Lecture 17: Aerobic Respiration

Question 1

Aerobic respiration equation & general facts

Answer 1

C6H12O6 + 6O2 = 6CO2 +ATP

• Take in O2
• Discharge CO2
• Produce ATP

Question 2

Gases croos surface by ____

Answer 2

DIFFUSION only

Question 3

Diffusion rate is listed by:

Answer 3

• E.g. surface are respiratory surface
• Thickness of respiratory surface
• metabolic demands

Question 4

where is the site of respiration?

Answer 4

• whole body in some cases (frogs, worms)
• respiratory organs
• -Gills
• -Trachae
• -Lungs

Question 5

How do gills work?

Answer 5

• Water flows in through mouth
• and out operculum (gill cover)
• Gill arch contains blood vessels, water passes over lamellae, O2 transferred. Countercurrent exchange

Question 6

Gill arch:

Answer 6

are a series of bony “loops” present in fish, which support the gills

Question 7

how much water do aquatic animals move per ml of O2

Answer 7

about 1|H2O (1000g)

Question 8

how much air do breathing animals transport per ml of O2

Answer 8

25ml

Question 9

insect trachea system:

Answer 9

• Pros of breathing air
• Tracheae act like bellows
• Tracheal system gets larger
when hypoxic and smaller when hyperoxic

Question 10

hypoxic =

Answer 10

deficiency in the amount of oxygen reaching the tissues

Question 11

hyperoxic =

Answer 11

excess amount in oxygen reaching the tissues

Question 12

mammalian lung surface area:

Answer 12

• Surface area: approx. 100 m2 (about half tennis court)

* Reduced in pneumonia, emphysema

Question 13

lungs mammals: FACTS

Answer 13

• Mammals – tidal collapsible system
– lungs are dead end sacs
– Ventilation cannot be constant and unidirectional; tidal
– limits air pO2
– Due to “dead space” in the alveoli and
lung capillaries
– There is always a volume of air left over from preceding breath
– Compensate = enormous SA and short diffusion path length
• but lose a lot of H2O

Question 14

respiration has to work with

Answer 14

circulation

Question 15

Blood transport of respiration gases:

Answer 15

• Respiration has to work with circulation
• RBCs
• Haemoglobin
• Protein
– 4 subunits that surround a
haem (Fe structure) group
– Reversibly bind to O2
– Each subunit can carry 1 O2 molecule
– Affinity = how readily Hb releases O2

Question 16

oxygen uptake + dissociation curves: (S curve)

Answer 16

•Low pO2, only 1 O2 bound to Hb
•Changes shape of Hb
– Makes it easier for other
subunits to bind
– So smaller increase in pO2 necessary
– Once 3rd molecule bound, need much higher pO2

Question 17

Factors affecting Hb O2 binding properties

Answer 17

• CO
• Hb composition
• DPG (2,3 diphosphoglyceric acid)
• pH (CO2)
• Temperature

Question 18

pH + CO2 affect on dissociation curve of oxygen uptake

Answer 18

BOHR EFFECT 
– CO2 reacts with H2O to
form carbonic acid
– Lowers pH, and structure of Hb changes
– Structure now has less affinity for O2 so curve shifts right
– O2 released at relatively lower pO2

Question 19

Temperatures affect on dissociation curve of oxygen uptake

Answer 19

increase in temperatures weakens bonds between Hb + O2

– Therefore less affinity and moves curve to right
– Impt for ectotherms b/c ++ T = ++ MR = ++ need for O2
– Fever
– exercise (also alters pH)

Question 20

description of dissociation curve:

Answer 20

x = PO2 (MM Hg) 
y= O2 saturation of haemoglobin (%) 

S shaped

Question 21

Birds lungs:

Answer 21

• Birds, mammals
• Birds – unidirectional rigid
system
– ↑ pO2 relative to mammals
– Also uses Countercurrent exchange
– Consequences = birds function better at high altitudes

Question 22

Bird lungs steps:

Answer 22

inhalation: inhaled air moves down trachea and into posterior air sacs
- expiration: air moves from posterior air sac to lungs
- Inhalation: Air moves from the lungs to the anterior air sacs
- Expiration: air moves out of the body via the trachea

Question 23

Quick & Ruben 2009 about respiration

Answer 23

The avian lung has the greatest known relative gas exchange surface area and thinnest barrier to oxygen diffusion, and in combination with anatomical specializations is the most efficient lung of all air-breathing vertebrates at oxygen extraction

Question 24

How to keep Abdominal air sac from collapsing during inhalation?

Answer 24

Modern birds have wide hips
• Great pelvic cross sectional area
• Egg passage AND accommodate large air sacs
-Synsacrum and integrated thigh with body wall provide bony and muscular support to suspend air sac and keep it from collapsing during negative pressure of inhalation
-Thigh mass closer to body center (angled up) supports air sac and doesn’t move much during walking

Question 25

Types of exchange in fish, birds + mammals

Answer 25

• Counter current exchange in fish
• Cross current exchange in birds
• Ventilated pool in mammals.