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The immune system Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What are antigens?

A

ANTIGENS are MOLECULES (usually proteins or polysaccharides) found on the SURFACE of CELLS

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2
Q

How does a pathogen activate the immune system?

A

When a pathogen (like a bacterium) INVADES the body, the antigens on its cell surface are IDENTIFIED AS FOREIGN, which ACTIVATES CELLS in the immune system.

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3
Q

The immune response involves SPECIFIC and NON-SPECIFIC stages. What are the SPECIFIC and NONSPECIFIC STAGES?

A

The NON-SPECIFIC responses happen in the SAME WAY for ALL MICROORGANISMS- whatever foreign antigens they have.

The SPECIFIC responses are ANTIGEN SPECIFIC it is aimed at SPECIFIC PATHOGENS. It involves white BLOOD CELLS called T and B LYMPHOCYTES.

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4
Q

What is a phagocyte?

A

A PHAGOCYTE is a type of WHITE BLOOD CELL that carries out PHAGOCYTOSIS (engulfment of pathogens)

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5
Q

Where are Phagocytes found?

A

They’re found in the BLOOD and in TISSUES and carry out a NON-SPECIFIC immune response.

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6
Q

How do phagocytes work?

Step 1

A

A Phagocyte recognises the ANTIGENS on the pathogens.

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7
Q

How do phagocytes work?

Step 2

A

The cytoplasm of the phagocyte moves around the pathogen, ENGULFING IT.

This may be made easier by the presence of OPSONINS-molecules in the blood that attaches to FOREIGN ANTIGENS to AID IN PHAGOCYTOSIS.

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8
Q

How do phagocytes work?

Step 3

A

The Pathogen is now contained in a PHAGOSOME (a type of VESICLE) in the cytoplasm of the Phagocyte

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9
Q

How do phagocytes work?

Step 4

A

A LYSOSOME (an organelle that contains DIGESTIVE ENZYMES) FUSES with the phagosome. The enzymes BREAK DOWN the pathogen.

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10
Q

How do phagocytes work?

Step 5

A

The Phagocyte then PRESENTS pathogen’s antigens.
It sticks the antigens on its SURFACE to ACTIVATE other immune system cells. When a phagocyte does this it is acting as an ANTIGEN PRESENTING CELL. (APC)

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11
Q

Neutrophils are a type of…..

A

Phagocyte

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12
Q

What is the role of neutrophils?

A

They’re the FIRST white blood cells to RESPOND to a pathogen inside the body.

Neutrophiles MOVE TOWARDS in response to signals from CYTOKINES (a protein that acts as messenger molecules)

Cytokines are released by cells at the site of the wound.

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13
Q

A T Lymphocyte is another type of …….

A

white blood cell

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14
Q

The surface of a T Lymphocyte is covered with …..

A

receptors

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15
Q

What is the role of receptors on the surface of a T Lymphocyte?

A

The receptors BIND TO ANTIGENS presented by APC’s

Each T Lymphocyte has a DIFFERENT RECEPTOR on its surface

When the receptor on the surface on the T Lymphocyte meets a COMPLEMENTARY ANTIGEN, it binds to it-so each T Lymphocyte will bind to a different antigen.

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16
Q

What happens to the T-lymphocyte once it binds to different antigens?

A

This ACTIVATES the T Lymphocyte-this process is called CLONAL SELECTION.

The T Lymphocytes then undergo CLONAL EXPANSION -it DIVIDES to produce clones of itself. DIFFERENT TYPES of T Lymphocytes carry out DIFFERENT FUNCTIONS.

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17
Q

What are T helper cells?

A

These RELEASE SUBSTANCES to ACTIVATE B LYMPHOCYTES and T KILLER CELLS.

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18
Q

What are T killer cells?

A

These attach to and KILL CELLS that are infected with a VIRUS.

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19
Q

What are T regulatory cells?

A

These suppress the IMMUNE RESPONSE from OTHER WHITE BLOOD CELLS.
This helps to stop immune system cells from mistakingly attacking host body cells

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20
Q

T Lymphocytes once activated can also become ……

A

memory cells

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21
Q

Phagocytes activate ……

A

T lymphocytes

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22
Q

T-lymphocytes activate …

A

B Lymphocytes, which divide into plasma cells

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23
Q

B-lymphocytes are another type of

A

White blood cell

24
Q

B Lymphocytes are covered with proteins called …

A

antibodies

25
Q

What is the role of antibodies?

