T6 Flashcards

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1
Q

What happens when plants and animals die?

A

Microorganisms surrounding them secrete enzymes that decompose dead organic matter into smaller molecules so they can respire.

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2
Q

What are the 5 ways scientists can estimate the time of death?

A

1) Body temperature
2) Degree of muscle contraction
3) Forensic entomology
4) Extent of decomposition
5) Stage of succession

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3
Q

Explain how body temperature is used in estimating TOD?

(Process of Algor Mortis).

A

Body heat (37 degrees) produced from respiration.

After TOD, Metabolic reactions slow down.

Temperature decreases and equates surroundings at approx 1.5 - 2 degrees per hour.

Factors such as air temperature, clothing, body weight can affect the cooling rate.

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4
Q

How the degree of muscle contraction affects TOD?

A

Rigor Mortis is the stiffening of muscles, 4-6 hours after death.

1) Oxygen can’t teach the muscles so they’re deprived of it.
2) Anaerobic Respiration therefore occurs.
3) Lactic acid is produced.
4) pH levels decreases due to lactic acid.
5) ATP can’t be produced as the enzymes that produce it are inhibited.
6) Stiffening of the muscles due to the Myosin and Actin becoming fixed.

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5
Q

A factor that affects Rigor Mortis?

A

Smaller muscles in the head contract first and larger muscles contract last.

Higher the temperature, faster Rigor Mortis occurs.

Wears off around 24-36 hours after TOD.

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6
Q

What is forensic entomology?

What are the factors affecting it?

A

When the body is quickly colonised by different variety of insects.

E.g. Flies are often the first to appear

Also identifying the stage of life cycle the insects in.

Factors like humidity, oxygen, temperature, drugs effect the insects.

Higher temperature means a faster metabolic rate.

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7
Q

How is the extent of decomposition used to estimate TOD?

Factors affecting decomposition?

A

Hours - few days: Body’s own enzymes and bacteria break down cells and tissues -> skin turns green.

Few days - few weeks: Microorganisms decompose the tissues and organs producing methane gas causing the body to become bloated -> skin blisters and peels off.

Few weeks - few months: Tissues begin to liquify and seep out into the area around the body.

Few months - few years: Only skeleton remains.

Decades - centuries: Skeleton disintegrates until there is nothing left on the body.

Factors include: Temperature, oxygen availability.

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8
Q

Explain how the different stages of succession can be used to estimate TOD?

A

Succession is how different organisms found in the dead body change over time.

Refer to forensic entomology.

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9
Q

Difference between succession in a dead body and plant succession?

A

Succession in a dead body, the early insects remain as other insects colonise it which doesn’t happen in plant succession.

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10
Q

Succession in general…

A

Pioneer species are the first species to colonise the area.

Secondary succession is when the initial environment is much harsher.

Last stage of succession is called the climax community and is more stable as the ground has more nutrients.

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11
Q

Structure of DNA?

A

It is made up of nucleotides.

Each nucleotide has 4 bases: ATCG.

A molecule of DNA consists of two strands of nucleotides joined together by complementary base pairing.

Contains the sugar Deoxyribose.

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12
Q

What is the process of DNA profiling?

A

1) DNA sample is obtained from blood, saliva, tissue.
2) PCR is used to amplify DNA, making millions of copies of specific regions.
3) A fluorescent tag is added to view the DNA under UV light.
4) Gel Electrophoresis is used to separate the DNA according to their length.
5) Gel is viewed under UV light and the DNA fragments appear as bands.

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13
Q

How a Polymerase Chain Reaction works? (PCR)

Clue: 955072

A

1) A reaction mixture that contains DNA sample, free nucleotides, primers and DNA polymerase.

Primers are short pieces of DNA that are complementary to the bases at the start of the fragment you want.

DNA polymerase is an enzyme that creates new DNA strands.

