Topic 6: Respiration

examples of processes driven by energy from respiration

1. anabolic reactions

2. active transport

3. movement

4. maintenance of body temperature

define aerobic respiration

oxidation of glucose in the presence of oxygen with the release of a large amount of energy

word and chemical equation for aerobic respiration

word eqn:
glucose + oxygen —> large amount of energy + water + carbon dioxide

chemical eqn:
C6H12O6 + 6O2 —> large amount of energy + 6H2O + 6CO2

definition of anaerobic respiration

breakdown of food substances in the absence of oxygen with the release of a relatively small amount of energy

word equation for anaerobic respiration in humans

glucose —> lactic acid + small amount of energy

word equation for anaerobic respiration in yeast

glucose —> ethanol + carbon dioxide + small amount of energy

what happens to breathing rate during strenuous exercise

1. muscles contract vigorously for faster movement, increased energy demand in muscles

2. breathing rate and heart rate increases to increase rate of respiration to release more energy

3. enables:
   - increased rate of oxygenated blood in lungs
   - increased rate of transport of oxygen and glucose to muscles
   - increased rate of removal of carbon dioxide produced

what if the increase in oxygen uptake by aerobic respiration is unable to meet oxygen demand in muscles

1. anaerobic respiration releases the additional energy required for increased muscle contraction

2. causes accumulation of lactic acid in muscles that can lead to fatigue

why does breathing rate and heart rate remain high after exercise

1. some lactic acid is sent to the liver to be oxidised into carbon dioxide and water

2. some lactic acid is converted into glucose and later glycogen for storage in liver and muscles.

3. addtional oxygen used to oxidise lactic acid is called oxygen debt

4. heart and breathing rate return to norm when all lactic acid has been oxidised (oxygen debt is paid)

parts of respiratory system

• trachea

• pharynx

• larynx (voice box)

• diaphragm

• internal intercostal muscles

• external intercostal muscles

• bronchi

• bronchioles

• alveoli

details of larynx (voice box)

• contains vocal chords

details of trachea (windpipe)

• 12 cm long

• supported by C-shaped rings of cartilage, which reinforces front and side of airways, helping to protect it

details of bronchi

• trachea divided into 2 bronchi, one to each lung

epithelium of airways (trachea and bronchi) are lined with what and for what reason

• mucus secreting cells
  traps dust and bacteria

• ciliated cells
  cilia on these cells sweep mucus up to the pharynx to be swallowed

details of bronchioles

• each bronchus divides rapidly into very fine bronchioles

details of alveoli

• clusters of air sacs at the end of bronchioles

• walls of alveoli are respiratory surfaces for gaseous exchange

details of diaphragm

• sheet of muscular tissue attached to the thoracic cavity

• changes volume of thoracic cavity for breathing

process of inhalation

1. diaphragm contracts and flattens

2. external intercostal muscles contract while internal intercostal muscles relax

3. ribs move upward and outward

4. volume of thoracic cavity increases

5. expansion of lungs cause air pressure inside to decrease

6. atmospheric pressure > pressure in lungs

7. air rushes into lungs

process of exhalation

1. diaphragm relaxes and arches upwards

2. external intercostal muscles relax while internal intercostal muscles contract

3. ribs move inwards and downwards

4. volume of thoracic cavity decreases

5. pressure of air in lungs increases

6. atmospheric pressure < air pressure inside lungs

7. air rushes out of lungs and into atmosphere

structural adaptations of alveoli and how they help

• one-cell thick wall: reduces diffusion distance for faster rate of diffusion of gases

• numerous alveoli: increases surface area to volume ratio for efficient gaseous exchange

• well supplied with capillaries: mantains steep concentration gradient for diffusion

• moisture on suface of inner walls: allows oxygen to dissolve in it

transport of oxygen

1. oxygen dissolves in moisture lining alveolar walls

2. oxygen diffuses into capillaries

3. oxygen binds to haemoglobin in red blood cells to form oxyhaemoglobin

REACTION IS REVERSIBLE depending on amount of oxygen in surroundings.

when blood passes through oxygen-poor tissues, reaction will reverse to be released to tissues

carbon dioxide to hydrogen carbonate reversible reaction

CO2 + H2O ⇌ (catalysed by carbonic anhydrase) H2CO3 ⇌ HCO3 + H

details on carbonic anhydrase

• enzyme found in red blood cells

• catalyses reversible reaction between carbon dioxide and water to form carbonic acid

ways carbon dioxide can be transported

1. as hyodrgencarbonate ions in the blood plasma (majority)

2. dissolving directly into blood plasma

3. binding to haemoglobin to form carbaminohemoglobin

how carbon dioxide is transported in body

1. in the tissues, concentration of carbon dioxide and water is high. carbonic anhydrase catalyses formation of carbonic acid H2CO3 from CO2 and H2O

2. carbonic acid dissociates to form hydrogen carbonate ions and hydrogen ions. hydrogen carbonate ions diffuse out of red blood cells and is carried in the plasma

3. in the lungs, hydrogen carbonate ions diffuse back into red blood cells where they are converted into carbonic acid. carbonic anhydrase catalyses conversion of carbonic acid into CO2 and H2O

4. CO2 diffuses out of capillary into the alveoli and is expelled during exhalation

respiratory diseases caused by smoking

1. chronic bronchitis

2. emphysema

3. lung cancer

causes of respiratory diseases

• smoking

• continual exposure and inhalation of polluted air

symptoms of chronic bronchitis

1. paralysed cilia

2. inflammation of the membrane of trachea and bronchi

3. excessive mucus

4. chronic cough

5. difficulty in breathing (narrowed airways)

6. lungs susceptible to infection

7. may result in emphysema and lung failure

signs and symptoms of emphysema

Developed from chronic bronchitis

1. chronic coughing from the chronic bronchitis

2. breakdown of the partition walls of the alveoli

3. alveoli enlarged and surface area is reduced

4. lungs expand and lose elasticity

5. great difficulty in breathing leading to strain on the heart

6. lung tissue is damaged beyond repair

signs and symptoms of lung cancer

1. uncontrolled growth of cells in small area of lungs may spread throughout lungs and block bronchioles

2. cancerous growth may eventually spread throughout body

3. difficulty breathing

4. blood in mucus in lungs