phase 1 week 2

Question 1

Describe the structure of bacteria

Answer 1

Single-celled prokaryotes with characteristic cellular organisation

Question 2

Describe gram-positive bacteria

Answer 2

has peptidoglycan ;ayers on the outside of the cell wall

stains purple

Question 3

Describe gram-negative bacteria

Answer 3

has one layer of peptidoglycan between the two membranes

stains pink

Question 4

Describe natural flora in the gut

Answer 4

normal flora is acquired soon after birth and changes with age. Benefits - competition and bi-products inhibit establishment of infection
vitamins (K&B) in the gut are produced by bacteria
the rate at which bacteria grow and divide depends on the nutritional state of the environment.

Question 5

How does bacteria replicate?

Answer 5

The genomic DNA replicates from the origin of replication and must be accurate
formation of a septum in the middle of a cell
division of the cell to give separate daughter cell

Question 6

How do bacteria cause virulence in the body?

Answer 6

they colonise, invade and release toxins

Question 7

describe some examples of other microbial defences of bacteria

Answer 7

antigenic mimicry, antigenic masking, encapsulation, invasion of the host’s immune response

Question 8

How does bacteria enter the body?

Answer 8

coughs, sneezes, vomit, bites from infected animals, exposure to infected body fluids through sexual intercourse or from sharing hypodermic needles

Question 9

What are viruses?

Answer 9

obligate intercellular parasites

Question 10

why do some viruses have an envelope?

Answer 10

they acquire a lipid bilayer as they bud from the surface of the cell

Question 11

What is the genetic material of a virus contained in?

Answer 11

A coat or capsid, made up from a number of protein molecules.

Question 12

How do viruses invade?

Answer 12

via inhaled water droplets
food or water
direct transfer from other infected host
from bites of vector arthropod

Question 13

Describe the life cycle of a virus

Answer 13

virus attaches to cell
virus penetrates the cell membrane and injects nucleic acid (RNA or DNA) into the cell
viral nucleic acid replicates itself using host cell machinery
new viral nucleic acids are packaged into viral particles and released from the cell. The host cell may be destroyed in the process

Question 14

what is the most common type of WBC?

Answer 14

phagocytes

Question 15

how do phagocytes kill pathogens in extravascular tissue?

Answer 15

enter the extravascular tissue, ingest microbes then die within hours

Question 16

where are macrophages found?

Answer 16

healthy macrophages are found in all tissues and organs

Question 17

what are macrophages?

Answer 17

differentiated monocytes found in tissue that can survive for long periods of time

Question 18

What do macrophages do?

Answer 18

they initiate and regulate inflammation, ingest microbes, clear dead tissue and initiate tissue repair

Question 19

What are dendritic cells?

Answer 19

Link between the innate and adaptive immunity
antigen presenting cells
they also produce cytokines for inflammation and stimulate adaptive immune responses

Question 20

What are mast cells?

Answer 20

found in the skin in the mucosal epithelium
both innate and adaptive
cytoplasmic granules - vasoactive amines e.g. histamines cause vasodilation and increased capillary permeability
proteolytic enzymes kill bacteria or inactivate toxins
synthesise lipid mediators and cytokines

Question 21

What are natural killer cells?

Answer 21

secrete cytokines that activate macrophages
contain granules which are released into the extracellular space at the point of contact with the infected cell and bring about apoptosis
usually kills viral cell

Question 22

What do eosinophils do?

Answer 22

many functions - inflammatory processes, trapping substances, killing cells, mainly anti-parasitic functions
allergy

Question 23

Describe the function of lymphocytes

Answer 23

each lymphocyte binds to a specific antigen
once activated, lymphocytes multiply to produce clones
some B lymphocytes differentiate to plasma cells which produce antibodies
helper t cells produce cytokines which stimulate antibody production
cytoxic t cells bind to and kill infected cells and cancer cells
memory b cells
B cells also display antigens and secrete cytokines

Question 24

What are lymph nodes for?

Answer 24

the site of immune response activation

Question 25

What is the function of the spleen?

Answer 25

blood-borne antigens are captured by antigen-presenting cells in the spleen

Question 26

What are the three outcomes from the complement cascade?

Answer 26

recruitment of inflammatory cells
opsonisation of pathogens
killing of pathogens

Question 27

what are the three complement cascade pathways?

Answer 27

classical pathway
MB-lectin pathway
alternate pathway

Question 28

What activates the classical pathway?

Answer 28

antigen:antibody complexes

Question 29

what activates the MB-lectin pathway?

Answer 29

lectin binding to pathogen surfaces

Question 30

What activates the alternate pathway

Answer 30

pathogen surfaces

Question 31

What are the primary lymphoid organs?

Answer 31

bone marrow

thymus

Question 32

what are the secondary lymphoid organs?

Answer 32

lymph nodes, spleen

Question 33

What is the role of the thymus?

Answer 33

maturation of T lymphocytes - CD4+ “helper” and CD8+ “killer”
selection of auto reactive cells for removal to prevent autoimmunity
Export a repertoire of T cells for life

Question 34

What are the 5 types of antibody?

Answer 34

IgM (5), IgA (2), IgD (1) ,IgG (1) , IgE (1)

Question 35

From the afferent lymph vessels to the efferent vessels, in what order does the lymph pass immune cells?

Answer 35

B cells
T cells
Plasma cells and macrophages