Topic 3A: Exchange and Transport Systems Flashcards
How do you calculate SA:V?
SA:V = SA / V
Why do organisms need to exchange things with their environment?
- Take in substances –> O2 for respiration , nutrients etc
- Remove waste products –> CO2, urea etc
- To remain at a constant temperature –> exchange heat
Do large organisms have a high or low SA:V?
low
Do small organisms have a high or low SA:V?
high
How does exchange work in single - celled organisms?
- Large SA:V
- All surface exposed to environment, can exchange enough via surface for whole cell
- Short diffusion distance = fast diffusion rate
How does exchange work in large, multicellular organisms?
- Small SA:V
- Too slow diffusion –> some cells deep in the body - large distance
- Cannot exchange enough substances through relatively small surface for their relatively large volume
What do large multicellular organisms therefore need?
- Exchange organs and mass transport systems to move substances in and out of the organism and supply cells
How does body size affect heat loss from an organism?
- Large volume but small SA = hard to lose heat
- Small volume but large SA = easier to lose heat
How does shape affect heat loss?
- Compact shape - small SA relative to volume - minimal heat loss
- Less compact - sticky outy bits - larger SA relative to volume - increases heat loss
How can organisms be adapted for water loss?
- Inc SA:V = inc water loss through surface
- Kidney structure adaptations to reduce water loss
How are mammals with high metabolic rates adapted?
Esp in cold environments
- Eat lots of high energy foods - e.g. seeds, nuts
- Thick fur
- Hibernate
How are large organisms in hot environments adapted?
- Have slow heat loss - low SA:V
- Large, flat ears - inc SA
- Spend lots of time in water to lose heat - e.g. hippos
What are features of specialised exchange surfaces?
(5 things)
- Large surface area
- Thin - short diffusion pathway
- Selectively permeable
- Mechanism to move environmental medium (ventilation)
- Mechanism to move internal medium (blood supply)
–> both maintain concentration gradient
How are gills structured?
- Gill arches
- 2 stacks of gill filaments –> inc SA
- Filaments covered in lamellae - with lots of capillaries
- Thin layer of cells - quick diffusion
How does water enter and leave fish?
- Water into open mouth with gills closed
- Mouth closes, gills open - down pressure gradient
- Water flows over gills and O2 diffuses into blood
How does counter-current flow work?
- Blood and water flow in opposite directions
- Maintains large concentration gradient
- Water always ahs much higher O2 concentration
- Equilibrium is never reached
- As much O2 as possible taken in from water
How does oxygen enter insects?
- Spiracles = holes in sides
- O2 moves down concentration gradient towards cells
- Through trachea then tracheoles - thin permeable walls
- O2 moves to individual cells directly
How is CO2 removed from insects?
- Moves down concentration gradient out of the insect
What else do insects do to help gas exchange?
- Rhythmic abdominal movements to move air in and out of spiracles
- When active fluid at ends of tracheoles taken in to inc SA and lower pressure to draw in air
How do insects prevent water loss?
- Can close spiracles
- Waterproof, waxy cuticle around body
- Hairs around spiracles to trap water vapour to reduce water potential gradient
How are leaves adapted for gas exchange?
- Most exchange is on mesophyll cells - high SA
- Gases move in and out via stomata
- Guard cells open and close stomata
How do plant stomata help reduce water loss?
- When guard cells are turgid - stomata open
- When dehydrated - lose water - flaccid - stomata close
- Close at night as there can be no photosynthesis so stop water loss at night
How do xerophytic plants reduce water loss?
- Sunken stomata - trap water vapour for low water potential gradient
- Curled leaves - protect from wind which would increase transpiration
- Hairs on epidermis - trap water vapour for reduced water potential gradient
- Reduced number of stomata - fewer places for water loss
- Thicker waxy cuticle - waterproof to reduce evaporation
Describe inspiration
- Diaphragm contracts - flattens
- External intercostal muscles contract - ribcage moves up + out
- Cavity volume increases, pressure decreases - lower than atmosphere
- Air moves in down pressure gradient
- Active process - needs energy
Describe expiration
- Diaphragm relaxes - domed
- External intercostal muscles relax - ribcage moves down + in
- Cavity volume decreases, pressure increases
- Air moves out down pressure gradient
- Passive process
How does forced expiration work?
