W6- Lecture 29- Causes of infections

Question 1

what is the size of a virus compared to cellular organisms and bacteria ?

Answer 1

Smaller than cellular organisms

1/100th size of bacteria

Question 2

name the components that form a virus

Answer 2

3 major components: genetic material- either DNA or RNA;
protein coat;
lipid envelope which is derived from the host cell.

Question 3

describe viral replication (in simple terms)

Answer 3

Viruses contain genetic material but no organelles

they rely on their host organelles/ systems to reproduce

They use surface protein(s) to bind to a cell, insert their genetic material into it

Question 4

describe the structure of a bacteria

Answer 4

Unicellular organisms
Cell membrane
Cell wall
No nucleus
Genetic material is DNA but not bounded by a membrane(plasmids)
Reproduce asexually
Some move using flagella and attach via fimbriae

Question 5

what do these three terms indicate about a bacterium’s shape?

coccus/cocci
bacillium/bacilli
spirilum/spirilli

Answer 5

coccus/cocci- round

bacillium/bacilli- rod shaped

spirillum/spirilli- spiral

Question 6

what is the difference between gram positive and negative bacteria cell walls?

Answer 6

gram-positive= one cell membrane one cell wall
one wall made of peptidoglycan

gram-negative=one cell membrane two cell walls
one wall made of peptidoglycan
second wall made of lipopolysaccharides + proteins

Question 7

which type of bacteria gram positive and negative is the immune system more to ?
and why ?

Answer 7

gram negative

because of the lipopolysaccharides + proteins can cause more serious disease

Question 8

how do we write bacteria names ?

Answer 8

genus then species
Capital letter for the Genus, lower case for species
(always in italics if possible if not then underline )

Question 9

describe the structure of fungi

Answer 9

Kingdom of their own
Eukaryotes
Cell membrane, cell wall, nucleus and cytoplasmic structures
Reproduce sexually and asexually

Question 10

name three types of fungi which are likely to cause disease

Answer 10

Yeasts - likely to cause disease

Moulds

Diamorphic fungi (can switch between types

Question 11

name three mild infections caused by fungal infections

Answer 11

thrush,
athletes foot,
ringworm

Question 12

name the three classes of parasites

with examples

Answer 12

Ectoparasites
live outside body
Fleas
Ticks
Endoparasites
Iive inside body
Worms
Epiparasites
a parasite which lives on another parasite
Malaria (mosquito)

Question 13

what are the two general classes of parasites

+example

Answer 13

Unicellular organisms- Protozoa

Worms- Helminths

Question 14

descibr the parasitic disease called giardia

+ life cycle

Answer 14

Cause bloody diarrhoea

Caught from drinking infected water

May be seen in stool under a light microsope

Cyst form aids survival + spread

Some protozoa have life stages alternating between proliferative stages and dormant cysts.
As cysts, protozoa can survive harsh conditions, such as exposure to extreme temperatures and harmful chemicals, or long periods without access to nutrients, water, or oxygen, in addition enabling a parasite to survive outside of the host, and therefore allowing transmission from one host to another.
Protozoa can reproduce by binary fission or multiple fission. Some protozoa reproduce sexually, some asexually, while some use a combination. An individual protozoon is hermaphroditic.

Question 15

describe malaria

• where it comes from
• what cells it infects

Answer 15

One of the biggest killers worldwide

Reproduce in female anopheles mosquito

Infect human red blood cells

Question 16

how many different types of malarial parasite?

• which is most severe
• why might treatment now might be a problem

Answer 16

4

Falciparum- most severe 
Resistance to treatment is now a problem in many areas
chloroquine sensitive malaria 
chloroquine resistant malaria 
multi-resistant malaria

Question 17

name three types of worms + structure

Answer 17

Cestodes (tapeworms)
Segmented, flat

Trematodes (flukes)
Unsegmented, flat

Nematodes (round worms)
Cylindrical, have digestive tract with lips, teeth and anus

Question 18

where can you get Cestodes (aka tapeworms) from ?

+ impacts

Answer 18

Tapeworms
Fish, pork, beef tapeworms

Malabsorption
Malnutrition in chronic disease
Cysts in muscle or brain

Question 19

what can Nematodes

(aka Round worms) form ?

Answer 19

Diarhoea / malabsorption

E.g. Elephantiasis

Question 20

name 5 types of Trematodes/flukes

Answer 20

Lung flukes
Liver flukes
Pancreatic flukes
Intestinal flukes
Blood flukes- Schistosoma (2nd most socioeconomically devastating parasiticdisease)

Question 21

describe the life cycle of a blood fluke/Schistosoma

+ causes of infection

Answer 21

Flukes have part of their life cycle in fresh-water snails and enter the body by penetrating the skin whilst the host is swimming.
The adult worms migrate to veins- some species to veins of ureter and bladder and others to the mesenteric veins, where the female lives inside a groove on the male.
The worms live there and lay eggs for the rest of the host’s life. Once produced, the eggs penetrate the vascular endothelium, enter the bladder or gut lumen, and are excreted in urine or stool.
The clinical disease is commonly found in children who play in the water, and is devastating socioeconomically. Symptoms are diarrhoea, fever, abdominal pain, hepatosplenomegaly or cystitis, urethritis and eventually bladder cancer.
1- fresh water snails
2- flukes penetrate skin
3- migrate to veins + Diarrhoea, fever and abdominal pain

