B3.1 gas exchange

gas exchange function

1. obtain gases for metabolism

2. release waste products

gas exchange occurs

diffusion - gases travel from high to low concentration to reach diffusion

structure to facilitate gas exchange (4)

1. large SA:V (branches+foldings)

2. permeability of O2 and CO2

3. thin tissue layer minimise diffusion distance

4. moist layer for gases to dissolve 

how is concentration gradient maintained (3) 

1. Dense capillary network around gas exchange surfaces

2. Continuous blood flow

3. Ventilation 

• With air for lungs

• With water for gills

Lungs

trachea

bronchus 

bronchiole 

alveli

lungs 

ribs 

intercostal muscle 

diaphragm 

definition for ventilation + gas exchange + cellular respiration

1. Ventilation : exchange of air between atmosphere and lungs - breathing

2. Gas exchange : exchange of O2 and CO2 between alveoli and bloodstream - passive diffusion 

3. Cellular Respiration : release of ATP from organic molecules 

exchange on ventilation rate

increase rate exercise > increase cellular respiration > increases uptake of oxygen > increase ATP - breath in faster

By product of cellular respiration increases: Co2 > blood gets acidified > proteins like RBC denatures > dont carry oxygen > dies.

To avoid Co2 accumulation - breath out faster > ventilation rate faster 

respiratory system (5)

1. air travels from nose&mouth - pharynx - trachea

2. air divides into two bronchi

3. right : 2 lobes, left : 3 lobes

4. bronchi - many bronchiole ( increases SA)

5. bronchiole - airsacs: alveoli ( gas exchange w bloodstream occurs)

structure of alveolus

1. thin epithelial layer ( one cell thick ) > minimuze diffusion distances

2. surrounded by rich capillaries layer > increase capacity for ge with blood 

3. spherical in shape > maximize SA for ge 

4. internal surface - covered with surfactant > dissolved gas better able to diffuse in bloodstream + reduce surface tention 

where is pneumocytes

(alveolar cells) - line the alveoli , comprise the majority of inner surface of lungs

what is alveoli made out of 

• type 1 + type 2 pneumocytes 

type 2 pneumocytes 

• secrete alveolar fluid → contain surfactant

how surfactant works 

• both alveoli have equal surface tension

• left one - smaller radius - higher pressure - hard to inflate, more likely to collapse 

• with surfactant: less surface tension, able to have same pressure - wont collapse 

adaptations for lungs(4)

1. surfactant - decrease pressure

2. short diameter of bronchiole - slow air flow increases efficiency 

3. many alveoli attached at the end - increase SA for gas exchange 

4. extensive capillaries around alveoli - short diffusion distance 

ventilation in antagonistic muscle 

exhalation 

1. external intercostal muscle - contracts → ribcage move out and up

2. diaphagram - contracts → move down and flattens

3. volume increase , pressure decrease → in thorax

4. air flows into the lungs - reaches atmospheric pressure

inhalation

1. internal intercostal muscle - contracts → ribcage move in and down

2. abdominal - contracts → pushes diaphragm into dome shape

3. volume decrease , pressure increase → in thorax

4. air flows out the lungs - reaches atmospheric pressure

measure lung volume

spirometry

spirometry trace

gas exchange in leaf

• stomata 

• guard cells control opening and closing of stomata 

adaptations of leaf 

waxy cuticle 

palisade layer

spongy mesophyill

xylem&pholem

stoma & guard cells

transpiration

• water lost by stomata 

Water vapour is lost via the stomata

• Diffuses down its concentration gradient into the atmosphere → creating negative pressure in the xylem

• Creates tension that further draws water up the xylem from the roots to the leaves.

Transpiration facilitates:

• Temperature regulation

• Absorption of water and minerals from soil

factors affecting transpiraton

• increase transpiration

  • wind: ^water concentration gradient

  • temperature : ^ saturation point of air 

  • light : ^ photosynthesis 

• decrease transpiration 

  • humidity : decrease water concentration gradient

hemoglobin (location, function , structure)

Location: RBC

Function : transport O2 to respiring tissue, transport byproduct Co2 to lungs

Structure : quaternary , conjucated protein - 4 polypetide with heme group

hemoglobin and oxygen

• coorporative binding

• structure changes - affinity for oxygen ^

why gamma polypetides have a greater affinity to O2 than beta ones

• more efficient delivery of O2 from placenta to fetus 

Co2 binds xx to hemoglobin 

allosterically 

• change the shape - less affinity for O2 

• O2 unloaded to areas with low PO2 but high PCO2 

how does Bohr Shift illustrates when there is ^ in Co2

• ^ in CO2 - ^ in carbonic acid → ^ pH

• bind allosterically → structure changes - lower affinity for O2

• O2 curve shift → release for respiring tissue