Cell Membrane Flashcards
Lessons 1 + 2
What is the purpose of the cell membrane?
Controls the movement of ions in and out the cell.
How does the membrane provide protection to the cell?
Provides attachment sites.
What does cholesterol do to the membrane?
Cholesterol controls the fluidity of themembrane.
How does low temperatures affect the fluidity of a membrane?
At low temperatures, the membrane has less kinetic energy so there is less movement of phospholipids and it is more tightly packed.
What sort of hydrocarbons allow for the tight packing of the membrane?
Saturated hydrocarbons - they only contain signle
How does high temperatures affect the fluidity of a membrane?
At high temperatures, the membrane has more kinetic energy so there is more movement and the membrane to be less tightly packed.
What sort of hydrocarbons allow for the less tightly packed membrane?
Unsaturated hydrocarbons - contain double bonds which causes the molecule to branch out so takes up more space and can’t be forced together.
What happens to the membrane at different temperatures when cholesterol is present?
At high temperatures, cholesterol causes the membrane to be more tightly packed and decreases fluidity.
At low temperatures, cholesterol causes the membrane to be less tightly packed and increases fluidity.
What is the structure and purpose of the nuclear envelope?
Formed from a lipid bilayer, regulates movement in and out of the cell,
What is the structure and purpose of the nuclear pores?
Complex of proteins that also control movement of substances in and out of the cell but is more selective.
What can move IN and what can move OUT the cell?
IN: Building blocks of RNA and DNA synthesis, ribosomal proteins, molecules providing energy.
OUT: Ribosomal subunits synthesised by the nucleolus.
What is the NLS and NES?
The NLS (nuclear localisation system) is an amino acid sequence that tags a protein for entry into the cell.
The NES (nuclear exiting system) is an amino acid sequence that tags a protein for exiting a cell.
What is the purpose of the golgi apparatus?
The golgi apparatus is a major site for carbohydrate synthesis. It also allows the modification and packing of proteins.
How does a vesicle move from the ER to the Golgi?
Vesicles bud off specialised exits off the ER with a COPII coat.
Incorrectly folded proteins remain in the ER.
COPII vesicles and coat shed and fuse vesicular tubular cluster.
Fuses with the cis-golgi.
KDEL receptors receive proteins back to the ER.
