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141 Cards in this Set
- Front
- Back
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Why is haemoglobin considered a complex protein?
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It has a quaternary structure
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How is haemoglobin composed?
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Four sub-units each containing a haem group
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What does each haem group contain?
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Iron ion which can associate with one oxygen molecule
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How many oxygen molecules can associate with haemoglobin/
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4
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The uptake of oxygen by haemoglobin is a...
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reversible reaction
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What substance is formed when oxygen combines with haemoglobin?
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Oxyhaemoglobin
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How is the amount of oxygen combined described?
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In terms of the percentage saturation of the haemoglobin
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Describe the effects, in terms of uptake, high O2 concentration (high pO2):
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More oxygen is loaded by Hb
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Describe the effects, in terms of uptake, low O2 concentration (low pO2):
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Less oxygen loaded by Hb
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When is oxyhaemoglobin more likely to unload?
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In an area of low O2 concentration
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Definition of partial pressure:
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The amount of a particular gas in a mixture of gases or a solution
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Explain the saturation of oxygen in the lungs:
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pp02 is high in the lungsHb has a high affinity for O2 at high pp02Hb becomes fully saturated as red blood cells pass trhough the pulmonary capillaries
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Explain how Hb reacts in tissue:
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Hb has a low affinity for O2 at a low ppO2Oxyhaemoglobin will release oxygenThis allows respiration to take place
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Why does the ODC start off steadily?
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The first O2 molecule combines relatively slowlyHowever once the 1 st oxygen molecule binds, Hb molecule changes shape
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Why does the ODC change shape after the first oxygen binds to the Hb molecule?
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Because the Hb shape has been altered it is easier for the 2nd and 3rd O2 to bind to the Hb
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Why does the ODC level off?
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It becomes harder for the fourth O2 molecule to bind
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How does CO2 affect haemoglobin saturation?
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If CO2 levels increase the saturation decreases
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How does CO2 affect a ODC?
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The curve shifts right (Bohr shift)
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Why does CO2 have an effect on Haemoglobin?
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CO2 dissolves into the blood making it more acidic and lowering the pH. This alters the tertiary structure of Hb.
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What happens when tissues respire?
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More CO2Shift to the rightHb now has a lower affinty and will release oxygen Extra oxygen is now available to the respiring cells
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What 5 properties do respiratory surfaces have?
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Large surface areaPermeableThin (short diffusion paths)MoistMaintains a conc. gradient
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State Fick's law?
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Rate of diffusion= SA x Diff in conc / Diffusion distance
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Describe and explain the trachea and its role:
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A tube like structure that carries air from the mouth to the lungsStrong cartilage to hold the tube open
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Describe and explain the bronchi and its role:
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Splits into two bronchi as it enters the lungs which allows air to travel to the left and right lung
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Describe and explain the role of the bronchioles?
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Bronchi further divide into smaller branches called bronchioles which supply alveoli with air
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Describe the structure of Alveoli:
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Small sacs at the end of the bronchioles, act as an interface between the air in the lungs and the blood
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How are alveoli adapted to their function?
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Large surface areaRich blood supply to maintain a conc. gradientOne cell thick for a thin diffusion pathway
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What is breathing a result of?
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A difference in pressure between air in the lungs and the air outside the body.Pressure inside the lungs is altered by changes in lung volume
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Explain the mechanism of inhalation:Step 1
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External intercostal muscles contractInternal intercostal muscles relax
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Explain the mechanism of inhalation:Step 2
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Rib cage moves outwardsDiaphragm contracts and moves down
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Explain the mechanism of inhalation:Step 3
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Lung volume increasesPressure in the lungs is less than outside and so air moves into the lungs
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Describe and explain the concentrations in the alveoli before diffusion:
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Blood from the pulmonary artery has a low ppO2 and a high conc. of CO2
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Describe how the gases are diffused in the alveoli:
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As blood reaches the capillaries, oxygen diffuses into the blood, moving from high ppO2 to low ppO2At the same time CO2 diffuse from the capillaries
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How does the circulation of blood by the heart maintain a conc. gradient?
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Blood is circulated away from the alveoli by contractions of the heart
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How do you calculate the pulmonary ventilation rate?
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PVR = Tidal volume x breathing rate
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What is the tidal volume?
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Natural breathing volume
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What is the inspiratory/expiratory reserve?
