Lecture 20/gas exchange I

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Bio 220 Lecture 20: Gas exchange I

Campbell, 5th, 826-832

I. Gas exchange
A. Function
For each cell, O₂is required for metabolism(ATP production).
- A running human can require 150 liters of O₂/hour. CO₂removal is required to maintainpH.

2000

B. Respiratory medium
The respiratory mediumis the direct source of O₂. For cells, it is the interstitial fluid. For efficient transfer by diffusion, the path has to be <1 mm.

C. Strategies
1. Ensure that all cells are <1 mm from the environment
a. Marine organisms 42.18
- flat and/or have internal cavities.
b. Insects with branching tracheae42.21

2. Specialized respiratory surfaces
- epithelial cells that are in contact with the respiratory medium

a. with air (lungs or skin)
- the major advantages are:
i. O₂content higher than water

- 200 ml/l vs 10 ml/l

ii. O₂diffuses faster in air
-O₂diffusion is 300,000 times greater in air

iii. less work is required to move air across
respiratory surface


Bio 220 Lecture 20: Gas exchange I Campbell, 5th, 826-832 I. Gas exchange A. Function For each cell, O₂is required for metabolism(ATP production). - A running human can require 150 liters of O₂/hour. CO₂removal is required to maintainpH.		2000
B. Respiratory medium The respiratory mediumis the direct source of O₂. For cells, it is the interstitial fluid. For efficient transfer by diffusion, the path has to be <1 mm. C. Strategies 1. Ensure that all cells are <1 mm from the environment a. Marine organisms 42.18 - flat and/or have internal cavities. b. Insects with branching tracheae42.21 2. Specialized respiratory surfaces - epithelial cells that are in contact with the respiratory medium
	a. with air (lungs or skin) - the major advantages are: i. O₂content higher than water - 200 ml/l vs 10 ml/l ii. O₂diffuses faster in air -O₂diffusion is 300,000 times greater in air iii. less work is required to move air across respiratory surface