2) DNA heated to 95 degreases to break hydrogen bonds between 2 strands of DNA.
3) Mixture is then cooled to between 50 and 65 degrees so the primers can bind (anneal) to the strands.
4) The reaction mixture is then heated to 72 degrees so the DNA polymerase can work.
5) DNA polymerase lines up free nucleotides along each template strand where complementary base pairing happens.
6) So 2 new copies of the fragment of DNA are formed in one cycle of PCR.

Cycle repeated and each PCR cycle doubles the amount of DNA:

1st Cycle: 4 DNA fragments.
2nd Cycle: 8 DNA fragments.
3rd Cycle: 16 DNA fragments.

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14
Q

Explain how Gel Electrophoresis works?

A

1) DNA is placed into wells in a slab of Gel covered in buffer solution which conducts electricity.
2) Electrical current causes the negatively charged DNA fragments to move towards the anode (positive electrode).
3) Short DNA moves faster and travel further.

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15
Q

Purpose of DNA profiling?

A

Used in paternity tests as we inherit half our DNA from our parents.

Used in animals to prevent inbreeding which causes health and reproductive problems, and also decreases the gene pool.

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16
Q

What is a pathogen?

A

A pathogen is any organism that causes disease.

E.g. Bacteria, fungi, all viruses.

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17
Q

What is HIV?

A

Human Immunodeficiency Virus infects and destroys T helper cells (white blood cells) which are responsible for activating other immune system cells.

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18
Q

Why does HIV need a host T helper cell?

A

1) HIV is spread through infected bodily fluids meeting mucosal surfaces (genitals through sexual intercourse).
2) HIV can only reproduce inside of the T helper cells as it doesn’t contain enzymes and ribosomes.

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19
Q

What is the process of HIV replication?

A

1) Proteins attaches to receptor molecules on cell membrane of the T helper cell.
2) Capsid released into the cell where it reveals the genetic material (RNA) into cytoplasm.
3) Reverse transcriptase is used to make complementary strands of DNA from viral RNA template.
4) Double stranded DNA is made and inserted into human DNA.
5) Host T helper cell enzymes are used to make viral proteins from viral DNA.
6) Viral proteins are assembled into new viruses.

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20
Q

How does HIV cause AIDS?

A

AIDS is when the immune system deteriorates then fails as a result of the T helper cells decreasing.

Having AIDS makes you vulnerable and leads to opportunistic infections.

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21
Q

Symptoms of AIDS?

A

Minor infections of mucous.

Number of T helper cells decrease further meaning more chance of infection from opportunistic infections.

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22
Q

Process of how Bacterium Mycobacterium Tuberculosis causes Tuberculosis (TB)?

A

Infection starts when tiny droplets containing the bacteria are inhaled into the lungs.

1) Phagocytes in the lungs take up the bacteria.
2) Bacteria replicate inside the phagocytes.
3) The immune system seals off infected phagocytes in structures called tubercles.
4) Inside the tubercles, bacteria become dormant so no symptoms are shown.
5) Dormant bacteria may become reactivated and overcome immune system.
6) Reactivation is more likely with someone with a weakened immune system.

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23
Q

Symptoms of TB?

A

Inflammation of the lungs -> severe coughing

Damages lungs -> Respiratory failure -> death

Lungs -> brain and kidney -> organ failure -> death

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24
Q

How can pathogens enter the body?

A

Cuts in the skin.

Digestive system from contaminated food.

Respiratory system from inhalation.

Mucosal surfaces like nose, mouth, genitals.

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25
Q

What barriers exist to prevent infection?

A

1) Stomach Acid - Acid kills pathogens but some may survive.
2) Skin - A physical barrier preventing pathogens from entering the bloodstream.
3) Gut and Skin Flora - Covered in harmless microorganisms called flora. They compete with pathogens for nutrients and space, limiting the number of pathogens.
4) Lysosomes - Found in tears, saliva, mucus etc. It kills bacteria by damaging cell walls and it makes bacteria burst open.

