biologyunit 1

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  • Created by: ricka
  • Created on: 25-04-13 14:09

Gas Exchange System

  • Larger surface area
  • small diffusion distance. Wall of alveoli arwe composed of single layer of flattened epithelial cells
  • Mechanisms maintain a high concentration gradient acroos gas exchange.


  • Air always flow from a high pressure to low pressure
  • Inspiration
    • Diaphragm contracts and flattens downwards and the external intercostal muscle contract, pulling the ribs up and out
    • Increases volume of the thorax and lugs which in turn stretches alveoli walls
    • Decrease in pressuree of air in alveoli
    • air flow in from high pressure to low pressure
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more on Gas Exchange System

  • Normal Expiration
    • Diaphragm relaxes and curves upwards and external intercostal muscle relax allowing ribs to fall
    • Decrese the volume of the thorax and lungs causing alweoli and bronchioles to shrink by elastic recoil
    • increases the pressure of air in alveoli above atmospheric
    • Air flows out from high oressure to low pressure
  • Forced expiration
    • Abdominal muscles contract, pushing the diaphragm upwards
    • interal intercostal muscle contral, pulling ribs down
    • this gives larger and faster expiration
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Pulmonary Ventilation

  • Pulmonary ventilation is the volume of air vetilating the lung each minute
  • Ventilation rate - calculated from pressure graph byt measuring time taken for one ventilation cycle
    • breaths per min = 60/cycle time (s)
  • tidal volume is the normal volume of air breathed in each breath.

Gas exchage                                     Ventilation

uses diffusion                                    uses mass flow

passive                                             active, thorax muscle needs ATP

gases move down own conc             all gases move together in

gradient                                              one direction

slow                                                    fast

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Lung Disease

  • asthma
    • Cause my physical factors called allergens and is triggered by inflammatory response
    • Histamines causes smooth circular muscles of bronchioles to contract (narrow) bronchoconstriction
    • epthelial cells also secrete more mucus which furthe blockes the air ways.
    • constricted bronchioles  reduces the tidal volume so alveolar air is replaced slowly concentration gradient is reduced
    • Less oxygen diffuses into the blood. So less oxygen is available for cellular respiration throughout the body.
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Lung disease

  • Pulmonary Tuberculosis
    • TB transmited by aerosol droplets from coughs and sneez of infected persons.
    • Bacterial cells breathed in and invade the epithelial cells of the alveoli and bronchioles. They then multiply forming lumps tubercles, bacteria remains alive but domant
    • Tubercles stimulate an inflammatory response by white blood cells resulting in formation of scar tissues - reducing elacticity of alveoli and thickens the wall
    • After a long period of time bacteria emerge from tubercles and start reproducing
    • damaged alveoli have a smaller surface area
    • TB can also spread through the bloodstream causing weakness of body
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Lung disease

  • Emphysema
    • Tar on cigarett smoke stimulates white blood cells to release inflammatory protease enzymes in the lungs
    • protease enzymes digest the protein elastin which forms elastic tissues in epithelial cells of alveoli. So it can no longer expand and recoil which in turn reduces tidal volume.
    • reducing oxygen gradient
    • severe cases epthelial cells are completely destroyed, alveoli merge together to form large air sacs- smaller surface area and thicker walls.
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Lung disease

  • Pulmonary Fibrosis
    • Particles stimulate and inflammatory response in the lungs which result in growth of fibrous scar tissue around the alveoli
    • scar tissue thickens the alveolar walls so that there is a longer diffusion pathway and a smaller surface area for oxygen diffusion
    • scar tissue also reduces the elasticity of the alveoli so norma passive exhalation is reduce. - smaller oxygen diffusion gradient so less oxygen reaches the blood.
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The heart

  • Cardiac Cycle
  • Both atria contract - atrial systole
  • both ventricles contract - ventricular systole
  • all chambers relax - diastole
  • Atrial systole
    • SAN contracts and transmit electrical impulse throughout atria which both contracts punp blood into ventircles so atrioventricular valves open
  • Ventricular Systole
    • impulse passes from the atrioventricular node  to purkinje fibres. But first it passes down the bundle of his
  • Diastole
    • atria and ventrials relax whil atria fill with blood
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The heart


  • Both atria fill with blood
  • electric impulse orginate from SAN which spread over the artria causing contraction.
  • Pressure is the atria rises. blood is forces throught the atrioventricular valves into the ventricles
  • impulse from SAN stimulate AVN (ARTIOVENTRICULAR NODE) to produce impulse that channels down the budle of his and then through purkinje fibres.
  • causing time for the ventricles to fill with blood.
  • Ventricals contract. blood is forced upwards which closes the AV valves and causing first heart sound, At this point pressure in ventricles rises
  • pressure in ventricales exceed that of the aorta and pumonary artyery blood if forced tho semilunar valves
  • ventricales relax and pressure falls below that in aorta so semilunar valves close again. secont heart sound.
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Coronary heart disease

