| A2 Level | Unit 1 | Unit 2 | Unit 3 | Unit 4 | Unit 5 | Unit 6 | Unit 7 | Unit 8 | Unit 9 | Unit 10 | Unit 11 | Unit 12 | Unit 13 | AS Level | Unit 1 | Unit 2 | Unit 3 | Unit 4 | Unit 5 | Unit 6 | Unit 7 | Unit 8 | Unit 9 | Unit 10 | Unit 11 | Unit 12 | Unit 13 |
AS Human Biology Unit 7
Text questions
| P119/Q1 |
Temperature affects the rate of enzyme controlled
reactions. At a low temperature processes of
metabolism in bacteria are slowed down, hence slower
growth of bacterial cells. |
|
| P120/Q2 |
The pressure of air in the microbiology labs is
below the atmospheric pressure
→ air (containing
micro- organisms) from the lab will not move to the
other parts of the building (due to negative
pressure gradient). |
|
| P120/Q3 |
Done in the course-book. |
|
| P124/Q4 |
Haemocytometer is used in carrying out the total
cell count =>all cells (dead and alive/viable) are
counted, hence a higher number obtained. Serial
dilutions and pouring plates are used in carrying
out the viable cell count, hence a lower number
obtained. |
|
| P126/Q5 |
Excessive use of antibiotics
→ resistant strains of
Mycobacterium tuberculosis
→ number of infections
caused by TB increased. |
|
| P127/Q6 |
ORT helps to replace the water lost through
diarrhoea and vomiting. |
|
| P133/Q7 |
A higher possibility of entering a human body (human
activities in fresh water reservoirs, e.g. lakes,
usually occur during daytime). |
Assignment
| P139/Q1 | Flagellate bacilli are rod-shaped bacteria with
a flagellum/tail (used for locomotion). |
|
| P139/Q2 | a) | 7 mm |
| b) | 7 mm = 7000 micrometers 7000 micrometers / 2000 = 3.5 micrometers |
|
| P140/Q3 | a) | Ability of a micro-organism to cause a disease
is called virulence. Virulence determinant is the
ability of a micro-organism to produce toxins. P. aeruginosa
produce toxins which break down proteins
making up host's cells
→ toxins destroy the host's cells. |
| b) | "Quorum sensing" refers to the critical density
of the bacterial population which will cause the concentration of messenger molecules around them to be high enough to trigger a change in their "behaviour" (→ production of toxins). |
|
| c) | Number of cells per cm3 |
|
| P140/Q4 | a) | Lag phase (1) (see fig 7.9 p.125) |
| b) | As fig 7.9 p.125 |
|
| P140/Q5 | a) | Toxins not produced by the bacteria
→ no/reduced
defensive reactions of the host organism
→ bacteria
more likely to reproduce/multiply in
numbers/colonise the tissues of the host. |
| b) | Toxins break down the proteins of the host's
cells → products of the breakdown (e.g. amino-acids)
can be used by the bacterium to synthesise its own
organic molecules or/and cause irritation
(→scratching
→ bacterial cells spread to unaffected
areas). |
|
| P140/Q6 | (Write you own summary) |
|
| P140/Q7 | Production of toxins by the bacterium is
triggered by an increased concentration of the
messenger molecules. Therefore, a drug which breaks
down (or binds with) the messenger substance will
delay/cancel the moment when the production of these
toxins is started. |
Examinations
| P141/Q1 | a) |
Adult worms do not have access to oxygen present in
the oxyhaemoglobin of the RBC in the human host/can
use glucose present in the human blood as substrate
for anaerobic respiration and produce ATP for
growth/reproduction. |
| b) | Eggs are shed with urine/faeces into fresh water → fresh water has less negative WP → hatching of the eggs |
|
| c) |
Cercaria in this way increase their chance of
entering their human host (human's body temperature
is higher than the temperature of water). |
|
| P141/Q2 | a) |
(i) RNA carries a code for the structure of DNA
which will be synthesized through the process of reverse transcription (RT). (ii) Reverse
transcriptase - an enzyme, which controls the
process of RT. |
| b) |
Bacterium, which causes the type of pneumonia as
well as the form of cancer mentioned in the question
is normally recognised and dealt with by
T-lymphocytes. The number of T-lymphocytes is
reduced due to HIV infection, hence the onset of the
diseases. |
|
| c) |
Vaccines (inharmful strains of bacteria) trigger the
process of acquiring active immunity (increased resistance of the organism to the virus). Vaccine → memory lymphocyte. If the same strain of the virus infects the organism, then: memory lymphocyte → rapid immunological response. If a different/mutated strain of the virus caused infection, then memory cells do not recognise the virus → rapid immunological response will not occur. |
|
| P142/Q3 | a) |
Total number of cells in the triple-lined
square = #cells Volume of suspension within the square: 0.2mm x 0.2mm x 0.1mm = 0.004mm3 #cells - 0.004mm3 Hence: ?cells = (1.0 x #cells) / (0.004) |
| b) |
?cells x 103 |