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26
Q

How do foreign antigens trigger an immune response?

A

Antigens are molecules found on the surface of cells.

So when a pathogen invades, antigens are recognised as foreign activating the immune system.

27
Q

Explain the process of Non-Specific immune response?

A

1) Immune system releases molecules that trigger inflammation when foreign antigens are recognised.
2) Molecules cause vasodilation (widening of blood vessels) so more blood can flow through and destroy the pathogen.
3) When viruses infect, cells produce proteins called interferons which help prevent them spreading but inhibiting the production of viral proteins and activate cells to kill the infected cells.
4) Phagocytes (macrophages and neutrophils) engulf pathogens. They are found in the tissues and respond first.

28
Q

How does Phagocytosis work?

A

1) Phagocytes recognise antigens on pathogens.
2) Phagocyte engulfs it.
3) Pathogen held in the vacuole in the cytoplasm.
4) Lysosome contains digestive enzymes that break down the pathogen when fusing.
5) Phagocyte activates other immune cells.

29
Q

In the specific immune response:

1) Phagocytes active T cells.
2) T helper cells activate B cells.

Explain what T cells are?

A

T cell is a type of white blood cell.

It’s surface is covered in receptors that bind antigens on antigen-presenting cells like macrophages.

Each T cell has a different shape receptor so when it finds a complementary antigen, it binds and divides, cloning itself.

30
Q

What is the role of T helper cells?

A

They release substances to activate B cells, T killer cells and macrophages.

31
Q

Purpose of T killer cells?

A

They attach to the antigens on pathogen infected cells and kills the cells.

32
Q

What’s the benefit of T memory cells?

A

It remembers the process so it’s more efficient next time so the specific immune response is faster as it would recognise the type of antigen in less time.

33
Q

T helper cells activate B cells.

What are B cells and explain its function?

A

B cells are another type of white blood cells.

It’s covered in unique antibodies (proteins). Which bind to antigens to form antigen-antibody complex.

So when an antibody finds a complementary antigen, it binds, activating B cells.

The activated B cell then divides (mitosis) into B effector cells and B memory cells.

34
Q

What do plasma cells (B effector cells) do?

A

They secrete lots of antibodies into the blood.

Antibodies then bind to to the antigens on pathogens.

35
Q

What are antibodies?

A

Antibodies are made of 4 polypeptide chains (2 heavy, 2 light chains) where each chain has variable and a constant region.

The variable region of the antibody form antigen-binding sites. Different region on all antibodies.

The hinge region allows flexibility when an antibody binds to an antigen.

The constant region allows binding to receptors on immune system cells. Same region on all antibodies.

36
Q

What holds polypeptide chains together?

A

Disulphide bridges

37
Q

What are the 3 purposes of antibodies?

A

1) Agglutinating pathogens - Antigen attaches multiple pathogens so the Phagocyte binds to the antigen engulfing multiple pathogens at once.
2) Neutralising Toxins - Antibodies produce antitoxins which bind to toxins produced by the pathogens.
3) Prevent binding to host cells - Antibodies bind to the antigens on the pathogens so they block the cell surface receptors so pathogens can infect host cells.

38
Q

Difference between membrane-bound and secreted antibodies?

A

Membrane bound antibodies have an extra section of protein that anchors them to the B cell membrane.

39
Q

What are introns?

A

Genes with sections that don’t code for amino acids.

40
Q

What are exons?

A

Genes with sections that do code for amino acids.

41
Q

How is mRNA modified during translation?

A

1) During transcription, introns and exons are copied into mRNA.

Pre-mRNA are strands that contain both intron and exons.

2) Splicing - This is when introns are removed, and exons join forming mRNA strands.

This occurs in the nucleus.

3) Alternate splicing - Sometimes exons are removed as well forming different mRNA strands.
4) This means more than one amino sequence and protein can be produced form a gene.

