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BIOMOLECULES AND CELLS > Respiration > Flashcards

Respiration Flashcards

1
Q

Why do animals mostly rely on aerobic metabolism for their energy requirements?

A
  • 20x more ATP is produced by aerobic compared to anaerobic

* some carbohydrates require oxygen for metabolism

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2
Q

What is the difference between ventilation and respiration?

A

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

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3
Q

Hypoxia

A

Low O2 (in blood or the environment)

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4
Q

Anoxia

A

Complete absence of O2 in the environment

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5
Q

Hypercampia

A

Excessively high CO2 levels in blood

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6
Q

What is partial pressure?

A

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

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7
Q

Why is air a better respiratory medium than water?

A
  • 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

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8
Q

Respiration in small animals, what type of movement occurs?

A
  • can take up O2 directly from the environment through the body surface
  • simple diffusion distributes O2 around the body, into cells and their cytoplasms
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9
Q

What is the only way respiratory gases are exchanged between the internal body fluids of an animal and the outside medium?

A

Diffusion

• if there is a concentration/partial pressure gradient - there will be a net movement of gases down the gradient

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10
Q

Why is there a greater demand in maintaining an adequate respiratory supply of O2 in larger, complex animals?

A
  • higher cellular metabolic rate
  • reduction in total surface area available for gas exchange
  • large, multicellular organisms are too large for diffusion
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11
Q

What is Fick’s law?

A

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

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12
Q

How do you maximise gas exchange?

A
  • increase SA
  • increase the pressure difference
  • decrease the diffusion distance
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13
Q

What are the 2 main components of a respiratory system?

A
  • Ventilation system
  • transport system
  • exchange site
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14
Q

What is an exchange sire primary characterised by?

A
  • 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

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15
Q

Why is a ventilation system required?

A
  • 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
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16
Q

What is the function of the internal transport (circulatory) system?

A
  • 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
17
Q

What are respiratory pigments and what do they do?

A

• 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

18
Q

What is the main vertebrate respiratory pigment?

A

haemoglobin

19
Q

How does haemoglobin increase the capacity to bind to oxygen?

A

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.

20
Q

What causes sickle cell anaemia?

A
  • 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

21
Q

What is anaemia and what are the symptoms?

A

When the body’s number of red blood cells (or amount hemoglobin) falls below normal
• people can tire very easily and feel weak

22
Q

Positive co-operativity

A

Binding of the first O2 molecule increases binding affinity of subsequent O2

23
Q

Describe the oxygen-binding curve

A

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)

24
Q

What factors affect the affinity of respiratory pigments for O2?

A
  • 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
25
Q

What affect does BPG have on Hb?

A
  • reversibly combines with part deoxygenated Hb and lowers its affinity for O2- thus releases remaining oxygen
  • O2 binding curve shifts right
26
Q

What happens to BPG levels in active tissue?

A
  • 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
27
Q

Effect of partial pressure on affinity to O2

A

A very LOW partial pressure of oxygen is needed before haemoglobin gives it up

  • higher partial pressure means affinity to O2 is high
28
Q

Why is fetal hemoglobin to the left of adult Hb in the oxygen binding curve?

A
  • 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
29
Q

What happens to BPG levels in RBCs during exercise or in high altitudes?

A
  • levels of BPG in RBCs increase

* helps Hb deliver more O2 to tissues where it is most needed

30
Q

What is the respiratory pigment in oxygen?

A

Myoglobin

31
Q

Compare and contrast Myoglobin to Haemoglobin

A

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

32
Q

In what 3 forms are CO2 transported in the blood?

A
  • 10% dissolved in plasma
  • 30% reversibly bound to Hb
  • 60% as bicarbonate
33
Q

What is CO2 converted to during transport? Why does this occur?

A
  • 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-
34
Q

How is the reverse reaction, where H2CO3 is converted to CO2, prevented?

A
  1. chloride shift
    • cl- enters the cell in exchange for HCO3- which exits into the plasma
  2. 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
35
Q

Describe the reactions that occur when co2 enters the blood from body tissue?

A

• 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

36
Q

Describe the reactions that occur when CO2 exits the blood and enters the lungs

A
  • 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
37
Q

When is the higher affinity of myoglobin to oxygen beneficial?

A
  • 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

BIOMOLECULES AND CELLS (32 decks)

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