Chapter 4 Flashcards
(15 cards)
explain what a protein channel is
- water-filled hydrophilic channels across membrane
- allow H2O - soluble ions to pass through
- they are selective
explain what facilitated diffusion is
- passive - relies on kinetic energy of the diffusing molecules
- no external input of ATP from respiration
- occurs down a conc gradient
- only occurs at specific points on the plasma
- protein channels + carrier proteins involve
explain why simple diffusion occurs
- when the conc of a molecule, atom or ion type differs across a membrane that is permeable
- due to the difference in conc it means the molecules have to move from a region of high conc to a region of low conc
- random kinetic motion
explain what affects the rate of diffusion
- the size of the conc gradient - diffusion distance
- surface area
- size of the molecule
- temp
explain what diffusion is
- the net movement of molecules or ions from a region where they are more highly concentration is lower until evenly distributed
explain why cholesterol is present in the cell membrane
- adds strength
- hydrophobic - prevents H2O loss + loss of ions
- limits other molecules movement without making it too rigid
- makes mem less fluid at higher temps
how could you reduce the uncertainty calculated
- have smaller intervals or a higher resolution
name and describe 5 ways substances move across the cell-surface mem into a cell
- diffusion - the movement if small, non-polar particles from an area of high conc to an area of low conc
- osmosis - the net movement of water from an area of high water potential to an area of low water potential
- facilitated diffusion - down a conc gradient via channel or carrier proteins
- co-transport - of 2 diff substances using a carrier protein
- active transport - against a conc gradient using ATP
give one similarity and two differences between the membrane structure and the fluid -mosaic model of the membrane
similarity:
- both have a phospholipid bilayer
difference:
- cholesterol isn’t present which it is in the fluid mosaic model
- no channel proteins which the fluid mosaic has
explain the function of ATP hydrolase in co-transport
- releases energy
- allows ions to be actively transported
the movement of Na+ out of the cell allows the absorption of glucose into the cell lining if the ileum
explain how
- generates a diffusion gradient
- Na+ moves in by co-transport bring glucose in with it
describe and explain two features you would expect to find in a cell specialised for absorption
- large surface area - faster rate of absortion
- large no. of carrier/channel proteins so faster rate
contrast the processes of facilitated diffusion and active transport
- active transport requires ATP whereas facilitated diffusion is passive
- facilitated diffusion requires something such as a carrier protein to aid the process whereas active transport only uses carrier proteins
explain how the transport of Na+ is involved in the absorption of glucose by epithelial cells
- sodium ions enter the blood via active transport using an Na+K+ pump
- against a conc gradient using ATP
- conc of sodium in ileum is higher that in the cell
- sodium ions enter cell down conc gradient via facilitated diffusion
- glucose ions absorbed into cell with sodium against their conc gradient
give 2 similarities in the movement of substances by diffusion and osmosis
- both move substances down a conc gradient
- both move substances across a membrane in a way that doesn’t require energy