A

Antibodies bind to ANTIGENS to form an ANTIGEN ANTIBODY COMPLEX.

Each B Lymphocyte has a different SHAPED ANTIBODY on its surface.

When the antibody on the surface of the B-lymphocyte meets a COMPLEMENTARY SHAPED ANTIGEN. it binds to it- so each B Lymphocyte will bind to a DIFFERENT ANTIGEN.

26
Q

What happens to the B Lymphocytes when it binds to different antigens?

A

This, together with substances RELEASED from T helper cells ACTIVATES the B Lymphocyte. This is another example of CLONAL SELECTION.

The activated B Lymphocytes DIVIDES, by mitosis, into PLASMA CELLS and MEMORY CELLS. This is another example of CLONAL EXPANSION.

27
Q

What is cell signalling?

A

Cell signalling is basically how cells communicate

28
Q

How does cell signalling work?

A

A cell may RELEASE (or present) a SUBSTANCE that BINDS TO the RECEPTORS on ANOTHER CELL- this causes a RESPONSE of some sort in the other cell.

29
Q

Why is cell signalling important?

A

Cell signalling is really important in the IMMUNE RESPONSE because it helps to ACTIVATE different types of WHITE BLOOD CELLS that are needed.

30
Q

Examples of cell signalling

A

For example, T HELPER CELLS release INTERLEUKINS (a type of CYTOKINE) that bind to the receptors on the B Lymphocytes. This ACTIVATES the B Lymphocytes -

The T helper cells are signalling to the B Lymphocytes that there’s a pathogen in the body.

31
Q

Plasma cells make more … to a specific antigen

A

antibodies

32
Q

What are plasma cells?

A

Plasma cells are clones of the b-lymphocyte (they’re IDENTICAL to the B-lymphocyte)

33
Q

What is the role of the antibodies?

A

They secrete LOADS of the ANTIBODY, specific to the antigen, into the blood.

These antibodies will bind to the antigen on the surface of the pathogen to form LOTS of ANTIGEN-ANTIBODY COMPLEXES.

34
Q

What is basic structure of an antibody?

A

Antibodies are GLYCOPROTEINS made from FOUR POLYPEPTIDE CHAINS- two HEAVY chains and two LIGHT chains. Each chain has a VARIABLE REGION and CONSTANT REGION.

35
Q

What is the Variable region?

A

The VARIABLE REGION of the antibody form the ANTIGEN BINDING SITE.

The SHAPE of the variable region is COMPLEMENTARY to the antigen.

The variable regions DIFFER between antibodies.

36
Q

What is the hinge region?

A

The HINGE REGION allows FLEXIBILITY when the antibody binds to the antigen.

37
Q

What is the CONSTANT REGION?

A

The CONSTANT region allows binding to RECEPTORS in IMMUNE SYSTEM CELLS e.g phagocytes.

The constant region is the SAME (i.e has the sequence of amino acids) IN ALL antibodies.

38
Q

What are Disulphide bridges?

A

DISULPHIDE BRIDGES (a type of bond) hold the polypeptide chains of the protein together.

39
Q

Antibodies HELP to CLEAR an INFECTION by Agglutinating pathogens.
What are Agglutinating pathogens?

A

Agglutinating pathogens - each antibody has TWO BINDING SITES, so an antibody can BIND to TWO PATHOGENS at the SAME TIME - the pathogens become CLUMPED TOGETHER.

Phagocytes then bind to the antibodies and phagocytose a lot of pathogens ALL AT ONCE.

Antibodies that behave in this way are described as agglutinins.

40
Q

Antibodies HELP to CLEAR an INFECTION by Neutralising toxins. What are Neutralising toxins?

A

Like antigens, toxins have DIFFERENT SHAPES.
Antibodies called ANTI TOXINS can BIND to the TOXINS produced by pathogens.
This PREVENTS the toxins from affecting HUMAN CELLS, so the toxins are neutralised (inactivated).
The toxin-antibody complexes are also phagocytosed

41
Q

Antibodies HELP to CLEAR an INFECTION by preventing the pathogen from binding to human cells.
What does the effect have on cells?

