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Biology Model Answers > Topic 6 > Flashcards

Topic 6 Flashcards

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1
Q

Question
Body farms use the bodies of pigs to study the changes in insect species on a body after death.
i. Describe how this study could be carried out

A

I.
-Standardisation of pigs studied eg same sex,breed,mass,age
- temperature should be controlled
-record the presence of different species of insects
-at regular intervals of the day 24/every day

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2
Q

ii. Explain how the results of this study could be used to help establish the time of death of a human

A

-record which insects are present on the human
-compare with results from investigations on pigs to determine time of death
-take into account which stages of the lifecycle are present

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3
Q

Describe how DNA profiling could be carried out to show that two snakes are different species.

A

-DNA obtained from 2 types of grass snake
- PCR used to produce fragments of DNA
- gel electrophoresis used to analyse the DNA samples
- gel electrophoresis used to separate fragments of DNA
-more differences in the pattern of bands produced would indicate that the snakes are different species

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4
Q

Describe the changes that occur inside the body in the first week after death

A

-body temperature falls
- rigor mortis- stiffening of muscle
- autolysis - breakdown of cells by enzymes in the body
- discolouration and bloating occurs

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5
Q

Describe the role of decomposers, such as microorganisms, in the carbon cycle.

A

-decomposers break down organic material from the dead body
- respiration takes place
- carbon dioxide is released into atmosphere

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6
Q

Devise a procedure using electrophoresis to compare amplified DNA from a modern human skull and a neanderthal skull

A
  • restriction enzymes are used to cut DNA into fragments
  • DNA samples are loaded into agarose gel
  • electric current is passed through
  • markers are added to visuals the bands
  • the position of bands produced can be compared
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7
Q

Explain the effect of ambient temperature on the rate of decomposition

A
  • an increase in temp will increase the rate of decomposition
  • an increase in temperature increase enzyme activity
  • an increase in temperature increases growth rate of decomposers / bacteria
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8
Q

Describe the infection control procedures hospitals have introduced

A

-hand wash stations
- doctors / nurses not to wear ties/watches/ long sleeves
-testing patients for the presence of antibiotic resistant bacteria before admission of infected patients
- increased wash of bedding and disinfecting bedding

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9
Q

Explain how changes in blood vessels result in the swelling seen at the site of inflammation

A

-histamine is released
- histamine causes arterioles to dilate
-this increases the blood flow to the site causing redness
- histamines also cause the permeability of capillaries to increase
- which allows blood plasma to leave capillary and enter tissues causing swelling

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10
Q

Explain why the prescence of microorganisms on the skin and in the gut help prevent pathogenic organisms multiplying in the body

A

-flora in the gut and skin are better adapted to the conditions
- therefore they can outcompete pathogenic organism
- bacteria in the gut secrets chemicals which help to destroy pathogens

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11
Q

What is meant by the term phagocytosis

A

-idea of binding the bacteria to the phagocytic cell
- idea that bacteria is engulfed by endocytosis into the cell
-bacteria is then inside a vacuole

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12
Q

What is meant by non specific response

A

-the body defends itself from a pathogen
- the response is not dependent on the specific virus

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13
Q

What is meant by infection

A

-bacteria inside tissue cells

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14
Q

Describe the role of antigen presentation in three body’s specific immune response to infection by viruses

A

-the macrophages present to T helper cells
- T helper cells are needed to activate T killer and B cells
- B cells act as an antigen presenting to cell
- B cells result in plasma cells that produce antibodies
- the infected (host cell) present s antigen to T killer cells
- T killer cells destroy infected host cell

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15
Q

Distinguish between the structure of bacteria and viruses

A

-bacteria’s are cells but viruses are not particles
- bacteria is surrounded by cell wall and plasmids where as viruses do not have plasmids
- bacteria are DNA but viruses can be DNA/RNA
- bacteria is circular genetic material but viruses are linear

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16
Q

Describe how infection with a bacterium results in the production of-plasma cells

A

Macrophage engulfs bacteria and displays bacterial antigen on its surface become APC
T helper cell activated – CD4 receptors bind to complementary antigen on macrophage clones of T helper cells and T memory cells produced
B cell meets bacteria and presents bacterial antigen on its surface APC
Activated T helper cell with complementary receptor binds to B cell
T helper cell produces cytokines
B cell divides to form clone of B effector cells and B memory cells
B effector cells differentiate to become plasma cells
Plasma cells produce antibodies
Antibodies stick to bacteria causing marking them and sticking them together so they can be engulfed by macrophages

