OCR A level Biology 12.5 Non-specific
animal defences against pathogens
What are non-specific defences? - correct answeralways present and working to
prevent against the invasion of pathogens. They target all/a range of pathogens. How
are non-specific defences classified? - correct answer--> Classified as primary (keeping
pathogens out) and secondary (getting rid of pathogens) Are Non-specific defences fast
or slow acting? - correct answerfast acting What are specific defences? - correct
answerspecific to each type of pathogen that invades the body and is known as the
'Specific Immune Response' Are specific defences fast or slow to respond? - correct
answerslower to respond What primary defences does the body have? - correct
answer1) physical barriers to prevent the entry of pathogens 2) expulsive reflexes 3)
blood clotting and wound repair 4) inflammatory response What are the physical
barriers? - correct answerskin, mucous membranes, lysozymes in tears, lysozymes in
urine, HCl in stomach, ear wax, hair and mucus in nose, mucus plug in the cervix How
does the skin act as a physical barrier? - correct answer- Prevents the entry of
pathogens - Skin contains a flora of healthy MO's that outcompete pathogens for space
on the body surface - Skin secretes 'sebum oil' an antibacterial substance which
prevents pathogen growth -The epidermis consists of layers of keratinocytes. -->
Keratinocytes migrate to the surface and dry out when their cytoplasm is replaced by
keratin. --> This surface layer of dead hardened cells is low in moisture, somewhat
acidic and has a high salinity which prevents MO's from growing and multiplying on the
skin Why are the airways lungs and digestive system always at risk of infection? -
correct answerbecause of the constant exposure to air and water/food from the
environment and the presence of exchange surfaces How to mucous membranes act as
a physical barrier? - correct answer- the airways, lungs and digestive system are lined
and protected by mucous membranes that consists of epithelial cells interspersed with
mucus secreting cells called goblet cells. - Mucus traps pathogens. It is sticky as it
contains long carbohydrate chains of the glycoprotein molecules. - Mucus contains
lysosomes which destroy bacterial and fungal cell walls and phagocytes which remove
remaining pathogens. - Also found in airways, gut, anus, genital, nose and ears How do
lysozymes in tears prevent infection? - correct answer--> Lysozymes break down the
cell walls of bacteria --> Tears also have antibodies in them How do lysozymes in urine
prevent infection? - correct answer--> lysozymes break down the cell walls of bacteria
How does HCl in stomach prevent infection? - correct answerHCl in stomach is strong
enough to kill many bacterial pathogens How does hair and mucus in nose prevent
, infection - correct answer--> Hairs in your nose and the mucus produced in your nose
trap larger particles containing pathogens. When you sniff or swallow the mucus and
pathogens move to the stomach. How are expulsive reflexes triggered? - correct
answer· Pathogens irritate areas prone to attack when they release toxins. These toxins
trigger 'Expulsive Reflexes' What are the expulsive reflexes and what do they do? -
correct answer--> Coughs and sneezes eject pathogen-laden mucus from the gas
exchange system --> Vomiting and diarrhoea expel the contents of the cut with any
infective pathogens. Why is bad if the skin is cut? And why is blood clotting needed? -
correct answerbecause the skin is breached and pathogens can enter the body. Blood
clotting is needed to rapidly seal the wound to prevent infection and blood loss. What
are platelets responsible for? - correct answerPlatelets are responsible for initiating an
'Enzyme Cascade' that results in the formation of a blood clot. What triggers the action
of platelets? And what do they do? - correct answerWhen platelets come into contact
with COLLAGEN in skin or the wall of the damaged blood vessel, they adhere to the
damaged area and release... 1.Thromboplastin: 2. Serotonin: 3. Calcium ions: What is
and what does thromboplastin do? - correct answerit is an enzymes that triggers a
cascade of reactions that lead to a blood clot forming. What is serotonin and what does
it do? - correct answera chemical signaller that initiates vasoconstriction of smooth
muscle in the walls of the blood vessel so the muscle narrows and reduces the blood
flow to the injured area What role do calcium ions play in the immune response? -
correct answeract as the cofactor for the enzymes thromboplastin and thrombin What is
prothrombin? Where is it found? What is it converted into and how? - correct answera
soluble protein. Contained in blood plasma. Changed into thrombin if thromboplastin is
present to catalyse the reaction (and calcium ions which are the cofactor for
thromboplastin) What is the role of thrombin? - correct answeracts as the enzyme that
causes fibrinogen to be converted to fibrin whose fibres help to seal the wound forming
a clot. (calcium ions act as the cofactor) What happens when the blood clot is formed? -
correct answer· It dries out forming a scab that keeps pathogens out. · Epidermal cells
below the scab start to grow, sealing the wound permanently while damaged blood
vessels regrow. · Collagen fibres are deposited to give the new tissue strength. · Once
the new epidermis reaches normal thickness, the scab sloughs off and the wound is
healed. Draw out the enzyme cascade that results in the formation of a blood clot? -
correct answer What is the inflammatory response? - correct answerThe inflammatory
response is a localised response to pathogens (or damage or irritants) resulting in
inflammation at the site of the wound. What is inflammation characterised by? - correct
answerpain, heat, redness and swelling of tissue. The presence of pathogens in the
_____ is detected by __________ called _____ - correct answertissues, specialised
WBCs, mast cells What 2 chemicals do mast cells release? - correct answerhistamines,
cytokines What do histamines do? - correct answer- Trigger vasodilation of blood
vessels in area which causes localised heat and redness. The increased temperature
helps prevent the pathogen reproducing. - Trigger an increase in the 'leakiness' of
