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Biology Edexcel > topic 6 > Flashcards

topic 6 Flashcards

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1
Q

what does a post mortem examination consist of?

A
  1. external examination
  2. internal examination: incision made down front of body, organs taken out for examination
    blood and tissue samples tested for toxins/ infections/ tumours
    stomach contents analysed to show when and where person alive
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2
Q

what type of cell are bacteria

A

prokaryotic (no nucleus or membrane bound organelles and do not produce a spindle during cell division)

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3
Q

bacteria cell walls

A

gram positive- walls that are thickened with additional polysaccharides and proteins

gram negative- thinner walls with surface layer of lipids for protection

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4
Q

what are viruses made of

A

1x strand of nucleic acid (RNA or DNA) enclosed within a protein coat

single OR double stranded

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5
Q

how do viruses infect cells

A
  1. enter host and use its metabolic systems to reproduce as they lack the internal cells required for growth and reproduction
  2. normal working of cell disrupted
  3. new virus particles bud from cell surface or burst out of the cell, causing cell lysis
  4. cell lysis= cell contents released into surrounding tissues- enzymes + chemicals damage other cells causing disease symptoms
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6
Q

what are viral envelopes

A

an outer envelope taken from the hosts cell surface membrane- thus contains lipids and proteins.

have glycoproteins from the virus itself. These are antigens; molecules recognised by the host’s immune system

Therefore, the envelope helps virus attach to the cell and penetrate the surface membrane, eg. HIV

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7
Q

how does a virus get inside a host cell

A
  1. virus attaches to host cell
  2. virus inserts nucleic acid
  3. viral nucleic acids replicate
  4. viral protein coats synthesised
  5. new virus particles formed
  6. cell lysis; viral particles released
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8
Q

examples of bacteria

A

salmonella food poisoning

cholera

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9
Q

examples of viruses

A

flu
measles
chicken pox
cold sores

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10
Q

debate about if viruses are living

A

YES - can reproduce, pass on genetic info from 1 generation to the next

NO- not capable of independent reproduction or energy use

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11
Q

what increases the risk of getting TB

A

close contact

poor health/ diet

overcrowded living conditions

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12
Q

what fluids transmit HIV

A

blood

vaginal secretions

semen

breast milk

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13
Q

types of HIV transmission

A

sharing needles

unprotected sex- breaks in skin, virus enters bloodstream

direct blood to blood- cuts and grazes, police

maternal: last few weeks

reduce- anti HIV drugs during last 3 months
giving birth via caesarean section

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14
Q

difference between non specific and specific immune response

A

non- ANY invading pathogens, immediate

specific- specific pathogens, delayed

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15
Q

what is an antigen

A

any foreign molecule the body recognises

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16
Q

3 types of non specific immune response

A
  1. lysozome
  2. inflammation
  3. phagocytosis
17
Q

what do lysozomes do

A

enzyme lysosome kills bacteria by breaking down their cell walls by hydrolysing the polysaccharide

found in: tears, salvia, nasal secretions

18
Q

what is inflammation

A

injury enables microbes + foreign material to enter body, so blood clots rapidly to seal the wound. Helps destroy invading microbes

19
Q

how does inflammation occur

A

damaged white blood cells and mast cells release HISTAMINE:

  1. arterioles in area dilate; increasing blood flow in capillaries at infected site
  2. increases permeability of capillaries; antibodies leak from the blood into the tissue, causing oedema because cells in capillary walls separate slightly

infecting microbes can now be attacked by intact white blood cells

20
Q

what is phagocytosis

A

phagocytes (white blood cells) from capillaries engulf bacteria and other foreign matter in blood and tissues

  • neutrophils
  • macrophages

bacterium with antigens on surface detected and engulfed by neutrophil or macrophage.
Bacterium enclosed in vacuole
Lysosomes fuse with the vacuole, releasing enzymes to destroy foreign material.

