide bond is __________. (Concept 5.4)

a covalent bond joining amino acids together to form a polypeptide

saturated fatty acid

a long-chain hydrocarbon with single covalent bonds in the carbon chain; the number of hydrogen atoms attached to the carbon skeleton is maximized - solid at room temperature

Which of the following lists represents the chemical components of a nucleotide?(Concept 5.5)

a nitrogenous base, a phosphate group, and a pentose sugar

A glucose molecule is to starch as __________. (Concept 5.5)

a nucleotide is to a nucleic acid right answer feedback:Correct. Nucleotides are the monomers that make nucleic acid polymers, just as glucose is the monosaccharide (monomer) from which starch (polymer) is constructed.

In a hydrolysis reaction, __________, and in this process water is __________. (Concept 5.1)

a polymer is broken up into its constituent monomers ... consumed

amino acids

a simple organic compound containing both a carboxyl (—COOH) and an amino (—NH2) group.

Manufacturers make vegetable oils solid or semisolid at room temperature by __________.(Concept 5.3)

adding hydrogen atoms to the fatty acid hydrocarbon chains, thereby converting carbon-carbon double bonds to single bonds

Based on complementary base pairing, you would expect the percentage of __________ to be equal to the percentage of __________. (Concept 5.5)

adenine ... thymine

secondary structure of protein

alpha helix and beta pleated sheet

Protein molecules are polymers (chains) of __________. (Concept 5.4)

amino acid molecules right answer feedback:Correct. Polymers of amino acids are called polypeptides. A protein consists of one or more polypeptides folded into specific conformations.

Which of the following categories includes all others in the list?

carbohydrate

Which of the following components of a tossed salad will pass through the human digestive tract and be digested the least? (Concept 5.2)

cellulose (in the lettuce) right answer feedback:Correct. Cellulose contains glycosidic linkages that cannot be broken by human digestive enzymes.

fatty acids

chains of carbon atoms bonded to hydrogen atoms

Which type of protein shields a newly forming protein from cytoplasmic influences while it is folding into its functional form? (Concept 5.4)

chaperonins right answer feedback:Correct. Chaperonins shield proteins from "bad influences" (interactions with other molecules in the cytoplasm) while they are folding into their functional forms.

At a conference, the speaker's grand finale was sautéing mealworms (insect larvae) in butter and serving them to the audience. They were crunchy (like popcorn hulls) because their exoskeletons contain the polysaccharide __________. (Concept 5.2)

chitin right answer feedback:Correct. Chitin is the structural polysaccharide found in arthropod exoskeletons.

What is the process by which monomers are linked together to form polymers? (Concept 5.1)

dehydration reaction right answer feedback:Correct. When monomers are linked together to form a more complex polymer, a water molecule is removed by dehydration reactions.

DNA

deoxyribonucleic acid, a self-replicating material present in nearly all living organisms as the main constituent of chromosomes. It is the carrier of genetic information. - sugar is deoxyribose

Carbohydrates are used in our bodies mainly for __________. (Concept 5.2)

energy storage and release right answer feedback:Correct. Simple sugar molecules, stored in polysaccharides such as glycogen in animals and starch in plants, are a major energy source for cellular work.

Some lipids are formed when fatty acids are linked to glycerol. These subunits are linked together by __________. (Concept 5.3)

ester linkages right answer feedback:Correct. In making a fat, each of the three fatty acid molecules is bonded to a glycerol molecule by an ester linkage type of covalent bond.

nucleic acids

genes made of DNA, made of monomers (nucleotides)

A polysaccharide that is used for storing energy in human muscle and liver cells is __________.(Concept 5.2)

glycogen

The enzyme amylase can break glycosidic linkages between glucose monomers only if the monomers are in the a form. Which of the following could amylase break down?

glycogen, starch, and amylopectin

The subunits (monomers) in cellulose are linked together by __________. (Concept 5.2)

glycosidic linkages

Which of the following terms can be correctly used to describe compounds that do NOT mix with water? (Concept 5.3)

hydrophobic

The fatty acid tails of a phospholipid are __________ because they __________. (Concept 5.3)

hydrophobic ... have no charges to which water molecules can adhere

The sex hormones estradiol and testosterone belong to which class of molecules?(Concept 5.3)

lipids right answer feedback:Correct. Steroids, such as estradiol and testosterone, are lipids based on their insolubility in water. The molecules are characterized by a carbon skeleton consisting of four fused rings of carbon atoms.

Steroids

lipids characterized by a carbon skeleton consisting of four fused rings

Denaturation

loss of normal shape of a protein due to heat or other factor

mRNA

messenger RNA; type of RNA that carries instructions from DNA in the nucleus to the ribosome

The lipids that form the main structural component of cell membranes are __________.(Concept 5.3)

phospholipids right answer feedback:Correct. Phospholipids have a hydrophilic head and two hydrophobic tails. This permits the phospholipids to be arranged in a bilayer, or double layer, which forms a boundary between the cell and its external environment.

tertiary structure of protein

protein structure is formed when the twists and folds of the secondary structure fold again to from a larger 3D structure

Which of the following represents a specific description of a polypeptide? (Concept 5.4)

right answer feedback:Correct. A polypeptide is a chain of amino acids that have been linked together by dehydration reactions.

The α helix and β pleated sheet represent which level of protein structure? (Concept 5.4)

secondary structure right answer feedback:Correct. Both the α helix and the β pleated sheet are localized regions of polypeptides held in a given structure by hydrogen bonds.

RNA

single-stranded nucleic acid that contains the sugar ribose

The polysaccharide that you are most likely to have eaten recently is __________. (Concept 5.2)

starch

Carbohydrates can function in which of the following ways? (Concept 5.2)

structural support and energy storage

The overall three-dimensional shape of a single polypeptide is called its __________.(Concept 5.4)

tertiary structure right answer feedback:Correct. The tertiary structure is determined by hydrogen bonds, hydrophobic R groups, ionic bonds between R groups, van der Waals interactions, and disulfide bridges.

primary structure of protein

the amino acid sequence of the polypeptide chain

The "primary structure" of a protein refers to __________. (Concept 5.4)

the sequence of amino acids along a polypeptide chain

One characteristic shared by sucrose, lactose, and maltose is that __________. (Concept 5.2)

they are all disaccharides right answer feedback:Correct. A disaccharide consists of two monosaccharides joined together by a glycosidic linkage.

Which of the following are pyrimidines found in the nucleic acid DNA? (Concept 5.5)

thymine and cytosine