Lecture 27-Gas Exchange

Lecture 27-Gas Exchange - Lecture 27- Gas Exchange The...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Lecture 27- Gas Exchange The Problem of Size -Volume of an organism increases faster than surface area; the surface area: volume ratio decreases as the organism gets larger in size -So, how does an organism get gases into its system if diffusion is impossible or very slow? Oxygen Availability: Partial Pressure -Partial pressure of oxygen: 160 mm Hg; a force -This gas will move spontaneously from high pressure to low pressure -Partial pressure of oxygen decreases with increased altitude (fewer molecules/unit volume) -Gas exchange always occurs by diffusion; very quickly through cell membranes (0.0000001 sec), but far too slowly through tissue in large animals (52 years for 1 meter). Fick’s Law of Diffusion R= D A ( c/d) where: R- rate of diffusion D- diffusion constant (medium in which gas exists) A- area across which diffusion takes place c- concentration (partial pressure) gradient d- the distance a molecule must travel -And, of course, the idea is to maximize R. Respiratory Surfaces -Must be wet in order to transfer gases 1. Surface of the organism -Across which the gas must diffuse -Maximize surface area: volume ratio; this is done well in single cells, flatworms, plants 2. Tracheal tubes (see below for picture) -Insects use this method of gas exchange -Insects breathe air by a respiratory system consisting of air conducting tubes called
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 3

Lecture 27-Gas Exchange - Lecture 27- Gas Exchange The...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online