42
Q

Briefly, what happens when a pathogen enters?

A

1) Pathogen enters.
2) Antigens activate immune system.
3) Non-specific immune response
4) Specific immune response

43
Q

What is the primary response?

A

It is the non-specific and specific response.

44
Q

What’s the purpose of T memory cells?

A

They remember the specific antigen so it can recognise it quicker.

45
Q

What’s the purpose of B memory cells?

A

They remember the antibodies required to bind to the antigen.

46
Q

What do T memory cells divide into?

A

T killer cell to kill the cell carrying the antigen.

47
Q

What do B memory cells divide into?

A

Plasma cells (B effector cells) that produce the right antibody to the antigen.

48
Q

What is active immunity?

A

When your immune system makes its own antibodies after being stimulated by an antigen.

Natural - become immune after catching a disease.

Artificial - become immune after a vaccination.

49
Q

What is passive immunity?

A

When you receive antibodies made by a different organism.

Natural - a baby becomes immune after receiving antibodies in the womb from the mother.

Artificial - when injected with antibodies.

50
Q

How do vaccines work?

A

They contain antigens that stimulate the primary immune response without the pathogen causing a disease.

Thus, showing no symptoms.

51
Q

Can vaccines only defend against one strain of a pathogen, and why?

A

No it can defend against multiple as different antigens are inserted to protect against the different strains.

52
Q

How are different strains of pathogens formed?

A

Through antigenic variation.

53
Q

What is the evolutionary race?

A

The race between pathogens and their host cells to outdo each other.

54
Q

How does HIV evasion mechanism work?

A

1) HIV kills the host cell it infects so it reduces the amount of immune system cells which reduces the chance of detection.
2) HIV has a high rate of mutation so it changed structure of antigens and forms new strains - antigenic variation. Thus, memory cells won’t work.
3) HIV disrupts the antigen presentation preventing the immune system cells from recognising and killing the infected cells.

55
Q

How does Mycobacterium Tuberculosis evasion system work?

A

1) When MT infects the lungs, the Phagocytes engulf them and the MT produces substances that prevent lysosome fusing with the vacuole. So the bacteria aren’t broken down and can multiple undetected.
2) It also disrupts antigen presentation in infected cells so immune system cells can’t recognise it.

56
Q

What are antibiotics?

A

They are chemicals that kill or inhibit the growth of microorganisms.

57
Q

What are the two different types of antibiotics?

A

1) Bactericidal - kill bacteria.

2) Bacteriostatic - inhibit growth.

58
Q

How do antibiotics work?

A

They work by interfering with the metabolic reactions that are crucial for the growth and life of the cell.

59
Q

What are the 2 ways antibiotic work?

A

1) Some inhibit the enzymes that’s are needed to make the chemical bonds in cell walls which prevents growth and equals a weakened cell wall so it can be burst by osmosis.
2) Some inhibit protein production by binding to bacterial ribosomes. This prevents enzyme production so it can’t carry out metabolic reactions.

60
Q

Why does antibiotics only work on bacterial cells?

A

1) They can’t damage mammalian cells as well don’t have cell walls.
2) Antibiotics don’t affect viruses because they use a host cells enzymes and ribosomes.

61
Q

How can Hospital Acquired Infections (HAI) be transmitted?

A

By poor hygiene from:

  • Hospital staff and visitors not washing their hands before and after visiting a patient.
  • Coughs and sneezes not being contained.
  • Equipment and surfaces not be sterilised.
62
Q

Why are people in hospitals more likely to catch infections?

A

People in hospitals have a weakened immune system.

63
Q

What are some codes of practise for Doctors?

A

1) Doctors shouldn’t prescribe antibiotics for minor bacterial.
2) Doctors shouldn’t prescribe antibiotics to prevent infections.
3) Doctor should use narrow spectrum antibiotics
4) Patients should take all of the antibiotics prescribed to the infections are fully cleared.