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Lipids 3
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1Recap: Triacylglycerols
- made of 3 [blank_start]fatty[blank_end] acids esterfied ([blank_start]ester[blank_end] linked) to a [blank_start]glycerol[blank_end] molecule
- they are neutral molecules (contain [blank_start]no[blank_end] charged groups)
- sometimes called [blank_start]neutral[blank_end] lipids
- form in which lipid energy stores are deposited in [blank_start]adipose[blank_end] tissues of animals (as fats) and in seed of oilseed [blank_start]plants[blank_end] (as oils)
- fats and [blank_start]oils[blank_end] from different sources has a characteristic distribution of [blank_start]fatty[blank_end] acids- Afatty
- Bester
- Cglycerol
- Dneutral
- Eno
- Fadipose
- Gplants
- Hoils
- Ifatty
2Phospholipids can be split into 2 types
- [blank_start]phosphoacylglycerols[blank_end] also called phospholipids
- [blank_start]sphingolipids[blank_end]- Aphosphoacylglycerols
- Bsphingolipids
3Phosphoacylglycerol
- a.k.a. [blank_start]phospholipid[blank_end]
- 2 fatty acids [blank_start]ester[blank_end] linked to glycerol
- also contain a [blank_start]phosphate[blank_end] group and other specific groups
- the phosphate group replaces the fatty acid on C number 3 of a triacylglycerol molecule
The 3rd carbon is a [blank_start]phosphodiester[blank_end] linked to a phosphate and an 'x' group- Aphospholipid
- Bester
- Cphosphate
- Dphosphodiester
4X groups
- in phosphoacylglycerol on the 3rd carbon on glycerol a [blank_start]phosphate[blank_end] group and an X group is phosphodiester linked
X groups are very [blank_start]polar[blank_end] molecules and are often charged, examples to know include:
- [blank_start]ethanolamine[blank_end] (ethanol + charged amine group)
- [blank_start]serine[blank_end] (NCC, with methanol as side chain)
- [blank_start]choline[blank_end]
- inositol (has a [blank_start]ring[blank_end] structure; not charged)
When choline is part of phosphoacylglycerols it is called [blank_start]phosphatidyl[blank_end] choline
- this is the same format for all X groups
Phosphatidyl serine, phosphatidyl inositol- Aphosphate
- Bpolar
- Cethanolamine
- Dserine
- Echoline
- Fring
- Gphosphatidyl
5Characteristics of Phosphoacylglycerols ([blank_start]phospholipids[blank_end])
- They are [blank_start]amphipathic[blank_end] (amphiphiles) > the molecule has one polar end ([blank_start]head[blank_end]) and one non-polar end (tail)
- this property allows them to carry out their [blank_start]biological[blank_end] functions
- fatty acid (acyl groups) are really [blank_start]non[blank_end]-polar therefore hydrophobic and point away from the [blank_start]polar[blank_end] phosphate group
- the polar phosphate group and the non polar fatty acids point in opposite [blank_start]directions[blank_end]
- phosphate is [blank_start]negatively[blank_end] charged
In phosphoacylglycerols the X group and the phosphate group are as far away as possible from the fatty acid/[blank_start]acyl[blank_end] chains (hydrophobic)- Aphospholipids
- Bamphipathic
- Chead
- Dbiological
- Enon
- Fpolar
- Gdirections
- Hnegatively
- Iacyl
6Arrangement of Phosphoacylglycerols (phospholipids)
- [blank_start]amphipathic[blank_end] (amphiphiles) molecules spontaneously form a number of specific structures including:
- [blank_start]monolayers[blank_end] > hydrophilic heads point down towards the liquid and [blank_start]hydrophobic[blank_end] tails point up towards the air (at a liquid-air interface) e.g. [blank_start]oil[blank_end] sitting on top of water
- [blank_start]micelles[blank_end] > hydrophobic tails all point inwards in a sphere
- bilayer > 2 [blank_start]monolayers[blank_end] put together, aqueous solutions on either side, very [blank_start]non[blank_end]-polar in the centre of the bilayer- Aamphipathic
- Bmonolayers
- Chydrophobic
- Doil
- Emicelles
- Fmonolayers
- Gnon
7Biological Membranes
- The phosphoacylglycerol or phospholipid [blank_start]bilayer[blank_end] is the basis of the biological membrane structure
- [blank_start]polar[blank_end] heads interact with the solution around the outside (the solvent)
- [blank_start]non[blank_end]-polar tails exclude water
- 2 [blank_start]monolayers[blank_end] squished together with polar heads at either side with non-polar tails in the middle
NOTE: acylglycerols [blank_start]cannot[blank_end] form bilayers for they are not amphipathic; fatty acid soaps are [blank_start]amphipathic[blank_end] for ester salts have a polar and non-polar region- Abilayer
- Bpolar
- Cnon
- Dmonolayers
- Ecannot
- Famphipathic
8[blank_start]Sterols[blank_end] are also found in membranes due to their amphipathic nature
e.g. cholesterol and [blank_start]stigmasterol[blank_end]
- its not only phospholipids found in biological [blank_start]membranes[blank_end]
- cholesterol has [blank_start]polar[blank_end] and non-polar regions (amphipathic) > polar regions interact with [blank_start]hydrophilic[blank_end] (water loving) heads and non-polar regions interact with [blank_start]hydrophobic[blank_end] (water hating) tails
- cholesterol is often found in [blank_start]animal[blank_end] membranes
- Stigmasterol is found in [blank_start]plant[blank_end] membranes and is also amphipathic- Astigmasterol
- BSterols
- Cmembranes
- Dpolar
- Ehydrophilic
- Fhydrophobic
- Ganimal
- Hplant
9Membrane Structure cont.
