Lipids & Biomembranes Flashcards
3 biological functions of lipids
- energy storage
- structural
- signalling
Energy storage
- fatty acids = carboxylic acids + hydrocarbon chains
- primary energy storage molecule
- usually an even number of carbons
Types of fatty acids:
Saturated = all single bonds Unsaturated = some double bonds Monosaturated = 1 double bond only Polyunsaturated = multiple double bonds
Nomeclature of Fatty Acids
- specify length followed by number of bonds seperated by colon
e. g. 18 carbons with 2 double bonds = 18:2 - carbons numbred from carboxyl end (COOH)
- triangle denotes double bond
Essential Fatty Acids
- essential but cannot be produced in body as we lack the ezyme required
e. g. omega-3 & omega-6 - must be obtained via: cold water fatty fish, nuts, seeds, plant oils
Storage Lipids: Tricylaglyserols (TAGs)
- glycerol esterified with 3 fatty acid chains
- energy storage molecules (oxidation of fatty acids produces ATP, TAGs are stored in adipocytes)
- important for heat insulation
- non polar
Saturated TAGs
- straight tails
- can pakc tightly
- hard fats e.g. butter
- unhealthy
- fat tails are in cis configuration
Unsaturated TAGs
- tails have kinks
- cannot pack tightly
- liquid at room temp
- healthier than saturated fats
Trans Fats
- isomer of cis configuration
- not common in nature
- better for food prep due to longer shelf life
- more resistance to high temps
- solid at room temp
- can b made by hydrogenation of natural unsaturated fats
- not healthy, increases risk of cardiovascular disease
Waxes
- long chain of saturated fatty acids combines with long chain alcohol linked via ester bonds
- hydrophobic
- high melting point
used in pharmeceuticals/cosmetics
Three Types of Structural Lipids:
- Glycerophospholipids (aka phospholipids)
- Sphingolipids
- Sterols
Glycolipids - type of phopholipid or sphingolipid
Glycerophospholipid (aka phospholipid)
- most abundant in cell membranes
- amphipathic
- structure: (glycerol backbone, phosphate head, 2 fatty acid tails)
- form bilayers
- head dictates class of phospholipid
- fatty acid tails modulate fluidity depending on length and whether saurated/unsaturated
Sphingolipids:
- structure: polar head, 2 hydrophobic tails. (no glycerol)
- linked by phosphodiester or glycosidic bonds
- amphipathic
- polar head defines class of sphingolipid
Glycolipids:
- not a type on its own - is a type of phospholipid or sphingolipid
- occurs when phospho or sphingo are glycosylated (sugar group attached to head)
- found in outer face of plasma membrane
- roles in cell reprogramming
Sterols:
e. g. most common: cholesterol
- structure: 4 fused rings, hydrocarbon side chain, hydroxyl group
- integral to biological membrane (rigidity, impermeability, integrity)
- seen in steroid hormones & bile acids
Biological Membranes - Structure: Polarity
structural lipid are insoluble in water but amphipathic:
- hydophobic group inside away from water
- hydrophilic groups woutside exposed to water
Biological Membranes - Function:
- exclusion of toxins and ions
- energy transduction
- cell movement
- interaction with other cells
- nutrient accumulation
Biological Membrane - Structure: 3 Sections
- fluid mosiac model: coponents move laterally around membrane
- lipid content: neg charged lipid on intracellular side of membrane
- protein component embedded into bilayer: hydrophobic portions in bilayer; hydrophillic protions sit intra/extracellularly
Biological membrane - Structure: Membrane Proteins
- integral proteins
- peripheral proteins
- lipid anchored proteins
Signalling Lipids:
- phospholipids that sit inner face act as eserve of messenger molecules
- these are releases iin repinse to extracellular signals e.g. chemical signal,
- hormones can act as extracellular messengers
Lipids:
- heterogenous class of organic compounds
- classified based on water solubility
- amphipahic
Examples of Open Chain Forms of Lipids
fatty acids, glycolipid, vitamins
Examples of Cyclic Forms of Lipids
cholesterol, steroid hormones, bile acids
