Exchange 2 Flashcards
Gas exchange at stomata?
- O2 out - high conc. in spongy mesophyll so diffuses out
- CO2 in
- CO2 constantly being used by cells in leaf (mostly palisade mesophyll) - maintains conc. gradient - lower in spongy mesophyll compared to atm
- to reduce water loss by evaporation - stomata close at night when no photosynthesis
Respiration & Photosynthesis equations?
R: C6 H12 O6 + 6O2 -> 6CO2 + 6H2O + ATP (night)
P: 6CO2 + 6H2O + Energy -> C6 H12 O6 + 6O2 (day)
Adaptations of leaves of dicotyledonous plants for gas exchange?
- thin and flat - large SA:V ratio.
- Stomata - many small pores that gases diffuse in and out of - every cell is a short diffusion pathway away from a stomata
- short diffusion distances - sources of air & cells r close as - many interconnecting air spaces between the stomata and mesophyll cells
- air spaces - diffusion more rapid than through water (& increases SA & allows diffusion pathways)
Stomata mainly on underside of leaves why?
underside often in shade so - cooler so - less water loss
Guard cells & stoma?
- every stoma surrounded by guard cells pair
- guard cells control the opening and closing of the stomata - important to control water loss
- guard cells turgid - stoma open
- guard cells flaccid - stoma closed
Similarities between gas exchange in plants & insects?
- Obtain gases they need from the air by diffusion down concentration gradients
- Movement of gases is controlled by pore like structures (spiracles/stomata)
Differences between gas exchange in plants & insects?
- Insects deliver air to cells via a system of tubes that are not present in the leaf
- Insect muscle contraction can assist with movement of the air (especially larger insects).
Xerophytes & adaptations?
plants that r adapted to survive in areas w limited water
- curled leaves - to trap moisture to increase local humidity (reduces water potential gradient from inside to outside of plants - applies to all)
- hairs - to trap moisture to increase local humidity
- sunken stomata - to trap moisture to increase local humidity
- thicker waxy cuticle - to reduce evaporation
- longer root network - to reach more water
- spines instead of leaves - reduces SA - reduce evaporation of water
Gas exchange in fish?
- fish r waterproof (due to scales) & hv small SA:V - gills
- obtain O2 from water but 30 times less O2 in water than air so - special adaptation to maintain conc. gradient so diffusion occurs
Rate of diffusion equation?
Fick’s Law:
Diffusion proportional to:
SA * diff in conc/length of diffusion path
Fish gill anatomy?
- 4 layers of gills on both sides of head
- gill arches - support gills & associated blood vessels
- gills made up of stacks of gill filaments
- each filament covered in gill lamellae - positioned at right angles to filament - site of exchange
- lamellae creates large SA
Ventilation of fish - bony?
- is: drawing water over exchange surface
- water kept moving over gills by ventilation system
- movements of mouth floor & operculum r coordinated to - produce stream of water: thru mouth, forced over gills & out thru opening on each side of head/operculum
Ventilation - buccal cavity in bony fish?
Taking water in:
- Operculum closed
- Fish opens its mouth & lowers the buccal floor (floor of it’s mouth)
- increases volume -> decreases pressure
- Movement of water from higher pressure to lower pressure (down the gradient) into the mouth
- Fish closes its mouth and raises the floor of mouth
- decreases the volume and increases the pressure
- Opens operculum
- Water moves down pressure gradient over gills and out of the gill slits (operculum)
Adaptations of fish for efficient gas exchange?
*exchange only happens on lamellae
- large SA:V - created by many gill filaments covered in many gill lamellae
- short diffusion distance - due to: capillary network in every lamellae (network so close to outside where O2 diffusing in from - short diffusion dis) & lamellae r very thin
- maintaining conc. gradient - counter current flow mechanism
Counter current exchange principle?
- when water flows over gills in opp direction to flow of blood in capillaries
- ensures equilibrium is never reached so - will never get same conc. O2 in blood as in water
- ensures diffusion gradient for O2 is maintained across length of gill lamellae
Counter-current flow example?
- Blood w high conc. O2 meets water w max conc. O2 – still conc. gradient so - diffusion takes place
- Blood with 0% conc. O2 meets water which has had most (but not all) oxygen removed – still a concentration gradient and diffusion takes place
Concurrent/parallel flow?
(blood and water flowing in the same direction)
- diffusion gradient would only be maintained across part of the length of the gill lamellae & only 50% of the oxygen available would be absorbed by the blood
- aka equilibrium reached halfway across the gill so no net diffusion of oxygen into the blood
Maintaining steep diffusion gradients for O2 - fish?
- constantly bringing it to exchange surface (lamellae) via ventilation
- carrying it away from exchange surface via mass transport in blood
2 types of fish?
Cartilaginous fish:
- sharks & rays
- no ventilation mechanism - hv to keep swimming for oxygenated water to flow over gills
- parallel flow in gills
Bony fish:
- most others
- use a ventilation mechanism
- counter current flow in gills