- membranes can also have [blank_start]carbohydrates[blank_end] associated with them
- membrane structure is [blank_start]not[blank_end] rigid > fluid [blank_start]mosaic[blank_end] structure
- proteins and carbohydrates can move within the [blank_start]plane[blank_end] of the membrane
[blank_start]integral[blank_end] proteins = proteins which span the membrane, may be made of multiple trans membrane segments or partly immersed in lipid layer
[blank_start]peripheral[blank_end] proteins = are loosely attached: [blank_start]electrostatic[blank_end] interaction, bonding to integral protein, hydrophobic anchor, bonding to phosphoacylglycerols via carbohydrate chain BUT normally electrostatic interactions or [blank_start]hydrogen[blank_end] bonding between polar heads but overall [blank_start]loosely[blank_end] attached- Anot
- Bcarbohydrates
- Cmosaic
- Dplane
- Eintegral
- Fperipheral
- Gloosely
- Helectrostatic
- Ihydrogen
10Why do we have proteins and carbohydrates in the membrane?
- cell [blank_start]recognition[blank_end] > to recognise specific cells
- extracellular [blank_start]enzyme[blank_end] activities; for reactions
- transport of compounds across the [blank_start]membrane[blank_end]- Arecognition
- Benzyme
- Cmembrane
11There are 3 types of diffusion of compounds across a membrane
- [blank_start]diffusion[blank_end]
- [blank_start]passive[blank_end] transport (facilitated diffusion)
- [blank_start]active[blank_end] transport- Adiffusion
- Bpassive
- Cactive
12[blank_start]Diffusion[blank_end] = the [blank_start]net[blank_end] movement of molecules in the direction of lower concentration
- solute passes across membrane from an area of higher concentration to an area of [blank_start]lower[blank_end] concentration
- driven by a [blank_start]concentration[blank_end] gradient
- [blank_start]small[blank_end] polar molecules diffuse through small gaps in the hydrophobic environment (the [blank_start]acyl[blank_end]/fattyacid chains)
- large [blank_start]polar[blank_end] molecules cannot (particularly if charged) diffuse
- uncharged, [blank_start]lipophilic[blank_end] (lipid loving) molecules can diffuse readily- ADiffusion
- Bnet
- Clower
- Dconcentration
- Esmall
- Facyl
- Gpolar
- Hlipophilic
13Passive transport a.k.a [blank_start]facilitated[blank_end] diffusion
- depends on the presence of specific [blank_start]proteins[blank_end] which transport the molecule from one side of the membrane to the other
- still requires [blank_start]no[blank_end] energy
- driven by the concentration [blank_start]gradient[blank_end]: moves from high --> low
- moves until an [blank_start]equilibrium[blank_end] is reached
- The [blank_start]activation[blank_end] energy is very high for diffusion of hydrophilic molecule through a bilayer > doesn't happen readily
- the activation [blank_start]energy[blank_end] of this diffusion of a hydrophilic molecule through the bilayer is lowered through the use of a transported [blank_start]protein[blank_end]- Afacilitated
- Bproteins
- Cno
- Dgradient
- Eequilibrium
- Factivation
- Genergy
- Hprotein
14Transporter proteins in facilitated diffusion/passive transport
- transporter proteins [blank_start]lower[blank_end] the activation energy of diffusion of hydrophilic molecules through the membrane
- transporter proteins make non-[blank_start]covalent[blank_end] interactions that replace [blank_start]hydrogen[blank_end] bonding, allowing molecules to pass through the bilayer
- large polar charged molecules are very hydrated (lots of hydrogen bonds with [blank_start]water[blank_end]) > we need to strip this hydration [blank_start]shell[blank_end] but this normally requires a lot of energy = high activation energy
- but transporter proteins lower this [blank_start]activation[blank_end] energy- Alower
- Bcovalent
- Chydrogen
- Dwater
- Eshell
- Factivation
15[blank_start]Active[blank_end] Transport
- also depends on the presence of specific transport [blank_start]proteins[blank_end]
- transport requires [blank_start]energy[blank_end]
