Organisms exchange Flashcards
what is the structure of gills?
Made up of gill filaments stacked in a pile
sticking out of filament are very thing lamella(Increase SA)
What is the counter current system?
Blood flow in lamellae runs opposite to water flow
Ensures a conc. gradient across whole length of lamella
Blood well loaded with oxygen meets point with max conc. of oxygen in water
Blood with little oxygen meets water which still has a little more oxygen
What are the parts of the human gas exchange?
Trachea - Flexible airway supported by rings of cartilage
Bronchi- Two diversions of trachea (one in each lung) it also has cartilage in small sections by muscles and elastic fibres
Bronchioles - Series of branching subdivisions of bronchi
Alveoli - Minute air sacs at end of bronchioles
Why is diffusion so efficient in human lungs?
Large SA - Alveoli
Walls of alveoli and capillaries are very thin
Alveoli and capillaries are very close
Surface of alveoli is moist to allow gases to dissolve
Steep conc. gradient maintained by ventilation and blood flow
What are tracer experiments?
Radioactive isotope 14C is used to make 14CO2. incorporated into sugars produced during photosynthesis
Autograph allows tracking of sugars -radioactive areas correspond to areas of phloem not xylem
what are ringing experiments?
Ring of protective outer bark layer and phloem is removed around circumference of stem
Stem above ring immediately swells due to accumulation of sugars
Non-photosynthetic tissues below ring wither and die
what are alveoli
Alveoli
Site of gas exchange is epithelium of alveoli
epithelium is very thin
each alveolus is surrounded by a network of pulmonary capillaries
What happens in protein digestion?
- Central peptide bonds of protein molecule are hydrolysed by endopeptidase
- Peptide bonds on terminal aa of polypeptide molecule are hydrolysed by exopeptidase to release dipeptides and single amino acids
- bonds between dipeptides hydrolysed by dipeptidase
what are the types of protein channel?
Aquaporins- water filled channels that allow water soluble ions to pass through
Ligand Gated - Channel opens in presence of specific molecule
Voltage gated-Channel can open due to change in voltage
How does the mass flow hypothesis work
- Sucrose moves from source to companion cells by facilitated diffusion down conc. gradient
- Hydrogen ions are actively pumped out of companion cell
- Sucrose is loaded into phloem cells with hydrogen ions via co-transport protein
- High conc. of phloem causes water to move in from xylem by osmosis
- This raises hydrostatic pressure at source
- At sink sucrose is actively transported into sink from phloem
- This lowers water potential so water leaves sieve tubes by osmosis
- Hydrostatic pressure at sink is lowered
- Therefore there is a pressure gradient so sucrose solution moves down it.
What is the basic structure of arteries, arterioles and veins
Tough protein fibres -resist pressure changes
Muscle layer -contract to control blood flow (only in arterioles)
Elastic layer -Maintains blood pressure by stretching and recoiling with heart cycle
Thin inner lining - smooth to reduce friction
What is the structure of an artery?
(Compared to vein)
Thicker muscle -smaller arteries constrict to control blood flow
Thicker elastic - Allows fibres to expand and recoils when heart relaxes to help maintain pressure
Small lumen -Keeps high pressure
What is the structure of a vein?
Wide lumen - Allows blood pressure to be low and blood flow to be slower
Thinner muscle layer
Thinner elastic layer - lower pressure
Valves -ensures blood doesn’t flow backwards
- skeletal muscles contract, squeezing veins, which increase pressure opening one valve and closing another
What is the structure of capillaries?
Thin walls - short diffusion pathway
highly branched - large SA
Narrow lumen- Red blood cells squeezed flat against side of capillary( SA - reduces diffusion pathway)
Narrow diameter - Can permeate tissues so no cell is far from a capillary
How is tissue fluid formed?
- Hydrostatic pressure forces tissue fluid out of capillaries, leaving behind large molecules and proteins
- Due loss of tissue fluid remaining blood has lower water potential and lower hydrostatic pressure
- Lower hydrostatic pressure and water potential tissue means water move back into capillaries
- Any leftover tissue fluid(normally 10%) is carried back to heart via lymphatic system