  • caused by blockage in the coronary blood system
    • cholesterol and other insoluble lipds collect on the inside of the coronary artery. - artheroma  -  cauing narrow lumen of the artery, restricting blood flow - atherosclerosis
    • atherome can harde to from a rough plaque
    • the plaque weakens the walls of the arteru so the pressure of the blood causes the local swelling - aneurism - if walls is very weak aneurism may burst causing blood lose and probable death
    • plaque can also encourage the formation of blood clot - thrombus
    • mobile clot from elsewhere in the blood stream can also be lodged in the atheroma. Clot gros until it completely blockes the artey forming coronary thrombosis
    • Thrombosis prevent oxygen reaching the cardiac cells dowstream from blockage so the cannot respire and so will eventuallt die.
    • Death of myocytes is myocardial infraction. (heart attack)
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The digestive system

  • ingestion - taking large pieces of food into the body
  • digestion - break down food by mechanical and chemical means
  • absorption - taking up the soluble digestion product into body cells
  • assimilation - using absorbed material
  • egestion - excretion of waste produces
    • mucosa  secretes digestive juices and absorb digested food, often folded to increase surface area. layer of columnar epithelial cell lining the mucosa- contain microvilli
    • epithelial cells are constantly warn awat by friction so must be replaced
    • submucosa contain blood vessels, lymph vessels and nerves to control mucles
    • muscle layer made up of smooth muscles. circular muscle  ( squeezes the gut when it contracts) longitudinal muscle (shorten the gut whe it contracts) - muscles are antagonistic
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Parts of the alimentary canal

  • Buccal cavity
    • teeth and tongue physically break down food so it contains a larger surface area
    • forms into a ball bolus
    • silvary glands secret silva which contains water to dissolve soluble substance
    • lysozymes to kill bacteria and salivary amylase to digest starch
    • during swalloing the trachea is blocked off by epiglottis to stop food from entering lungs
  • Gullet
    • no digestions takes place here
    • no villi and only a few glands secret mucus
    • peristalsis wave of circular muscle contraction done by circluar anf longitude muscles
  • stomach
    • three layers of muscles to churn the food into liquid called chyme
    • chime graduallt released to small inetestine by spincter, region of thick circular muscle that act as a valve.
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The Alimentary Canal

  • Small intestine
    • First 30 cm of small intestine is called the duodenum
    • Almost all digestion takes place here, pancreatic juice and bile are realised
    • pancreatic juice released through the pancreatic duct
    • bile doesnt contain any enzymes but contains bile salt to aid lipid digestion amd sodium hydroxide to neutralise stomach acid.
    • rest of small intestine is called ileum
      • ileum has a large surface area as it contains vill and also micrivilli.
      • short diffusion distance
      • and also high concentration gradient.
  • large intestine
    • comprises caecum appendix, colon and rectum
    • Lots of gland secretinc mucus 
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Digestion of carbohydrates

  • Salivary Amylase
    • start digestion of starch in the mouth.
    • very little digestion, amylase is quickly denatured in the stomach.
    • reduce bacterial infection
  • pancreatic amylase
    • Digests all the remaining starch in duodenum
    • amylase digests starch molecule 
    • glycogen also digested here
  • disaccharidases
    • membrane of ileum epithelial cells complete digestion of disaccarides to monosaccharides
      • maltose ------> glucose   (maltase)
      • sucrose ------> glucose + fructose  (sucrase)
      • lactose -------> glucose + galactose  (lactase)
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Absorption of Glucose

monosaccharides are absorbed from the gut but actve transport called coupled active transport

  • active transport protein is the sodium-potassium ATPase. continuously pumps sodium ions out of epithelial cells and potassium ions into cells
  • using energy from hydrolysis of ATP
  • large build up of sodium ions in lumen of gut
  • facilitated diffusion protein is the sodium glucose co-transporter protein
  • sodium ions are pumped out again by Na/K ATPase to restore gradient. K ons diffuses out through K ion channels 
  • High concentration of glucose inside epithelial cell. Diffuses into the tissue fluid of the villus by facilitated diffusion
  • Glucose enters the blood capillary by diffusing through gaps between the cpullary endothelial cells
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How V.cholerae causes diarrhoea

  • Cholera bacterium adheres to the epithelium and secretes cholera toxins CT. CT enters the epitelial cells and activates chloride ions channels in the membrane
  • this cause chloride ions to diffuse out of the cells into the lumen
  • this lowers the water potential in lumen of the gut
  • Water is lost from cells to the lumen by osmosis, producing diarrhoea and dehydration

Treatment for diarrhoea Oral rehydration therapy solution made of glucose and salt (NaCl) 