21
Q

action at site of infection; non specific immune response

A

chemicals released by bacteria and damaged cells at the site of infection attracted pathocytic white cells.

NEUTROPHILS arrive first. engulf 5-20 bacteria before becoming inactive + dying

MACROPHAGES arrive- larger, longer lived cells destroy up to 100 bacteria by phagocytosis and digest debris from damaged cells and foreign matter.

ingested material enclosed in vacuole

Lysosomes containing digestive enzymes fuse with vacuole, enzymes are released which destroy bacteria and other foreign material

22
Q

how does the body prevent spread of infection in blood and lymph

A

action of macrophages in lymph nodes, spleen and liver

tissue fluid drains into lymphatic vessels

fluid (lymph) flows along lymph vessels. It passes through lymph nodes and returns to the blood via lymphatic and thoracic ducts.

as lymph passes through lymph nodes, any present pathogens activate lymphocytes and macrophages- which can then destroy the microbes

23
Q

what are lymphocytes

A

white blood cells that help defend the body against specific diseases.

Circulate in the blood and lymph and gather in large numbers at site of infection

24
Q

give 2 types of lymphocytes

A

B and T cells

both respond to antigens, proteins, other foreign ‘proteins’

25
Q

how are antigens detected

A

most antigens= protein molecules with large size and molecular shape which allows lymphocytes to identify which ones are foreign.

Response by lymphocytes= specific immune response

26
Q

what does interferon do

A

provides non specific defence against viruses + some bacteria

27
Q

what protein do microbe infected cells produce

A

interferon. it diffuses into surrounding cells- where it prevents microbes from multiplying. It inhibits microbial protein synthesis + limits the formation of new microbe particles

28
Q

what are B lymphocytes

A

cells produced in bone marrow which has one specific type of antigen receptor on its surface.

Activated when its receptor binds to complimentary antigen

29
Q

How are B lymphocytes activated and what happens

A
  1. receptor binds to antigen with complementary shape
  2. B cell secretes antibodies in response
  3. antibodies bind to the antigens on microbe cell surface membrane. Act as labels; allowing phagocytes to recognise and destroy the cell
30
Q

antibody def

A

specific protein molecules of a class known as immunoglobins

31
Q

what are T lymphocytes

A

produced in bone marrow, mature in thymus gland

1 specific type of antigen receptor on its surface, which binds to the antigen with complimentary shape

32
Q

what are the 2 types of T cells

A

helper

killer

33
Q

what do T helper cells do when activated

A

stimulate B cells to divide and become cells capable of producing antibodies. enhance phagocyte activity

34
Q

what do T killer cells do

A

destroy any cells with antigens on their surface membrane that are recognised as foreign. This increases body cells infected with pathogens and transplant tissues

35
Q

how are T helper cells activated

A
  1. when biological material is engulfed by macrophages, protein fragments (peptides) from the material become attached to proteins in the cell.
  2. presented on macrophages cell surface membrane- where they are displayed as antigen presenting cells (APCs)
  3. signal alerts immune system of presence of foreign antibodies
  4. T helper cell with complimentary shaped (CD4) receptors on its surface binds to the antigen on the surface of the antigen - presenting cells
  5. once activated by this binding, each T helper cell divides to produce a clone of active T helper cells and a clone of T memory cells
  6. If individual is exposed to same antigen in future, immune system response faster.
36
Q

how are B cells cloned

A

complementary receptors on the surface of B cells bind to non self antigens and become APCs

AP B cells bind with active, cloned T helper cells that are presenting the same antigen

once attached, T helper cells release cytokines chemicals- which stimulate division and differentiation of the B cells

37
Q

when cloned, what 2 clones of cells are produced

A
  1. B effector cells: differentiate to produce plasma cells, which releases antibodies into the blood and lymph. Short lived
  2. B memory cells: respond quicker to same antigen in future. Longer lived
38
Q

what is B cell division known as

A 
clonal selection (primary immune response)
symptoms experineced

Biology Edexcel (8 decks)

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