- Internal intercostal muscles contract also
- Ribcage pulled further down and in
- Intercostal muscles move antagonistically
How are gases exchanged into the blood?
- Out of alveoli
- Across alveolar epithelium
- Across capillary endothelium
- Into haemoglobin in blood
- Down diffusion gradient (concentration)
- CO2 moves opposite way
How are alveoli adapted for gas exchange?
- Thin exchange surface - alveolar epithelium = 1 cell thick = short diffusion pathway
- Large SA - millions of alveoli
- Steep conc gradient - ventilation and blood supply maintain conc gradient
What is tidal volume?
- Volume of air in each breath
What is ventilation rate?
- Number of breaths per minute
What is forced expiratory volume?
- Max volume that can be exhaled in 1 second
What is forced vital capacity?
- Max volume possible to forcefully breathe out
What is tuberculosis?
- TB bacteria in lungs surrounded by immune system cells
- Form small hard lumps - tubercles
- Infected tissue dies - damages exchanage surface
What are the consequences of tuberculosis?
- Tidal volume decreases
- Fibrosis is caused further dec tidal volume
- Less air can be inhaled - need to breathe faster for enough O2
What are symptoms of tuberculosis?
- Cough
- Coughing blood and mucus
- Chest pain
- Shortness of breath
What is fibrosis?
- Formation of scar tissue in lungs
- Due to infection or substances like asbestos
What consequences are there to fibrosis?
- Scar tissue - thicker and less elastic - less lung expansion - less air held - reduced tidal volume and FVC
- Slower diffusion - longer pathway - need more ventilation to get enough O2 into lungs
What are symptoms of fibrosis?
- Shortness of breath
- Dry cough
- Chest pain
- Fatigue
- Weakness
What is asthma?
- Inflamed / irritated airways
- Smooth muscle lining bronchioles contracts
- Airways constrict
- Reduced air flow in and out of lungs
- Less O2 in alveoli and blood
What does asthma cause?
- Reduces forced vital capacity
What are asthma symptoms?
- Wheezing
- Tight chest
- Shortness of breath
What is emphysema?
- Caused by smoking / pollution
- Inflames tissue
- Attracts phagocytes - enzyme produced which breaks down elastin in alveoli
What is caused by emphysema?
- Less stretch and recoil
- Alveoli walls destroyed - reduced SA
What are symptoms of emphysema?
- Shortness of breath
- Wheezing
What are general effects of lung disease?
- Reduced rate of gas exchange in alveoli
- Less O2 able to diffuse into blood - body cells receive less - reduced rate of aerobic respiration
- Less energy released - tired and weak
What are the stages to dissect lungs?
- Lab coat, clean, sharp, rust-free tools
- Cut down trachea down gap in C shaped cartilage rings
- Continue cutting down one bronchi - should see bronchioles
- Cut off lung piece - spongy from air trapped in alveoli
- Wash hands and disinfect surfaces
How would you inflate lungs?
- Attach rubber tube and inflate with foot / bike pump
- Deflate on their own due to elastin in alveoli walls
- Don’t blow down them - could suck in stale air
- Put lungs in plastic bag at start to stop bacteria in the lungs from being released into the room
How would you dissect gills?
- Lab coat
- Put fish on a board (dissection or cutting)
- Push back operculum, remove gills with scissors
- Cut gill arch through bone at top and bottom
- Observe gill filaments
- Wash hands and disinfect surfaces
How can you dissect insect gas exchange systems?
- Bigger insects better - one humanely killed recently
- Dissecting pins through legs on dissecting board
- Cut and remove part of exoskeleton from abdomen
- Fill abdomen with saline solution with syringe
- See silvery grey thin tubes - tracheae - filled with air so grey
- Examine under microscope
- Should see chitin rings in tracheae walls - support
What are ethical issues with dissections?
- Morally wrong to kill animals for dissections –> lots of organs usually from animals already killed for meat
- Animals for dissection not always raised humanely or killed humanely
