Introduction Respiration may be defined in two ways:Cellular respiration (1)it is the process by which cells oxidize

nutrient molecules to obtain energy in the form of ATP

Gas exchange (1)it is the exchange of gases specifically

carbon dioxide and oxygen between an organism and its external environment

Introduction

(1)External Respirationis involved in the exchange of gasses between the external environment and the respiratory organs

Gas exchange in humans is of two stages:

Introduction Gas exchange in humans is of two stages:

(2) Internal Respiration involves the exchange of gasses between body fluids and the tissue cells.

Aims of Gas Exchange A. To collect oxygen from the

environment so as to provide the final electron acceptor in the electron transport chain during cellular respiration. This produces the desired product: energy in the form of ATP

B. To expel carbon dioxide- a by-product of cellular respiration- from the body tissues to the environment

Breathing Humans exchange gasses with the

environment through breathing. The rate at which breathing occurs as well as

its rhythm is mainly controlled by brain centres located at the medulla oblongata and the Pons

The control centre of the medulla monitors pH of the blood and the cerebrospinal fluid and reacts to its slightest changes

Blood pH Normal: 7.35-7.45 Lowering of blood pH indicates an

increase in carbon dioxide concentration Increase in the normal pH value

indicates a decrease in carbon dioxide concentration which entails lack of oxygen in the blood

Methodology 100mL lime water was

poured into a 125mL Erlenmeyer flask

A drinking straw was inserted to the flask

While breathing normally, air was blown into the solution in the flask

Results As air was blown into the flask the

solution of calcium hydroxide became cloudy

Calcium hydroxide solution before blowing air into the flask

Calcium hydroxide solution after blowing air into the flask

Discussion Lime water which was used in the

experiment is made up of concentrated calcium hydroxide in its diluent- water.

The solution is clear and basic As the subject started to blow into the

solution, it was observed that the limewater turned cloudy to white.

The change in color of the solution was due to the increased concentration of CALCIUM CARBONATE

Discussion Calcium Carbonate is a

white solid that precipitated from the reaction of calcium hydroxide with carbon dioxide in the air blown in the flask

Ca(OH)2 +CO2 CaCO3 + H2 O

Discussion As the concentration of carbon dioxide was

increased in the limewater, the solution turned more cloudy due to the increase in the production of the product calcium carbonate.

By this procedure we can measure the amount of CO2 expelled by a subject qualitatively

Faster change in color = more CO2 expelled

Methodology The number of breaths per minute of the subject were taken after doing the following:

a. Normal unforced breathing while sitting down

b. Unforced breathing while sitting down after vigorous exercise

c. Unforced breathing while sitting down after holding breath

d. While hyperventilating

Results Activity Breathing Rate

(seconds)Minimum time for lime to change color

Sitting quietly 20.7 2 min 16 sec

Hyperventilating 33.2 1 min 52 sec

After exercise 34.4 1 min 36 sec

Holding breath 39.0 2 min 26 sec

Results As the activity becomes more strenuous

breathing rate increases As the activity becomes more strenuous

the rate of change of color of the lime water also increases.

Discussion More strenuous

activity requires more energy for an organism

Discussion Energy is present in the body in the form

of ATP ATP is produced via cellular respiration Respiration needs oxygen as the final

electron acceptor in the Electron Transport Chain

Respiration produces carbon dioxide as its by-product

Discussion ATP need = Oxygen need ATP production = Carbon Dioxide

production Increase in CO2 makes blood acidic Medulla increases breathing rate once it

discovers change in blood pH

Methodology A simple spirometer was

set up A large jug was calibrated

by pouring 100mL lots of water and marking every level

After filling up the jar with water the pan was inverted over a bowl already with water

A rubber tubing was inserted into the jug

The remaining air in the jug was sucked off using the rubber tubing

Methodology A. Taking the maximum

amount of air the lungs could hold while keeping his nose closed, the subject blew all the air he can blown into the jug though the rubber tube

Methodology B. The subject took in

normal amount of air and blew into the jug through the tube the normal amount he does during relaxed exhalation

Results Activity Volume of air Volume of oxygen

A. Forced breathing 1500 mL 315mL

B. Normal breathing 400 mL 84 mL

Discussion During forced breathing where the subject

inhaled and exhaled maximally the subject produced 1500mL of air

This value is the lung’s Vital Capacity This is the sum of the volume of air inspired

forcefully after normal inspiration, normal inspiration and volume of air expired forcefully after normal expiration.

This volume is approximately 4600 mL in males and 3400 mL in females normally

Discussion The amount of air released by the subject

on the second part of the exercise was 400mL . This was the lung’s Tidal Volume

Tidal volume is usually 500mL in humans

Discussion It was termed tidal

volume for mammals breathe by a mechanism called “tidal breathing” in which the air inhaled goes to the lungs the same way as it comes out.