3A Exchange and Transport Systems (#2) Flashcards
Why do organisms need to exchange materials with their environment?
to take up nutrients and O2
to release waste products of metabolism(urea and CO2)
to maintain a constant body temp (crucial for survival)
Exchange rates in single and multi cellular organisms
single-celled - easier and faster due to short diffusion distance
multi-cellular- harder and slower due to larger diffusion distance
SA:V and exchange
larger and organism= smaller SA:V= slower rate of diffusion
smaller organism= larger SA:V= faster rate of diffusion
Ways to increase SA:V
- folding surface of cell membrane (increase SA)
- developing long, thin, elongated shaped cells
- large vacuoles, push organelles to the sides of the cell for easier diffusion
Unicellular Organisms
- large SA:V
- easier exchange of materials
Developments in Multicellular organisms for exchange
(provides more efficient way to exchange materials)
- exchange organs -> organs in charge of exchanging substances from outside body to inside
- mass transport system -> transports materials from exchange organs to cells in the body
Heat exchange and size
larger organism -> smaller SA:V -> harder to lose heat
smaller organism -> larger SA:V -> easier and quicker heat loss -> need a higher metabolic rate to generate heat and stay warm
Heat exchange and shape
compact shape -> smaller SA:V
less compact shape -> larger SA:V -> need a higher metabolic rate to produce heat and maintain body temp
Behavioural and Physiological adaptations to facilitate exchange
small desert mammals- high SA:V- lose water easier-> adapted to have smaller kidneys to produce less urine
Elephants- hard to cool in summer-> large ears, stay in water a lot
small mammals in cold regions-> store nuts as energy store for high metabolic rate
Gas exchange surface
boundary between outside environment and inside environment of an organism.
have a large SA
thin for a short diffusion pathway
steep concentration gradient across exchange surface
Gas exchange in single-celled organisms
(absorb and release materials through cell-surface membrane)
large SA, thin surface meaning a short diffusion distance so oxygen can partake in biochemical reactions as soon as it diffuses in, no need for specialised exchange system
Gas exchange in Fish- Gill
gill filaments -> thin plates that increase SA (increasing rate of gas exchange and diffusion) covered in lamellea, increase SA further
gill lamellae-> increase SA more, have blood capillaries and thin surface cells to increase diffusion between water and blood
Gas exchange in Fish- Counter-Current System
blood flows through lamellae in one direction and water flows over it in the opposite direction.
- water with a higher O2 concentration always flows by blood with a lower O2 concentration
- maintains a steep concentration gradient across whole length of gill
- oxygen always flows from water to the blood
Gas exchange in dicotyledonous plants
Mesophyll adapted for their function as they have a large SA
- found inside the leaf, gases move through stomata on lower epidermis of leaf and into mesophyll
- stomata opens to allow gas exchange and closes to prevent too much water loss, guard cells open and close stomata
Gas exchange in insects
air enters the trachea via pores on the surface of insect called spiracles, O2 travels down it’s own concentration gradient towards the cells, trachea branch off into tiny tracheoles that have permeable cells and go into individual cells. Oxygen diffuses directly into respiring cells. CO2 diffuses out and travels down it’s own concentration gradient towards the spiracles and out.
