Communicable disease

Question 1

Why do we feel sick?

Answer 1

Bacteria produce toxins that damage tissues.
Viruses live and reproduce inside our cells causing damage.

Question 2

What are some common viral diseases?

Answer 2

HIV
TMV
Measles

Question 3

What are some symptoms of measels?

Answer 3

• fever
• red rash
• can be fatal
• spread by droplets

Question 4

What are some symptoms of HIV?

Answer 4

• Initially like flu
• attacks immune system
• AIDS is when the immune system stops working
• sexual contact
  body fluids

Question 5

What are some symptoms of TMV?

Answer 5

• Discolouration of leaves
• Poor growth due to lack of photosynthesis.

Question 6

What is an example of a fungal disease?

Answer 6

Rose black spot
- blackspots on leaves
- Leaves fall early
- Poor photosynthesis
- Poor growth

Question 7

How does vaccination work?

Answer 7

• Inject with dead or weakened pathogen
• white blood cells produce anitbodies
• white blood cell rememebrs hwo to make antibodies
• antibodies produced rapidly on injection
• pathogen destroyed before you show sysmptoms.

Question 8

What are some natural defences againt disease?

Answer 8

• Stomach acid
• mircoorganisms in the intestine
• Mucosal surfeces - (e.g nose and mouth) which contain the enzyme lysozyme. This kills bacteria by damaging their cell wall causing them to burst open.
• Skin = barrier

Question 9

How does inflammation occur?

Answer 9

Immune System cells recognise
foreign antigens on the surface of the pathogen and release chemical messengers called histamines which trigger inflammation. These molecules
trigger local vasodilation increasing the blood flow to the affected area. They also increase the permeability of
blood vessels in that area enabling white blood cells to leave capillaries

Question 10

What are interferons?

Answer 10

Anti-viral proteins called interferons are released
by affected tissues. These prevent viral replication
by inhibiting the production of viral proteins. They
also activate immune system cells to kill those
cells which are affected.

Question 11

What is phagocytosis?

Answer 11

A phagocyte recognises the antigens on the cell surface membrane of a pathogen,
as being foreign. The cytoplasm of the phagocytes moves around to engulf the pathogen in a phagocytic vacuole.
Lysosomes fuse with the vacuole releasing enzymes which digest the pathogen. Only
the antigens are not destroyed, these are moved to the cell surface membrane and
displayed there. The phagocyte has become an antigen presenting cell (APC)

Question 12

What are T cells?

Answer 12

T cells have receptors on their cell surface membrane. There are millions of different T cells each with different receptors. when a T cell finds an antigen presenting cell which has antigens its receptors
can bind to it becomes activated.
The activated T cell divides rapidly by mitosis and differentiates into three types of T cells.

Question 13

What are the three types of T cells?

Answer 13

T killer cells attach to the antigens on the surface of affected cells and kill them

T Memory cells retain a memory of the antigen. they live for many years in the immune system.

T helper cells release chemicals

Question 14

What are B cells?

Answer 14

B cells have many antibodies on
their cell surface membrane. Each
B cell has a different antibody.
When one of the antibodies meets a complementary antigen it binds to it. This, along with substances released by T helper cells activates the B cell.
It divides rapidly by mitosis and
differentiates into two types of B

B memory cells retain a
memory of the antibody
and stay in the immune system for many years
B effector cells are also
known as B plasma
cells, they produce
large quantities of
antibodies

Question 15

What are bacteriostatic antibiotics?

Answer 15

Limit the growth of bacteria by interfering with bacterial proetin production , DNA replication, or other aspects of bacterial cellular metabolism

Question 16

What is the structure of a virus?

Answer 16

• Contains a core of nuclei acid that’s either DNA or RNA. For HIV its RNA.
• they have no plasma membrane, no cytoplasm and no ribosomes
• HIV carries an enzyme called reverse transcriptase.
• The protein coat around the core is called the capsid.
• Some viruses have an extra outer layer, (envelope), stolen form the cell membrane of a previous host cell.

Question 17

How does HIV replicate?

Answer 17

The attachment protein attaches to a receptor molecule on the cell membrane of the host T helper cell. The capsid is released into the cell, where it uncoats and releases the genetic material (RNA) into the cell’s cytoplasm.
Inside the cell, reverse transcriptase is used to make a complementary strand of DNA from the viral RNA template. From this double stranded DNA is made and inserted into the human DNA. Host cell enzymes are used to make viral proteins from the viral DNA found within the human DNA. The viral proteins are assembled into new viruses, which bud from the cell and go on to infect other cells.

Question 18

What are the mechanisms in non- specific immune response?

Answer 18

• Inflammation
• Production of anti-viral proteins (interferons)
  Phagocytosis

Question 19

What is the T helper Activation in the humoural response?

Answer 19

• Bacterium is engulfed by a macrophage. Antigens are displayed on the surface of the macrophage and acts as an anitgen presenting cell. (APC)
• Macrophage APC binds to T helper cell with complementary receptor proteins
• The T helper cell is activated and divides by mitosis to form T memory cells and active T helper cells.

Question 20

What happens in the effector stage in the humoural response?

Answer 20

• B cells with a complementary receptor bind to the anitgens upon a bacterium, itself becoming an APC.
• An activated T helper cell from before with a complementary receptor protein to the antigens binds to the B cell APC. It produces cytokines.
• Cytokines stimulate the B cell to divide by mitosis and form B memory cells and B effector cells
• B effector cellls differntiat einto plasma cells
• Plasma cells synthesise anitbodies

Question 21

What is the cell mediated response?

Answer 21

Host cells displays its antigens and becomes an antigen presenting cell.
- T killer cell with complementary receptor proteins binds to the APC .
- Cytokines secreted by actived T helper cells stimulate T killer cell to divide by mitosis
- T killer cell differentiate to form active T killer cells and memory cells
- The infected cell lyses and dies.

Question 22

How is TB transmitted?

Answer 22

-TB is transmitted when uninfected people inhale these droplets
- Once inside the lungs, TB bacteria are engulfed by phagocytes. The bacteria may be able to survive and reproduce while inside phagocytes
Individuals with a healthy immune system will not develop TB at this stage
- Over time the infected phagocytes will become encased in structures called tubercles in the lungs where the bacteria will remain dormant
-It is possible for the bacteria to become activated and overpower the immune system at a later stage, such as during an HIV infection when the immune system is compromised; the person will then develop TB
This is known as the active phase of TB
The length of time between infection and developing the disease can vary from a few weeks to a few years
The first symptoms of TB will include developing a fever, fatigue, coughing and lung inflammation
If left untreated the bacteria will cause extensive damage to the lungs which can result in death due to respiratory failure
TB may also spread to other parts of the body where it can lead to organ failure if not treated promptly