2 Cell recognition and immune system

Question 1

What is the function of lymphocytes

Answer 1

Lymphocytes distinguish the body’s own cells and molecules from those that are foreign

Question 2

Name the defenses which protect the human body from pathogens

Answer 2

• Some are immediate defenses like the skin making a barrier •phagocytosis.
• There are also less rapid more specific but longer lasting responses.
• They involve white blood cells called lymphocytes

Question 3

Outline the process of phagocytosis

Answer 3

• Phagocytes have several receptors which attach to chemicals on the surface of pathogens
• Lysosome within phagocyte migrate towards the phagosome
• They release their lysozyme into the phagosome which hydrolyse the bacterium

Question 4

What is a antigen

Answer 4

~ An antigen is any part of an organism which is recognized as foreign by the immune system and then it stimulates an immune response

Question 5

State the immune response which is non specific

Answer 5

-Phagocytosis are non specific and occur whenever there is an infection

Question 6

What is the role of receptors in T cells during cell mediated immunity

Answer 6

• Receptors on a specific helper T cell will fit exactly onto these antigens
• This attachment activates the T cell to divide rapidly by mitosis and make a clone of genetically identical cells

Question 7

Why are cytotoxic T cells important

Answer 7

• Cytotoxic T cells kill abnormal cells and body cells that are infected by pathogens
• They do this by producing a protein called perforin that makes holes in the cell surface membrane
• The cell surface membrane becomes freely permeable to all substances and so cell death occurs

Question 8

Define role of plasma cells

Answer 8

~ Plasma cells secrete antibodies in the blood plasma

~ These antibodies cause the destruction of the antigen