Structure and Role of Lipids Flashcards
What is a lipid
Heterogeneous group of water insoluble (immiscible) molecules that are soluble in non polar solvents
Which lipids are the major source of energy
TAG
Which lipids are involved in cell signaling
DAGs
What are fatty acids
Amphipathic long chain hydrocarbons with a carboxylic acid head group
How are fatty acids classified
Based of number of C atoms and whether the FA is saturated
What are cis-conformation fatty acids
Fatty acids with functional groups on same side resulting a a kink
What are trans conformation fatty acids
Fatty acids with functional groups on opposite sides resulting in a linear fatty acid
What is the alpha carbon
The first one next to a functional groups
How are free fatty acids transported in blood
Non-esterified form conjugated to albumin
How long are short chain fatty acids
2-6 carbons
How long are medium chain fatty acids
6-12 carbonss
How long are long chain fatty acids
12-21 carbons
How long are very long chain fatty acids
21+ carbons
What are essential fatty acids
Fatty acids that we are unable to synthesise effectively and have multiple unsaturated C=C bonds
What are the two key essential fatty acids
w-3 fatty acid/ alpha linolenic (18:3)
w-6 fatty acids/ linoleic acid (18:2)
What are the functions of the essential fatty acids
Precursors for many biomolecules and for membrane stability (eicosanoid and endocannabinoids/ signalling molecules)
What are glycerolipids
Lipids with a glycerol backbone esterified to 1,2 or 3 fatty acids (MAG, DAG, TAG)
What are glycerophospholipids
Polar, amphipathic compounds based on DAGS with a charged head group (phosphate) which can be linked to other functional groups
What causes glycerophospholipid derivatives
Large range of head groups attached to phosphate so have distinct biological properties
What are sphingophosphlipids
Phospholipids where the backbone is the amino alchemical sphingosine and has a long chain hydrophobic chain complexed to a FA by an amide linkage to produced ceramide, the ceramide is the esterified to a choline head group (phosphocholine) (to produce Sphingomyelin)
What are glycoshingolipids
Have a ceramide backbone but no phosphate linkage e.g. cerebrosides and gangliosides
How are triacylglycerols produced
Addition do new acyl group to DAG by diglyceride acyltransferase (DGAT)
Where is the major store for triacylglycerols
Cytoplasm of white adipose tissue
How much energy do triacylglycerols yield
6x more than equivalent masses of protein ans carbohydrates
How long can triacylglycerols be stored
Weeks (long term)
What are the two types of fat stores
White and brown adipose tissue
How is TAGS stored in white adipose tissue
Fat stored as a single droplet (energy store)
How is TAGs stored in brown adipose tissue
Fat stored as multiple droplets with more mitochondria for body temp maintenance
What are sterols/steriods
Biologically active compounds with four rings arranged in a specific molecular configuration
What is the function of sterols/steriods
Component of cell membrane to alter fluidity
Signalling molecules
What are examples of steroids
Cholesterol, testosterone, dexamethasone
Which fat soluble vitamins are involved in cell signaling
A and D
Which lipids are components of cell membranes
Phospholipids/ glycerophospholipids, sterols, sphingolipids
Which lipids are involved in cell signaling
Sterols, DAG, phosphatidylcholine (glycerophospholipid derivative)
What are the function of lipids in cell membranes
Separation of different fluid compartments (e.g. organelles)
Selective transport
Signal transduction
What % of membranes are lipids
40-60%
How is the packing of lipids in cell membrane affected by amount of unsaturation
Double bonds cause more kinks push lipids apart making the membrane looser and more fluid (Liquid disordered/ ld)
Fewer double bonds so less kinks and less fluid or liquid ordered /lo
What are lipid rafts
The liquid ordered regions of membrane that are involved in endocytosis, cell polarity and cell signalling transduction
What % of membrane lipid is cholesterol
30%
What is the function of cholesterol in membranes
Packs in between lipids to improve packing and contribute to stability of membrane by regulating fluidity through degree of packing
Why do animal cells not have cell walls
Cholesterol maintains integrity of membrane with flexibility
Which part of membranes are cholesterol rich
Lipid rafts