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Extra volume required for a deep breath
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What is the residual volume?
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Air that remains in the lungs to prevent the collapse of alveoli
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What is the vital capacity?
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the maximum amount of air a person can expel from the lungs
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List 5 risk factors that increase the probability of lung disease:
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SmokingAir pollutionGenetic make-upInfectionsOccupation
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What is fibrosis?
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Formation of scar tissue of the epithelium of the lungs
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What happens in fibrosis?
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the scar tissue is thicker and less elastic, lungs are less able to expand so tidal volume is reduced and the breathing rate is faster.
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What is asthma?
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Inflamed airways
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What happens with asthma?
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White blood cells in the linings of bronchi release histamine. This causes the contraction of the smooth muscle of the bronchioles restricting the airways. Large quantities of mucus are also produced.
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What happens during emphysema?
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Inflammation attracts phagocytes which produce an enzyme that breaks down the elastin in the alveoli. The alveoli can no longer recoil to force all the air out of the alveoli. The SA is also reduced.
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What is tuberculosis caused by?
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An infection by a bacteria which can be spread by aerosol droplets
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What happens during TB?
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The bacteria enters the lungs and causes the white blood cells to replicate and build a wall around the bacteria. This forms a hard lump, decreasing the SA.
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The plasma membrane is described as...
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A fluid mosiac
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What is the plasma membrane made up of?
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Proteins, phospholipids and carbohydrates.
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The phospholipid molecules form...
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A bilayer which is constantly moving about
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What forms the mosaic?
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The protein molecules are unevenly distributed.
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Why can only certain substances pass through the membrane?
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Selective permeability
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What is cholesterol role in the membrane?
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Decreases permeability and increases the stability
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What is the phospholipid bilayer role in the membrane?
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Restricts the passage of ions and polar molecules
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What is the role of a carrier protein?
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Aid the transport of ions and polar molecules
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What is the role of other protein molecules?
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They act as specific receptors for hormones
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Why are glycolipids important?
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They aid cell recognition
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Name the different types of protein in a membrane:
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Protein moleculesChannel proteinsCarrier proteinsEnzymesGlycoproteins
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Diffusion is the...
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net movement of molecules from a higher concentration to a lower concentration until they are equally distributed
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List the four factors that affect the rate of diffusion:
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TemperatureSurface areaConcentration differenceThickness of exchange surface
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How does the temperature affect diffusion?
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It increases the kinetic energy
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How does the surface area affect diffusion?
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There is more space for molecules to pass through
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How does the concentration affect the rate of diffusion?
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As the concentration difference increases so does the rate
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How does the thickness of the surface affect the rate of diffusion?
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the thinner the surface the faster the molecules will travel through it
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What is Fick's law?
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Rate of diffusion = Area of surface x Diff. in conc./ Thickness of surface
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What is facilitated diffusion?
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The transport of substances across a membrane by trans-membrane protein molecules
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Facilitated diffusion is a ... diffusion process.
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Passive
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Name two types of transport proteins:
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Carrier and Channel proteins
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How can the rate of facilitated diffusion be limited?
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Limited by the number of transport proteins
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Give the definition of osmosis:
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The net movement of water molecules from a solution with a higher water potential (wp) to a solution with lower wp
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How is water potential created?
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Free water molecules move and collide with the membrane
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What units is wp measured in?
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kPa
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What is an isotonic solution?
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a solution that has equal water potential to that inside the cell
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What is a hypertonic solution?
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a solution that has a lower wp than the inside of the cell. Water will therefore leave the cell.
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What is a hypertonic solution?
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a solution that has a higher wp than inside the cell. This causes water to diffuse by osmosis into the cell.
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What is active transport?
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Active transport uses energy to move molecules and ions across membranes, usually against the conc. gradient.
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What is required for active transport to occur?
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A specific carrier proteinATP
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Describe the process of active transport:
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1. A molecule binds to the carrier protein
2. The protein changes shape 3. This moves the molecule across the membrane 4. The protein releases it |
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What is HIV?
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A virus that infects and kills helper T-cells, preventing an immune response
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When does HIV develop into AIDs?
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When the levels of helper T-cells are critically low
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Describe the structure of HIV.
