BIO 121 Lecture Notes - Lecture 27: Adenine, Thiol, Guanine

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coralimpala133

23 Nov 2020

School

Tunxis Community College

Department

Biology

Course

BIO 121

Professor

Quilty

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Document Summary

The tertiary structure of a protein molecule is the overall shape assumed by each individual polypeptide chain. This 3-d structure is determined by four main factors that involve interactions. They include both weak interactions (hydrogen bonds, ionic bonds, and among r groups (side chains) belonging to the same polypeptide chain hydrophobic interactions) and strong covalent bonds. Hydrogen bonds form between r groups of certain amino acid subunits. An ionic bond can occur between an r group with a unit of positive charge and one with a unit of negative charge. Hydrophobic interactions result from the tendency of nonpolar r groups to be excluded by the surrounding water and therefore to associate in the interior of the globular structure. Covalent bonds known as disulfide bonds or disulfide bridges ( s s ) may link the sulfur atoms of two cysteine subunits belonging to the same chain.

Related Questions

1. The level of protein structure that is stabilized primarilyby non-covalent interactions between the side chains within asingle polypeptide chain is refered to as its:

A) primary structure

B) secondary structure

C) tertiary structure

D) quaternary structure

E) none of the above

2. Collagen, a strong fibrous protein found in connectivetissue, bone, and the extracellular matrix, has a structure inwhich three left-handed helices wind around each other to form aright-handed triple helix. The primary structure of collagen has arepeat unit of -(Gly-X-Pro)- Which of the following bonds stabilizethe collagen triple helix? (mark all that apply)

A) Hydrogen bonds between hydroxyproline residues

B) Hydrogen bonds between N-H and C=O

C) Ionic bonds between amino acid side chains

D) Hydrogen bonds between charged amino acids

3. The non-covalent forces that stabilize the Beta-strandconformation of peptides include:

A) H-bonds between amide C=O and amide NH

B) Van der Waals packing between the peptide backbone atoms

C) Van der Waals packing due to side chain interdigitation

D) Only A and B above

E) None of the above

4. What is the approximate length difference of a 22-kDasingle-stranded ?-helical protein segment vs. a 22-kDasingle-stranded ?-strand protein segment? Assume a mean residuemass of 110 Da. Show work.

5. Circular dichroism measurements have shown that the peptidebackbone of poly-l-lysine (KKKKKKK) adopts a random coilconformation at pH 7.0, but becomes ?-helical as the pH is raisedabove 10. This observation is known as the

magentaotter572

Protein Structure

a.Different function of proteins and examples:

b. Protein building blocks:

1. atomic composition of building block:

2. "parts" or "functional groups" of the building block:

c. Importance of side chain (R group):

d. Hydrophobic amino acids characteristics:

e. Hydrophilic amino acids characteristics:

f. Charged amino acids characteristics

Copy and complete the table below regarding the characteristics and which groups in the polypeptide interact together at each structural level of the protein.

	characteristics	groups interacting
Primary structure
Secondary structure
Tertiary structure
Quartenary structure

Value: 2

Choose the correct statement(s). You may choose more than one answer.

[mark all correct answers]
a. Proteins are the building blocks of amino acids.

b. Enzymes are a type of protein.

c. Quartenary structure consists of two or more polypeptide chains interacting.

d. Amino acids are made of carbon, hydrogen, nitrogen and phosphorus.

e. The primary structure of a protein is formed due to the interaction of side groups.

Value: 3

Put the following statements regarding the structural levels of a protein formation in the correct order.

Below is a sequence of events. Place them in the order they should occur, number 1 being the first item. Select the step number from the drop down next to each item.

Items to order:

1. Individual amino acids are bonded together via peptide bonds.

2. Two or more polypeptide chains interact via bonds.

3. Hydrogen bonds form between neighboring amino acids within a polypeptide chain allowing the chain to coil or form pleated sheets.

4. Side groups (R) of the individual amino acids interact with each other allowing the protein to assume its three dimensional shape.

Value:4

Put the following statements regarding the structural levels of a protein formation in the correct order

Individual amino acids are bonded together via peptide bonds.	1 2 3 4
Two or more polypeptide chains interact via bonds.	1 2 3 4
Hydrogen bonds form between neighboring amino acids within a polypeptide chain allowing the chain to coil or form pleated sheets.	1 2 3 4
Side groups (R) of the individual amino acids interact with each other allowing the protein to assume its three dimensional shape.	1 2 3 4

Value: 5

Hydrophobic amino acids will be found _______________.

a. In the interior (inner core) of a protein, away from the watery environment.

b. in the interior of a plasma membrane.

c. Both A and B

d. Neither

Value: 6

A protein's function is defined by ____________.

a. enzymatic reactions

b. it's shape.

c. chain of nucleotides.

d. the presence of carbon and hydrogen.

Value: 7

Which of the following is NOT considered a protein function?

a. transport of substances across membrane

b. enzymatic reactions

c. provides structural support

d. carries genetic information

1. Amino acid changes in the primary structure of the protein arenot capable of causing changes in the
overall shape of a protein.
a.) True
b.) False

2. An alpha helix:
a.) is destabilized by the amino acid alanine
b.) can only form by hydrogen bonding between different polypeptidechains
c.) can only form when cysteines form disulfide bridges within thisstructure
d.) all of the above
e.) none of the above

3. What will likely happen if two aspartates at pH 5 are next toeach other in a polypeptide chain?
a.) The side chains of these amino acids will be uncharged andthere will be no effect.
b.) The side chains of these amino acids will be charged and theywill attract each other.
c.) The side chains of these amino acids will be charged and theywill repel each other.
d.) Not enough information is given to determine the effect.

4. Consider the amino acid phenylalanine. Which of the followingbest describes where you predict this
amino acid would be found?
a.) This amino acid is hydrophobic and would be on the surface of aprotein that is in the middle
of a membrane.
b.) This amino acid is hydrophilic and would be on the surface of aprotein that is in the middle
of a membrane.
c.) This amino acid is hydrophobic and would be in the interior ofa protein that is in the middle
of a membrane.
d.) This amino acid is hydrophilic and would be in the interior ofa protein that is in the middle of
a membrane.
e.) Not enough information is given to determine.

5. The difference between fetal and adult hemoglobin with regard tooxygen binding occurs because fetal
hemoglobin has an amino acid substitution in one of its chains thatresults in a histidine being replaced by a
serine.
a.) True
b.) False

BIO 121 Lecture Notes - Lecture 27: Adenine, Thiol, Guanine

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