A

Preventing the pathogens binding to human cells - when antibodies bind to the antigens on pathogens, they may BLOCK the cell surface RECEPTORS that the pathogen needs to BIND TO HOST CELLS.

This means the pathogen CAN’T ATTACH or INFECT THE HOST CELLS.

42
Q

What is the primary response?

A

When a PATHOGEN enters the body for the FIRST TIME, the ANTIGEN on its surface ACTIVATES the IMMUNE SYSTEM. This is called the PRIMARY RESPONSE.

43
Q

Why is Primary response slow?

A

The primary response is SLOW because THEY’RE ARENT MANY B-LYMPHOCYTES that can make the antibody needed to bind to it.

Eventually, the body will produce ENOUGH of the right antibody to overcome the infection. Meanwhile, the infected person will show SYMPTOMS of the DISEASE.

44
Q

What does the immune system do with the exposure of foreign antigens?

A

After being exposed to an antigen, both T and B lymphocytes produce MEMORY CELLS. These memory cells REMAIN IN THE BODY for a LONG time.

45
Q

What do Memory T lymphocytes do in the body?

A

MEMORY T LYMPHOCYTES remember the SPECIFIC ANTIGEN and will recognise it the second time.

MEMORY B LYMPHOCYTES record the specific ANTIBODIES needed to bind to the antigen

The person is now IMMUNE -their immune systems has the ABILITY to respond quickly to second infection.

46
Q

Why is the SECONDARY RESPONSE described as faster?

A

If the SAME PATHOGEN enters the body again, the immune system will produce a QUICKER, STRONGER immune response-the SECONDARY RESPONSE.

47
Q

Why is CLONAL SELECTION significant in the secondary response?

A

CLONAL SELECTION happens FASTER. MEMORY B LYMPHOCYTES are activated and divide into PLASMA CELLS that produce the right antibody to the antigen.

MEMORY T LYMPHOCYTES are activated and divide into the CORRECT TYPE of T LYMPHOCYTE to kill the cell carrying the antigen.

48
Q

Why does the SECONDARY response prevent any symptoms?

A

The secondary response often gets rid of the pathogens BEFORE you begin to show any SYMPTOMS.

49
Q

why are stains added?

A

STAINS are added to the sample to make DIFFERENT CELLS easy to see.

50
Q

How does a NEUTROPHIL LOOK like?

A

Its nucleus is ‘MULTI LOBED’. The cytoplasm of a Neutrophil is GRAINY.

51
Q

How does a LYMPHOCYTE look like?

A

A Lymphocyte is much smaller than the neutrophil. The nucleus takes up most of the cell and there is very little cytoplasm.

52
Q

What does a MONOCYTE look like?

A

Biggest white blood cell and a type of PHAGOCYTE.

It has a KIDNEY-SHAPED cytoplasm and a non-grainy cytoplasm.

53
Q

Describe the function of Neutrophil, T helper cells and B lymphocytes.

A

Neutrophil: Engulfs pathogens

T helper cell: Release interleukins to activate other cells

B lymphocyte: Divide to form plasma cells

54
Q

IgG is a type of antibody, as well as an agglutinin and opsonin. Suggest how IgG works.

A

IgG can bind two pathogens at the same time, so the pathogens become agglutinated/clump together.

55
Q

A scientist is looking at a blood smear under the microscope.
Explain how she will be able to tell the difference between neutrophil and a B-lymphocyte

A

The nucleus of the neutrophile will have THREE LOBES.

The nucleus of the B-lymphocyte will not have lobes and will take up most of the cell

The cytoplasm of the neutrophile will be grainy.

The B-Lymphocyte will be smaller than the neutrophile.

56
Q

A person had chickenpox as a child. She was exposed to the virus that causes it again as a teenager but did not experience any symptoms. Explain why.

A

When the person caught chickenpox for the first time, her B and T lymphocytes produced memory cells.

When she was exposed to the virus for the second time, the memory B Lymphocytes divided into plasma cells to produce the right antibodies for the virus.

The memory T lymphocytes divided into the correct type T Lymphocyte to kill the virus.

The secondary response was quicker and stronger, so got rid of the pathogen before she showed any symptoms.

Biology (18 decks)

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