animal defences against pathogens
What are non-specific defences? - correct answeralways present and working to
prevent against the invasion of pathogens. They target all/a range of pathogens. How
are non-specific defences classified? - correct answer--> Classified as primary (keeping
pathogens out) and secondary (getting rid of pathogens) Are Non-specific defences fast
or slow acting? - correct answerfast acting What are specific defences? - correct
answerspecific to each type of pathogen that invades the body and is known as the
'Specific Immune Response' Are specific defences fast or slow to respond? - correct
answerslower to respond What primary defences does the body have? - correct
answer1) physical barriers to prevent the entry of pathogens 2) expulsive reflexes 3)
blood clotting and wound repair 4) inflammatory response What are the physical
barriers? - correct answerskin, mucous membranes, lysozymes in tears, lysozymes in
urine, HCl in stomach, ear wax, hair and mucus in nose, mucus plug in the cervix How
does the skin act as a physical barrier? - correct answer- Prevents the entry of
pathogens - Skin contains a flora of healthy MO's that outcompete pathogens for space
on the body surface - Skin secretes 'sebum oil' an antibacterial substance which
prevents pathogen growth -The epidermis consists of layers of keratinocytes. -->
Keratinocytes migrate to the surface and dry out when their cytoplasm is replaced by
keratin. --> This surface layer of dead hardened cells is low in moisture, somewhat
acidic and has a high salinity which prevents MO's from growing and multiplying on the
skin Why are the airways lungs and digestive system always at risk of infection? -
correct answerbecause of the constant exposure to air and water/food from the
environment and the presence of exchange surfaces How to mucous membranes act as
a physical barrier? - correct answer- the airways, lungs and digestive system are lined
and protected by mucous membranes that consists of epithelial cells interspersed with
mucus secreting cells called goblet cells. - Mucus traps pathogens. It is sticky as it
contains long carbohydrate chains of the glycoprotein molecules. - Mucus contains
lysosomes which destroy bacterial and fungal cell walls and phagocytes which remove
remaining pathogens. - Also found in airways, gut, anus, genital, nose and ears How do
lysozymes in tears prevent infection? - correct answer--> Lysozymes break down the
cell walls of bacteria --> Tears also have antibodies in them How do lysozymes in urine
prevent infection? - correct answer--> lysozymes break down the cell walls of bacteria
How does HCl in stomach prevent infection? - correct answerHCl in stomach is strong
enough to kill many bacterial pathogens How does hair and mucus in nose prevent
, infection - correct answer--> Hairs in your nose and the mucus produced in your nose
trap larger particles containing pathogens. When you sniff or swallow the mucus and
pathogens move to the stomach. How are expulsive reflexes triggered? - correct
answer· Pathogens irritate areas prone to attack when they release toxins. These toxins
trigger 'Expulsive Reflexes' What are the expulsive reflexes and what do they do? -
correct answer--> Coughs and sneezes eject pathogen-laden mucus from the gas
exchange system --> Vomiting and diarrhoea expel the contents of the cut with any
infective pathogens. Why is bad if the skin is cut? And why is blood clotting needed? -
correct answerbecause the skin is breached and pathogens can enter the body. Blood
clotting is needed to rapidly seal the wound to prevent infection and blood loss. What
are platelets responsible for? - correct answerPlatelets are responsible for initiating an
'Enzyme Cascade' that results in the formation of a blood clot. What triggers the action
of platelets? And what do they do? - correct answerWhen platelets come into contact
with COLLAGEN in skin or the wall of the damaged blood vessel, they adhere to the
damaged area and release... 1.Thromboplastin: 2. Serotonin: 3. Calcium ions: What is
and what does thromboplastin do? - correct answerit is an enzymes that triggers a
cascade of reactions that lead to a blood clot forming. What is serotonin and what does
it do? - correct answera chemical signaller that initiates vasoconstriction of smooth
muscle in the walls of the blood vessel so the muscle narrows and reduces the blood
flow to the injured area What role do calcium ions play in the immune response? -
correct answeract as the cofactor for the enzymes thromboplastin and thrombin What is
prothrombin? Where is it found? What is it converted into and how? - correct answera
soluble protein. Contained in blood plasma. Changed into thrombin if thromboplastin is
present to catalyse the reaction (and calcium ions which are the cofactor for
thromboplastin) What is the role of thrombin? - correct answeracts as the enzyme that
causes fibrinogen to be converted to fibrin whose fibres help to seal the wound forming
a clot. (calcium ions act as the cofactor) What happens when the blood clot is formed? -
correct answer· It dries out forming a scab that keeps pathogens out. · Epidermal cells
below the scab start to grow, sealing the wound permanently while damaged blood
vessels regrow. · Collagen fibres are deposited to give the new tissue strength. · Once
the new epidermis reaches normal thickness, the scab sloughs off and the wound is
healed. Draw out the enzyme cascade that results in the formation of a blood clot? -
correct answer What is the inflammatory response? - correct answerThe inflammatory
response is a localised response to pathogens (or damage or irritants) resulting in
inflammation at the site of the wound. What is inflammation characterised by? - correct
answerpain, heat, redness and swelling of tissue. The presence of pathogens in the
_____ is detected by __________ called _____ - correct answertissues, specialised
WBCs, mast cells What 2 chemicals do mast cells release? - correct answerhistamines,
cytokines What do histamines do? - correct answer- Trigger vasodilation of blood
vessels in area which causes localised heat and redness. The increased temperature
helps prevent the pathogen reproducing. - Trigger an increase in the 'leakiness' of
