Exchange Flashcards
Why do small organisms not need a specialised exchange surface?
have a very high SA:Vol so diffuse all oxygen in through membrane
State ficks law
rate of diffusion = (surface area * difference in conc.) / length of diffusion pathway
Exchange in single celled organism
- small w/ large SA:Vol
- O2 + CO2 diffuse across one cell thick membrane
Describe respiration in the tracheal system
- oxygen used for respiration
- conc. gradient set up btw. atmosphere (high) and cells (low)
- oxygen diffuses in through spiracle + tracheae
- muscle contraction pumps gases through
Explain why tracheoles filled w/ water
So that during exercise (anaerobic respiration), water moves into cells by osmosis due to water. pot gradient set up by lactate. This draws air into tracheoles in which diffusion takes place more rapidly
List adaptations of insects for efficient gas exchange
- tracheoles thin walls -> short diff. path
- highly branched -> short diff. path + large SA
- tracheae tubes filled w/ air -> faster diffusion in air
- fluid moves into tissues from tracheoles -> more air
for fast diff. + larger SA - abdominal pumping -> maintains conc. gradient
Features of fish gills for efficiency
- v. large SA -> flat filaments w/ lamellae folds
- thin walled/flat -> close contact water, short diff. path
- good blood circulation -> conc. gradient maintained
- water ventilation -> conc. gradient maintained
Concurrent vs Countercurrent
Concurrent: same direction of flow so equilibrium reached, half O2 taken up
Countercurrent: opposite direction of flow so conc. gradient maintained, 100% O2 taken up
Adaptations of leaves for gas exchange
- many stomata -> short diff. path as no cell is far
- many air spaces in mesophyll -> gases readily in contact w/ mesophyll cells
- large SA of mesophyll cells -> rapid diff.
Respiration formula
oxygen + glucose -> carbon dioxide + water
Photosynthesis formula
carbon dioxide + water -> glucose + oxygen
Adaptations to limit water loss in insects
- small SA:V ratio -> minimise area of water loss
- waterproof covering (chitin) covered in waterproof cuticle
- spiracles close -> reduce water loss
Adaptations to limit water loss in plants (xerophytes)
- thick cuticle forms waterproof barrier
- rolling up of leaves -> region of still air becomes saturated w/ H2O decreasing water pot. gradient
- hairy leaves/stomata in pits -> trap moist air next to leaf reducing water pot. gradient
Why are lungs needed?
Remove lots of CO2 and absorb lots of O2
-> humans have lots of cells and high metabolic rate
Pathway of air in the lungs (plus a feature)
trachea (cartilage to prevent collapse)
bronchi (mucus trap dirt + cilia waft it up to throat)
bronchioles (muscle lined to control air flow)
alveoli (elastic fibres allow them to stretch and recoil)
Process of inspiration (active)
- external ic contract, internal ic relax
- ribs pulled up and out as thorax vol. increases
- diaphragm contracts increasing vol. of thorax
further - less air pressure in lungs
- air forced in as atmospheric pres. > pulmonary pres.
Process of expiration (largely passive)
- internal ic contract, external ic relax
- vol. of thorax decrease as ribs move in and down
- diaphragm relaxes, is pushed up by contents of
abdomen decreasing vol. of thorax further - more air pressure in lungs
- air forced out as pulmonary pres. > atmospheric pres.
note: under normal breathing, recoil of elastic tissue main reason for air being forced out
Why is diffusion rapid btw. alveoli and capillaries?
- r.b cells slowed in cap’s -> more time for diffusion
- thin endothelium which r. b cells flattened against + thin epithelium -> short diff. pathway
- alveoli + p.capillaries have large SA
- constant ventilation of air + blood maintains conc.
gradient
Risk factors for lung disease (COPD)
smoking air pollution genetic make-up infections occupation
Order of digestive tract
mouth, pharynx, oesophagus, stomach, ileum, colon, rectum
2 stages of digestion
Physical - food broken down into smaller pieces to be ingested
Chemical - hydrolysis of insoluble mols into smaller soluble ones using enzymes
Examples of carbohydrases
amylase (starch)
maltase (maltose)
sucrase (sucrose)
lactase (lactose)
Carbohydrate digestion
- sal. amylase hydrolyses starch -> maltose + minerals salts maintain optimum pH
- acids in stomach denature amylase + stop hydrolysis
- amylase from pancreatic juice in ileum mixes w/ food, resumes hydrolysis + contains alkaline salts to
maintain neutral pH - muscle lining pushes food along ileum, epithelial lining produces membrane-bound maltase
- maltose hydrolysed into a.glucose
Lipid digestion
- lipids split into micelles by bile salts in emulsification -> increases SA so lipase action sped up
- lipase from pancreas hydrolyses ester bond in triglycerides to form monoglycerides and f. acids
Protein digestion
Large complex mols hydrolysed by different peptidases.
- endopeptidases hydrolyse pep. bonds in central region creating many mols
- exopeptidases hydrolyse pep. bonds on terminal end of a.acids releasing a.acids + dipeptides
- dipeptidases hydrolyse bond in dipeptide (membrane-bound)
Where are products of digestion absorbed?
In the ileum: folded + possesses villi
Features of villi for absorption
thin walls, large SA, good blood supply etc.
- muscle to mix contents of ileum, maintain diffusion gradient
- epithelial cells contain microvilli, further increasing SA
Describe processes involved in absorption of products of lipid digestion from ileum to lymph vessels
- micelles contain bile salts + f. acids
- these make f.acids + m.glycerides more soluble in water
- products absorbed by diffusion into epithelium
- triglycerides reformed in ep. cells
- chylomicrons move out of cell by exocytosis into lymphatic capillaries
