2.1 Gas Exchange, Cell Membranes and Transport Flashcards
State Fick’s Law
Rate of diffusion ∝ (surface area × difference in concentration) / (thickness of gas exchange surface)
Explain the anatomical adaptations in organisms with respiratory systems that maximise gas exchange
- many small alveoli - increase area of diffusion surface
- very thin alveoli and capillary walls - decrease diffusion distance
- constant unoxygenated blood flow through capillaries and new oxygen supply through breathing - maintains difference in concentration
Explain the role of goblet cells and ciliated epithelial cells in the respiratory system
goblet cells: secret mucus to trap pathogens/irritants before they can reach alveoli
ciliated epithelial cells: have “hairs” that brush up mucus that has trapped pathogens/irritants to be swallowed, so they do not cause infection
Describe the structure and properties of phospholipids
- Phosphate group connected to glycerol and two fatty acid tails
- phosphate head is hydrophilic, fatty acid tails are hydrophobic causing the formation of phospholipid bilayer
List the components of cell membranes and give a function for each
phospholipid bilayer - allows lipid soluble substances and not water soluble, allows flexible and self sealing membrane
cholesterol - adds strength, and holds tails together to restrict movement
glycolipid/glycoprotein - chemical markers/antigens
channel protein - allows larger molecules to enter
Explain why the cell membrane is called a fluid mosaic, and the evidence that suggests the existence of the model
- fluid - free movement of components of the membrane
- mosaic - made of many different parts
- mouse proteins added to human membrane mixed with human proteins - shows fluidity
- froze and split bilayer - could see multiple components showing mosaic
Explain how different factors affect phospholipid membrane structure/fluidity
- at high temps more cholesterol - less fluidity
- at low temps more cholesterol - more fluidity
- more saturated fatty acids - less fluidity
- higher temp - more fluidity
- too high temps - proteins denature, bonds break, membrane breaks down
- alcohol presence - phospholipids rearrange to face alcohol, disrupting structure
Define and explain simple diffusion, and give examples of molecules which can be transported this way
- high to low concentration
- no ATP needed
- molecules pass through phospholipid membrane
- lipid-soluble molecules and very small, noncharged molecules can
Define and explain facilitated diffusion, and give examples of molecules which can be transported this way
- high to low concentration
- no ATP needed
- molecules pass through transmembrane protein (channel/carrier)
- large/polar/charged molecules
Define and explain active transport, and give examples of molecules which can be transported this way
- low to high concentration
- ATP needed (hydrolysed to ADP and Pi, Pi then reacts with carrier protein to change its shape)
- larger molecules and ions
Define osmosis
diffusion of water molecules across a partially permeable membrane from high to low concentration
Define and explain exocytosis/endocytosis, and give examples of molecules which can be transported this way
- endo (taking molecules into the cell), exo (excreting molecules out of cell)
- require ATP to form vesicle
- much larger molecules, an example is phagocytosis (endocytosis) or newly formed proteins (exocytosis)
PRACTICAL
Explain how you would investigate the impact of ethanol (or other factors) on membrane permeability and why choose beetroot?
IV: ethanol conc
DV: % absorbance of solution (using colorimeter)
CVs: time left in water, size of beetroot piece (measure pieces/use apple corer)
Method:
soak beetroot pieces in water overnight, wash and blot dry, fill boiling tubes with diff ethanol concs, add beetroot into each for 30 mins then remove, mix solution and add to cuvettes, and measure % absorbance (after calibrating)
Conclusion:
more ethanol = less % absorbance
Why Beetroot?
contains betalains in vacuoles, leakage can be observed by colour that leaks into solution
