Biochemistry 2280A Lecture Notes - Lecture 4: C-Terminus, N-Terminus, Protein Folding

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lavenderimpala925

1 Nov 2018

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Driving force behind protein folding into tertiary structure: entropy, the driving force is hydrophobic interactions, it hates interacting with water. They all gather together and minimize their extent to associate with water: this happens when protein folds, the side chains are all distributed in the unfolded polypeptide, but nonpolar side chains are hydrophobic. Irreversible denaturation: the unfolding is irreversible, add urea to the protein, gradually unfold the protein, it will refold, folding is driven by the sequence of protein. It is a spontaneous process: cooking an egg, the protein comes out of the solution. They precipitate: the major of protein of egg white is called albumen. It has lots of cysteine residue in it: they are not present as disulfide bond, when you heat up the egg, the protein unfolds. Disulfide bonds can occur because cysteine is not at where they normally supposed to be: crosslinking occurs.

Related Questions

1. A sequence of amino acids in a certain protein is found to be â Ser â Gly â Pro â Gly â

The sequence is most probably part of a(n):

a. beta turn

b. antiparallel beta sheet

c. alpha-helix

d. parallel beta-sheet

e. alapha-sheet

2. Which statement about peptides bonds is NOT TRUE?

There is perfectly free rotation about the peptide bond.

The peptide bond has partial double-bond character.

The peptide bond is shorter than a normal carbon-nitrogen single bond.

The peptide bond usually has a trans configuration with respect to the alpha-carbons of the two amino acids involved in the peptide bond.

Peptide bonds are made via condensation of an amine and a carboxylic acid with loss of water.

3. Which of the following statements about proteins is FALSE?

	Active proteins are generally very loosely structured.
	In water-soluble proteins, hydrophobic amino acid residues are generally buried and not exposed to water.
	Primary structure determines tertiary structure.
	Secondary structure is regular, recurring arrangements in space of nearby amino acid residues in a polypeptide.
	Quaternary structure involves the interaction of subunits in a protein with more than one polypeptide chain.

maroonwallaby335

Proteins are naturally occurring polymers formed by condensation reactions of amino acids, which have the general structure

In this structure, –R represents –H, –CH₃, or another group of atoms; there are 20 different natural amino acids, and each has one of 20 different R groups. (a) Draw the general structure of a protein formed by condensation polymerization of the generic amino acid shown here. (b) When only a few amino acids react to make a chain, the product is called a “peptide” rather than a protein; only when there are 50 amino acids or more in the chain would the molecule be called a protein. For three amino acids (distinguished by having three different R groups, R1, R2, and R3), draw the peptide that results from their condensation reactions. (c) The order in which the R groups exist in a peptide or protein has a huge influence on its biological activity. To distinguish different peptides and proteins, chemists call the first amino acid the one at the “N terminus” and the last one the one at the “C terminus.” From your drawing in part (b) you should be able to figure out what “N terminus” and “C terminus” mean. How many different peptides can be made from your three different amino acids?

purpleyak702

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

Biochemistry 2280A Lecture Notes - Lecture 4: C-Terminus, N-Terminus, Protein Folding

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