Biological membranes Flashcards
What are all cell membranes and organelle membranes composed of?
-a phospholipid bilayer
What do cell membranes provide?
-a partially permeable membrane and they’re the sites of chemical reactions and have a role in cell communication
What is the fluid mosaic model?
mixture and movement of the phospholipids, proteins, glycoproteins and glycolipids the membrane is made of.
What do the phospholipids align as and why?
-As a bilayer due to the hydrophilic heads being attracted to the water and the hydrophobic tails being repelled by the water
What do extrinsic proteins provide?(peripheral proteins)
-mechanical support or they make glycoproteins/glycolipids. The function of these is cell recognition or receptors
-they have hydrophilic R groups
What are intrinsic/integral proteins?
-they are also transmembrane proteins
-protein carriers or channel proteins involved in the transport of molecules across the membrane
-they have amino acids with hydrophobic R groups on their external surfaces which interact with the hydrophobic core of the membrane, keeping them in place.
What do protein channels fill with?
-water to enable water soluble ions to diffuse
What do carrier proteins do?
They bind with other ions and larger molecules such as glucose and amino acids and change shape to transport them to the other side of the membrane
What does cholesterol do?
-restricts the lateral movement of other molecules in the membrane
-controls fluidity and permeability of the membrane
-prevents water and dissolved ions from leaking out of the cell
what factors affect membrane structure and permeability? (temperature)
-temperature-high temperatures increase the kinetic energy of the phospholipids so that they move even more. This increases the fluidity of the membrane, increasing the permeability and the structure can start to break. It makes it easier for particles to move across the membrane
-it also denatures the carrier and channel proteins in the membrane
What factors affect membrane structure and permeability?(solvents)
Organic solvents such as alcohol can dissolve the phospholipid bilayer in membranes. This damage causes the fluidity of the membrane to increase and become more permeable
Simple diffusion
-the net movement of molecules from an area of higher concentration to an area of lower concentration until equilibrium is reached.
-process does not require ATP
-for molecules to diffuse across the membrane, they have to be lipid soluble and small
Facilitated diffusion
- a passive process, down the concentration gradient, through proteins
-movement of ions and polar molecules, which cannot simply diffuse, can be transported across the membranes by facilitated diffusion using protein channels and carrier proteins
Osmosis
-the movement of water from an area of higher water potential to an area of lower water potential(more negative) across a partially permeable membrane
What is a hypotonic solution?
-when the water potential of a solution is more positive(closer to zero) than the cell
-cell could eventually swell or burst