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CCEA A2 1 Full Unit Summary notes
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A summary of each topic within CCEA A2 1. Each topic is condensed down to 1-3 pages with the key information needed. Notes were created using goodnotes.
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summary notes for Biology A2-1
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Summary notes A2 -1 Biology CCEA
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Class notes Unit A2 1 - Physiology and Ecosystems Biology for CCEA A2 Level, ISBN: 9781780731001
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Voorbeeld van de inhoud
, Homeostasis & The KidneyHomeostasis - the maintenance of constant or steady state
conditions within the body
Excretion - the removal of the toxic waste
products of metabolism
Osmoregulation - the control of the water potential of body
fluids
Ultrafiltration - the filtration of plasma and small
substances into the bowman's capsule
Reabsorption - when filtered useful products are selectively
reabsorbed into the bloodstream
Ultrafiltration Loop of Henle
The ascending limb secretes sodium and chloride
Blood entering the glomerulus has a high ions into the medulla by active transport, creating
hydrostatic pressure for a number of reasons: a very low water potential in the medulla. The
• The short distance from the heart filtrate consequently becomes more dilute.
• The fact that the afferent arteriole is wider than
the efferent arteriole As a result of the low water potential in the
medulla and the permeability of the descending
• The coiling of capillaries in the glomerulus which limb, water moves out of the descending limb by
restricts blood flow osmosis. Therefore, the filtrate becomes more
concentrated as it moves down the limb.
The high hydrostatic pressure forces the smaller
components of the blood into the bowman's
capsule whilst the bigger components remain in Osmoregulation
the glomerulus. The collecting duct is where water regulation takes
place. Reabsorption in the collecting ducts can be
The walls of the glomerulus contain small pores controlled by varying the permeability of the
and the bowman's capsule is lined with podocytes. collecting duct walls. ADH is crucial in this process.
The basement membrane is the effective filter.
The role of ADH:
Reabsorption • solute potential becomes more negative and is
Useful blood products which were lost to the detected by osmoreceptors in the hypothalamus
glomerular filtrate are reabsorbed back into the • the posterior lobe of the pituitary body releases
blood as the filtrate passes along the PCT. Glucose more ADH into blood
and amino acids are selectively reabsorbed by • this causes the walls of collecting ducts and DCT
facilitated diffusion and active transport. to become more permeable and aquaporins open
• more water is reabsorbed and so solute potential
of blood returns to normal and a smaller volume of
concentrated urine is produced
, Immunity
Barriers to pathogen entry Antibody-mediated immunity
Skin - the skin provides a tough physical barrier • bacteria enter the body
that most pathogens cannot penetrate
• the antigen is recognised by the correct
Lysozyme - contained in tears, saliva, and sweat. It is B-lymphocyte
anti-bacterial as it is able to digest bacteria cell • the B-lymphocyte attaches to the antigen and
walls becomes sensitised
• the sensitised B-lymphocyte divides by mitosis
Mucus - can trap pathogens and prevent them to form plasma cells and memory cells
from penetrating the underlying membranes • plasma cells are short-lived but produce many
Stomach acid - Provides a low pH which denatures antibodies
the enzymes of the pathogen, killing it • memory cells remain in the body for a long time
to recognise the antigen if infected again
Non-specific immune response • the antibodies produced by plasma cells will
• Phagocyte moves towards the pathogen as it is attach to the antigens and clump them together,
attracted to the chemicals it produces forming an agglutination
• phagocyte membrane invaginates to begin to
enclose the pathogen Active vs Passive immunity
• as the pathogen is engulfed, the membrane forms (long term) (short term)
a vesicle (phagosome) around the pathogen
• lysosomes move towards the plagosome and fuse Active Passive -
with it
• hydrolytic enzymes are released by the lysosome Natural: Natural:
into the phagosome, hydrolysing the pathogen immunity from mother via
developed through placenta or
Cell-mediated immunity having had the
disease
colostrum
• host cell infected with viruses presents viral
antigens on its surface membrane Artificial:
• the viral antigen is recognised by the correct Artificial: injection of
T-cell with the complimentary receptor by vaccination -
antibodies
• the T-cell attaches to the viral antigen and
becomes sensitised Blood types
• the sensitised T-cell divides by mitosis to form 4 Blood group Antigens on RBCs Antibodies in plasma
different types of cell -
A A anti-b
• killer T-cells destroy infected cells before the
viruses reproduce B B anti-a
• memory cells remain in the body to recognise the AB A&B none
antigen if infected again O None both
• helper T-cells stimulate an immune response
• suppressor T-cells stop the response
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