how do the killer t cells recognize infected cells

ATI TEAS 7

ATI TEAS Practice Science Test

1. How do killer T cells recognize infected cells?

A. The B cells flag the infected cells with amino acids.
B. Tiny bits of the virus's RNA are left around the cell.
C. Macrophages show up to help consume the infected cell.
D. The T cells have receptors that recognize the proteins the virus leaves on the surface of the cell.

Correct answer: D

Rationale: Killer T cells recognize infected cells by detecting viral proteins displayed on the surface of these cells. The T cells possess receptors specifically designed to identify these viral proteins, allowing them to target and eliminate the infected cells. Choice A is incorrect because B cells are not directly involved in the recognition process of infected cells by killer T cells. Choice B is incorrect because tiny bits of the virus's RNA being left around the cell is not how killer T cells primarily recognize infected cells. Choice C is incorrect because while macrophages play a role in immune responses, they do not directly assist in the recognition of infected cells by killer T cells.

2. Which of the following neurotransmitters slows down the activity of neurons to prevent overexcitation?

A. Acetylcholine
B. Dopamine
C. GABA
D. Serotonin

Correct answer: C

Rationale: The correct answer is C: GABA (gamma-aminobutyric acid). GABA is an inhibitory neurotransmitter that slows down neuronal activity, helping to prevent overexcitation in the brain. It counterbalances the effects of excitatory neurotransmitters like glutamate, playing a crucial role in maintaining the balance of neuronal activity in the brain. Acetylcholine (Choice A) is primarily an excitatory neurotransmitter involved in muscle movement and cognitive functions. Dopamine (Choice B) plays a role in reward-motivated behavior and motor control. Serotonin (Choice D) is involved in regulating mood, appetite, and sleep but is not primarily responsible for slowing down neuronal activity to prevent overexcitation.

3. Which of the following is the primary physical barrier the body uses to prevent infection?

A. mucus membranes
B. stomach acid
C. skin
D. urine

Correct answer: C

Rationale: The correct answer is 'C: skin.' The skin is the primary physical barrier the body uses to prevent infection. It acts as a protective shield that prevents harmful microorganisms from entering the body. The outer layer of the skin, known as the epidermis, acts as a tough physical barrier that blocks the entry of pathogens. Additionally, the skin has special immune cells that can help fight off invaders that manage to breach the physical barrier. Choices A, B, and D are incorrect. While mucous membranes, stomach acid, and urine play important roles in the body's defense against pathogens, the primary physical barrier is the skin, which covers the entire body and provides a robust protective barrier.

4. Which term refers to the resistance of a liquid to flow?

A. Density
B. Viscosity
C. Surface tension
D. Boiling point

Correct answer: B

Rationale: Viscosity is the term that refers to the resistance of a liquid to flow. It is a measure of how thick or sticky a fluid is and determines how easily a liquid can flow. Density (A) is a measure of how much mass is contained in a given volume and is not related to the resistance of a liquid to flow. Surface tension (C) is the property of a liquid that allows it to resist an external force due to the cohesive nature of its molecules, but it is not directly related to the resistance of a liquid to flow. Boiling point (D) is the temperature at which a liquid changes to a vapor and is not a measure of the resistance of a liquid to flow.

5. What is the shape of the DNA molecule?

A. Linear
B. Circular
C. Double helix
D. Straight chain

Correct answer: C

Rationale: The correct answer is C: Double helix. The shape of the DNA molecule is a double helix, a structure first described by James Watson and Francis Crick in 1953. This shape consists of two strands twisted around each other in a spiral. The double helix structure allows DNA to be compactly stored within the cell nucleus and provides stability to the molecule. Options (A) Linear, (B) Circular, and (D) Straight chain are incorrect as they do not accurately represent the shape of the DNA molecule. DNA is not linear but rather forms a twisted double helix; it is not circular like a ring but has a spiral structure, and it is not a straight chain but a twisted ladder-like structure.