The plasma membrane Flashcards
Which parts of phospholipids are Hydrophilic and hydrophobic?
- head = hydrophilic (polar)
* tail = hydrophobic (non-polar)
How are phospholipids organised?
They organise themselves to keep their hydrophilic “heads wet” and hydrophobic “tails dry”
What is the Fluid mosaic model?
- a two-dimensional liquid. Restricts the lateral diffusion of membrane components
- regions within the membrane that contain lipid rafts, proteins, and glycoproteins
What does the basic structure of a membrane consist of?
- phospholipids (75%): MAIN COMPONENT
- cholesterol (20%): attached between phospholipids and between layers
- polar glycolipids in the external layer (5%)
What is Cholesterol?
Cholesterol is a steroid lipid. It is a useful structural lipid for membranes, lipid rafts.
What does membrane fluidity enable?
It allows the movement of membrane components which are required for cell movement, growth, division section and the formation of cellular junctions
What is a glycolipid?
- a lipid covalently attached to an oligosaccharide
~ forms part of cell membrane and glycocalyx
How is the glycocalyx formed?
- from glycoproteins (a membrane protein) containing associated oligossacharides
What is the function of the phospholipid bilayer?
To regulate what enters and exits the cell, altering PH and charge. Involved in cell recognition as well as playing a big role in cell signalling (e.g through hormones)
Explain membrane permeability
The cell membrane is selectively permeable.
- lipid bilayer is permeable to non-polar molecules and hormones
(slightly permeable to small uncharged polar molecules like water)
- it is impermeable to ions and large molecules
What allows cells to build concentration gradients?
- The selective permeability
What are the types of membrane transport?
- Passive transport: e.g diffusion
- Active transport: e.g primary&secondary
- Vesicular: e.g endocytosis
What are the types of facilitated transport?
- Channel mediated
- Carrier mediated
How does facilitated diffusion allow regulation?
Selective permeability can be regulated to maintain homeostasis. E.g insulin’s hormone through its receptor up-regulates glucose transporters
What is osmosis?
Osmosis is the diffusion of water through a semi-permeable membrane.
~ diffusion through the lipid bilayer occurs through transmembrane protein channels called aquaporins
Active transport involves the expenditure of energy from….
hydrolysis of ATP
What is Active transport used for?
Used to transport essential ions against their concentration gradient (helps maintain tonicity, volume and charge)
Compare the two types of active transport
- primary active transport uses energy from the hydrolysis of ATP where as secondary active transport uses energy stored by an ionic concentration gradient
What is primary active transport?
Movement against a concentration gradient (mainly ions)
What is secondary active transport?
A transporter protein couples the movement of an ion down its electrochemical gradient (grace has been made by primary active transport) to uphill the movement of another molecule or ion
What is Symport and Antiport?
Symport is where molecules travel in the same direction and Antiport is where they go in opposite directions.
What is vesicular transport used for?
- Used for endocytosis and exocytosis
- Used for inter-organelle transport
~ endocytosis is classified into receptor mediated endocytosis, phagocytosis and pinocytosis
