Chapter 15 Proteins and enzymes

Classify each of the following amino acids as nonpolar.

-Met -leucine

What functional groups are found in all α-amino acids?

-a carboxylic acid group -an amino group on the alpha carbon

Classify each of the following amino acids as polar

-histidine -T

Give the three-letter and one-letter abbreviations for alanylcysteine.

Ala-Cys,AC

Identify the amino acids and type of cross-link that occurs between the following side groups in tertiary protein structures: −CH2−CO−NH2 and HO−CH2−

Asparagine and serine are both polar neutral amino acids; their R groups can interact by hydrogen bonding.

Identify the amino acids and type of cross-link that occurs between the following side groups in tertiary protein structures: −CH2−CO−O− and NH+3−(CH2)4−

Aspartic acid is a polar acidic amino acid, and lysine is a polar basic amino acid; their R groups interact by forming a salt bridge (ionic bond).

What are isoenzymes?

Enzymes with different combinations of polypeptide subunits that catalyze the same reaction in different tissues of the body.

What are some differences between each of the following pairs? dipeptides and tripeptides

Dipeptides contain two amino acids, whereas tripeptides contain three amino acids.

What type of interaction would you expect between the R groups of the following amino acids in a tertiary structure? cysteine and cysteine

Disulfide bond

____ has a tertiary structure that recognizes the substrate

Enzyme

Why do chemical reactions in the body require enzymes?

Enzymes catalyze the reactions in the body.

Give the three-letter and one-letter abbreviations for glycylalanylvaline.

Gly-Ala-Val,GAV

What type of interaction would you expect between the R groups of the following amino acids in a tertiary structure? serine and aspartic acid

Hydrogen Bond

What type of interaction would you expect between the R groups of the following amino acids in a tertiary structure? leucine and leucine

Hydrophobic interaction

Identify the amino acids and type of cross-link that occurs between the following side groups in tertiary protein structures: −CH2−CH(CH3)−CH3 and CH3−

Leucine and alanine are both nonpolar amino acids; their R groups have a hydrophobic interaction.

What are some differences between each of the following pairs? essential and nonessential amino acids

Nonessential amino acids can be synthesized by the body, but essential amino acids must be supplied by the diet.

What are some differences between each of the following pairs? polar and nonpolar amino acids

Polar amino acids have hydrophilic R groups, whereas nonpolar amino acids have hydrophobic R groups.

What is the overall charge of a polar neutral amino acid at a pH below its pI?

Positive (1+)

What type of interaction would you expect between the R groups of the following amino acids in a tertiary structure? glutamic acid and lysine

Salt bridge

Give the three-letter and one-letter abbreviations for serylphenylalanine.

Ser-Phe,SF

_____ has a structure that fits the active site of an enzyme

Substrate

Identify the amino acids and type of cross-link that occurs between the following side groups in tertiary protein structures: −CH2−SH and HS−CH2−

The polar neutral amino acid cysteine contains the −SH group; two cysteines can form a disulfide bond.

What are some differences between each of the following pairs? secondary and tertiary protein structures

The secondary structure depends on hydrogen bonds to form a helix or a pleated sheet. The tertiary structure is determined by the interactions of R groups such as disulfide bonds and salt bridges, and determines the three-dimensional shape of the protein.

Give the three-letter and one-letter abbreviations for valylisoleucyltryptophan.

Val-Ile-Trp,VIW

Three peptides each contain one molecule of valine and two molecules of serine. Use their three-letter abbreviations to write the possible tripeptides they can form. Enter the amino acids separated by dashes. For example, Cys-Tyr-Cys. Enter the primary structures separated by commas.

Val-Ser-Ser,Ser-Ser-Val,Ser-Val-Ser

Choose an equation that represents an enzyme-catalyzed reaction.

ensyme + substrate ←−→ enzyme-substrate complex → enzyme + products

the combination of an enzyme with the substrate is referred to as

enzyme substrate complex

The _____ atoms of the ______ groups and the hydrogen atoms attached to the ______ atoms form ________or _______

oxygen, carbonyl, nitrogen, α-helices, β-pleated sheets.

State whether the following statements describe primary, secondary, tertiary, or quaternary protein structure. Peptide bonds join amino acids in a polypeptide chain.

primary

State whether the following statements describe primary, secondary, tertiary, or quaternary protein structure. Adjacent chains of polypeptides are held together by hydrogen bonds between the O of the carbonyl group of one chain and the H of an amide bond in another chain.

quaternary

State whether the following statements describe primary, secondary, tertiary, or quaternary protein structure. Hydrogen bonding between amino acids in the same polypeptide gives a coiled shape to the protein.

secondary

State whether the following statements describe primary, secondary, tertiary, or quaternary protein structure. R groups interact to form disulfide bonds or ionic bonds

tertiary