AP Biology : Immune System

Study concepts, example questions & explanations for AP Biology

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Example Questions

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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:

I only

II and III

III only

II only

I and III

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 I and cytotoxic T-cells

MHC II and T-helper 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 #31 : Immune System

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

Adipose cells

White blood 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.

Example Question #32 : Immune System

Which of the following functions is NOT performed by the lymphatic system?

Possible Answers:

Returns interstitial fluid to the bloodstream

Provides additional oxygen for body tissues

Elicits an immune response in the presence of an infection

Transports fat digestates and places them into the bloodstream

Correct answer:

Provides additional oxygen for body tissues

Explanation:

The lymphatic system is responsible for removing excess fluid from the interstitium and returning it to the bloodstream. The fluid will travel through lymph nodes, which monitor for the presence of microbes in the blood. If microbes are present, the lymph nodes will mount an immune response. The lymphatic system also reroutes fat digestates from the small intestine's capillaries and drains them into the veins of the neck. Lymphatic vessels do not assist in the transfer of oxygen to body tissues. 

Example Question #33 : Immune System

The lymphatic system is involved in all except which of the following processes?

Possible Answers:

Transport fats and fat-soluble vitamins that are absorbed via the digestive tract

Transport red blood cells for destruction in the spleen

It is a crucial component of the immune system

Maintain blood volume by reducing fluid loss to the extracellular compartment

Correct answer:

Transport red blood cells for destruction in the spleen

Explanation:

Red blood cells generally do not leave the circulatory system; thus there are very few opportunities for lymphatic vessels to pick up red blood cells in the extracellular space.

The lymphatic system plays a key role in transporting immune cells, such as lymphocytes, throughout the body. When fats are emulsified and digested in the small intestine, they are transported into the lymph rather than into the blood. When plasma and fluids leak out of capillaries, the lymphatic system is responsible for collecting and returning these fluids to circulation. A fault in this function of the lymphatic system results in edema.

Example Question #34 : Immune System

What is the most likely mechanism a virus could use to evade the immune system that causes periodic outbreaks in an individual over a long period of time?

Possible Answers:

The virus manages to attack immune cells needed to control the infection

The virus is continually evolving and manages to vary its antigenic signature so that it can evade detection

The virus remains dormant until a stimulus, such as stress or infection with another pathogen, reactivates the virus 

The virus is actively causing infected cells to secrete factors that suppress the immune system

Correct answer:

The virus remains dormant until a stimulus, such as stress or infection with another pathogen, reactivates the virus 

Explanation:

Some viruses evade the immune system using a mechanism known as latency. The virus essentially becomes dormant, usually in cells such as neurons that have few major histocompatibility (MHC) class I molecules. The combination of limited to no active viral replication combined with residence in cells with few MHC lass I molecules allows the virus to evade routine immune monitoring.

When conditions arise, such as fever due to infection caused by another pathogen or emotional stress, the virus can becomes reactivated and can result in an outbreak.

Example Question #4 : Understanding Other Immune System Components

Which of the following statements is a commonality between T-cell receptors and B-cell receptors?

Possible Answers:

Both receptors have variable regions that form an antigen binding site

Both receptors consist of both heavy chains and two light chains to form the antigen binding domain 

Both receptors are able to bind to intact antigens

Both receptors recognize antigens in conjunction with major histocompatibility complex (MHC) proteins

Correct answer:

Both receptors have variable regions that form an antigen binding site

Explanation:

T-cells generally serve to recognize antigens and escort them to B-cells to elicit a response (helper T-cells) or to recognize antibodies bound to infected cells (cytotoxic T-cells). B-cells, in contrast, will directly secrete antibodies against the antigen after binding of the antigen at the membrane.

Both types of cells have receptors that can bind to antigens, allowing for recognition and communication. Other commonalities include the presence of a transmembrane domain and the presence of a variable region, which will allow for specificity in antigen binding.

The similarities are mainly structural, and the receptors have many functional differences. T-cell receptors will only bind fragments of antigens, while B-cell receptors will bind full molecules. Only T-cell receptors will interact with major histocompatibility complexes (MHC). Though the structure of both receptors types is determined by peptide chains, B-cells use heavy and light chains, while T-cells use alpha and beta chains.

Example Question #5 : Understanding Other Immune System Components

The spleen is an organ of the __________.

Possible Answers:

circulatory system

immune system

digestive system

respiratory system

Correct answer:

immune system

Explanation:

The spleen plays a key role in the immune system as one of the blood filtration centers of the body. It is also involved as a lymphatic organ, allowing filtrates from the blood to be distributed to the body via lymph.

Example Question #35 : Immune System

Which cells of the immune system are largely responsible for phagocytosis?

Possible Answers:

Antibodies

Macrophages

T helper cells

B cells

Correct answer:

Macrophages

Explanation:

Macrophages and neutrophils are the major cells of the immune system responsible for phagocytosis. Phagocytosis means ingestion of material. Therefore these cells work as "garbage collectors" within the body. Cells destined for destruction are tagged for phagocytosis by special molecules.

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