Which of the following types of cells produce and release antibodies?
Natural killer cells.
Cytotoxic T-cells.
Plasma B cells.
Helper T-cells.
The Correct Answer is C
Antibodies are produced by specialized white blood cells called B lymphocytes (or B cells).
When an antigen binds to the B-cell surface, it stimulates the B cell to divide and mature into a group of identical cells called a clone.
The mature B cells, called plasma cells, secrete millions of antibodies into the bloodstream and lymphatic system.
Choice A, Natural killer cells, is not the correct answer because natural killer cells are a type of white blood cell that play a major role in the host-rejection of both tumours and virally infected cells.
Choice B, Cytotoxic T-cells, is not the correct answer because cytotoxic T-cells are a type of white blood cell that kills cancer cells, cells that are infected (particularly with viruses), or cells that are damaged in other ways.
Choice D, Helper T-cells, is not the correct answer because helper T-cells are a type of white blood cell that plays an important role in the immune system by helping other white blood cells fight infections.
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Related Questions
Correct Answer is B
Explanation
Calcium ions play a crucial role in initiating muscle contraction.
When a muscle cell is stimulated to contract by an action potential, calcium channels open in the sarcoplasmic membrane and release calcium into the sarcoplasm.
Some of this calcium attaches to troponin, which causes it to change shape. This shape change exposes binding sites for myosin on the actin filaments.
Myosin’s binding to actin causes cross-bridge formation, and muscle contraction begins.
The other ions mentioned in the question do not have this specific role in muscle contraction.
Potassium ions are important for maintaining the resting membrane potential of cells, but they do not bind to the troponin complex.
Phosphorus ions are important for energy metabolism but do not bind to the troponin complex.
Sodium ions are important for generating action potentials but do not bind to the troponin complex.
Correct Answer is D
Explanation
It can self-renew by dividing and develop into the three primary germ cell layers of the early embryo and into extra-embryonic tissues such as the placenta.
A fertilized egg is a totipotent stem cell and as such can develop into any specialized cell found in the organism.
Choice A is not correct because totipotent cells do not fight infectious diseases.
Choice B is not correct because totipotent cells do not aid in the maturation of sex cells.
Choice C is not correct because totipotent cells do not carry electrical impulses.
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