Respiration Flashcards
What is respiration?
Respiration is the process by which an organism exchanges gases between themselves and the environment.
All species respire to release energy from their food to fuel cellular processes.
Name and describe three mechanisms of respiration.
1) Aerobic cellular respiration - organisms use oxygen to extract energy from food (oxygen is acting as the electron acceptor in the respiration pathway)
2) Anaerobic cellular respiration - Organisms do not use oxygen to extract energy from food but instead use a different compound (e.g. nitrate and sulfur)
3) Fermentation - The anaerobic degradation of a substance such as glucose to smaller molecules such as lactic acid or alcohol with the extraction of energy.
Fermentation doesn’t use the ETC so is NOT considered respiration.
What are some benefits of anaerobic and aerobic respiration?
Aerobic respiration - a lot more energy for the organism - in some cases 19 times more energy than anaerobic respiration - this may have allowed for the evolution of multicellularity and larger organism size
Anaerobic respiration - quickly release energy - can occur in low oxygen
How did respiration evolve?
First life forms respired anaerobically - not much oxygen in the atmosphere 4 billion years ago
Photosynthetic bacteria evolved roughly 3.4-3.5 billion years ago - photosynthesis produces oxygen cause the atmosphere of the environment to change - oxygen was toxic to a lot of organisms back then - because it affects vital chemical pathways - suddenly there were many organisms spewing toxic gas into the environment
2.8-2.9 billion years ago - aerobic respiration evolved - organisms were starting to adapt to the changing environment - organisms that respire aerobically had an advantage - the great oxygenation event occurred abt 2.4 billion years ago (when oxygen began accumulated)
Oxygen was reacting with other chemicals like carbon, sulphite, or ion - it was also staying in the oceans - eventually enough accumulated in the ocean so that it is started leaking out into the atmosphere but was still reacting with chemical in the atmosphere or in terrestrial environment - therefore only recently oxygen levels started to accumulate in the atmosphere - rather that as soon as photosynthetic bacteria evolved
Where did mitochondria come from?
Mitochondria evolved via endosymbiosis where a host cell engulfed a prokaryotic cell.
Mitochondria evolved due to the benefits of aerobic respiration
Two hypothesis regarding the organisms involved:
(1) Eukaryote host engulfed an aerobic prokaryote
(2) Prokaryote host engulfed a facultative anaerobic prokaryote
This is the endosymbiotic theory
How does the great oxygenation event correlate with the evolution of giant insects?
Traditional hypothesis: the greater amount of oxygen in the environment allowed adults to meet their energy needs - insects have a system of trachea that they use to get oxygen - if they get larger - they need more trachea to meet their oxygen demands but then there’s less space for other muscles and organs - large insects can be limited by the amount of space they can give to trachea - but if there’s greater oxygen level in the atmosphere then they can get to larger sizes without the need for more trachea
Another hypothesis - some insects have aquatic larvae and higher oxygen levels in water can be toxic to these larvae - one way to counteract the effect of this toxicity is to have larger body size
Describe how bacteria and archaea respire.
Bacteria and archaea can respire aerobically, anaerobically, or both.
Respiration occurs in the cytoplasm of the cell because they are prokaryotes and therefore do no have organelles.
Anaerobic bacteria use other compounds such as hydrogen sulfide or methane, instead of using oxygen.
3 types:
Obligate aerobic bacteria - cannot survive without oxygen
Obligate anaerobic bacteria - cannot survive in the presence of oxygen
Facultative anaerobic bacteria - can grow without oxygen but use oxygen of present
How do fungi respire?
Most fungi are aerobic, but some are anaerobic.
Most anaerobic fungi are found in deep ocean in sediments there.
Hyphae are branching filamentous structure that are the main mode of vegetative growth in fungi. In soil, hyphae absorb oxygen from tiny air spaces in between soil particles.
Oxygen and carbon dioxide can move across the thin outer wall of hyphae by absorption.
Most fungi grow underground in soil so they must acquire their gases from underground too.
How do plants respire?
All parts of a plant need to respire.
Plants obtain oxygen via diffusion through:
Stomata (leave and stems)
Lenticels (stems of woody plants and some roots)
Plants also obtain oxygen via absorption through roots.
Describe the role of plant roots in respiration
Roots have adaptations depending on the oxygen environment.
Aerial roots known as pneumatophores are useful in environments with anoxic or waterlogged soil.
Not all aerial roots are used for respiration but the ones that are, are called pneumatophores.
Aerenchyma are small air pockets in plant tissue. Allows for exchange of gases from exposed parts of the plants to submerge parts.
In stagnant water (not much oxygen) - the aerenchyma are much bigger in these species of plant
Describe the process of respiration in plant leaves.
Stomata allow gas exchange through tiny openings
Stomata are present in the sporophyte (diploid) generation of all land plants.
Stomata can open and close, depending on plant condition and environmental conditions
Stomata density and aperture (how many stomata there Is and how big they are) - can vary depending on environmental factors including atmospheric carbon dioxide concentration, light intensity, and air temperature
In conditions of low carbon dioxide - there tends to be a reduction in size and increase in density of stomata - to get more co2 for photosynthesis
Dumbell shaped guard cells tend to open more quickly than the kidney shaped stomata
What are the 5 different types of gas exchange system in animals?
Direct diffusion, integumentary exchange, trachea (insects), gills, lungs.
Not all animals will fit neatly into these categories - some may use multiple types of gas exchange like frogs who have lungs and also do integumentary exchange
What are the four possible stages of respiration in animals?
1) Breathing
2) Gas Exchange
3) Circulation
4) Cellular respiration
What factors influence the respiratory system of an animal?
- Environment
- Size of the organism
- Ecological requirements
The environment in which an organism lives can affect how it respires - all types of gas exchange require a moist or wet surface because gases must first dissolve into the liquid to be able to diffuse across the membrane - therefore exchange across the skin whch is know as integumentary exchange would not be suitable in really dry environments because the skin would be dry so gas exchange can’t happen
Complexity of the respiration system depends on the size of the organism and ecological requirements - predatory bird require a lot of energy - require a lot of oxygen - there respiratory system would have different requirements to that of an earthworm for example
Which animals are capable of respiring through the process of direct diffusion?
Small animals (<1mm diameter) can obtain oxygen via diffusion.
Direct diffusion of oxygen across the outer membrane can supply oxygen to all cells
Larger animals cannot use this method because diffusion would not be able to provide oxygen quickly enough
Examples:
Flatworms
Sponges are hollow and have choanocytes which help to suck water in and push it out to ensure that oxygenated water is going over all cells that will require oxygen
