membrane transport ✅ Flashcards
In a phospholipid what is polar and non-polar
polar - phosphate head
non-polar - fatty acid tail
what do phospjolipds consist of
a molecule of glycerol two fatty acid tail and a phosphate group
What way do the hydrophobic tails face and head
inwards - tails
outwards - heads
why can large molecules not pass through the bilayer
because the hydrophobic region is tightly packed and has low permeability to larger molecules
why can polar molecules not pass through the lipid bilayer
polar molecules and ions through the hydrophobic tails because they have a hydrophilic nature which means they will not interact with hydrophobic fatty acids
tails
What is the function of the phospholipid bilayer
provides a barrier to the movement of substances in and out of the cell
3 factors of Integral proteins
• amphipathic
• embedded in phospholipids bilayer
• can be embedded across both /one layer of
What type of membrane proteins
integral
peripheral
3 factors of peripheral proteins
• hydrophilic
• attached either to surface of integral proteins
• inside or outside the cell
What are the 4 functions of membrane proteins
Transport
Receptors
Immobilised enzymes
Cell adhesion
What is the function of transport proteins
allow ions and polar molecules to travel across membrane
What are the two types of transport proteins
Channel and carrier
Explain channel proteins
these form holes/pores through which molecules can travel through
Explain carrier proteins
undergo conformationa change to transport substances across a membrane
Transport proteins
allow the cell to control which substances enter or leave
What are the receptors used for
binding of peptide hormones
the binding generates a signal that triggers a series of reactions inside the cell
What are immobilised enzymes
They are integral proteins with the active site exposed on the surface of the membrane
What happens in cell adhesion
allows cells to attach to neighbouring cells within a tissue
what is the purpose of glycoproteins in cell-to cell recognition
act as markers or antigens
In simple diffusion what way do the molecules move
down the conc gradient (high to low)
Example of simple diffusion in oxygen
oxygen diffuse into cells from capillaries
Example of simple diffusion in c02
carbon dioxide diffuses out of cells and into capillaries
What are the 3 factors that affect the way substances move across the membrane
- steepness of conc gradient
- temp
- surface area
Explain how the steepness in conc gradient affects the rate at which substances move across membrane
- the greater the diff in conc across a membrane , the higher the rate of diffusion
Explain how the temperature affects the rate at which substances move across membrane
the higher the temp the higher the rate of diffusion
(molecules have more kinetic energy move faster)
Explain how the surface area affects the rate at which substances move across membrane
the greater the surface area the higher rate of diffusion
What is the diffusion like in large molecules
they diffuse more slowly (require more energy to move )
what is the diffusion like in uncharged molecules
diffuses faster as they move directly across the phospholipid bilayer
explain the diffusion of non-polar
diffuse more quickly as they are soluble in non-polar phospholipid bilayer
Define osmosis
the diffusion of water molecules from a dilute solution (high water potential) to a more concentrated solution (low water potential) across a partially permeable membrane (down conc gradient )
what are aqua porins
channel proteins that allow water to pass through membranes more freely
Facilitated diffusion is used for substances that cannot pass through the phospholipid bilayer
large molecules
polar molecules
ions
what does facilitated diffusion involve
transport proteins
down a conc gradient
no energy required (passive )
explain the process of a carrier proteins
the substance to be transported attaches to a binding site causing a conformational change in the carrier protein
define active transport
the movement of molecules and ions across a cell membrane from a region of lower concentration to higher concentration (against )
what are the factors do active a transport
• against conc gradient
• requires energy from respiration
• requires carrier proteins
What is the role of ATP in action transport
ATp provides energy (produced during respiration) which allows carrier proteins to change shape
ATP hydrolysed to release energy
define selective permeability
the ability of the membrane to differentiate between different types of molecules only allowing some molecules through by blocking others
what is simple diffusion dependent on
size
hydrophilic/ hydrophobic nature of molecules
what are glycoproteins
cell membrane proteins that have a carbohydrate chain attached on the extra cellular side
What are glycolipids
lipids with carbohydrate chains attached
What are the functions of glycoproteins/lipds
• The carb chain enables them to act as receptor molecules which allows them to bind with substances at the cell surface
Why is the cell membrane described as “fluid”
the phospholipids and proteins can move around within their own layers
why are cell membranes described as mosaics
because the scattered pattern produced by the proteins within the bilayer looks like a mosaic (from above )
What does the fluid mosaic model involve
phospholipids
cholesterol
glycoproteins/lipds
integral and peripheral proteins