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1) A core that contains genetic material such as, RNA and reverse transcriptase
2) A capsid 3) An envelope layer made from a membrane of a previous host cell 4) Attachment protein that attached to helper T-cells |
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How does HIV replicate?
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1) An attachment protein attached to a receptor molecule on the T-helper cell
2) The capsid is released into the cell where it uncoats and releases RNA 3) A DNA strand is made fromviral RNA template 4) This is inserted into the human DNA strand5) Host cell enzymes create viral proteins from the viral DNA 6) The viral proteins produce new viruses which |
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Phagocytosis is carried out by...
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white blood cells
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What is produced in phagocytosis?
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Phagocyte such as a macrophage
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Describe the process of phagocytosis.
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1) The pathogen is detected, and the phagocyte is attracted to it by the chemicals released
2) The pathogen is engulfed by the macrophage3) The pathogen enters the cytoplasm in a vesicle4) Lysosomes fuse with the vesicle releasing lysozyme 5) The lysozyme hydrolyses the pathogen |
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What happens to the pathogen after its hydrolysed in phagocytosis?
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1) Waste materials are ejected from the cell
2) An antigen presenting cell is produced |
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How is an antigen presenting cell useful?
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T-cells can not respond to antigens directly. An APC will process and present the antigen to the T-cells
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What is specific immunity?
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A specific response to a specific antigen on the surface of a cell or pathogen that has been recognised as a non-self
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Give the definition of an antigen.
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An antigen is a molecule, usually a protein that stimulates an immune response resulting in the production of specific antibodies
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Why do our own body cells have antigens?
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To identify each cell and to ensure they are not destroyed in an immune response
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Give the definition of an antibody.
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A protein/glycoprotein made in response to foreign antigens
- has binding sites which bind specifically to antigen. They are produced by B cells |
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Describe the structure of an antibody.
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- complex quaternary structutre
- four polypeptide chains - Y shaped- main part is the heavy chain - the light chain can be changes and is the binding site |
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Why can antibodies only bind to specific antigens?
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The binding is specific to certain antigens, form an antigen-antibody complex
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How do antibodies destroy pathogens?
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They cause agglutination and allow phagocytes to digest many pathogens at the same time
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What happens during a humoral response, with antibodies?
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The B cells that clone into plasma cells to produce antibodies specifically bind to the invading pathogens antigens
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What happens during cellular response?
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1) Phagocyte engulfs the pathogen, hydrolyses it, presents the antigens on its surface
2) T cell with specific antigen receptor binds to presented antigen 3) Once binded, the T cell is activated and divides by mitosis creaing clones to help fight the infection |
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What happens during clonal selection?
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1) A specific T cell binds to presented antigen
2) T cell is activated and clones to produce many T cells with complimentary receptors |
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List the two roles of a T cell.
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1) T Cytotoxic cells
2) T helper cells |
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What does a T cytotoxic cell do?
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Locates and destroys pathogens. They release perforin which puts holes in the cell membrane. Or release nitric oxide which is toxic to pathogens
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What is the role of T helper cells?
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1) Release chemicals that attract phagocytes and B cells
2) Activate B cells 3) Stimulate T cytotoxic cells |
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How are B cells activated?
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1) A T cell binds to the complimentary antigen presented and activate a B cells
2) T helper cells release chemicals that signal the B cell clone |
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What do B cells produce?
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1) Plasma cells
2) Memory cells |
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What are plasma cells?
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Produce specific antibodies
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What are memory cells?
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Remain in the body to respond to the pathogen quicker if are-infection occurs
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How do antibodies destroy bacteria?
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1) Antibodies bind to the bacteria surface
2) Damage the bacterial cell membrane 3) Bacterial cell lyses leading to its destruction |
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How do memory cells help to destroy pathogens?
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1) Memory cells encounter specific antigen
2) Memory cells are activated and divide rapidly3) Memory cells clone into plasma cells and more memory cells 4) Plasma cells produce specific antibodies without the time consuming primary response |
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What is the secondary response?
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When memory cells are activated to produce antibodies
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Why is a secondary response usually effective?
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Most pathogens have the same antigens on their surface and are recognised by the memory cells
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What is antigenic variability?
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A change in the antigen which makes it more difficult to develop vaccines
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How does antigenic variability occur?
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Some pathogens have antigens that mutate and change shape meaning memory cells can not detect them and a secondary response is not initiated.
