AP Biology : Understanding Antibodies and Antigens

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #1 : Understanding Antibodies And Antigens

What happens antibodies for a specific antigen when that antigen is presented in the body?

Possible Answers:

The body will multiply the antibodies to the antigen

The body will create alternative forms of the antibody

The body will destroy the antibodies and uptake the antigen

The body will attack the antibodies that are attacking the antigen

The body will make antibodies with similar structure to the antigen

Correct answer:

The body will multiply the antibodies to the antigen

Explanation:

The immune system is very adaptive. The body has many antibodies that will each recognize different antigens. If an antibody binds to an antigen, the antibody will be copied so that the body can quickly recognize the threat if it is exposed to the antigen a second time. This process is known as the adaptive immune response.

When an antigen is presented for a second time, antibodies to the antigen are released. These antibodies bind to the antigen, labelling it for attack by immune cells and preventing it from interacting the membrane proteins on the host cells.

Example Question #2 : Understanding Antibodies And Antigens

Which of the following statements describes the primary role of major histocompatibility complex (MHC) class I molecules?

Possible Answers:

Activation of the complement cascade

Stimulate production of interferon gamma

Presentation of short peptide fragments that are recognized by cytotoxic T-cells

Presentation of short peptide fragments to MHC class II molecules

Correct answer:

Presentation of short peptide fragments that are recognized by cytotoxic T-cells

Explanation:

Major histocompatibility complex (MHC) class I molecules are found on virtually all cells in the body. They function in routine immune monitoring through presentation of short peptide fragments derived from degradation of intracellular proteins contained within the cell. The T-cell receptor on cytotoxic T-cells interacts with MHC class I, and if a foreign pathogen or peptide is presented, the cytotoxic T-cell becomes activated to kill infected cells. The same system also functions for detection of potential cancer cells.

Example Question #3 : Understanding Antibodies And Antigens

An antibody can be best classified as which of the following?

Possible Answers:

A protein

A cell

A virus

An enzyme

Correct answer:

A protein

Explanation:

Antibodies are proteins created by the immune system in order to neutralize foreign objects. An antibody would not be classified as an enzyme because it does not catalyze chemical reactions. When a foreign pathogen enters the body, it will have foreign receptors on its surface. These foreign receptors are known as antigens. When a pathogen is destroyed, immune cells can carry a sample of the antigen to the T-cells for identification. The T-cells help activate B-cells that will synthesize an antibody against the particular antigen. The selected B-cells differentiate into plasma cells and secrete antibody proteins into the blood, which bind the antigens and label the pathogen as foreign. This label attracts other immune cells to attack and destroy the pathogen.

Example Question #4 : Understanding Antibodies And Antigens

Which of the following correctly describes the relationship between an antigen and an antibody?

Possible Answers:

Each antibody recognizes a variety of different antigens

Each antigen has a number of different antibodies that will bind to it

The antigen and antibody are perfectly complimentary to one another

Antibodies attack antigens and neutralize their effects

Antibodies are only made once antigens enter the body

Correct answer:

The antigen and antibody are perfectly complimentary to one another

Explanation:

Antibodies are continuously made in the body in different shapes and forms. They are then sent into the blood stream to test for the presence of compatible antigens. Each antibody can only bind to one antigen, and each antigen can only bind to one antibody. Think of them like a codon-anticodon pair; there is only one possibility for them to form a perfectly complementary pair. Once the correct antibody binds to an antigen, they are tagged and used to stimulate production of more antibodies. The antibodies are only capable of binding and tagging the antigens. Cytotoxic T-cells are then able to recognize antibody binding patterns and actually destroy the infected cell.

Example Question #5 : Understanding Antibodies And Antigens

Major histocompatibility molecules (MHC) are critical for the functioning of the immune system. These proteins are utilized allow for communication between the immune system and the cells. MHC I are utilized to show which cells are in fact part of the body and which are foreign. MHC II are utilized to show the immune system when there is an intruder.

MHC I molecules are derived from chromosome 6. On chromosome 6, there is a specific gene that encodes for the molecule. On the gene, there are 3 locus (A, B, C) which allows for variability in the binding site of the MHC I molecule. The MHC gene is co-dominance and therefore adds to its diversity. During development, the gene is transcribed into MHC I molecules. However, some of these are broken down and react with a particular MHC I molecule. The reaction allows for the MHC I molecule to surface onto the cellular membrane and to self-identify the protein for the cytotoxic T-cell.

