Membranes and Transport Flashcards
(40 cards)
What is the Role of Membranes?
Compartmentalisation (the formations of separate area), transport, cell to cell signaling, site of chemical reactions and environment
Explain meaning of “Fluid mosaic” model
Fluid - Phospholipid create a viscous layer which is free to move
Mosaic - Proteins with varying size, shape and position were distributed throughout like tiles of a mosaic
What are phospholipids mainly made of?
Hydrophilic head - phosphate group, phosphoester bond
Hydrophobic tail - glycerol, Ester bond, fatty acid tail
What are some structural properties of the phospholipid bilayer?
- Allows membrane fluidity/flexibility
- fluidity allows for breaking/remaking of membrane (exocytosis/ endocytosis)
- Has hydrophobic/ hydrophilic layers that restrict entry and exit of substances
How thick is a membrane on average?
7.5nm
What is the role of Cholesterol in animal membranes?
Stability/ flexibility (Mechanical stability)
What is active transport
Movement of molecules or ions into or out of a cell from a region of lower concentration to a region of higher concentration. Also requires energy
What is Osmosis
The diffusion of water across a partially permeable membrane
What I’d Diffusion
It is the Net movement of particles from a region of higher concentration to a region of lower concentration. Also rellies on energy by particles
What is Facilitated diffusion
Movement down a gradient across a membrane through protein channels
What is bulk transport
(Endocytosis)
Active movement of large molecules
Also requires energy
What is Ficks law?
Surface area x gradient
———————————
Membrane thickness
What are the small hydrophobic molecules that can pass through the phospholipid bilayer freely?
O2, Co2, N2, Benzene
What are the small uncharged polar molecules that can diffuse through the phospholipid bilayer?
H20, glycerol, ethanol
What are the ions that cannot pass through the phospholipid bilayer easily?
H+, Na+, HCO3, K+, Ca2+
What are the larger uncharged polar molecules that cannot pass through the phospholipid bilayer freely?
Amino acids, glucose, nucleotides
What two types of proteins does facilitated diffusion use?
Channel proteins
Carrier proteins
What’s the difference between integral proteins and peripheral proteins?
Integral - permanent
Peripheral - temporary
What are some examples of integral proteins?
Channel and Carrier
What is the structure of a channel protein?
- Hydrophobic R group - Non-polar amino acid outside of protein associate directly with the lipid bilayer
- Hydrophilic R groups - Polar amino acids are located internally and face aqueous solution
What’s the roles of intrinsic carrier proteins?
- Passive and active transport
- Active transport often includes a change in shape
What’s the roles of intrinsic channel proteins?
- hydrophilic channel
- passive movement (diffusion) of polar molecules and ions
What’s the roles of intrinsic glycoproteins?
- Recognition site
- Chemical ell signalling ( e.g Neurotransmitters)
- Cell adhesion
- Embedded proteins with attached carbohydrate chains
What’s the roles of extrinsic proteins?
- Hydrophilic groups on outer surfaces to interact with polar heads of phospholipids
- serve as receptors
