Chapters 4 & 5

Define monomer

"one part"; the single building block unit of a polymer

The composition of an amino acid's R group characterizes whether that amino acid is neutral (polar or nonpolar), acidic, or basic, and determines how it interacts in cells. Arginine, with its reactive R group, is often found at the active sites of enzymes, where it participates in chemical reactions.

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As a researcher in a protein lab, you analyze two different proteins for their shape and the amino acids they contain. Your results show that the two proteins have exactly the same numbers and types of amino acids, but they have different shapes. What is the best explanation for these results? A. Each protein has a unique linear sequence of amino acids. B. With only 20 amino acid types to work with, many proteins must have the same numbers and types. C. Proteins from the same functional class (enzymatic, structural, etc.) contain exactly the same amino acids. D. All proteins have the same numbers and types of amino acids. Differences between proteins are all based on shape.

Each protein has a unique linear sequence of amino acids. Explanation: In the same way that the same letters can be arranged to make different words with different meanings, the same amino acids can be arranged in different linear sequences to form different proteins with different shapes and functions.

Which of these is a carbonyl group?

C.

What statement about a methyl functional group is correct? A. A methyl group is polar B. A methyl group may be negatively charged. C. A methyl group consists of a carbon bonded to three hydrogen atoms.

C. A methyl group consists of a carbon bonded to three hydrogen atoms.

Which of the following is not attached to the central atom is an amino acid? A. An amino functional group B. A carboxyl functional group C. An oxygen D. A side chain ("R group")

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

Molecules that have the same chemical formula (same numbers of each atom) but different three-dimensional shapes are called _____. A. Enantiomers B. Functional groups C. Isomers D. Hydrocarbons E. Isotopes

C. Isomers-- Isomers of carbon compounds can arise in several different ways.

Which polymers are composed of amino acids? A. Carbohydrates B. Monomers C. Proteins D. Nucleic acids

C. Proteins Proteins are composed of amino acids joined together

Proteins perform a variety of functions in living organisms. The protein lysozyme (shown in the figure) is found in tears and saliva where it prevents infection by catalyzing the destruction of specific molecules on the surface of many kinds of bacteria. To which functional class of proteins does lysozyme belong?

Enzymatic protein Enzymatic proteins, or enzymes, are chemical agents that selectively speed up chemical reactions without being consumed by the reaction.

Which of functional groups listed below behaves as an acid?

F. By donating hydrogen ions, carboxyl groups act as an acid.

Which of these is a carboxyl group?

F. This is a carboxyl group.

Define cis-trans isomers

Cis-trans isomers maintain the same covalent partnerships, but the atoms may be arranged differently.

Define isomer

Compounds with the same molecular formula (same number of atoms of the same elements), but different structures

Which of these functional groups is characteristic of alcohol?

D. Hydroxyl groups are characteristic of alcohol.

Which of these is a hydroxyl group?

D. This is a hydroxyl group.

Which of these groups is characteristic of thiols?

E. Thiols are characterized by the presence of a sulfhydryl group.

Define polymer

Large molecules made from bonding many parts (monomers) together

Which characteristics best describe the side chains in the part of the protein in contact with the phospholipid tails of the membrane? Charged - acidic; hydrophilic Non-polar; hydrophobic Charged - basic; hydrophilic Polar; hydrophilic

Non-polar; hydrophobic Explanation: The side chains in the section of the protein that is embedded in the membrane will be in contact with the fatty acid core of the membrane, which is hydrophobic.

Match the following in the correct pairs Proteins Simple sugars Amino acids Nucleic acids Carbohydrates Nucleotides

Polymer Monomer Proteins Amino Acids Carbohydrates Simple sugars Nucleic Acids Nucleotides https://mediaplayer.pearsoncmg.com/assets/secs-bio-condensation-and-hydrolysis-reactions

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 Explanation: 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.

The four main categories of large biological molecules present in living systems are _____.

Proteins, nucleic acids, carbohydrates, and lipids

These figures show the four levels of protein structure: primary, secondary, tertiary, and quaternary structure. Which level of protein structure is characteristic of some, but not all, proteins?

Quaternary level of protein structure Explanation: Quaternary structure results from the aggregation of two or more polypeptide subunits, and not all proteins are composed of more than one polypeptide.

Which of the three different representations of protein structure is most useful for studying the interior shapes formed by the folds of the protein?

Ribbon. In the ribbon view, a smooth line or string traces the backbone's path, flattening into a ribbon when helix or sheet-like shapes are formed.

Which of the three different representations of protein structure is most useful for studying the exterior of the protein?

Spacefill. The spacefill representation shows the space occupied by the protein, hiding the interior, and allowing close examination of the shapes and properties of the exterior of the protein.

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

The tertiaterm-36ry 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.

Define structural isomers

They differ in the arrangement of covalent bonds and in covalent partners.

True or false? Enzymes in the digestive tract catalyze hydrolysis reaction.

