Gas Exchange Flashcards
1
Q
What is gas exchange?
A
- Exchange of substances between animal/plant and surroundings
- Ultimately occurs at cellular level
2
Q
Why is gas exchange important?
A
- gas is required by metabolic reactions (Calvin cycle needs CO2)
- gas is produced by metabolic reactions (O2 created through photosynthesis)
- Especially important in respiration and photosynthesis
- most organisms need some level of O2 for energy
3
Q
Energy flow in aerobic living systems
A
- photosynthetic organisms; in chloroplasts; CO2 goes in and O2 and carbohydrates come out
- cellular respiration in mitochondria: take in the O2 and other organic molecules and use for respiration; CO2 comes out and ATP produced
4
Q
Cellular respiration (in humans)
A
- Take in sugar + oxygen = carbon dioxide + ATP energy
o 3 steps of aerobic respiration; glycolysis, citric acid cycle, phosphorylation)
o Anaerobic: produces lactic acid and only a little bit of ATP (less steps; just glycolysis and fermentation)
5
Q
Measures of gas availability
A
- Partial pressures: the pressure of one component in a mixture, were it present by itself (kPa)
- Saturation: amount of gas present in a given volume (mg/L OR ppm)
- Percent: Air is 78% nitrogen, 21% oxygen, 0.04% CO2
** at a given temperature water holds less O2 than air, but roughly the same amounts of CO2**
and oxygen content of water varies with temperature and salinity - Cold water has more oxygen; freshwater has more oxygen
6
Q
Obligate anaerobes
A
- survive only under very low oxygen
- use anaerobic respiration or fermentation
- uses something other than O2 in electron transport chain (can be sulfite, nitrate, iron, manganese, mercury etc)
- Oxygen is poison (for various reasons - ex: sulfide based enzymes deactivated by O2 because it transforms sulfide into disulfide)
- ex: Neocallimastix ; in cow rumen - breaks down cellulose
7
Q
What is colustridium botulinum
A
- causes botulism
- adults are poisoned by oxygen but endospores aren’t so when there is oxygen they are dormant; as soon as put into anaerobic environment start to grow - problem with home canning
8
Q
Microaerophiles
A
- survive only under very low oxygen (0-10%)
- usually use anaerobic respiration
- mechanisms to counter toxicities of oxygen
- need some oxygen to grow
- ex: campylobacter (cause of gastro)
9
Q
Faculative anaerobes
A
- grow best under anaerobic conditions, but not poisoned by oxygen
- ex: ragworm, actinomyces
10
Q
Obligate aerobes
A
- use O2 in electron transport chain
- carry out anaerobic cellular respiration BUT only under stress for a short period of time
- two main types of responses: 1) conformers: conform level of oxygen to supply in environment (ex: sea urchin)
2) Regulators: demand may exceed supply - continuum between conformers and regulators
- regulators can only regulate over specific ranges; may regulate at low temps when O2 consumption is lower and then conform at high temps when metabolic rate is high
11
Q
Critical partial pressure
A
- Critical oxygen pressure at which
regulators become conformers - May be affected by acclimation/
acclimatization
12
Q
Oxygen conformers
A
- internal O2 varies with ambient O2
- metabolic rate depends on internal O2 and therefore ambient O2
- most sedentary marine invertebrates
- many ectotherms, few protozoa
13
Q
Oxygen regulators
A
- internal O2 less dependent on ambient O2
- internal O2 is lower than ambient O2
- organisms can regulate how much oxygen it can take from environment since it needs much less than what is available
- metabolic rate maintained when ambient O2 changes within a certain range
- O2 regulates in critical organs (especially vertebrates)
- Rising temperatures means higher metabolic rate which means more O2 required
14
Q
Diffusion
A
- gases moving from high to low concentrations
15
Q
Respiratory structures in animals
A
- All animals: exchange site
- Large animals: ventilatory system to ensure sufficient volumes pass through the exchange site; circulatory system to transport gases
- Skin
- Gills
- Special “gills”
- Lungs
- Trachea
16
Q
Respiratory Structure: Skin
A
- Diffusion is enough for small animals (<1mm); or slightly larger animals if they are really flat
- Unicellular and some multicellular organisms
- No ventilatory or circulatory system
- Even some larger animals have no particularly special respiratory structure
- Marine or aquatic (because dessication is a danger)
- Dense network of capillaries to facilitate exchange
- Ex: catfish, leeches, lungless salamanders, Borneo flat headed frog
17
Q
Respiratory Structure: Gills
A
- Outfolding of body’s surface that are suspended in water
- Most aquatic animals
- 3 Kinds:
1) tuft
2) filament
3) lamellar (crustaceans and fish) - Frogs and insects with larval aquatic stages will have gills
- Function to increase surface area and therefore oxygen uptake
- Correlation of activity level and gill development (study: mackerels are fast moving, toad fish are slow moving; mackerel has more extensive gill area)
18
Q
Respiratory Structure: Special gills
A
- Book gills in horseshoe crabs; not actually gills, but function same way, waved through water and somewhat enclosed
- Book lungs in spider and scorpions (terrestrial); gill-like structure enclosed in chamber, similar function as gills, plates of highly vascularized tissue arranged like pages of a book, fused to chamber wall and held apart by special structures
19
Q
Respiratory Structure: Lungs
A
- Localized respiratory organ
- Entirely internal exchange sites
- Represent an infolding of the body surface; happens during embryonic development
- Divided into numerous pockets
- Occasionally found in aquatic organisms
- Mostly in terrestrial animals to reduce water loss
- Respiratory tree of sea cucumbers, simple marine organism
- Simple lung in some fish (lungfish, only air OR combination of lungs and gills)
- Simple lungs in terrestrial organisms; just sacs (earthworm, terrestrial molluscs, crabs)
- “True” lungs pouching off lower pharynx (tetrapods; some amphibians, reptiles, birds, mammals)
- Amphibians with reduced lung (all use skin for some exchange)
- All reptiles have lungs (some simple, some complex)
- Birds, mammals, endotherms require lots of O2 - have complex lungs (humans alveolar lungs w/gas ex. only at alveoli)
- Larger mammals have greater lung volume because more cells need more oxygen
20
Q
Bird lungs
A
- Highly efficient
- Air sacs on either side of lung, serve as reservoirs to keep air flowing through the lungs
- Site of gas exchange in parabronchi (tiny air tubes)
- One way system
- Two cycles of inhalation and exhalation required for air to pass through entire system
- Why so important? high altitudes and flying is physically demanding
- Smaller birds have more air sacs than larger birds to be more efficient in O2 uptake because they lose energy faster, higher metabolic rate and must work harder than larger birds to fly same distances
21
Q
Respiratory Structures: Trachea
A
- Insects have tracheal tubes
- Limits body size
- Trachea can be 2 micrometers in diameter
- Can close spiracles to limit water loss
- Gas exchange occurs across tracheoles, which can be 0.6 micrometers across
22
Q
- Trachea and aquatic insects
A
- Although some have gills, many aquatic or semi-aquatic insects still have trachea
- Some aquatic insects carry air bubbles
into the water with them (ex: diving
beetles) - Some aquatic insects (particularly larvae)
draw air in through tail-end trachea that
they keep at the water surface (ex:
mosquito larvae) - Some can circulate water through their
trachea when they are in the water (ex:
dragonflies)