Question 22

describe prions
size 
nucleic acid ?
how it causes disease 
how to destroy

Answer 22

Smallest infective agents known
lack nucleic acids (not a living organism )
Proteins fold abnormally and accumulate, mainly in neural tissue
They are very difficult to destroy
Concerns over cleaning surgical instruments
extremely heat resistant

Question 23

name 5 prion diseases

+ describe

Answer 23

CJD- fatal, degenerative neurological disease
Affects 1 in a million people each year
Transmitted through contaminated human growth hormone, surgical instruments and corneal grafts
Variant CJD- typically occurs in young adults
BSE- occurs in cattle
Scrapie- occurs in sheep
Kuru- similar to vCJD,
occurred in Papua New Guinea in 1950s
thought to be spread by cannibalism

Question 24

describe growth requirements for micro-organisms (bacteria )

Answer 24

Every living organism requires nutrients to meet their energy needs and for the synthesis of their building blocks

Nutrient provide the necessary elements such as carbon, hydrogen, oxygen and nitrogen (CHON)

Microbes are very successful in obtaining nutrients from variety of sources. This helps them inhabit all possible environments

Growth and reproduction require synthesising new molecules.

Energy is needed to build those molecules.

Question 25

name and describe the two pathways of metabolism

Answer 25

Catabolic pathways
Break down molecules to produce energy. (larger substrates, smaller products)
Anabolic pathways
Use energy to combine small molecules into macromolecules (energy+ source of elements especially carbon)

Question 26

what are the primary nutritional groups

Answer 26

source of energy

source of electron donor

source of elements (carbon)

Question 27

name two examples of each primary nutritional group

Answer 27

source of energy
Phototrophs: uses sunlight energy to produce its energy (photophosphorylation)
Chemotrophs: extract energy from chemical bonds mainly by oxidation of electron donor compounds.

source of the electron donor
	Organic compounds  (organotrophs) e.g. Sugar, fat...etc
	Inorganic molecules: (lithotrophs)
	e.g.  Ferrous iron  	to	ferric iron 
	Amonia  nitrite

source of elements (carbon)
Autotrophs: produce complex organic compunds from simple inorganic ones
Heterotrophs: consume organic molecules as a source of carbon.

Question 28

what does the prefix in terms of energy mean 
auto- 
hetero-
photo-
chemo-

Answer 28

auto- using carbon dioxide
hetero- using organic compounds
photo- using light
chemo- using chemical compounds such as hydrogen, sulfur and nitrogen

Question 29

using the relevant prefixes(auto- hetero-photo-chemo-) describe ;

humans
plants
nitrifying bacteria

Answer 29

humans- Chemoheterotrophs
plants- Photoautotrophs
nitrifying bacteria- Chemoautotrophs

Question 30

name 6 physical requirements for growth

Answer 30

Temperature
Water
	PH
	Osmolarity
Oxygen
Pressure
Light
Physical space availability

Question 31

why is temperature important for growth

Answer 31

Temperature affect protein structure and fluidity of the cytoplasm and the cytoplasmic membrane.
Minimum growth temperature: lowest temperature that a given organism can carry out its metabolic activities
Maximum growth temperature
Optimum growth temperature: temperature at which metabolic activity is at its peak and thus growth rate is the highest.

Question 32

what optimum temperature would you expect pathogenic bacteria to be?

Answer 32

same as human cells- approx 37C

Question 33

describe why water is important for bacteria growth

Answer 33

Essential for life
Virtually all bacteria requires ‘wet’ habitat. As drying kills most bacteria
Water activity (Aw): thevapour pressureof a sample divided by that of pure water at the sametemperature.
Bacteriausually require at least Aw= 0.8 (G-ve requires higher 0.97), andfungiat least 0.7 (water Aw= 1).
Low Aw reflects high concentrations of solutes (hypertonic solution).
Bacterial growth correlate to Aw more accurately than to absolute water content

Question 34

decribe the PH effect on bacteria growth

Answer 34

PH effect: High or low PH inhibit microbial growth except for few!
Acidic conditions are body defense mechanism e.g. stomach and vagina (via fermentation by normal flora)
Acidophiles can tolerate acidic conditions. Some are obligate acidophiles
Alkalinophile lives in alkaline media like soil and alkaline water (e.g. Vibrio cholerae).
In both, intracellular PH is near normal

Question 35

describe the Classification of Organisms Based on O2 Requirements

Answer 35

Obligate aerobes: requires O2 for energy production (respiration)
Anaerobes : do not use O2 for energy production
Facultative Anaerobes: can survive with or without O2
Microaerophiles: can tolerate oxygen levels from 2-10% (limited ability to detoxify hydrogen peroxide and superoxide radicals)
Aerotolerant: Anaerobes but have some enzymes that detoxify oxygen’s poisonous forms.

Question 36

describe the defence systems of the body against microbes

Answer 36

Skin
Mucus membranes
Stomach acid
Commensal microflora
Immune system
Innate
Learnt
Behaviour  (e.g. good hygiene practices)