After translation, MHC II molecules are transported to the endosome. When a pathogen binds to the proper MHC II binding site, these molecules are then presented to T-Helper cells. In comparison, MHC I molecules interact with endogenous antigens whereas MHC II molecules interact with exogenous antigens.

Based on the passage, where is the interaction between the MHC II molecule and the particular antigen occur? 

I. Endoplasmic reticulum 

II. Endosome

III. Cytoplasm 

Possible Answers:

I only

I, II, and III

III only

II only

II and III

Correct answer:

II only

Explanation:

According to the passage, after the MHC II molecules are fully synthesized in the endoplasmic reticulum, they are transported to the endosome. Foreign molecules are transported into the cell where they are degraded in the endosome as well. From there, the degraded pathogen interact with the MHC II molecule. 

Example Question #6 : Understanding Antibodies And Antigens

Major histocompatibility molecules (MHC) are critical for the functioning of the immune system. These proteins are utilized allow for communication between the immune system and the cells. MHC I are utilized to show which cells are in fact part of the body and which are foreign. MHC II are utilized to show the immune system when there is an intruder.

MHC I molecules are derived from chromosome 6. On chromosome 6, there is a specific gene that encodes for the molecule. On the gene, there are 3 locus (A, B, C) which allows for variability in the binding site of the MHC I molecule. The MHC gene is co-dominance and therefore adds to its diversity. During development, the gene is transcribed into MHC I molecules. However, some of these are broken down and react with a particular MHC I molecule. The reaction allows for the MHC I molecule to surface onto the cellular membrane and to self-identify the protein for the cytotoxic T-cell.

After translation, MHC II molecules are transported to the endosome. When a pathogen binds to the proper MHC II binding site, these molecules are then presented to T-Helper cells. In comparison, MHC I molecules interact with endogenous antigens whereas MHC II molecules interact with exogenous antigens.

Based on the passage, where is the interaction between the MHC I molecule and the particular antigen occur? 

I. Endoplasmic reticulum 

II. Endosome

III. Cytoplasm 

Possible Answers:

III only

II only

I and III

II and III

I only

Correct answer:

I only

Explanation:

From the passage, the MHC I molecule's blueprint is on chromosome 6. Therefore, the DNA must have been transcribed in the nucleus then translated in the ribosome. These ribosomes are on the endoplasmic reticulum. While in the endoplasmic reticulum, some of these proteins are degraded and react with a particular MHC I molecule.  

Example Question #7 : Understanding Antibodies And Antigens

Major histocompatibility molecules (MHC) are critical for the functioning of the immune system. These proteins are utilized allow for communication between the immune system and the cells. MHC I are utilized to show which cells are in fact part of the body and which are foreign. MHC II are utilized to show the immune system when there is an intruder.

MHC I molecules are derived from chromosome 6. On chromosome 6, there is a specific gene that encodes for the molecule. On the gene, there are 3 locus (A, B, C) which allows for variability in the binding site of the MHC I molecule. The MHC gene is co-dominance and therefore adds to its diversity. During development, the gene is transcribed into MHC I molecules. However, some of these are broken down and react with a particular MHC I molecule. The reaction allows for the MHC I molecule to surface onto the cellular membrane and to self-identify the protein for the cytotoxic T-cell.

After translation, MHC II molecules are transported to the endosome. When a pathogen binds to the proper MHC II binding site, these molecules are then presented to T-Helper cells. In comparison, MHC I molecules interact with endogenous antigens whereas MHC II molecules interact with exogenous antigens.

Based on the passage, which MHC molecule and T-cell is targeted post-organ transplant to avoid rejection of the organ? 

Possible Answers:

MHC I and T-helper cells. 

MHC II and cytotoxic T-cells 

MHC II and T-helper cells 

MHC I and cytotoxic T-cells

None of these

Correct answer:

MHC I and cytotoxic T-cells

Explanation:

According to the passage, MHC I and cytotoxic t-cells are responsible for identifying the body's own protein. During organ transplant, foreign MHC I molecules are presented into the body. The host's cytotoxic T-cells will recognize these as foreign and will attack. 

Example Question #8 : Understanding Antibodies And Antigens

The chemical reaction in the immune system that protects the body from pathogens is a result of antibodies created by which of the following?

Possible Answers:

Platelets

Glandular cells

White blood cells

Adipose cells

Red blood cells

Correct answer:

White blood cells

Explanation:

White blood cells is the correct answer here. After pathogen has entered the body, the antibodies to combat it are created by B cells that are a part of the white blood cells in the human body.

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