Intermediate 2 Biology Unit 3 : Animal...
Transcript of Intermediate 2 Biology Unit 3 : Animal...
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Blood
Intermediate 2 Biology
Unit 3 : Animal Physiology
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Composition of Blood
• Blood contains
– Red blood cells
– White blood cells
– platelets
– plasma
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Plasma
• Watery, yellowish fluid • Suspended in plasma
– Proteins e.g. Antibodies
• Transports water-soluble substances to within diffusion distance of living cells. – Glucose – Amino acids
• Carbon dioxide transported as bicarbonate ions (as CO2 with water to form an acid which can cause problems)
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Red Blood Cells
• Very small and numerous
• Flexible – squeeze through tiny capillaries to deliver oxygen to cells
• Biconcave disc shape – large surface area in relation to volume
• No nucleus
• Cytoplasm rich in haemoglobin
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Haemoglobin
• Haemoglobin combines with oxygen to increase the oxygen-carrying capacity of blood.
• Association
– Haemoglobin combines with oxygen when the oxygen concentration is high
• Dissociation
– Haemoglobin rapidly releases oxygen when oxygen concentration is low
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Association and dissociation
haemoglobin oxygen oxyhaemoglobin +
Association
(in lungs)
dissociation
(in tissues)
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Oxygen affinity
• Haemoglobin has a high affinity for oxygen when oxygen concentration in the environment is high
• Haemoglobin has a low affinity for oxygen when the oxygen concentration in the environment is low.
• Affinity – Tendency to combine with oxygen
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oxygen dissociation curve
• Partial pressure of oxygen (pO2) – Measure of concentration of oxygen – Measured in kPa
• The oxygen dissociation curve shows saturation of haemoglobin at different partial pressures of oxygen (pO2).
• High pO2 – haemoglobin saturated with oxygen • Low pO2 – oxyhaemoglobin gives up its oxygen to
respiring cells (dissociates)
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oxygen dissociation curve
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Respiring cells
• Actively respiring cells have a low oxygen tension (2.7kPa)
• Alveolar air has a high oxygen tension (13kPa)
• In lungs haemoglobin is loaded with oxygen – It moves along a concentration gradient from the
alveolar air (High oxygen concentration) to the blood (low oxygen concentration)
• In respiring tissues oxygen is unloaded – Diffuses from a high concentration in the blood to a
low concentration in the respiring cells.
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White Blood Cells
• White blood cells
– Contain a nucleus
– Can change shape and squeeze through capillary walls
• Types of white blood cell include
– Monocytes
• Phagocytosis
– Lymphocytes
• Antibody production
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Phagocytosis
• Bacteria are engulfed and destroys by phagocytic cells, e.g. monocytes or macrophages
• Stages of phagocytosis – Bacteria releases a chemical and the phagocyte moves towards
it – The phagocyte adheres to the bacteria – The cell membrane changes shape and engulfs the bacteria in a
phagocytic vacuole – Lysosomes fuse with the vacuole releasing powerful digestive
enzymes – Bacteria is digested – Products of digestion are absorbed into the cytoplasm of the
phagocyte
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Phagocytosis
• Dead bacteria and phagocytes can accumulate at the site of infection forming pus.
• Macrophages can be found in liver, spleen and lymph
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Immunity
• Immunity – An organism’s ability to resist infection
• Phagocytosis is an example of non-specific
immunity – Providing protection against a range of
microorganisms
• Antibody production is an example of a specific immune response – Each antibody is specific to a particular antigen – Thee antibody and antigen are complementary
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Antigens
• An antigen is a protein molecule that is recognised as “foreign” by the body’s lymphocytes
VIRUS
antigens
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Antibody
• Y-shaped molecule
• Produced by lymphocytes
• Receptor sites are specific to an antigen
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• When an antibody attaches to its complementary antigen, the antigen is rendered harmless
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Immunological memory
• Primary response – Infection by disease-causing organism – Latent period when the lymphocytes respond and start to
produce antibodies – Often person suffers symptoms of the disease
• Secondary response – Exposure to the same antigen – Memory cells remain in blood from first infection and as a
result antibodies • Produced more rapidly • Produced at a high concentration • Remain in the bloodstream for a longer time
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Primary and secondary response
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Immunity
• Natural acquired immunity
– The person has been exposed to the disease-causing organism
– Memory cells remain in bloodstream
• Artificially acquired immunity
– Vaccinations contain a small dose of the antigens
– Lymphocytes are stimulated to produce antibodys
– Memory cells remain in bloodstream