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What is a mono-clonal antibody?
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An antibody that is only specific to one antigen
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What is a vaccine?
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An injection of antigens from a dead or attenuated pathogen that stimulate an the production of antibodies.
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What is the effect of a vaccine?
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You are immune to the pathogen without getting any symptoms
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What is herd immunity?
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Vaccines protect those that have had them and reduce the occurrence of the disease, protecting those who are not vaccinated
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What are the disadvantages of taking a vaccine orally?
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1) The vaccine could be broken down by enzymes in the gut
2) The molecules of the vaccine may be too large to be absorbed into the gut |
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Why are booster vaccines given?
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To ensure there are memory cells
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What is passive immunity?
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Antibodies are not produced by the individual, eg. given by the mother or an antiserum
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Why is passive immunity short term?
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- no contact with the pathogen
- no memory cells are produced - however it takes effect immediately - antibodies are broken down |
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What is active immunity?
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Immunity provided by the memory cells that are produced after a primary immune response
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Why is active immunity long term?
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- exposed to the pathogen
- takes time to work - memory cells are produced |
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What are the ethical issues associated with vaccines?
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1) testing involves the use of animals
2) human testing 3) who can afford it? 4) side-effects |
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What are the benefits of monoclonal antibodies?
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Monoclonal antibodies can to made to bind to a specific antigen or molecule
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Describe how monoclonal antibodies are used to treat cancer.
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1) Monoclonal antibody is made to bind to tumour markers
2) Anti-cancer drugs are attached to the antibody3) The antibody binds only to the tumour markers 4) The drug will only accumulate where there are cancer cells |
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Describe how monoclonal antibodies are used for pregnancy tests.
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1) The antibodies for hCG are bound to a coloured bead
2) Urine is applied and the hCG will bind to the antibody 3) The urine moves up the stick to the test strip where there are immobolised antibodies to hCG which attach to the beads 4) The coloured beads will become concentrated at the test strip turning it blue |
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Describe how monoclonal antibodies are used to test for HIV.
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1) HIV antigens are bound to the bottom of a well plate
2) The patients blood plasma is added. If there are any HIV antibodies these will bind to the antigen 3) The well is washed out and another antibody with an enzyme attached is added. This will attach to the primary antibody 4) The well is washed again and a solution with a substrate is added to the well whch reacts with the enzyme causing it to change colour |
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In a test for HIV why is the well plate washed?
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To remove any unbound antibodies
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What is HIV?
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A virus that infects and kills the T-helper cells, preventing an immune response
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When does HIV develop into AIDs?
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When the levels of helper T-cells drop critically low
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Where does transcription take place?
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In the nucleus
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Why does transcription take place?
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DNA is too big to pass out through the nuclear pores
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What is made during transcription?
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mRNA
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Which enzyme is used in transcription?
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DNA helicase
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Why is mRNA spliced?
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To remove the introns
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Describe the process of transcription.
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1) DNA strand is separated by helicase
2) RNA polymerase attaches complimentary nucleotides to the DNA template 3) This forms a strand of pre-mRNA 4) Splicing occurs to remove the introns, the exons are joined together 5) When polymerase reaches a stop codon it releases mRNA 6) mRNA contains only exons and is small enough to pass out of the nucleus |
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Which base is replaced in transcription and with what?
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T with U (urasil)
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Which bonds are broken in transcription?
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Hydrogen bonds between the DNA strands
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When does translation occur?
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At the ribosomes in the cytoplasm
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What happens during translation?
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Amino acids are joined together to form a polypeptide chain following the sequence of codons on the mRNA strand
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Describe the process of translation.
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1) mRNA attaches itself to a ribosome
2) A tRNA molecule with a complimentary anti-codon attaches to the the first codon on mRNA3) A 2nd tRNA molecule attached itself to the next codon 4) The two amino acids attached to the tRNA are joined by a peptide bond, tRNA moves away 5) Process continues until a stop codon is reached on the mRNA. The polypeptide moves away |
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What is different about transcription in prokaryotes?
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mRNA is produced directly from the DNA without splicing as there are no introns
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What are the differences between mRNA and tRNA?
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1) mRNA is longer as it contains more base pairs2) mRNA is a straight chain whereas tRNA is clover shaped3) tRNA has more hydrogen bonds4) tRNA has an amino acid attachment site
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