membrane structure Flashcards
(27 cards)
why is the accept model of membrane structure termed ‘fluid - mosaic’
as it is a flexible structure with components that can move around within the membrane which gives it a fluid like quality
what does hydrophilic mean
water loving - so the molecule is attracted to water
what does the term hydrophobic mean
water hating - so the molecule repels water
what is an intrinsic protein
proteins that go through the membrane
what is the function of intrinsic proteins
their function is transport
examples of some intrinsic proteins
channel and carrier proteins which take part in facilitated diffusion
what regions do intrinsic proteins have
non polar and polar so hydrophobic and hydrophilic regions
what is an extrinsic protein
proteins that don’t go through the membrane they are found on the surface of the bilayer
what is the function of extrinsic proteins
they provide structural support and form recognition sites
how are extrinsic proteins recognition sites
as they identify cells and receptors sites for hormone attachment
what determines the position of a protein in the membrane
by its structure and whether is has hydrophilic or hydrophobic regions
what is a glycolipid
are lipids which combine with a polysaccharide
where are glycolipids found and what are there functions
they are found in the outer layer of the membrane and are involved in cell to cell recognition
what is a glycoprotein
its a protein combined with a polysaccharide
where are glycoproteins found and what are there functions
they are found on the outer layer of the membrane and they have a role in cell to cell recognition and signalling and cell adhesion
what is the collective name for glycolipids and glycoproteins on the outer source e of a membrane
the glycocalyx
how can a carrier protein transport a a molecule against a concentration gradient
a carrier protein can transport a molecule against a concentration gradient by active transport which requires energy
what is the width of the membrane
between 6-8 nm
describe and explain how glucose which is a water soluble molecule can pass through the bilayer
As glucose is water soluble it can’t pass through the phospholipid bilayer therefore it uses carrier proteins and diffuses by facilitated diffusion
describe and explain how Vitamin A which is a lipid soluble molecule can pass through the bilayer
It can pass directly through the bilayer through the phospholipid layer by diffusion
When beetroot discs are cut with a borer and immersed in a solution of ethanol at 15°C, the red pigment begins to leak out of the cells into the ethanol turning it red - why does the the leakage of pigment occur
as ethanol dissolves phospholipids as they contain lipids which creates gaps in the pores membrane leading to the leakage of pigment
When the experiment (beetroot) was repeated again at 30°C instead of 15°C, the time taken for the ethanol to turn red decreased. - explain why
as the increased temperature increases the kinetic energy of the membrane molecules which increase the rate of diffusion of dye across the membrane
how does the solubility in lipids affect the rate of diffusion through a membrane and why
when lipid solubility increases the rate of diffusion also increases as lipid soluble substances can diffuse through the membrane more easily that water soluble substance
name 3 factors that affect the rate of facilitated diffusion of a substance through a membrane
- concentration
-how large the surface is
-temperature
