Cell immunity

Question 1

What is the definition of a pathogen?

Answer 1

a harmful microbe that can damage tissues in our bodies

Question 2

What is the definition of a non-specific immune response and name the types of the non-specific immune responses.

Answer 2

our immediate response to infection and is carried out in exactly the same way regardless of the pathogen

Physical barriers and phagocytosis

Question 3

What are the physical non-specific barriers, which prevent pathogens from entering our body?

Answer 3

• Our body cavities (e.g. eyes, nose, mouth, genitals)
• Eyes = enzymes in tears destroy micro-organisms
• The trachea
• Our stomach
• The insides of our intestines and the surface of our skin are covered in harmless bacteria which will compete with any pathogenic organisms and reduce their ability to grow.

Question 4

what is the definition of a specific immune response and what are specific immune responses?

Answer 4

happens after the non-specific response and is an attack aimed at a particular antigen.

It is slower and provides long term immunity

It involves the activation of two types of immune cells: T lymphocytes and B lymphocytes

Question 5

How do pathogens get destroyed by phagocytosis?

Answer 5

Chemical products of pathogens act as attractants, causing the phagocytes to move toward the pathogen.

Phagocyte attaches to the surface of the bacteria

Engulfs bacteria to form a vesicle (phagosome)

Lysosome fuses its membrane with the phagosome and breaks the cell wall.

Lysozymes destroy ingested bacteria by hydrolysis of their cell walls.

The soluble products from the breakdown of the pathogen are absorbed into the cytoplasm of the phagocyte

the phagocyte releases insoluble dissolved substances out of the cell

Question 6

Why are antibodies only effective against a specific pathogen?

Answer 6

• Antigens have a specific shape/tertiary structure
• Which the antibodies are complementary to antigen and a antigen-antibody complex forms

Question 7

What is the definition of antigens?

Answer 7

any part of an organism or substance that is recognised as non-self by the immune system and stimulates an immune respose

Question 8

Where are lymphocytes produced?

Answer 8

in the bone marrow by stem cells

Question 9

What are T-cells?

Answer 9

lymphocytes matured in the thymus gland and associated with cell-mediated immunity

Question 10

What does cell-mediated immunity mean?

Answer 10

immunity involving body cells

Question 11

How do T-lymphocytes distinguish invader cells from normal cells?

Answer 11

• phagocytes that have engulfed and hydrolysed a pathogen present have some of the pathogen’s antigens on their own cell-surface membrane
• body cells invaded by a virus present have some of the viral antigens on their own cell-surface membrane
• transplanted cells from individuals of the same species have different antigens on their cell -surface membrane
• cancer cells are different from normal body cells and present antigens on their cell-surface membrane

Question 12

What is antigen presentation?

Answer 12

When macrophages expose antigens from the pathogens on their surface

Question 13

How do T-cells respond to infection by a pathogen?

Answer 13

• When phagocytes engulf pathogens, they present antigens on its cell-surface membrane
• Receptors on a specific helper T cell fit exactly onto these antigens
• this attachment activates the T-cel to divide rapidly by mitosis and form a clone of genetically identical cells
• the cloned T cells either: develop into memory cells, stimulate phagocytes to engulf pathogens by phagocytosis, stimulate B cells to divide and secrete their antibody, or activate cytotoxic T cells.

Question 14

How do cytotoxic T cells kill infected cells?

Answer 14

produce perforin ( a chemical protein) which makes holes in the cell-surface membrane. These holes mean the cell membrane becomes freely permeable to all substances and the cell dies as a result

Question 15

What is the definition of a clone?

Answer 15

a group if genetically identical cells or organisms formed from a single parent

Question 16

How does humoral immunity work?

Answer 16

B cell with complementary antibodies to the antigen on the pathogen, binds to the pathogen

B cell engulfs pathogen (endocytosis) and presents the antigens on its surface

T helper cells bind to the antigens presented and stimulate the B cell to divide by mitosis = forms clones (clonal selection)

Clones differentiate into plasma cells or memory cells

Question 17

How do Memory cells (B/T) work?

Answer 17

made during the specific immune response after a new infection by a pathogen (called a primary infection) B and T memory cells remain in the blood if person is reinfected by the same pathogen (called a secondary infection) the memory cells will recognise the pathogen and produce antibodies RAPIDLY and to a LARGE amount therefore the pathogen is killed before it can cause harm = immunity

Question 18

What are antibodies and how do they protect us?

Answer 18

proteins with specific binding sites synthesised by B cells. They react with an antigen on the surface of the non-self material by binding to them

Question 19

What is immunological memory?

Answer 19

when new t helper cells develop memory cells that survive for long periods of time

Question 20

Draw and label an antibody?

Answer 20

Question 21

What makes the binding site specific to the antigen?

Answer 21

Each binding site consists of a sequence of amino acids that form a specific 3-D shape that bonds directly to a specific antigen

Question 22

What is the scientific name of an antibody? Other than globular, what type of protein is it?

Answer 22

immunoglobin

it is a glycoprotein

Question 23

What does the constant region do?

Answer 23

it is the region that determines the mechanism used to destroy the pathogen

Question 24

What is the purpose of the hinge region in an antibody?

Answer 24

it gives flexibility to the antibody molecule which allows the antigen-binding site to be placed at different angles when binding to antigens

Question 25

What is agglutination?

Answer 25

when antibodies can cause microbes to stick together = easier for phagocytes to engulf them

Question 26

What are monoclonal antibodies?

Answer 26

Antibodies with the same tertiary structure Antibody produced from identical B cells

Question 27

How are monoclonal antibodies used to cure cancer?

Answer 27

* Monoclonal; antibodies are produced that are specific to antigens on cancer cells * These antibodies are given to a patient and attach themselves to the receptor of the cancer cells * they attach to the surface of their cancer cells and block the chemical signals that stimulate their uncontrolled growth

Question 28

how do our body cavities protect the body from infection

Answer 28

our body cavities (eyes, nose, ears, mouth, and genitals) are lined with a mucus membrane that contains the enzyme lysozyme which hydrolyses the cell wall of bacteria and kills them as they burst.

Question 29

how does the trachea protect the body against pathogens

Answer 29

The **trachea** (windpipe) contains goblet cells that secrete mucus. Pathogens that we inhale become trapped in the mucus, which is swept toward the stomach by the action of ciliated epithelial cells.

Question 30

ow does the stomach protect the body against pathogens

Answer 30

Our **stomach** contains gastric juices which are highly **acidic** these will denature proteins and kill any pathogens that have been ingested in our food and drinks.