Respiration Flashcards
Why do animals mostly rely on aerobic metabolism for their energy requirements?
- 20x more ATP is produced by aerobic compared to anaerobic
* some carbohydrates require oxygen for metabolism
What is the difference between ventilation and respiration?
Ventilation
• movement of the medium (air, water) over a gas exchange surface
• action of breathing is purely ventilation
Respiration
• oxidation of the end-products of glycolysis (by o2 in eukaryotes)
• breathing (non-technical usage) or physiological respiration
Hypoxia
Low O2 (in blood or the environment)
Anoxia
Complete absence of O2 in the environment
Hypercampia
Excessively high CO2 levels in blood
What is partial pressure?
Component of total pressure contributed by a single (free) gas within a mixture of gases
• rate of diffusion b/w air and body fluids depend on the difference between its partial pressures
Why is air a better respiratory medium than water?
- oxygen diffuses 8000x more rapidly in air than in water
* Water is denser and more viscous than air - more energy is required to move water over a gas exchange site than air
Respiration in small animals, what type of movement occurs?
- can take up O2 directly from the environment through the body surface
- simple diffusion distributes O2 around the body, into cells and their cytoplasms
What is the only way respiratory gases are exchanged between the internal body fluids of an animal and the outside medium?
Diffusion
• if there is a concentration/partial pressure gradient - there will be a net movement of gases down the gradient
Why is there a greater demand in maintaining an adequate respiratory supply of O2 in larger, complex animals?
- higher cellular metabolic rate
- reduction in total surface area available for gas exchange
- large, multicellular organisms are too large for diffusion
What is Fick’s law?
Rate of gas exchange =
(SA x Concentration gradient x diffusion coefficient)/diffusion distance
• diff. distance by itself in denominator - shows it is the most important factor
How do you maximise gas exchange?
- increase SA
- increase the pressure difference
- decrease the diffusion distance
What are the 2 main components of a respiratory system?
- Ventilation system
- transport system
- exchange site
What is an exchange sire primary characterised by?
- a large surface area
- small diffusion distance between respiratory medium and the blood or bw the blood and tissues
- a highly vascularised respiratory surface
Gases DIFFUSE across the exchange site
Why is a ventilation system required?
- To keep a constant supply of medium moving across the respiratory exchange site
- improves rate of gas exchange
- ensures that fresh supplies of O2-rich medium are supplied to the exchange surface
What is the function of the internal transport (circulatory) system?
- moves the dissolved O2 from the exchange site to the respiring tissues
- also transports co2 away from the metabolising tissue
- essential because diffusion is exceedingly slow even over moderate distances
What are respiratory pigments and what do they do?
• they increase the oxygen-carrying capacities of blood
They are:
• complexes of proteins and metal ions
• have a characteristic colour that changes when its binds O2
What is the main vertebrate respiratory pigment?
haemoglobin
How does haemoglobin increase the capacity to bind to oxygen?
Haemoglobin is a 4 globin protein subunits, each containing a heme group
• each heme group contains an Fe2+
• each heme group can combine with 1 o2 molecule
Therefore Haemoglobin can bind to 4 oxygen molecules.
What causes sickle cell anaemia?
- when an abnormal form of hemoglobin (HbS) is produced
* HbS clump together making red blood cells sticky and causing them to form into a curved sickle shape
What is anaemia and what are the symptoms?
When the body’s number of red blood cells (or amount hemoglobin) falls below normal
• people can tire very easily and feel weak
Positive co-operativity
Binding of the first O2 molecule increases binding affinity of subsequent O2
Describe the oxygen-binding curve
Venous blood - low pO2 in the blood (only a small amount of O2 is bound to Hb)
Lungs - high pO2 (a large amount of O2 is bound to Hb)
What factors affect the affinity of respiratory pigments for O2?
- type of respiratory pigment (e.g. myoglobin, haemoglobin)
- pH - blood circulating through active tissues has a lower pH and H+ ions bind to the haemoglobin molecule in place of O2 (lowers affinity for O2)
- BPG - lowers the affinity for O2
What affect does BPG have on Hb?
- reversibly combines with part deoxygenated Hb and lowers its affinity for O2- thus releases remaining oxygen
- O2 binding curve shifts right
What happens to BPG levels in active tissue?
- pH levels fall and BPG is produced
- the working tissue needs more oxygen, therefore release of BPG allows oxygen to be bumped off the haemoglobin and into the tissue
Effect of partial pressure on affinity to O2
A very LOW partial pressure of oxygen is needed before haemoglobin gives it up
- higher partial pressure means affinity to O2 is high
Why is fetal hemoglobin to the left of adult Hb in the oxygen binding curve?
- left is lower partial pressure of O2
- this means that fetal Hb has the higher affinity to oxygen even at low pO2 because it wants to hold onto the oxygen for longer - does not want it to go back to the mother
What happens to BPG levels in RBCs during exercise or in high altitudes?
- levels of BPG in RBCs increase
* helps Hb deliver more O2 to tissues where it is most needed
What is the respiratory pigment in oxygen?
Myoglobin
Compare and contrast Myoglobin to Haemoglobin
MYOGLOBIN :
• monomeric (Hb is tetrameric - has 4 subunits)
• higher affinity than Hb for O2
• binds O2 at PO2 values much lower than Hb
• provides an O2 reserve in muscles
In what 3 forms are CO2 transported in the blood?
- 10% dissolved in plasma
- 30% reversibly bound to Hb
- 60% as bicarbonate
What is CO2 converted to during transport? Why does this occur?
- converting CO2 to H2CO3 decreases the partial pressure of pCO2 - causes more CO2 to diffuse out of tissues
- if carbonic acid concentration increases, reaction will reverse - to prevent this chloride shift occurs
- when CO2 enters, CA converts it to H2CO3 which dissociates to H+ and HCO3-
- HCO3- enters blood plasma in exchange for Cl-
How is the reverse reaction, where H2CO3 is converted to CO2, prevented?
- chloride shift
• cl- enters the cell in exchange for HCO3- which exits into the plasma - H+ ions are left behind in the RBCs and and join the Hb causing O2 to leave Hb and enter the tissue. Since H+ is in Hb, pH is not lowered
Describe the reactions that occur when co2 enters the blood from body tissue?
• co2 enters the RBCs and Cl- ions come with it
• CO2 is converted into H2CO3
• H2CO3 –> H+ and HCO3-
• HCO3- exits the cell as cl- ions enter
This prevents the buildup of H2C03 and hence the production of CO2
Describe the reactions that occur when CO2 exits the blood and enters the lungs
- chloride is shifted out fo the cell and the . bicarbonate (HCO3-) enters the cell
- reverse reaction occurs where co2 is remade
- this causes co2 to enter the alveoli and be breathed out
When is the higher affinity of myoglobin to oxygen beneficial?
- acts as an O2 reserve in muscles
- it binds to O2 at very low partial pressures
- there is a slow release of oxygen when it is needed during activities like running
- Myoglobin has fast uptake and slow release
