Cell membranes Flashcards
What is the cell membrane selectively permeable to?
Water and some solutes
What substances move through the cell membrane more easily than water soluble substances?
Lipid soluble substances
What are the two types of lipid soluble substances?
Small uncharged molecules
Non-polar substances
What are some examples of small uncharged molecules?
Oxygen
Carbon dioxide
Where do small uncharged molecules dissolve and diffuse?
Dissolve in the hydrophobic tails of the phospholipids
Diffuse across the cell membrane
Where do non-polar molecules dissolve and diffuse?
Dissolve in phospholipids
Diffuse through cell membranes
Can polar molecules and charged ions easily diffuse through the phospholipids?
No
What are some polar molecules and charged ions?
Polar molecules: glucose and amino acids
Charged ions: Na+
What are polar molecules and charged ions examples of?
Water soluble substances
Where do polar molecules and charged ions pass?
Through intrinsic protein molecules
Either channels or carrier proteins
What is the permeability of the membrane affected by?
Temperature
Organic solvent
How does temperature affect the permeability of the membrane?
Increased temperature increases membrane permeability
Molecules moving through the membrane will have more kinetic energy
Will diffuse more quickly
How does organic solvents affect the permeability of the membrane?
Ethanol dissolves/emulsifies the phospholipids
May denature the proteins
Results in gaps or holes within the cell membrane/membrane becomes more porous
Acetone has a similar effect to ethanol
What are the six types of transport across the membrane?
Diffusion
Facilitated diffusion
Co-transport
Active transport
Bulk transport (endo/exocytosis)
Osmosis
What is the difference between active and passive transport?
Passive transport: not requiring ATP provided by the cell
Active transport: requires ATP provided by the cell
