Download Phagocytosis POWERPOINT RLE

Homework
Homework booklet
3.2.2 All cells arise from other cells
INCLUDING the exam questions
TO HAND IN Monday 4th January
Today we are covering from the
specification:
What is the first line of
defence against disease?
What is the first line of
defence to disease?
Barriers to entry.
What is the name we give to
disease-causing
microorganisms?
PATHOGENS
How do the following features
prevent the entry of
pathogens?
-
Hydrochloric acid in the stomach
Skin
Ability of blood to clot
Mucus in respiratory system
Tears
5 minutes!
Physical barriers to infection
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Which system in the body is
concerned with destroying
pathogens?
The immune system
Key terms
•
•
•
•
•
Antigen
Pathogen
Antibody
Lymphocyte
Immune system
10 minutes
What is an antigen?
A substance, e.g. protein, that causes an immune
response.
They have a specific shape.
Self antigens are found on the surface of your own
cells – your immune system does not respond to
these.
Non-self antigens are found on the surface of all
other cells (and viruses).
What is an antigen?
Antigens allow our bodies to recognise:
- Pathogens
- Cells from other organisms of the same
species
- Abnormal body cells
- Toxins
Why are antigens important?
Discuss…
They enable our bodies to defend themselves by
recognising pathogens and stimulating an immune
response, leaving our own cells unharmed.
If the same antigen is encountered a second time,
the immune response is faster and greater –
immunity.
Discuss:
Some viruses, e.g. influenza and HIV have
antigenic variability.
1. Suggest what is meant by the term ‘antigenic
variability’.
2. What is the advantage of this to the virus?
3. What is the disadvantage to the host?
The immune response
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Homework
Homework booklet
3.2.2 All cells arise from other cells
INCLUDING the exam questions
TO HAND IN Monday 4th January
The non-specific immune response
- Inflammation (not on specification)
- Phagocytosis (important!)
What is phagocytosis?
from Ancient Greek:
- φαγεῖν (phagein) meaning “to devour”
- κύτος, (kytos) , meaning “cell”
-osis, meaning "process"
The cellular process of engulfing solid particles via the
cell membrane to form an internal phagosome by
phagocytes.
What happens during inflammation?
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TASK
Use the diagram to help you describe the
process of phagocytosis. Use the following
key terms:
Phagocytosis
Phagosome
Lysozyme
Engulf
Cell membrane
One more thing to add to your
explanation:
• Phagocytes can display the antigens on their
cell surface.
• They are then known as an antigenpresenting cell.
• This is useful for other white blood cells
(lymphocytes) to help them ‘recognise’
infection.
Phagocytosis flow chart
Phagocytes – originate from bone marrow / foetal liver
• Pathogen recognised as foreign – pathogen is antigenic; chemotaxis
• Pathogen attached to phagocyte by antibody and surface receptors
• Engulfed by phagocyte by endocytosis – invagination of plasma cell membrane to form a
phagosome (a membrane bound vesicle containing the pathogen)
• Lysosomes (containing lysins & hydrolytic enzymes) fuse to phagosome
• Release of H2O2, HCl, free radicals into phagosome
• Digest pathogen – harmless products removed (egested / excreted) or used by
phagocyte
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• Phagocyte also displays antigenic components on external surface of plasma cell
membrane (antigen presentation) to start immune response
art; pas
art; act
nat ; act
art ; act
nat ; pas
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Artificial immunity
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Non-specific immune response
The non-specific or innate immune response quickly
targets a wide range of pathogens and foreign substances.
Phagocytosis, inflammation and the antimicrobial
proteins lysozyme and interferons are all part of this
immune response.

Lysozyme is an enzyme that disrupts the cell walls of
gram-positive bacteria by digesting the peptidoglycan.
It is found in human tears, saliva and lysosomes.

Interferons are proteins produced by virus-infected
body cells in response to the virus. Interferons trigger
the production of a second protein that inhibits viral
replication by binding to mRNA coded by the virus.
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Specific immune response
The specific or adaptive immune response can target
a specific pathogen, although it is slower to act than the
non-specific response.
It features two main types of
response to pathogens:

the cellular or cell-mediated
response involves highlyspecialized cells that target
pathogens inside cells.

the humoral or antibodymediated response targets
pathogens in body fluids with
antibodies.
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Non-specific immunity: true or false?
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Phagocytosis flow chart
Phagocytes – originate from bone marrow / foetal liver
• Pathogen recognised as foreign – pathogen is antigenic; chemotaxis
• Pathogen attached to phagocyte by antibody and surface receptors
• Engulfed by phagocyte by endocytosis – invagination of plasma cell membrane to form a
phagosome (a membrane bound vesicle containing the pathogen)
• Lysosomes (containing lysins & hydrolytic enzymes) fuse to phagosome
• Release of H2O2, HCl, free radicals into phagosome
• Digest pathogen – harmless products removed (egested / excreted) or used by
phagocyte
• Phagocyte also displays antigenic components on external surface of plasma cell
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membrane (antigen presentation) to start immune response
15 minutes – Label your diagram of phagocytosis. Summarise and add the
extra information to the correct part of the flow diagram.
To Do:
1. Read pages 102 & 103.
2. Add any extra information from the diagram
in the book onto your flow diagram.
3. Answer summary questions 1 & 2.
10 minutes
Spot Quiz
1. Are phagocytes an example of specific or nonspecific immunity?
2. What is formed when a phagocyte infolds and
engulfs a pathogen?
3. What do lysosomes contain?
4. What is the process called when vesicles bind
and release their contents from the cell
membrane?
5. What cell organelle manufactures proteins?
6. What cell organelle releases vesicles e.g.
lysosomes?
What are lymphocytes?
Lymphocytes are a type
of white blood cell
(leukocyte) found in the
blood and lymph nodes.
Lymphocytes recognise
antigen molecules on the
surface of pathogens, and
co-ordinate the immune
response against that
pathogen.
Collectively, lymphocytes can recognize millions of different
antigens, due to the large variation of lymphocytes produced.
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Different types of lymphocytes
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Cellular immune response
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Humoral immune response
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Effector mechanisms
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