Biochemistry : Identifying Specific Protein Functions

Study concepts, example questions & explanations for Biochemistry

varsity tutors app store varsity tutors android store

Example Questions

← Previous 1

Example Question #1 : Identifying Specific Protein Functions

Which of these is not a valid classification of protein function?

Possible Answers:

Signaling molecules

Receptors

All of these are functions of proteins

Structural elements

Enzymes

Correct answer:

All of these are functions of proteins

Explanation:

Proteins are the most diverse group of macromolecule. They can be fibrous (structural) or globular (receptors, enzymes, signaling molecules, and more).

Example Question #2 : Identifying Specific Protein Functions

Which of these amino acids is unlike the others?

R, K, C, D, E

Possible Answers:

K

D

C

R

E

Correct answer:

C

Explanation:

Cysteine (C) is the only amino acid of the group to possess an uncharged R group at normal blood pH levels.

Arginine (R) and lysine (K) have positively charged R groups, and are considered basic. Aspartate (D) and glutamate (E) have negatively charged R groups, and are considered acidic.

Example Question #3 : Identifying Specific Protein Functions

Which of these amino acids is unlike the others?

S, A, T, Q, N

Possible Answers:

A

Q

T

N

S

Correct answer:

A

Explanation:

Alanine (A) is the only hydrophobic amino acid in the group.

Serine (S), threonine (T), glutamine (Q), and asparagine (N) have polar, uncharged R groups.

Example Question #4 : Identifying Specific Protein Functions

Which of the following statements best describes low-density lipoproteins as compared to other lipoproteins?

Possible Answers:

They have the highest protein content

They have a higher content of triglycerides than very low-density lipoproteins

They have the most triglycerides and least protein

They have the highest content of cholesterol and cholesterol esters

Correct answer:

They have the highest content of cholesterol and cholesterol esters

Explanation:

Low-density lipoproteins have the highest content of cholesterol and cholesterol esters. There are essentially five classes of blood lipoproteins: chylomicrons, very-low-density lipoproteins, intermediate-density lipoproteins, low-density lipoproteins, and high-density lipoproteins. Chylomicrons have the lowest density of the five classes of lipoproteins. This is because the have the highest proportion of triglycerides and the least lowest proportion of protein. Very-low-density lipoproteins are a bit more dense than chylomicrons; however, the relative amount of triglycerides is still high. Intermediate-density lipoproteins which are formed from the very-low-density lipoproteins have a higher density than very-low-density lipoproteins due to the fact that they have less than half of the amount of triglycerides as very-low-density lipoproteins. Low-density lipoproteins have the highest amount of cholesterol and an even lesser amount of triglycerides than intermediate-density lipoproteins. Lastly, high-density lipoproteins are the densest of the lipoproteins due to the fact that they have the highest amount of protein in relation to the amount of triglycerides they contain.

Example Question #5 : Identifying Specific Protein Functions

A an excess intake of __________ leads to its conversion to triglycerides.

Possible Answers:

nucleic acids

carbohydrates

water

vitamins

Correct answer:

carbohydrates

Explanation:

The dietary intake of carbohydrate, in excess of the fuel requirement of the liver, leads to their conversion into triacylglycerols. These triacylglycerols are packaged into very-low-density lipoproteins (VLDL's) and released into the circulation for delivery to the various tissues (primarily muscle and adipose tissue) for storage or production of energy through oxidation. VLDL's are, therefore, the molecules formed to transport endogenously derived triacylglycerols to extra-hepatic tissues. The fatty acid portion of VLDL's is released to adipose tissue and muscle in the same way as for chylomicrons, through the action of lipoprotein lipase.

Example Question #6 : Identifying Specific Protein Functions

The cell requirement for cholesterol as a membrane component is satisfied by which of the following?

Possible Answers:

Intermediate-density lipoproteins

High-density lipoproteins

Glycoproteins

Low-density lipoproteins

Correct answer:

Low-density lipoproteins

Explanation:

A cell's necessity for cholesterol as a part of the cell membrane is accomplished by two ways: either it is synthesized from within the cell by the cell, or it is supplied by low-density lipoproteins and chylomicrons. The dietary cholesterol that goes into chylomicrons is supplied to the liver by the interaction of chylomicron remnants with the remnant receptor. In addition, cholesterol synthesized by the liver can be transported to extra-hepatic tissues if packaged in very-low-density lipoproteins (VLDL's). In the circulation VLDLs are converted to low-density liporoteins through the action of lipoprotein lipase.

Example Question #7 : Identifying Specific Protein Functions

Very-low-density lipoproteins are degraded by which of the following?

Possible Answers:

Lipoprotein lyase

Lipoprotein hydrolase

Lipoprotein dehydrogenase

Lipoprotein lipase

Correct answer:

Lipoprotein lipase

Explanation:

Very-low-density lipoprotein (LDL) triglycerides are broken down by lipoprotein lipase forming intermediate density lipoproteins. Intermediate density lipoproteins can either be brought into the liver through a receptor-mediated event or it may be further digested to form low density lipoproteins. LDL may be brought into the liver also by a receptor-mediated even in the liver. 

Example Question #8 : Identifying Specific Protein Functions

__________ can be converted into variant forms of high density lipoproteins.

Possible Answers:

Nascent high-density lipoproteins

Nascent intermediate-density lipoproteins

Nascent low-density lipoproteins

Nascent chylomicrons

Correct answer:

Nascent high-density lipoproteins

Explanation:

High density lipoproteins (HDL's) are converted into spherical lipoprotein particles through the accumulation of cholesterol esters. This accumulation converts nascent HDL to HDL2 and HDL3. Any free cholesterol present in chylomicron remnants and intermediate-density lipoproteins can be esterified through the action of the HDL-associated enzyme, lecithin-cholesterol acyltransferase (LCAT). LCAT is synthesized in the liver and so named because it transfers a fatty acid from the second carbon position of lecithin to the hydroxyl group on the third carbon of cholesterol, generating a cholesterol ester and lysolecithin. The activity of LCAT requires interaction with apoA-I, which is found on the surface of HDLs.

 

Example Question #9 : Identifying Specific Protein Functions

Which is not a function of apoprotein-100?

Possible Answers:

Uptake of remnant intermediate-density lipoproteins by liver

Assembly and secretion of chylomicrons

Activates lipoprotein lipase

Assembly and secretion of very-low-density lipoproteins

Correct answer:

Assembly and secretion of chylomicrons

Explanation:

Apoprotein-100 is not responsible for the secretion and assembly of chylomicrons. That is the responsibility of apoprotein-48. Apoprotein-48 is a shortened version of apoprotein-100. The exclusive apolipoprotein of low density lipoproteins (LDL's) is apoB-100. LDL's are taken up by cells via intermediate-density lipoprotein receptor-mediated endocytosis. The uptake of LDL's occurs predominantly in liver (75%), adrenal glands, and adipose tissue. As with intermediate-density lipoproteins, the interaction of LDL's with LDL receptors requires the presence of apoB-100. Apoprotein-48 is also responsible for activation of lipoprotein lipase and uptake of chylomicron remnants by liver. Chylomicrons function in the transport of dietary triglycerides and cholesterol from intestine to peripheral tissues

Example Question #10 : Identifying Specific Protein Functions

How are gap junctions regulated?

Possible Answers:

 concentration

 concentration

 concentration

 concentration

Correct answer:

 concentration

Explanation:

Gap junctions are are closed at high  concentrations and open at low  concentrations.

← Previous 1
Learning Tools by Varsity Tutors

Incompatible Browser

Please upgrade or download one of the following browsers to use Instant Tutoring: