Chapter 7: Respiration (Revision Pack)

List of Topics1. Aerobic Respiration2. Anaerobic respiration

a. In Human Muscles (lactic acid & E)b. In Yeast (Ethanol, CO2 & E)

3. Respiratory structures & Breathing mechanismsa. Protozoa (Plasma Mbrane)b. Insects (Tracheal System)c. Fish (Gill Filament)d. Amphibians (Skin, Lungs, Mouth)e. Humans (Lungs & Alveoli)

4. Gaseous Exchange & Transport of Gases 5. Regulatory Mechanisms of O2 & CO2 in the body6. Effects of Smoking7. Respiration in plants

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Respiration: Breakdown Glucose → Release Chemical EChemical E in the form of ATP Equation:

1. Aerobic (in presence of oxygen) 2. Anaerobic (in the absence of oxygen)Occurs in Mitochondria Occurs in CytoplasmSlowly, in staged Rapid, to supply E for Muscle ContractionGlucose completely oxidised Glucose not completely oxidisedEquation: Equation:

38 ATP / 2898kJ 2 ATP / 150 kJ

Vigorous exercise Breathing & heartbeat rate ↑ => supply more O2 for rapid muscle contraction Not enough → anaerobic respiration Lactic acid accumulates in muscle cells -> cause muscular ache Incurs oxygen debt (O2 used < O2 supply) Rapid breathing continues (payback) O2 used to oxidise lactic acid → CO2 + water + E When all lactic acid is oxidized, oxygen debt paid

In YEAST Anaerobic = FermentationEquation: Glucose ethanol + CO2 + E (210kJ)

(enzyme Zymase)

3. Respiratory structures & Breathing mechanismsRESPIRATORY SURFACE adapted for MAX gaseous exchange

1) Large total surface – increase Surface area to Vol ratio, ↑ rate of diffusion2) Moist Respiratory Surfaces – facilitate oxy to dissolve3) Thin wall (one cell thick) – allows gases to diffuse across easily (simple diffusion)4) Covered / filled with Blood Capillaries (some) – ↑ rate of gaseous exchange

Organism AdaptationBreathing Mechanism

Inhalation ExhalationProtozoamicrorg:

Cell Mbrane, large total surface area to volume ratio

O2 In: Simple diffusion down concentration gradient

CO2 Out: Simple diffusion down concentration gradient

FishGill arch: 1 pair of gill filamentsOperculum - cover gillsGill rakers – strain food particles

1) Plate like projections: Lamella = increase surface area2) Gill filaments richly supplied by capillaries3) Thin epithelial cells of gill filaments

Mouth open > floor of mouth lowered > volume of pharynx cavity increase > Pressure in cavity decrease > outside higher water pressure close operculum > water enters mouth

Mouth close > Floor of mouth raised > vol of pharynx cavity decrease > pressure in cavity increase > high water pressure inside open operculum > water leaves mouth

Direction of water flow over gill lamella = opposite of blood flow - To max rate gaseous exchange diffusion

InsectsTracheal System1) Trachea → branched into 2) Tracheols

Tracheols – close end- directly connected to fluid round body cells1) Highly branched fine tubes = ↑ surface area2) Moist tracheal walls3) Thin epithelial walls of tracheols

Trachea: connected to pores in abdomen = spiracles- supported by rings of chitin (prevent collapsing)Breathing through rhythmic movement of bodyAbdominal muscles relax > Pressure in trachea decrease> valves of spiracles open > air pulled into body

Abdominal muscle contract> Pressure in trachea increase> air forced out of of body through spiracles

Amphibians(In water)Skin: Thin & moist & supplied w capillariesMouth: Lining of mouth cavity many capillaries

When active, use Lungs: 1) inner walls highly folded ↑ surface area2) Thin walls3) Layer of moisture on walls of lungs4) Network of capillaries on lung walls

2 steps: air into mouth first then lungs & vice-versa- Cause lungs no ribs/diaphragm to expand

Floor of mouth lowers > vol of mouth cavity ↑ > pressure ↓ > air enters mouth through nostrils > Nostrils close> mouth floor raise up > pressure increase > glottis open > Air push into lungs

Nostrils still closed > Floor of mouth lowers > Vol in mouth cavity ↑ > pressure ↓ > glottis opens > air flows from lungs into mouth, lungs shrink > nostrils open, floor of mouth raised > air forced out

Humans Trachea (rings of cartilage) → Bronchus → Bronchioles → Alveolus

Alveolus1) Numerous alveoli: ↑ surface area2) Moist walls3) Thin walls4) Network of capillaries

Ext intercostal muscles contract, Int relax > rib cage move upwards > diaphragm muscles contract > diaphragm flattens > vol of thoracic cavity ↑ > pressure ↓ > air in the atmosphere forced into lungs

Int intercostal muscle contract, Ext relax > rib cage moves inwards and downwards > diaphragm muscles relax > curve inwards > vol of thoracic cavity ↓ > pressure ↑ > air in the lungs forced out

4. Gaseous Exchange & Transport of Gases

At alveolus,Partial pressure of O2 higher in air compared to blood, O2 diffuse from air into bloodPartial pressure of CO2 lower in air compared to blood, CO2 diffuse from blood into air

At body cells,Partial pressure of O2 higher in blood compared to cells, O2 diffuse from blood into cellsPartial pressure of CO2 lower in blood compared to air, CO2 diffuse from cells into blood

Transport of O2

- RBC – contains hemoglobin (4 heme grps, each bind with one O2 molecule)- Hemoglobin + oxygen ⤑ oxyhemoglobin- Unstable complex, will break down and release O2 when lack of O2

Transport of CO2

1) Diffuse into blood plasma2) Combines with hemoglobin to form carbaminohemoglobin 3) As bicarbonate ions in blood plasma

In the RBC, with enzyme carbonic anhydrase,carbon dioxide + water ⇋ carbonic acid ⇋ hydrogen ion + bicarbonate ionEquation:

5. Regulatory Mechanisms of O2 & CO2 in the body

Central chemoreceptors = in breathing control centre = in medulla oblongata = regulates CO2

- High conc of CO2 → form carbonic acid → lower pH value in blood → stimulates central chemoreceptors → breathing control centre send nerve impulse to → intercostal and diaphragm muscles → rate of breathing and ventilation increase → removes more CO2 → CO2 level returns to normal

Peripheral chemoreceptors = in carotid bodies & aortic bodies = more sensitive to O2 conc levelDuring rigorous exercise/ high altitude, low oxygen level → stimulates peripheral chemoreceptors → send nerve impulse to breathing control centres → which send nerve impulse to intercostal & diaphragm muscles AND to heart → rate of ventilation increase → Rate of heart beat increase to carry more O2 & glucose to muscle cells

6. Effects of Smoking

Tar = carcinogenic = cause lung cancerTar deposits = cause persistent cough & shortness of breathCarbon monoxide = reduction of oxygen supply by binding to hemoglobin = shortness of breathOxides of nitrogen = dissolves in moisture of trachea = form acids and wear away mbrane of epithelial cellsRespiratory diseases, bronchitis, narrowing & inflammation of air passage ways, etc…