Chapter 1- Cells- Membranes Flashcards
Draw structure of a phospholipid
Martha.
Draw and label the structure of membranes
Do it
(Explain how the hydrophilic and hydrophobic properties of phospholipids help to maintain structure of cell membrane)
-what is the structure of a phospholipid? And what is this called?
Consists of a polar head (hydrophilic) made from glycerol and phosphate and 2 non-polar fatty acid tails (hydrophobic)
2) called amphipathic
(Explain how the hydrophilic and hydrophobic properties of phospholipids help to maintain structure of cell membrane)
What does hydrophilic and hydrophobic mean?
Hydrophilic- substance is attracted to water
Hydrophobic- are not attracted to water
(Explain how the hydrophilic and hydrophobic properties of phospholipids help to maintain structure of cell membrane)
- fatty acid ‘tails’ don’t strongly attach one another membranes what does this allow?
Fluid or flexible which allowed animal cells to have variable shapes and also allows process of endocytosis
(Explain how the hydrophilic and hydrophobic properties of phospholipids help to maintain structure of cell membrane)
Why do phospholipids arrange in a double layer?
As when phospholipids are mixed with water the phosphate heads are attracted to the water but the tales are attracted to each other not the water
(Explain how the hydrophilic and hydrophobic properties of phospholipids help to maintain structure of cell membrane)
What is the primary function of membranes?
To form a barrier which ions and hydrophilic molecules cannot easily pass
What does cholesterol do in phospholipids?
1) Role in determining membrane fluidity which changes the temp
2) disrupts the regular packaging of the hydrocarbon tails of phospholipid molecules so prevents them from crystallising and behaving as a solid
3) restricts fluidity of membrane
4) reduces permeability to hydrophilic particles such as sodium ions and hydrogen ions
5) due to shape can help membranes curve to become concave which helps formation of vesicles during endocytosis
What does proteins create in phospholipids?
Creates extreme diversity in membrane function
Wha role does intergralproteins have in phospholipids?
Are hydrophobic and are embedded in the hydrocarbon chains in the centre of the membrane- many are transmembrane- they extend across the membrane, with hydrophilic parts projecting through regions
What does peripheral protein remain bound to in phospholipids?
Hydrophilic so remain on surface- some have a single hydrocarbon chain attached to them which is inserted into the membrane, anchoring the protein to the membrane surface
What are the 6 functions of membrane proteins?
1) hormone binding site (hormone receptor)
2) immobilised enzymes with the active site on the outside
3) cell adhesion to form tight junctions between groups of cells in tissues and organs
4) cell to cell communication
5) channels for passive transport to allow hydrophilic particles across by facilitated diffusion
6) pumps for active transport which use ATP to move particles across the membrane
What are the 2 transport mechanisms in regard to functions of membrane proteins?
Protein channels (facilitated) and protein pumps (active)
definition of diffusion
Net movement of particles from a high region concentration to a low concentration
Definition of osmosis
Net movement of water molecules across a semi-permeable mebrane from a high region of low solute concentration to a high concentration
Definition of simple diffusion
Small, non-polar molecules can freely diffuse across the membrane - passive diffusion across semi-permeable membrane
Definition of facilitied diffusion
Larger, polar substances (ions, macromolecules) can’t freely diffuse and require assistance of transport proteins (carrier proteins/channel proteins to help their movement)
Explain the role of protein pumps and ATP in active transport across membranes:
- what is active transport?
Is the passage of materials against conc. gradients (low–>high)
(Explain how the hydrophilic and hydrophobic properties of phospholipids help to maintain structure of cell membrane)
What does active transport require?
Requires use of protein pump which uses ATP energy to translocate the molecules against the gradient
(Explain how the hydrophilic and hydrophobic properties of phospholipids help to maintain structure of cell membrane)
What does hydrolysis of ATP causes?
A conformational change in the protein pump takes place using the energy from ATP resulting in forced movement of substances
(Explain how the hydrophilic and hydrophobic properties of phospholipids help to maintain structure of
Protein pumps are what for given molecules? Which allows them to?
Are specific for given molecules allowing them to regulate movement
(Explain how the hydrophilic and hydrophobic properties of phospholipids help to maintain structure of cell membrane)
Draw protein channel, Carrier protein and protein pump
Lallalal
(Explain how vesicles are used to transport materials with a cell between the ER, Golgi apparatus, plasma membrane)
-how does a polypeptide get to the ER?
There designed for secretion and contain an initial target sequence which directs the ribosome to the ER
(Explain how vesicles are used to transport materials with a cell between the ER, Golgi apparatus, plasma membrane)
What happens when polypeptide reaches ER?
Continues to be synthesised by ribosomes into lumen of ER, where signal sequence is removed from Nascent chain
