biological membranes Flashcards
explain why facilitated diffusion requires no metabolic energy?
particles have their own kinetic energy and are able to move by themselves
moves down a concentration gradient
explain why glucose cannot pass through cell membrane by simple diffusion
large molecule
phospholipid bilayer acts as a barrier
outline the role of membranes within cells
compartmentalisation
attachment sites for enzymes
site of chemical reactions e.g the ETC
cell signalling
explain the role of the membrane in the rough endoplasmic reticulum
compartmentalisation
separates ribosomes from the cytoplasm
suggest and explain how low pH might cause the red pigment to leak out of beetroot cells
denatures tertiary structure of proteins
membrane permeability increases
explain why steroid hormones like progesterone are able to pass through membranes
fat soluble
dissolves in phospholipid bilayer
what molecules can pass through plasma membranes
water
oxygen
carbon dioxide
state how the structure of the cell surface membrane allows potassium ions to enter or leave the cell
channel proteins
how does the fluid mosaic model describe the structure of the plasma membrane
phospholipid bilayer
proteins free to move
proteins scattered through membrane
explain how the structure of phospholipid molecules allow for the formation of plasma membranes
phosphate head is hydrophillic
heads face the water
fatty acid tails are hydrophobic
face away from water
describe the structure of the RER
phospholipid bilayer
flattened sacs
covered with ribosomes
explain how the Casparian strip prevents ions from reaching the xylem by the apoplast pathway
forces them to go through the plasma membrane
phospholipid bilayer repels charged ions
Why can’t Na+ and K+ simply diffuse through the membrane
Polar
Hydrophilic
Charged
Insoluble
