3.3 Exchange and Transport Flashcards
What is digestion?
Larger biological molecules hydrolysed to smaller molecules that can be absorbed across cell membranes
How are carbohydrates digested?
•pancreatic and salivary gland amylase will hydrolyse starch into maltose
•membrane bound disaccharidases in ileum epithelial cells hydrolyse maltose into glucose (co-transport with Na+)
How are proteins digested?
•endopeptidases: hydrolyse peptide bonds between aa in middle of polypeptide chain (smaller peptide chains)
•exopeptidases: hydrolyse peptide bonds between aa at the end of a polypeptide chain (remove terminal aa)
•membrane bound dipeptidases: hydrolyse peptide bonds between 2 aa (dipeptides to aa)
How are lipids digested?
•bile salts emulsify lipids into smaller droplets- increase SA for faster hydrolysis action by lipase
•micelles form from bile salts, monoglycerides, glycerol=make them more soluble and they are absorbed by diffusion.
•inside cell: modified back into triglycerides by Golgi body and ER
•vesicle moves to cell surface membrane to be released by exocytosis
What is a chylomicron?
In the Golgi body, (modified) protein is added to the lipids and it is packed in a vesicle and released by exocytosis
Why are micelles important?
•micelles form from bile salts, monoglycerides, glycerol and fatty acids
•micelles make fatty acids more water soluble
•micelles carry fatty acids to epithelial cells of ileum
=fatty acids released from micelles are absorbed into cell by simple diffusion
What do very small organisms use for gas exchange compared to larger organism?
•small: have a very large SA:V + small distances so can do simple diffusion
•large: smaller SA:V + larger distances + higher metabolic rates so gas exchange systems
What is a consequence of a larger SA:V for small organism?
Lose heat more quickly so to compensate they have a higher metabolic rate. More Respiration so more heat energy to maintain temp.
How do terrestrial insects have an efficient gas exchange system?
- Large no. of tracheoles branching to each cell (large SA for rapid diffusion and short diffusion distance)
2.thin tracheal walls (short diffusion distance)
3.use of O2 and making of CO2 sets up steep conc. gradient
How do terrestrial insects minimise water loss?
1.have small SA:V less surfaces for evaporation
2.waterproof exoskeleton so less evaporation
3.spiracle valves close
What are the methods of gas exchange in terrestrial insects?
- Diffusion: conc. gradient when respiring
2.mass transport: abdominal muscles relax and contract to move gases on mass, so more air/O2 enters to maintain conc. gradient
3.anaerobic respiration: lactic acid lowers water potential of muscle cells so they gain water by osmosis from tracheoles=
•tracheole volume decreases so more air drawn in
•gases move faster in air than H2O
•greater SA exposed to air
How are insects able to obtain oxygen?
1.air enters through spiracles
2.travels down tracheae
3.diffusion gradient in tracheae as oxygen is used in respiration
4.tracheae associated with all cells (branching)
5.O2 diffuses into cells
6.ventilation replaces air in tracheae
What makes gas exchange in fish efficient?
•large SA:V=lots of gill filaments with lots of gill lamellae
•short diffusion distance=capillary network in every lamellae + very thin lamellae
•maintain conc. gradient=countercurrent flow, ventilation (fresh water), capillaries (good blood circulation)
What is the countercurrent flow in fish?
1.blood + water flow in opposite directions (blood always meets H20 with a higher O2 conc.)
2.equilibrium is not reached
3.diffusion gradient is maintained across the entire length of gill lamellae
What are the steps in inspiration?
1.external intercostal muscle contract
2. Diaphragm muscle contracts and flattens
3.Ribcage moves upwards + outwards
4. Volume of thoracic cavity increases
5.Pressure in thoracic cavity decreases
6.air moves into the lungs, down the pressure gradient
What are the steps in expiration?
1.internal intercostal muscles contract
2.Diaphragm muscle relaxes and domes
3. Ribcage moves downwards + inwards
4.Volume of thoracic cavity decreases
5. Pressure of thoracic cavity increases
6. Air is drawn out of the lungs, down pressure gradient
What features of the alveolar epithelium make it an efficient exchange surface? (+lungs?)
•single layer of cells - short diffusion distance
•each surrounded by a network of capillaries - steep conc. gradient
•many- large SA for rapid diffusion
•permeable- allows diffusion of O2/CO2
Lungs:
•ventilation brings in air with higher O2 conc. and removed air with lower O2 conc. (conc. gradient of O2 maintained)
•good circulation of blood
What is the pathway taken by O2 from air to blood?
- Trachea, bronchi, bronchioles
- Down pressure gradient
- Down diffusion gradient
- Across alveolar epithelium
- Across capillary endothelium
How is pulmonary ventilation calculated?
PV= tidal volume * ventilation rate
Tidal volume:vol of air enters+leaves at normal resting breath (0.5dm3)
Ventilation rate:breaths per minute
What are adaptations of xerophytic plants to reduce water loss?
•sunken stoma with hairs traps water vapor and increases humidity to lower water potential gradient
•curled leaves to protect from wind
•reduced no. of open stomata
•thick waxy cuticle to reduce evaporation
How are plants adapted for efficient gas exchange?
•short diffusion distance: thin leaves
•steep diffusion gradient: palisade use up CO2 for photosynthesis
•large SA: spongy mesophyll has lots of air space
How could you find the surface area of a leaf?
1.draw around leaf on graph paper
2.count squares
3.multiply by 2 (2 sided)
Why might the rate of H2O uptake not be the same as the rate of transpiration by a plant?
Water used in photosynthesis , hydrolysis, for turgid, made in respiration