  • If both Na and glucose are present in the lumen, they bind to sodium-glucose co-transporter protein. transport only woks if both molecules are present
  • tranporter proteins carries the Na and glucose into the cells down the concentration gradient
  • this lowers the water potential inside the epithelial cells. water diffuses from the lumen into the epithelial cells of osmosis this rehydrating cells
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The Immune System

Non-specific immune system

  • Phagocytosis
    • Phagocytes crawl throug the blood the tissue fluid in response to chemical released by micrones or white blood cells
    • when they reach the microbes they surround and engulf it through the process of phagocytosis. Microbe is now trapped in the membrane sace called phagosome
    • phagosome hen fuses with lysosomes small vesciles containing lysozymes released into the phagosome. lysozymes digests enzymes and kills the microbes.
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The Immune System

The specific immune system - involves the lymphocytes cells 

  • Antigens - on the outer surface of the cell

B-Lymphocytes and antibodies

  • White blood cells that make antibodies - (antibody is a protein molecule that can bind specifically to an antigen.
  • Antibodies all have a similar structure composed of 4 polypeptide chains (2heavt chains and 2 light chains) joined together by strong disupohide binds to form Y-shaped structure. 
  • Y is called constant region 
  • ends of the Y are called the variable regions
  • variable regions are where the antigens bind to form a highly specific antigen-antibody complex 
  • B-cellls have many membrane-bound antibody molecules on its surface and can also secrete soluble antibodies into its surrounding
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Immune system

  • macrophages and antigen presentation
    • infection starts when cells with non-self antigens enter the blood and tissue fluid. 
    • these foreign antigens need to be presented on antigen-presenting cells in order to initiate the specific immune response.
    • many body cells can act as antigen-presenting cells but the most important are the macrophages - they are most numerous phagocytosis.
    • macrophage also secretrs chemical to stimulate the next stage of the immune response - clonal selection
  • helper T-cells and Clonale Selection
    • antigen presenting cells interact with helper T-cells in the blood and bind tightly to each other.
    • antigen-presenting cell to helper T-cell stimulates the helper T-cell to release chemical - cytokines.
    • cytokines stimulate immature T and B lymphocytes cells to activate, proliferate and differentiate. when activated lymp cells divide repeatedly by mitosis. This is called clonal selection because only selected cells are cloned.
    • B and T lymph with identical bidnign sites have specific complement binding site to foreign antigen.
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The Immune system

  • T-cells and cellular immunity
    • Activated T-lymphocytes differentiate into cytotoxic T-cells These cytotoxin cells bind to antigens in infecting pathogen cells and kill them by making pores in their cell membrane, which allows water to diffuse in so that the cell lyses - bursts. cellular immunity because it is killed directly by lymph cells
  • B-cells and Humoral Immunity
    • activatedd B-lymph differentiate into plasma cells - anitbodies are carried around the blood lymph and tissue fluid binding kills cells in various ways-
      • binding antigens on viruses and bacteria attaching to cells and infect them
      • binfing to free toxin proteins they change the shape of the active region so that these proteins can no longer take part in the reaction that caused disease
      • linking cells toether, each antibody molecule has two antigen-binding sites (one on each arm of the Y) antibodies can stick together into large clumps. -agglutination- it immobilises viruse and cells and they can easily be destroyed by phagocytes or cytotoxic T-cells
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The Immune System

  • Memory Cells and Immunological Memory
    • clone army of B and T cells only last for a few days, after which the cells are destroyed and recycled by phagocytes.
    • some activated B and T cells differentiate into memory cells
    • memory cells remain in the blood for many years after the infection and memory B cells continue to secret antibodies in small quantities.
    • this means that the same antigen will be identified much more quickly.
    • memory cells will quickly divide to form a new clone army - secondary immune response.
  • active immunity - antigen received
    • natural - achieved through the primary immune response following an infection
    • artificial - achieved through injection of modified antigens (vaccination)
  • passive immunity - antibodies recieved 
    • naturaly - achieved through the passing of antibodies from mother to chld through placenta and milk
    • artificial - achieved through injection of antibodies (antiserum)
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Monoclonal Antibodies

Unique tertiary structure of each antibody protein allows it to bind specifically and tightly to one particular antigen.

Making monoclonal antibodies

  • Inject a mouse with the antigen protein that you want antibodies for. The mouse will show a primary immune response and make a clone army of B-lymphocytes with antibodies specific for that antigen.
  • After a few days extract B-lymphocyte cells from the rabit;s blood. the blood contains a mixture of thousand of different B-cells, each making their own specific ntibodies. Dilute the blood cells into hundreds of wells in an immunoassay plate 
  • Test each well for production of the antibody require and grow the B-cells from that well in the culture flask, they multiply by mitosis.
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