BIOL10004 Lecture Notes - Lecture 6: Membrane Transport, Biological Membrane, Monounsaturated Fat
14 Jun 2018
School
Department
Course
Professor
BIOL – Lecture 6
Biological membranes and transport
Lipids
• insoluble in water - hydrophobic
• dissolve readily in organic solvents
• composed mainly of C, H & O
• differ from carbs due to a smaller proportion of oxygen
• may contain other elements
o e.g. phosphorus and nitrogen
common lipids
• long chain of hydrocarbons with a carboxylic acid
• long chain fatty acids can be saturated or unsaturated
o single-bonds between carbon atoms - saturated
o when there is a double bond between some carbon atoms, creating a kink –
unsaturated
▪ monounsaturated – one double bond
▪ polyunsaturated – more than one double bond in the chain
membrane lipids – phospholipids
• amphipathic
find more resources at oneclass.com
find more resources at oneclass.com
• often form closed vesicles in water
o amphipathic nature allows membranes to form when mixed with water
o micelle – singular layer of phospholipid form a vesicle where heads face
water and tails face inwards where it can squeeze out all the water
o large bilayered vesicle – inside and outside is water
• biological membranes are comprised of phospholipid bilayers
o proteins with carbohydrates are on the outside of the cell – presented
outside, not inside → membrane is therefore asymmetric
o 50% of plasma membrane is protein
roles of biological membrane proteins and glycoproteins
• enzymatically active
• surface receptor sites for stimuli
o can pick up if there is a particular substance outside the cell that they want to
take in
• cell identity markers – determinants of individuality
o transmembrane and integral proteins, particularly glycoproteins
• cell adhesion and cytoskeletal attachment sites
o to bring two neighbouring cells together
o cytoskeleton can be wound along the whole inside of the cell and attached to
the membrane
• transport – moving molecules across the bilayer
o transmembrane proteins
▪ these and integral proteins are deeply embedded, while peripheral
proteins can easily be washed away
o small and lipid-soluble molecules can cross easily
cell membranes as selectively permeable
depending on type, molecules may cross the membrane via:
1. diffusion (including osmosis)
2. facilitated diffusion
3. active
transport
4. endocytosis
find more resources at oneclass.com
find more resources at oneclass.com
