Rev Sci Summary Respiration

Maris Stella High School GCE O Level Science Biology Revision Summary

Name: ___________________ Class (Index No.): ____ ( ) Date: _____________

Respiration Revision Summary Aerobic and Anaerobic Respiration Similarities: - Both involve breakdown of food to release energy (in ATP) to allow cells to do work - Both are chemical reactions, involving enzymes, occurring within cells Differences Aerobic Respiration Breakdown of food in the presence of oxygen Releases large amount of energy Products: Carbon dioxide and water Occurs generally in all living cells in presence of oxygen

Anaerobic Respiration Breakdown of food in the absence of oxygen Releases small amount of energy Products: Animal cells (eg. Muscle) – Lactic acid Yeast – Ethanol and carbon dioxide (Alcoholic fermentation) Occurs in skeletal muscle cells when additional energy is needed in the presence of insufficient oxygen

Mechanism

Location

Definition

Respiration, Breathing, Gaseous Exchange Aerobic Respiration Breakdown of food substances in the presence of oxygen with the release of large amounts of energy. Carbon dioxide and water are released as waste products. In all living cells, occurs in mitochondria (for eukaryotes)

Breathing Movement of air in and out of the lungs (inhalation and exhalation).

Gaseous Exchange Exchange of gases between air in the alveoli and blood in the capillaries surround the alveoli.

Along respiratory tract (from nostrils to lungs)

Between alveoli in lungs and surrounding blood capillaries.

Chemical reaction depends on: 1. Availabillity of glucose 2. Availability of oxygen 3. Temperature (affects enzymes)

*Physical mechanism due to actions of: 1. Intercostal muscles attached to ribs 2. Ribcage 3. Diaphragm

Physical exchange facilitated by: 1. Film of water on inner walls of alveoli 2. Very thin alveolar walls 3. Constant flow of blood in capillaries, constant flow of air in and out of lungs 4. Network of capillaries surrounding, small, numerous alveoli

*Not required in Science Bio syllabus

The Respiratory System in Man

Feature Hairs in nostrils Mucus produced by gland cells lining nasal passages, trachea and upper half of bronchi Cilia lining nasal passages, trachea, and upper hallf of the bronchi C-shaped rings of cartilage around trachea and bronchi Elastic nature of lungs Pleural membranes with pleural fluid Millions of alveoli in the lungs

Function Filters incoming air by trapping dust Mucus traps dust and bacteria, prevents entry of these particles into alveoli Sweep mucus with trapped dust up airways into pharynx Support airways to ensure it is always kept open, prevents lumen from collapsing when pressure in thoracic cavity falls Allows lungs to expand and contract easily during breathing Reduce friction when they rub against the ribcage Provide a large surface area for maximum gaseous exchange

Alveolar Structure and Function

Structure/ Feature Numerous and small alveoli Richly supplied with blood capillaries One cell thick epithelium (thin walls) Film of water on inner walls of alveoli Constant flow of blood through capillaries Breathing movements exchange air in alveoli constantly

Function/ Rationale Increase surface area to volume ratio for gaseous exchange Increase surface area for gaseous exchange Decrease diffusion distance for rapid gaseous exchange Oxygen dissolves into film of water before diffusing through alveolar walls Diffusion gradient of gases maintained Diffusion gradient of gases maintained

Experiments in Respiration

Apparatus/Chemicals used Caustic potash (KOH) Limewater Hydrogen carbonate indicator Oil Spirometer

Function Absorb carbon dioxide Test for presence of carbon dioxide Test for presence of carbon dioxide Used to cover the surface of liquids to prevent oxygen from dissolving into the liquid Used to measure volume of air inhaled or exhaled by a person