Biology Chapter 5

If a strand of DNA has the nitrogen base sequence 5'-ATTTGC-3', what will be the sequence of the matching strand?

3'-TAAACG-5'; Adenine pairs with thymine and guanine pairs with cytosine.

What holds phospholipids together in a bilayer formation?

hydrophilic and hydrophobic interactions with water; The hydrophobic tails interact with each other and are repelled by water, while the heads are hydrophilic and are attracted to water. This dual nature causes groups of phospholipids to assemble into distinct layers to minimize tail contact with water and maximize head contact with water.

What functional feature(s) does the phosphate group contribute to the structure of a phospholipid?

- negative charge to interact with water - place to attach another small charged molecule The phosphate attaches to the glycerol and provides a place for another small molecule to attach to the phospholipid. The phosphate has a charge, so it interacts with polar water molecules.

How many hydrogen atoms can be attached to carbon B?

1; If you had trouble with this question, review the following material: Each carbon atom can form four bonds. A double bond counts as two bonds, so carbon B has a total of three bonds so far and it can form one more single bond with a hydrogen atom.

How many fatty acids are in a phospholipid?

2; Two fatty acids are attached to the glycerol and make up the tails of the phospholipid.

If a DNA double helix is 100 nucleotide pairs long and contains 25 adenine bases, how many guanine bases does it contain?

75; 100 nucleotide pairs are a total of 200 nucleotides. Because of base pairing, if there are 25 adenine there must also be 25 thymine. This leaves 200-50 = 150 nucleotides to be divided evenly between guanine and cytosine.

Which of the following statements about the formation of polypeptides from amino acids is true?

A bond forms between the carboxyl functional group of one amino acid and the amino functional group of the other amino acid; A hydroxyl group is removed from the carboxyl group of one amino acid and hydrogen is removed from the amino group of the other amino acid, allowing a bond to form between the two groups.

Which molecule is less soluble in water--a fat or a phospholipid? Why?

A fat molecule is less soluble in water because it has three non-polar fatty acids and no polar or charged head like a phospholipid has; The replacement of one of the fatty acids with a polar chemical group makes phospholipids more soluble in water than fats.

Which molecule is a nucleotide?

ATP; A nucleotide consists of three parts: a nitrogenous base, a pentose sugar, and one or more phosphate groups. ATP consists of a nitrogenous base (adenine), a pentose sugar, and three phosphate groups.

Which of these illustrates the secondary structure of a protein?

Alpha helices and beta pleated sheets are characteristic of a protein's secondary structure.

Which complex carbohydrate contains only a-1,4-glycosidic linkages?

Amylose; Amylose is formed from a-1,4-glycosidic linkages of glucose.

Which of the following is not attached to the central carbon atom in an amino acid?

An oxygen; The central carbon atom in an amino acid is bonded to an amino functional group, a carboxyl functional group, a side chain, and hydrogen.

Which of these images shows the correct orientation of phospholipids in a biological membrane?

Biological membranes are made of phospholipids that have assembled with the polar heads facing out to interact with the water, and the non-polar tails pushed together in the interior of the membrane.

Which part of an amino acid is always acidic?

Carboxyl functional group; The carboxyl group (COOH) contains two oxygen atoms that tend to pull electrons away from the hydrogen atom, so this group tends to lose a proton and is acidic.

Which of the following complex carbohydrates is listed with its correct function?

Cellulose: structural component of plant cell walls; Cellulose is indeed the main structural component of plant cells walls.

Which molecule is not a carbohydrate?

Lipid; A lipid is a hydrophobic polymer, not a carbohydrate.

Which of the following statements about monosaccharide structure is true?

Monosaccharides can be classified according to the spatial arrangement of their atoms; This statement is true.

Which monomers make up RNA?

Nucleotides; Nucleotide monomers make up nucleic acids.

Which polysaccharide contains a modified monosaccharide?

Peptidoglycan; The N-acetylglucosamine and N-acetylmuramic acid units that make up peptidoglycan are composed of modified glucose monomers.

