W1 Flashcards
What role does the hydrophobic effect play in protein folding?
a. The hydrophobic effect is the second law of thermodynamics.
b. It allows for amino acids in a polypeptide chain to associate and avoid contact with water.
c. Proteins only fold when they become insoluble in water.
d. It causes an overall decrease in the entropy of the system
b
Which of the following pairs of functional groups can interact to form a hydrogen bond?
1. A phosphate and a phenyl ring.
2. A tertiary amine and an ether.
3. A carboxyl and an amide.
4. An aldehyde and a carbonyl.
carboxyl and amide
A hydrogen bond requires both a donor (H bonded to an electronegative atom) and an acceptor (electronegative atom with a lone pair of electrons). The lone pairs of electrons on the carbonyl oxygen of the carboxyl group and amide group can act as acceptors. The H on the OH and NH2 groups of the carboxyl and amide groups, respectively, act as donors.
The other incorrect answers may not have an acceptor with a lone pair of electrons or a hydrogen that can be used as a donor.
Sucrase is an example of a:
- transporter
- enzyme
- co-enzyme
- hormone
enzyme
Sucrase is an enzyme that binds specifically to sucrose and catalyzes its breakdown into glucose and fructose.
Proteins that catalyze chemical reactions are classified as:
- Enzymes
- Catalases
- Hormones
- Proteases
1
Enzymes are a class of proteins that help catalyze, or speed up, chemical reactions.
Proteases and catalases are proteins that fall under the enzyme classification, but an enzyme is the parent or general group name, with proteases and catalases being enzymes that catalyze distinct reactions.
Hormones are signalling molecules that carry out their function by binding to other proteins. There are one or two rare examples of hormones that have enzymatic activity but binding is their main mechanism of action.
Which ONE of the following pairs of functional groups can interact by forming a hydrogen bond at physiological pH?
- Two amides
- Two phenyl rings
- Two aldehydes
- Two esters
A hydrogen bond requires two functional groups where one functional group acts as a donor and the other as an acceptor.
Aldehydes and esters can act as hydrogen bond acceptors through their lone pairs of electrons, but not as donors, as they lack an H atom bound to an electronegative atom.
A single amide can act as a hydrogen bond donor and acceptor.
Phenyl rings are hydrophobic and cannot act as a donor or acceptor.
Which ONE of the following non-covalent forces can contribute the MOST to a molecule (e.g. drug or cofactor) that interacts with a soluble protein?
* A disulfide bond
* Ionic interactions
* Van der Waals forces
* The hydrophobic effect
ionic
When considering non-covalent interactions between molecules, it is the number of strong, intermolecular interactions that dictates the strength of binding.
Ionic interactions are the strongest of the non-covalent forces and are much stronger than Van der Waals forces. They can be either interactions between full positive and negative ions, or hydrogen bonds that involve an unequal sharing of electrons creating a partial positive and partial negative charge.
The hydrophobic effect arises due to hydrophobic molecules avoiding water but is not considered a force. Hydrophobic interactions do arise due to the aversion of water, but a soluble protein would have hydrophilic groups at its surface to interact with water or the molecule.
Disulfide bonds are covalent interactions. They are commonly found within proteins, but are uncommon between binding partners.
Which ONE of following is FALSE about co-factors?
* They can assist in the proper folding of proteins.
* They can be metal ions.
* They are inorganic molecules.
* They can be tightly or loosely bound to other proteins.
Some co-factors can be tightly or even covalently bound, while others can be loosely bound. But all bind to their enzyme to assist with folding into its proper structure and/or its function. Co-factors can be metal ions, but they can also be small organic molecules.
