Membranes Flashcards
What molecules make up phospholipids?
glycerol and fatty acids
The glycerol forms an ester link with 2 fatty acids. the 3rd C is bonded to choline(hydrophilic) through a phosphate linkage.
what does Amphipathic mean?
Both hydrophilic and hydrophobic
what do membranes do? (4)
- compartmentalise metabolic activities
- separate and protect cell components
- provide a “scaffold” for signaling
- medium for cell energy generation
when does a membrane voltage occur?
- when immobile charges are not balanced
2. when charge transport is not fully balanced
how can cell voltages be measured. Both internal and external
voltages across membranes can be measured using microelectrodes.
internal voltages can be measured using voltage sensitive dyes.
How are membranes maintained?
Protein synthesis occurs in ribosomes on the ER
Vesicle trafficed through Golgi appuratus
Shell joins membrane through exocytosis and the protein is released out the membrane. The old membrane buds off during endocytosis.
What is Exocytosis and Endocytosis?
Exocytosis- form of active transport. Cell transports molecule out of the cell. Vesicle molecule is transported in is incorporanted into the membrane.
Endocytosis- when substances are brought into the cell. Material is surrounded by part of the plasma membrane to form a vesicle.
Describe the structure and function of the ER
Made of tube-like sacs (cisternae). Highly mobile and space interconnected.
Rough- protein synthesis as it has ribosomes
Smooth- lipid synthesis
Describe the structure and function of the Golgi Appuratus.
Packs proteins into membrane bound vesicles so they can be sent to their destination.
Made up of a collection of fused, flattened, membrane enclosed disks (cisternae)
Plants have smaller and more than animals.
How do chloroplasts communicate?
using Stromules (extensions of membrane)
Do transport proteins have a hydrophilic or hydrophobic region towards the inside of the phospholipid bilayer?
Hydrophilic
The inside of the bilayer is hydrophobic
what is the name given to the net driving force for the movement of a molecule resulting in the combination of the chemical and electrical gradient?
The electrochemical gradient
What does the Nernst Equation describe?
allows the comparison of the concentration gradient and voltage differences
Name and describe the 2 types of passive transport proteins
Channels- provide aqueous pores for ion passage. Are selective or gated (need stimuli). Can be examined using a patch clamp.
Carrier- undergo conformational change that exposes ion binding sites to different sides of membrane
Which active transport protein type establishes electrochemical gradients?
Pumps
