Respiration in Humans (part 3): Effects of tobacco smoke on Human Health

1. Effects of tobacco smoke on Human Health

2. Smoking kills A lighted cigarette produces smoke Smoke contains many chemicals (4000) Cause cancer and harm to health • • • Harmful substances are grouped into: 1. tar 2. nicotine 3. carbon monoxide 4. irritants

3. Tar Brown sticky substance (accumulates in lungs) ▪ 1. Contains carcinogenic (cancer-causing) chemicals which cause lung cancer (abnormal cell division of the epithelium) → resulting in lumps of tissue which may block off air sacs reducing efficiency for gaseous exchange 2. Paralyses cilia lining air passages → prevents dust removal from lungs and trachea

4. Nicotine ▪ Addictive drug present in tobacco ▪ Causes adrenaline release → heartbeat rate + blood pressure increases ▪ Makes blood clot easily → increased risk of blood clots in blood vessels

5. Carbon monoxide ▪ Combines with haemoglobin to form carboxyhaemoglobin – reduces O2transport efficiency of RBCs → Death if concentrations in the air are increased by 1% ▪ Increases rate of fatty substance deposition → narrowing arterial lumen (increases risk of atherosclerosis) ▪ Damages the lining of blood vessel → increased risk of blood clotting in the arteries

6. Irritants ▪ e.g. hydrogen cyanide, acrolein and formaldehyde ▪ Paralyse cilia in air passages → increased risk of 1chronic bronchitis and 2emphysema

7. Chronic bronchitis Breathing irritant particles may cause chronic bronchitis Signs of chronic bronchitis - The epithelium lining the airways e.g. bronchi becomes inflamed - Excessive mucus is secreted by the epithelium - The cilia on the epithelium are paralysed. Mucus and dust cannot be removed - The airways become blocked, making breathing difficult - The person has to cough persistently to clear his airways to breathe. This increases the risk of getting lung infections

8. Emphysema - A result of persistent and violent coughing Signs of emphysema ➢Violent coughing breaks down the partition walls between the alveoli ➢The surface area of the lung for gaseous exchange decreases ➢The lungs become inflated with air ➢The lungs lose their elasticity ➢Breathing becomes difficult. The person wheezes and suffers severe breathlessness

9. Cancer Definition: Cancer is an uncontrolled division of cells producing outgrowths or lumps of tissue ➢ Smoking causes tar & irritant particles to stick inside the lungs & damage the cells ➢ damaged cells grow abnormally & multiply ➢ lung cancer ➢ lumps of cancerous cells block air tubes in the lungs ➢ the person cannot breathe & so dies

11. Gaseous Exchange in Green Plants • Occurs mainly through stomata of leaves and young stems • O2from atmosphere diffuses into the intercellular air spaces of the leaves and stems • O2dissolves in the moisture lining the cell walls and diffuses into the cells • O2diffuses from cell to cell to reach those cells that are not directly exposed to the air

12. Gaseous Exchange in Green Plants • CO2produced from tissue respiration diffuses out of the cells and into the intercellular air spaces, then into the atmosphere via the stomata • The cuticle layer hinders the movement of gases. However some gaseous exchange does occur across the cuticle and is extremely important at night when the stomata are closed

13. Gaseous Exchange in Green Plants • In old woody stems, a layer of waterproof cork tissue develops beneath the epidermis. • Openings called lenticels are formed in the cork layer for gaseous exchange

14. Gaseous Exchange in Green Plants • Roots require O2for tissue respiration • O2dissolved in the soil solution diffuses into the root hairs and inner cells of the root • CO2diffuses out of the roots through the surfaces of the root hairs

15. Things to note: • O2intake and CO2release by green plants can only be detected at night or when plants are placed in darkness • When plants are placed in sunlight, photosynthesis and respiration occur at the same time • During the day, rate of photosynthesis is much greater than the rate of respiration • More O2is released than the cells can use for respiration • As a result, excess O2diffuses out of the leaves through the stomata • Since the amt. of CO2produced during tissue respiration is not sufficient for photosynthesis, plants take in CO2from the atmosphere

16. Differences between Respiration and Photosynthesis Respiration Photosynthesis Energy is released Energy is stored in carbohydrate molecules CO2and H2O are used whereas O2is given off An anabolic process, resulting in the building up of carbohydrate molecules Occurs only in cells containing chlorophyll and in the presence of sunlight Results in the gain of dry mass O2is used, and CO2and H2O are given off A catabolic process, resulting in the breakdown of carbohydrate molecules Occurs at all times in all cells, independent of chlorophyll and sunlight Results in loss of dry mass