ch3 cell membrane Flashcards
triglyceride molecule’s structure?
one glycerol molecule and three fatty acids (hydrophobic)
phospholipid molecule structure?
a phosphate group (hydrophilic) and two fatty facids (hydrophobic)
channel proteins
provides channels for certain substances to pass through
carrier proteins
bind to certain substances and transport them to the other side
receptors
bind to chemical messengers and turn on certain activities
antigens
glycoproteins for cell recognition
enzymes
speed up chemical reactions
permeability of cell membrane
。core of phospholipid bilayer is hydrophobic
1) small, non-polar molecules:
。e.g. oxygen, carbon dioxide, glycerol, fatty acids, vitamin A and D
。dissolve in phospholipid bilayer and move across
2) small, polar molecules
。e.g. water, urea, amino acids, glucose
。repelled by the phospholipid bilayer, transported by the channel proteins or carrier proteins
3) small ions
。e.g. sodium ion, calcium ion
。repelled by the phospholipid bilayer, transported by the channel proteins or carrier proteins
4) large molecules
。e.g. starch, tryglycerides, proteins
。cannot move across
factors affecting permeability
1) temperature
。temperature increase -> more kinetic energy -> less closely packed -> permeability increase
。boiling can damage the membrane -> fully permeable
2) organic solvents
。dissolves phospholipids -> damage membrane -> permeability increases
cell membrane is fluid in nature
。can change shape and fuse (e.g. phagocytosis, cell division)
diffusion
。net movement of particles from a higher concentration to a lower concentration
。no net movement when reaches equilibrium state
。passive process, no energy needed
factors affecting diffusion
1) concentration gradient
。steeper concentration -> higher rate of diffusion
2) surface area
。larger area -> higher rate of diffusion
3) distance
。shorter distance -> higher rate of diffusion
4) temperature
。higher temperature -> higher rate of diffusion
5) size of particles
。smaller -> higher rate of diffusion
6) nature of particles
。non-polar particles -> higher rate of diffusion
importance of diffusion
。exchange materials : obtain oxygen and nutrients, remove waste like carbon dioxide
。involved in many life process: obsorption of nutrients in small intestine, gas exchange in lungs
osmosis
。net movement of water molecules from a region of higher solute concentration to a region of a lower solute concentration until equalisation of concentration on both sides
。water potential of distilled water is 0 (highest)
experiment with dialysis tubing
。change in liquid level in capillary tube is the change in water potential
