factors affecting membrane structure Flashcards
what do membranes do
they control the passage of different substances into and out of cells
what happens if membranes lose their structure
they lose control of this and cell processes will be disrupted
what are the factors affecting membrane structure
temperature
the presence of solvents
why do some organisms temperature vary with their environment
many organisms do not generate heat to maintain their body temperature so their temeprature varies with their environment
what does increasing the temperature do to the lipids in the membrane
it gives all molecules more kinetic energy and these molecules move faster. this makes a membrane more fluid and it begins to lose its structure and creates gaps in the membrane. if temperature continues to increase the cell will eventually break down completely. this will therefore increase the permeability of the membrane making it easier for particles to cross it.
why is the permeability of the membrane affected by increasing temperature
at higher temperatures, carrier and channel proteins will be denatured which are involved in transport across the membrane.
what else do higher temperatures do to the membrane structure
they affect the way membrane embedded proteins are positioned and functioned. if some of the proteins that are enzymes in mmebranes drift sideways it could affect the reactions they catalyse.
it could increase fluidity which affect the infolding of the plasma membrane during phagocytosis and change the ability of cells to signal to other cells by releasing chemicals by exocytosis.
what does the presence of cholesterol do
it buffers the effects of increasing heat as it reduces the increase in membrane fluidity
what does changing temperature do to the phospholipids of the membrane
it alters their movement but doesnt drastically change their integral molecular structure.but proteins arent as stable as lipids.
what is different about the proteins in the membrane compared to the lipids
proteins arent as stable as lipids
what does high temperatures do to the proteins in the membrane
high temperatures cause the atoms within their large molecules to vibrate and this breaks the hydrogen bonds and ionic bonds that hold their structure together - they unfold. the tertiary structure changes and cant change back when they are cool (denatured)
what is under the plasma membrane
cytoskeleton threads made up of proteins. if both the membrane embedded proteins and the cytoskeleton threads become denatured, the plasma membrane will form apart. it will become more permeable as holes appear in it.
what happens if membrane embedded enzymes are denatured
they stop functioning as the shape of the active site of the enzymes change shape and this slows the rate of reaction
what is essential in forming the phospholipid bilayer and why
water is essential in forming the phospholipid bilayer because the hydrophobic (non polar) tails are orientated away from the water forming a bilayer with a hydrophobic core. the charged (hydrophillic) heads interact with water helping to keep the bilayer intact.
what do organic solvents do to the membrane
they dissolve in the membrane as they are less polar than water or even non polar. this disrupts cells.
