Biology- food and health

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Why is cholesterol in the body?

Found in cell membranes and skin, steriod hormones, bile, transported as lipoproteins;

  • High-density lipoproteins- unsaturated fats, protein and cholesterol. Carry cholesterol from body tissues to the liver. High levels reduce blood cholesterol levels because the cholesterol is broken down. Reduce deposition. more benificial to health
  • low-density lipoproteins- staurated fats, protein and cholesterol. From lover to body tissues. If there is too much staurated fats, concentration of LDLs rises. This causes deposition in artery walls. 
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Selective breeding

  • breed animlas with desirable traits
  • artificial selection
  • increases the benfit to humans
  • select a pair that display the desired characteristics 
  • the pair reproduce 
  • the offspring are sorted to selct those with the best combination of characteristics
  • offspring reproduce
  • careful selction and controlled reproduction continues for many generations
  • the required characteristics become more exaggerated
  • instead of natural selection, we apply teh selction pressure
  • marker assisted DNA is now being used to recognise the desired charateristic 
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Preventing food spoilage

  • cooking
  • pasteurising
  • drying, salting and coating in sugar
  • smoking
  • pickling
  • irradiation
  • cooling and freezing
  • canning
  • vacuum wrapping
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Using microorganisms

ADAVANTAGES:

  • faster production
  • production can increased or decreased accoriding to demand
  • no animal welfare issues
  • good source of protein for vegetarians 
  • no aminal fat or cholesterol

DISADVANTAGES:

  • grown on waste
  • isolation of the protein
  • protein needs to be purified to ensure that it is uncontaminated
  • infection- ideal conditions for pathogenic organisms 
  • palatability- doesnt taste like proteins sources
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Phagocytosis

Two types of phagocytes; neutrophils (bone marrow) and macrophages (travel as monocytes)

  • when a pathogen invades, recognised by foreign antigens
  • antibodies attach to foreign antibodies
  • phagocytes act as receptors which bind to the antibodies already attached to the pathogen
  • phagocyte engulfs the pathogen by folding membrane inwards 
  • pathogen trapped inside phagosome 
  • lysosomes fuse with phagosome and release enzymes called lysins to digest the bacterium
  • harmless product absorbed by cytoplasm
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Antibodies

  • produced by lymphocytes 
  • complementary to an antigen
  • Y-shaped
  • 4 polpeptde chains hed by disulfide bridges
  • constant region enables the antibody to attach to phagocytic cells 
  • variable region- specific shape, result of amino acid sequence
  • hinge regions allow flexibilty 

Neutralistation- antibodies cover the pathogen binding sites to prevent the pathogen from binding to a host cell and entering the cell 

Aggulination- a large antibody can bind many pathogens together. The group of pathogens is too large to enter the host cell 

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Communication between cells

  • release cytokines- act as instructions
  • receptor complementary to antigen 
  • send distress signals- parts of pathogen attach to plasma membrane which can be detected 
  • antigen presenting- macrophages in lymph nodes act like phagocytes, dont fully digest it, separate antigens into membrane which become antigen-presenting cells , which finds lymphocytes that can neutralise the antigen
  • macrophages release monokines that attract neutrophils, stimulate B cells to differentuate and release antibodies
  • T cells and B cells and macrophages release interleukins whihc stimulate differentiation 
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The specific immune response

  • foreign antigens dtected by T lymphocytes and B lymphocytes
  • presnatation of foreign antigens increases the chance that the correct B and T lymphocytes will locate the antigens
  • Macropahges become antigen-presenting cells.
  • selction of B and T cells is clonal selction
  • lymphocytes increase in number by clonal expansion
  • B and T lymphocytes differentiate into; 
    - T helper cells release cytokines taht stimulate B cells to develop and stimulate phagocytosis
    - T killer cells attack and kill infected body cells
    - T memory cells

    -B lymphocytes become plasma cells  releasing antibodies
    - B memory cells remain as immunological memory

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