-regular abdominal movements keep the flow of air in and out
How insects control water loss
when losing too much water the spiracles are closed by muscles
waterproof waxy cuticle an hairs around the spiracles to reduce evaporation
how plants control water loss
stomata are normally open in the day-> water enters guard cells and they become turgid
when plant is dehydrated, water leaves guard cell and it becomes flaccid, closing the stomata
Xerophytic adaptations for water loss
- stomata in sunken pits-> traps water vapour, reducing conc gradient between the leaf and the air, reduces evaporation form leaf
- hairs around epidermis -> traps water vapour to reduce conc gradient
- curled leaves with stomata inside to protect from wind
- less stomata so less places for water loss
- thicker waxy waterproof cuticle to reduce evaporation
Structure of the Human Gas Exchange System
- air travels down trachea (down pressure gradient)
- trachea splits into two bronchi (bronchus) which go into the lungs
- bronchus branches off into smaller bronchioles which end at air filled sacs called alveoli (where gas exchange takes place)
The Intercostal Muscles
Layers of muscle between the ribs, 3 layers - (only need 2) - External Intercostal muscles and Internal intercostal muscles
Ventilation- Inspiration
External IM and diaphragm contract. The ribcage moves outwards and upwards and diaphragm flattens
- increases thoracic cavity, decreasing the pressure in the lungs to below atmospheric pressure
- air flows down the pressure gradient down the trachea and into the lungs - active process
Ventilation- Expiration
External IM and diaphragm flatten, the ribcage to moves downwards and inwards and diaphragm curves upwards.
-decreases the thoracic cavity and increases the pressure in the lungs to above atmospheric pressure, forcing air out of the lungs (as it moves down the pressure gradient) - passive process
Ventilation- Forced Expiration
Internal IM contract and External IM relax, pulling the ribcage further downwards and inwards, reducing the thoracic cavity further - during this time, the opposing movement of the two IMs are Antagonistic (active process - requires energy)
Alveoli Structure
- walls of each alveoli is made up of one layer of thin flat epithelial cells called - alveolar epithelium
- the capillaries that cover it have walls made up from capillary endothelium
- alveoli walls have protein elastin in them, helps them to recoil to normal shape after inhaling and exhaling air
Movement of O2 and CO2 through GES
air with oxygen moves down trachea, into bronchus of each lung, into bronchioles and to alveoli (down a pressure gradient)
Oxygen diffuses across alveolar epithelium and capillary endothelium into the haemoglobin in the blood (happens down diffusion gradient)
-CO2 travels down it’s own diffusion and pressure gradient in opposite direction to be breathed out
Factors affecting rate of diffusion - alveoli
thin exchange surface- alveolar epithelium is only one cell thick meaning short diff pathway (faster diff)
large SA- lots of alveoli, large surface area for gas exchange
-steep conc gradient of O2 and CO2 maintained by constant flow of blood and ventilation
Tidal volume
vol of air in each breath (0.4-0.5 dm3)
Ventilation rate
amount of breaths per min
Forced Expiration Volume (FEV)
max vol of air that can be breathed out in 1 second
Forced Vital Capacity (FVC)
max mol of air that can be breathed out after taking in a deep breath
Pulmonary Tuberculosis
caused by bacteria, when in the lungs, the Immune system cells detect it and build a wall around it. This forms a hard small lump - tubercle. Infected tissue around the tubercle will die reducing the SA left for gas exchange -> reduces tidal vol, breathe more to take up more air -> increased ventilation rate (can also cause fibrosis- reduces tidal vol further)
Fibrosis
formation of scar tissue in the lungs, (can happen due to subs like asbestos and dust). scar tissue is thicker and less elastic, lungs can’t expand as much to hole air-> reduced tidal vol and FVC
reduces rate of gas exchange as is slower over scarred membrane
have an increased ventilation rate to get more air into the lungs and oxygenate blood
Asthma
airways become inflamed and irritated ( caused by allergic reactions), smooth lining of the bronchioles contracts and releases a large amount of mucus which constricts the airway -> hard to breathe
FEV reduced severely
can be relieved by drugs (inhalers) that cause bronchioles muscles to relax
Emphysema
caused by smoking or long term exposure to air pollution
foregin particles become trapped in the alveoli causing inflammation this attracts phagocytes, they release an enzyme that breaks down elastin in the alveoli -> alveoli can’t recoil to expel air as well (remains trapped in alveoli) leads to destruction of alveoli walls reducing the SA and rate of gas exchange
may have increased ventilation rate
Effect of lung disease on Gas exchange
reduces rate of gas exchange, less O2 in bloodstream, cells receive less oxygen and aerobic resp is reduced, less energy released -> may feel tired or weak