- can be [blank_start]against[blank_end] a concentration gradient- AActive
- Bproteins
- Cenergy
- Dagainst
16[blank_start]Primary[blank_end] Active Transport e.g. sodium-[blank_start]potassium[blank_end] pumps in animal cells
- the cell wants high [blank_start]potassium[blank_end] concentration inside the cell and low [blank_start]sodium[blank_end]
- outside the cell is high sodium and low potassium
- so you would expect the ions to diffuse down their concentration [blank_start]gradient[blank_end] therefore increase sodium inside and decreasing potassium
- however a protein called the [blank_start]sodium[blank_end]-potassium pump keeps the ion gradients intact
- the ions are [blank_start]actively[blank_end] pumped [blank_start]against[blank_end] their concentration gradient
- primary active transport involves the direct [blank_start]hydrolysis[blank_end] of ATP which provides the [blank_start]energy[blank_end] required for the transport
1. [blank_start]3[blank_end] sodium ions and 1 [blank_start]ATP[blank_end] bind to the pump > ATP phosphorylates the pump and causes it to change [blank_start]shape[blank_end] and deliver the sodium ions to the outside
2. at the same time ion binding sites open up on the extracellular face of the pump and picks up 2 [blank_start]potassium[blank_end] ions
3. as potassium binds the pump releases its inorganic [blank_start]phosphate[blank_end] > the release causes the pump to change [blank_start]shape[blank_end] and deliver the potassium ions to the inside of the cell- APrimary
- Bpotassium
- Cpotassium
- Dsodium
- Egradient
- Fsodium
- Gactively
- Hagainst
- Ihydrolysis
- Jenergy
- K3
- LATP
- Mshape
- Npotassium
- Ophosphate
- Pshape
17[blank_start]Secondary[blank_end] active transport
- a substance such a glucose is pumped from a region of lower concentration to a region of [blank_start]higher[blank_end] concentration
- requires [blank_start]energy[blank_end]
- but energy does not come [blank_start]directly[blank_end] from ATP
- it comes from the energy stored in a sodium ion [blank_start]gradient[blank_end] (which was initially created by ATP)
- because ATP does not fuel the pump directly this process is called [blank_start]secondary[blank_end] active transport
- to pump glucose [blank_start]against[blank_end] its concentration gradient, the pump takes up both [blank_start]sodium[blank_end] and glucose from the outside of the cell and then changes [blank_start]shape[blank_end], depositing both inside the cell
a pump that transports 2 substances in the same direction is called a [blank_start]symport[blank_end] protein
- the sodium ions that enter the cell are later returned to the outside by the sodium-[blank_start]potassium[blank_end] pump- ASecondary
- Bhigher
- Cenergy
- Ddirectly
- Egradient
- Fsecondary
- Gagainst
- Hsodium
- Ishape
- Jsymport
- Kpotassium
18[blank_start]Osmosis[blank_end] = the process by a which a solvent passes across a semi-[blank_start]permeable[blank_end] membrane from a solution with a low osmotic pressure to one which a [blank_start]high[blank_end] osmotic pressure
- a semi-permeable membrane is one that allows the passage of [blank_start]solvent[blank_end] but not solute- AOsmosis
- Bpermeable
- Chigh
- Dsolvent
19Tonicity
- biological membranes are [blank_start]selectively[blank_end] permeable not semi-permeable
- allow free passage of [blank_start]solvents[blank_end] and some solutes but not all
- [blank_start]tonicity[blank_end] = due to the osmotic pressure exerted only by the solutes which [blank_start]cannot[blank_end] pass across the selectively permeable membranes
- the state of a solution in respect to [blank_start]osmotic[blank_end] pressure- Aselectively
- Bsolvents
- Ctonicity
- Dcannot
- Eosmotic
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- Biochemistry Quiz on Lipids 3, created by sophie waddington on 03/05/2018.
- Author
- sophie waddington
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- English
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