Which of these is a phospholipid?

Phospholipids are composed of a phosphate group, a glycerol, and fatty acids.

structure is the sequence of amino acids in a protein.

Primary

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

Primary level

There are four levels of protein structure. These figures show primary, secondary, tertiary, and quaternary protein structure. Which level(s) of protein structure may be stabilized by covalent bonds?

Primary, tertiary and quaternary levels of protein structure; The primary structure of a protein is the specific linear sequence of amino acids forming the protein. The amino acids are joined by covalent peptide bonds. Tertiary structure, producing the unique structure of a protein, is stabilized by interactions among the R groups on each amino acid in the protein. Tertiary structure may be stabilized by covalent bonds, called disulfide bridges, that form between the sulfhydryl groups (SH) of two cysteine monomers. Tertiary structure may also be stabilized by weaker interactions, including hydrogen bonds between polar and/or charged areas, ionic bonds between charged R groups, and hydrophobic interactions and van der Waals interactions among hydrophobic R groups. Many globular proteins are made up of several polypeptide chains called subunits stuck to each other by a variety of attractive forces but rarely by covalent bonds. Protein chemists describe this as quaternary structure.

Which polymers are composed of amino acids?

Proteins; Proteins are composed of amino acids joined together.

structure is the result of two or more protein subunits assembling to form a larger, biologically active protein complex.

Quaternary

Which of these is NOT a lipid?

RNA; RNA is a nucleic acid

structure describes the alpha-helices and beta-sheets that are formed by hydrogen bonding between backbone atoms located near each other in the polypeptide chain.

Secondary

structure is achieved when a protein folds into a compact, three-dimensional shape stabilized by interactions between side-chain R groups of amino acids.

Tertiary

Which feature of large biological molecules explains their great diversity?

The many ways that monomers of each class of biological molecule can be combined into polymers; Biological molecules belong to four main classes, and are constructed from only 40 to 50 common monomers (and a few rare ones) made of only a few of the 92 naturally occurring elements. The diversity of biological molecules is due to differences in the arrangements of the monomers in each molecule.

Sort the images according to the level of structure in the proteins shown.

The tertiary and quaternary structures of proteins—how they fold into their overall three-dimensional shapes, and how different protein subunits come together to interact—both ultimately depend on the primary structure, the sequence of amino acids in the proteins. A different sequence of amino acids will lead to different secondary structures and a different shape of the overall protein.

True or false? Peptidoglycan is a polysaccharide found only in bacteria.

True

True or false? Enzymes in the digestive tract catalyze hydrolysis reactions. (catalyze means speeds up)

True; Enzymes in the digestive tract break down food molecules, which is a process that occurs by hydrolysis.

Proteins are polymers of _____.

amino acids; Proteins are polymers of amino acids.

A function of cholesterol that does not harm health is its role _____.

as a component of animal cell membranes; Cholesterol is an important component of animal cell membranes.

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

carbohydrate

The secondary structure of a protein results from _____.

hydrogen bonds; Electronegative oxygen and nitrogen atoms leave hydrogen atoms with partial positive charges.

The two strands of a DNA double helix are held together by _____ that form between pairs of nitrogenous bases.

hydrogen bonds; Nitrogenous base pairs are joined by hydrogen bonds.

Which of these is rich in unsaturated fats?

olive oil; Olive oil is a plant oil, and most plant oils are rich in unsaturated fats.

Tertiary structure is NOT directly dependent on _____.

peptide bonds; Peptide bonds link together the amino acids of a protein's primary structure.

What type of bond joins the monomers in a protein's primary structure?

peptide; The amino acids of a protein are linked by peptide bonds.

A nucleotide is composed of a(n) _____.

phosphate group, a nitrogen-containing base, and a five-carbon sugar; These are the components of a nucleotide.

This figure is an example of a(n) _____.

saturated fat; The fatty acid tails lack double bonds.