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

Describe a dehydration reaction

When two amino acid monomers are positioned so that the carboxyl group of one is adjacent to the amino group of the other, they can be joined through a dehydration reaction. This reaction forms a peptide bond. Explanation: Proteins are complex molecules made of many repeating amino acid monomers linked together by covalent peptide bonds. Recognizing amino acids and understanding how they are linked together into polypeptides provides a foundation for understanding the three-dimensional architecture of proteins.

Tertiary structure of a protein is...

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

Secondary structure of protein is...

formed by folding and twisting of amino acid chain. It describes the alpha-helices and beta-sheets that are formed by hydrogen bonding between backbone atoms located near each other in the polypeptide chain.

Quaternary structure of a protein is...

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

Primary structure of protein is...

the sequence of amino acids in a protein.

Which of the following statements about the formation of polypeptides from amino acids is true? A. A bond forms between the carboxyl functional group of one amino acid and the amino functional group of the other amino acid. B. Polypeptides form by condensation or hydrolysis reactions. C. A bond can form between any carbon and nitrogen atom in the two amino acids being joined. D. The reaction occurs through the addition of a water molecule to the amino acids.

A. A bond forms between the carboxyl functional group of one amino acid and the amino functional group of the other amino acid. Explanation: 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 part of an amino acid is always acidic? A. Carboxyl functional group B. Side chain ("R group") C. Amino functional group D. None of the above

A. Carboxyl function group Explanation: 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 functional groups shown above is most likely to gain a proton and become positively charged? A. The amino group is most likely to gain a proton. B. The hydroxyl group is most likely to gain a proton. C. The carboxyl group is most likely to gain a proton.

A. The amino group is most likely to gain a proton. Explanation: An amino group acts as a base and can pick up protons from the surrounding medium, becoming positively charged.

Which of the functional groups behaves as a base?

A. The electronegativity of nitrogen means that amino groups tend to pick up hydrogen ions.

Which of the following best describes cis-trans isomers? See Concept 4.2 (Page) A. They differ in their spatial arrangement around inflexible double bonds. B. They are mirror images of each other. C. They differ in the arrangement of covalent bonds and in covalent partners. D. They have the same number of atoms of the same elements but different structures. E. They are long chains of hydrogen and carbon atoms.

A. They differ in their spatial arrangement around inflexible double bonds. Explanation: Cis-trans isomers maintain the same covalent partnerships, but the atoms may be arranged differently.

Which one of these is an amino group?

A. This is an amino group, NH2.

Which functional group is not present in this molecule?

A. carboxyl B. amino C. hydroxyl D. sulfhydryl

Variations in the reactive properties of different organic molecules are most closely associated with _____. A.the presence or absence of functional groups B. the orientation of the carbon skeleton, as either ringed or linear C. the number of carbon atoms comprising the molecule's skeleton D. the presence or absence of double bonds E. the number of asymmetric carbon atoms present

A. the presence or absence of functional groups. Explanation: Functional groups are the most common participants in chemicals reactions.

Visualize the structural formula of each of the following hydrocarbons. Which hydrocarbon has a double bond in its carbon skeleton? A. C3H8 B. C2H4 C. C2H2 D. C2H6

B. C2H4

How do isomers differ from one another? A. Isomers differ in charge. B. Isomers differ in the arrangement or bonding of atoms. C. Isomers differ in molecular formulas.

B. Isomers differ in the arrangement or bonding of atoms. Explanation: Isomers may differ in the covalent arrangements of their atoms or the position of double bonds within the molecule and thus have different chemical properties.

Which monomers make up RNA? A. Polymers B. Nucleotides B. Amino acids D. Simple sugars

B. Nucleotides Explanation: Nucleotides make up nucleic acids

Which of these is a phosphate group?

B. Of the choices, this is the only one that contains phosphorus.

Which of these groups plays a major role in energy transfer?

B. Phosphate groups are a component of ATP.

Which of the three different representations of protein structure is most useful for observing the path of the protein chain from one amino acid to the next?

Backbone. In the backbone view, a line traces the backbone's path directly from one amino acid to the next. Each sharp turn off the line indicates the position of an amino acid along the protein chain.

Proteins can be visualized in many ways, each of which highlights a specific aspect of the protein.

1. If you wanted to show the 3-dimensional shape of a protein, including all of the atoms composing it, you should use a space-filling model. 2. If you wanted to show the general shape of a protein, along with some important functional details such as folds and coils, you should use a simplified diagram. 3. If you wanted to show the 3-dimensional shape of a protein, including the backbone structure, folds, and coils, you should use a ribbon model. 4. If you wanted to show a generalized protein in which the focus is on the protein's function rather than its structure, you should use a simple shape. 5. If you wanted to show the 3-dimensional shape of a protein by showing the amino acid side chains and their interactions, you should use a wireframe model. Explanation: Proteins are complex molecules made of many amino acid monomers. Depending on the focus and goal of the illustration, depictions can range from very detailed to very simple. Space-filling models show every atom, and wireframes show all side chains. Simplified diagrams and shapes use very general shapes to represent proteins.

Define amino group

A functional group consisting of a nitrogen atom bonded to two hydrogen atoms. An amino group acts as a base and can pick up protons from the surrounding medium, becoming positively charged.