17
Q

How does the body respond to bacteria

A

Macrophage engulfs virus and displays bacterial antigen on its surface become APC
T helper cell activated – CD4 receptors bind to complementary antigen on macrophage clones of T helper cells and T memory cells produced
B cell meets virus and presents bacterial antigen on its surface APC
Activated T helper cell with complementary receptor binds to B cell
T helper cell produces cytokines
B cell divides to form clone of B effector cells and B memory cells
B effector cells differentiate to become plasma cells
Plasma cells produce antibodies
Antibodies stick to viruses causing marking them and sticking them together so they can be engulfed by macrophages
Cell infected by virus puts viral antigen on its surface APC
T killer cell with complementary receptor binds to infected cell
Activated T helper cells bind to T killer cells with complementary receptors. T helper cells release cytokines T killer cells divide to form clones of active T killer cells and T memory cells
Activated T killer cell releases enzymes which make pores in cell surface causing it to burst killing cell and virus

18
Q

Explain the role of T cells within a vaccine

A
  • vaccinated person will have memory T cells
  • memory T cells will recognise antigen’s specific to set virus
  • T helper cells activate B cells and T killer cells
  • T killer cells destroy cells infected with virus
19
Q

What is PCR and why is it used

A

PCR is used to amplify fragments of DNA. This is important because the DNA sample collected at a crime scene doesn’t contain enough material for accurate analysis.

20
Q

What are the 3 stages of PCR

A

Denaturation
Annealing
DNA synthesis

21
Q

What happens in denaturation in PCR

A

Add DNA nucleotides/polymerase/primers to your sample
Addition of heat (95) needed to separate the 2 strands of the DNA molecule

22
Q

What happens in annealing in PCR

A

2 DNA strands that have now been separated by the heat are going to be cooled and be joined by primers
The temperature (55)for this step should allow the primers to bind to specific segment

23
Q

What happens in DNA sythsies in PCR

A

Make more copies of DNA
DNA polymerase can now bind to primer
DNA polymerase will begin to work on both of these strands and it will use the DNA nucleotides as its building material to amplify the DNA
Temperature at this step should be a little warmer than previous (70)
The temperature (70) has to be specific for the DNA polymerase to be used - optimum temp

24
Q

what happens after 3 stages of PCR

A

End of A cycle 1 - you have 2 double stranded DNA molecules
A cycle 2
Start with 2 DNA strands then you repeat A cycle 1 and end with 4 double stranded DNA

25
Q

What is rigor mortis

A

Muscles begin to stiffen due to chemical changes in muscle tissue
Begins with smaller ,muscles and move to larger ones
Rules of rigor:
-Begins within 10 hours
-Whole body stiffens within 12-18hours
-Stiffening disappears after 24hours

26
Q

What is algor mortis

A

In death a body no longer generates warmth and begins to cool down
Temperature drop used to estimate time since death

27
Q

What is liver mortis

A

Discoloration of the body after death due to gravitational settling of blood
Begins 30 mins-3 hours after death
Skin gets purple and waxy
Lips ,finger and toenails become pale or turn white
Hands and feet turn blue
Eyes start to sink into skull

28
Q

What are the 4 stages of decompostion

A

Fresh
Bloat
Decay
Dry

29
Q

What happens in fresh stage

A

Time of death
-Heart stops
-Skin gets tight and gray
-cells start to die
-Muscle relax
-Bladder/bowels empty

30
Q

What happens in bloat stage

A

Skin begins slipping/marbling
-Greenish discoloration
-Further destruction is caused by insect activity

31
Q

What happens in decay stage

A

10-20 days after death
-Body begins to collapse and leaves a flattened body
-Large volume of body fluid drain from body

32
Q

What happens I’m dry stage

A

20-365 days after death
-Remaining flesh on deteriorates and body dries out
-Body is dry and continues to decay very slowly
-Mostly reduced to hair and bones

33
Q

What order do insects arrive on body

A

Flies arrive within hours of death
Carrion beetles arrive within a few days
During the dry stage of decomposition carpet beetles arrive

34
Q

What factors affect inset growth rate

A

Temp
Food quality
Oxygen levels
Day length/season

35
Q

What are the stages of TB (bacterial disease)

A
  • first stage may be symptomless - infected phagocytes are sealed in tubcerles in lungs as a result of an inflammatory response
    -bacteria lie dormant inside tuberclers
  • when immune system becomes weakend the bacteria become active again and slowly destroy the lung tissue leading to breathing problems/coughing/weight loss
    -TB can then spread to other areas - fatal
36
Q

What are the stages of HIV (viral infection)

A

-HIV destroys T cells in immune system leadings to aids
- the first symptom of HIV are flu symptoms
-after several weeks HIV antibodies appper in blood - HIV positive
- symptoms then disappear until immune system becomes weakend again - leads to AIDS
- sytmpms of aids include weight loss/dementia/cancer - can leads to death

Biology Model Answers (8 decks)

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