Question 1

What element makes protein different from carbohydrate and fat?

Accepted Answer

Nitrogen is the element that makes protein different from carbohydrates and fats. While carbohydrates and fats are made up of primarily carbon, hydrogen, and oxygen, proteins contain nitrogen in addition to these three elements. This is why proteins are important for building and repairing tissues, while carbohydrates and fats are primarily used for energy.

Question 2

The process of transferring the amine group from one amino acid to another is called

Accepted Answer

The process of transferring the amine group from one amino acid to another is called transamination. This process is important in amino acid metabolism and is carried out by enzymes called transaminases. Transamination reactions play a crucial role in the synthesis of non-essential amino acids in the body as well as in the metabolism of nitrogenous waste. The other options, gene expression and alteration, are not related to this process, while deamination refers specifically to the removal of an amine group from an amino acid.

Question 3

The process through which mRNA copies genetic information from DNA and carries it to the ribosome is called

Accepted Answer

The process described in the question is transcription, where mRNA is created by copying genetic information from DNA in the cell nucleus before it moves to the ribosome for translation. Option A, translation, is the process where mRNA is decoded by the ribosome to make a protein. Option B, deamination, is the process where an amino group is removed from a molecule. Option C, denaturation, is the process where a protein loses its shape due to changes in temperature or pH.

Question 4

A complete protein

Accepted Answer

A complete protein contains all 9 essential amino acids, which are amino acids that the human body cannot produce on its own and must obtain from food sources. It is not necessary for a complete protein to contain all 20 amino acids, and it can still be considered complete even if some of its amino acids have been denatured. The composition of di- and tripeptides does not determine the completeness of a protein.

Question 5

In the body, buffers are very important in

Accepted Answer

Buffers are crucial in maintaining the pH of bodily fluids within a narrow range in order to maintain proper acid-base balance. This is necessary for many physiological processes to function properly. The other answer choices do not accurately reflect the role of buffers in the body.

Question 6

In phenylketonuria (PKU), which amino acid becomes conditionally essential?

Accepted Answer

In PKU, the body is unable to properly metabolize phenylalanine, leading to a build-up of this amino acid and potentially harmful byproducts. As a result, individuals with PKU must follow a low-phenylalanine diet, which may limit their intake of tyrosine, the amino acid that is normally synthesized from phenylalanine. Therefore, tyrosine becomes conditionally essential in individuals with PKU who are unable to get enough of it from dietary sources.

Question 7

MOST of the proteins in the body are synthesized from

Accepted Answer

Proteins are composed of amino acids, and there are 20 different types of amino acids that can be used to build them. Therefore, MOST proteins in the body are synthesized from twenty amino acids.

Question 8

Of the 20 amino acids relevant to the human body, how many are considered nonessential?

Accepted Answer

There are 11 nonessential amino acids that the human body can synthesize on its own.

Question 9

Which of the following is the MOST complete protein from a plant source?

Accepted Answer

Soybeans are the most complete protein from a plant source as they contain all the essential amino acids needed by the body. Green beans may contain some protein, but it is not a complete protein. Bread and apples do not contain significant amounts of protein.

Question 10

Which of the following is NOT a component of an amino acid molecule?

Accepted Answer

Amino acids consist of a central carbon bonded to an amine group (NH2), an acid group (COOH), a hydrogen atom, and a side chain or R-group. Fatty acid groups are not found in amino acids.

Question 11

The twisting, spiral shape formed by the sequence and chemical properties of its amino acids refers to what part of a protein's structure?

Accepted Answer

The twisting, spiral shape formed by the sequence and chemical properties of its amino acids refers to the secondary structure of the protein. The primary structure refers to the linear sequence of amino acids, while the tertiary structure refers to the overall 3D shape of the protein and the quaternary structure refers to the arrangement of multiple protein subunits.

Question 12

What dictates the structure of a protein molecule synthesized by the body?

Accepted Answer

The structure of a protein molecule synthesized by the body is dictated by the DNA inside the nucleus of the cell. The sequence of nucleotides in the DNA determines the sequence of amino acids in the protein, which in turn determines its structure and function.

Question 13

Egg whites stiffen when they are whipped. The change that occurs in the protein is called

Accepted Answer

The change that occurs in the protein is called denaturation, which is the process of breaking down the natural structure of a protein molecule. Whipping egg whites introduces air into the protein, causing it to unfold and form new bonds with other proteins, thereby stiffening and forming peaks.

Question 14

The part of the protein molecule that carries nitrogen is the

Accepted Answer

The amine group (-NH2) is the part of the protein molecule that carries nitrogen. The acid group (-COOH) is the part that carries oxygen and hydrogen. The side chain or R-group varies in each amino acid and does not necessarily contain nitrogen. The hydrogen group does not carry nitrogen.

Question 15

Two amino acids are joined together by a peptide bond to form a dipeptide. What is the by-product of this process?

Accepted Answer

When two amino acids are joined together by a peptide bond, a molecule of water is released as a by-product. This is called a condensation reaction. Therefore, the correct answer is B, water.

Question 16

In what structure of the mammalian cell are proteins synthesized?

Accepted Answer

Proteins are synthesized in ribosomes, which may be free in the cytoplasm or attached to the endoplasmic reticulum. The nucleus contains DNA and directs the cell's activities, but it does not directly synthesize proteins. The cell membrane plays a role in transport of materials in and out of the cell, but it is not involved in protein synthesis. The mitochondria are the organelles responsible for cellular respiration and energy production, but not protein synthesis.

Question 17

Which of the following foods is a source of complete protein?

Accepted Answer

Chicken is a complete protein source, meaning it contains all essential amino acids necessary for the body to build and repair tissues. Broccoli, apples, and whole grain bread do not contain all essential amino acids in sufficient amounts to be considered a complete protein source.

Question 18

Which of the following is a body protein that is stored in a gland and secreted to an organ to restore normal body conditions or balance?

Accepted Answer

Hormones are body proteins that are stored in glands and secreted to an organ to restore normal body conditions or balance. Enzymes catalyze chemical reactions, antibodies are involved in the immune response, and buffers help maintain pH balance in a solution.

Question 19

How many strings of amino acids does a polypeptide consist of?

Accepted Answer

A polypeptide consists of more than ten strings of amino acids. A single polypeptide chain typically contains hundreds to thousands of amino acids.

Question 20

Which part of an individual amino acid distinguishes it from other amino acids?

Accepted Answer

The side chain, also known as the R-group, is the part of an amino acid that distinguishes it from other amino acids. The central carbon, amine group, and acid group are common features among all amino acids.

Quiz 6: Proteins: Crucial Components of All Body Tissues