11. Lipids Flashcards
How many carbon and C=C bonds does palmitic acid have?
16 C, 0 C=C
How many carbon and C=C bonds does oleic acid have?
18 C, 1 C=C
How are fatty acids metabolised after digestion?
- carbon backbone oxidised in acetyl-CoA
in the presence of oxaloacetate : acetyl-CoA combines with oxaloacetate to undergo TCA cycle to produce 3 NADH, 1 FADH2, 2 CO2, 1 ATP and regenerated as oxalacetate
in the absence of oxaloacetate (due to low carb diet etc): acetyl-CoA forms ketone bodies.
Oxaloacetate is synthesised from sugars. In a low carb diet / fasting –> oxaloacetate is consumed to form glucose via gluconeogenic pathway, unavailable for reaction with acetyl CoA
What are the names of 2 of the ketone bodies that can be formed in fatty acid metabolism?
acetoacetate, D-3-hydroxybutyrate
What is the main function of lipoproteins?
To transport cholesterol and triacylglycerols/triglycerides
What are the 6 types of lipoproteins, in ascending order of density?
- Chylomicrons
- Chylomicron remnants
- Very low density lipoproteins (VLDL)
- Intermediate-density lipoproteins (IDL)
- Low-density lipoproteins (LDL)
- High-density lipoproteins (HDL)
What do chylomicrons transport?
Triglycerides,cholesterol and other lipids (from the diet) away from the samll intestine
What do chylomicron remnants transport?
Carry cholesterol-rich residues to liver (for liver to absorb)
What do Very low density lipoproteins (VLDL) transport?
Exports excess triacylglycerols and cholesterol from liver into bloodstream.
- cholesterol + fatty acids from triacylglycerols / triglycerides combine and carried as cholesteryl esters
What do Intermediate-density lipoproteins (IDL) transport?
- Breaks down remnant cholesteryl esters into cholesterol and fatty acids
- fatty acids are uptaken by tissues (normal tissues)
What do Low-density lipoproteins (LDL) transport?
LDL carry cholesterol in bloodstream (bad cholesterol)
What do High-density lipoproteins (HDL) transport?
It packs up cholesterol released into the plasma and delivers to liver for excretion (good cholesterol)
Biological cell membranes have several functions. 2 of the functions are:
- Prevent molecules from leaking out of the cell
- Prevent unwanted molecules from diffusing in
This function is performed by which part of the cell membrane?
Lipid bilayer
Another function of biological cell membranes is that they contain transport systems to take up or remove molecules – selective permeability.
which part of the cell membrane performs this function?
Protein components which act as pumps/channels in cell
Although the biological cell membrane is mainly lipid and proteins, what do they contain also/
carbohydrates linked to lipid and proteins (glycolipid and glycoprotein)
Why might most unsaturated fatty acids in phospholipids be in the cis rather than the trans conformation?
Phospholipid bilayer – cell membrane
- Cis double bond introduces a kink that prevents packing of the fatty acid chains. Cis double bonds maintain fluidity of the cell membrane.
What are the components of phospholipids?
- Glycerol backbone
- 2 fatty acids bonded to glycerol backbone
- 1 phosphate attached to glycerol backbone
- 1 alcohol group bonded to phosphate group
Can refer to notes for better visualisation
Phospholipids are synthesised from diacylglercol (glycerol + 2 fatty acids) and phosphate-alcohol group. In this synthesis, either the diacylglucerol molecule or the alcohol group must be ____ by ____________________________
Activated, addition of phosphate group (phosphorylation)
Glycolipids are sugar-containing lipids, where sugar residues are always on the ____ side of the membrane
extracellular
What are glycolipids made of ?
- Sphingosine backbone
- 1/2 fatty acid groups
- 1 sugar group
What is the name of the simplest glycolipid?
Cereboside
- 1 sphingosine, 1 fatty acid, 1 sugar
A sphingosine molecule is made of ___ and __
amino acid, alcohol (amino-alcohol)
what is the most complex sphingolipid and what do they do?
Gangliosides
- binding immune cells to sites of injury in inflammatory response
What is cholesterol made of?
- Steroid nucleus (4 hydrocarbn chains linked together)
- Long hydrocarbon tail
What are 2 functions of cholesterol?
1) modulates the fluidity of animal cell membranes (cholesterol is embedded in lipid bilayer)
- During low temp, Cholesterol prevents phospholipids from packing too tightly, maintaining fluidity
2) Precursor of steroid hormones such as progesterone and testosterone
What are the 3 derivatives of cholesterol?
- Bile – breakdown product of cholesterol
- Vitamin D
- Steroid hormones
Other than phospholipid bilayer, what other structure can phospholipids form, under what condition?
Micelle
- Only forms when there is only 1 fatty acid chain (salts of fatty acids)
- When there are 2 fatty acid chains, too bulky to fit into interior of micelle → steric hindrance
Membrane proteins
Myelin contains ____% of protein.
What does myelin do?
18%
- It is high in fat, and acts as an insulator of electrical signals
in the dendron (nerve cell), myelin sheath over the main part –> electrical signals cannot be passed through in areas with myelin over it, electrical signals “jump” → effective transfer
Typical plasma membranes contain ____% of protein
50%
Mitochondria membranes consist of ____% protein.
75%
- Electron transport chain –> channel proteins to pump protons and electrons
Association of proteins with lipid bilayer
What are peripheral proteins?
Proteins that are bound to cell membrane by electrostatic and hydrogen-bond interactions
- interact with hydrophilic head of phospholipid bilayer, on the surface of membrane
Association of proteins with lipid bilayer
What are integral proteins?
Proteins that form extensive interaction with hydrocarbon chains (hydrophobic part) of membrane lipids
- are embedded within membrane
The fluidity of phospholipid bilayer of cell membranes are determined by? [2]
- Fatty acid composition (cis vs trans)
- Cholesterol content
The outer and inner surfaces of the biological membrane are structurally and functionally symmetric. True or False?
False
- Outer and inner surfaces of biological membranes have different components and different enzymatic activities
How is the assymetry of biological membranes preserved?
Insertion of membrane proteins + assymetrical distribution of lipids
What are the 3 types of membrane proteins associated with the phospholipid bilayer?
- Pumps
- Carrier proteins
- Channels
Pumps use what kind of transport? (active transport/diffusion/facilitated diffusion etc)
Primary active transport involving use of ATP
Pumps use what kind of transport? (active transport/diffusion/facilitated diffusion etc)
Secondary active transport
with no use of ATP
- utilises gradient of one ion to drive transport of another against its gradient.
Carrier proteins
Carrier proteins can be classified into antiporters, symports and uniporters. What is an antiporter?
It is a carrier protein that transports 2 different ions in opposite directions at the same time
Carrier proteins
What is a symporter?
(membrane) carrier proteins which carry 2 species of ions in the same direction at the same time.
What is a uniporter?
(membrane) carrier proteins which carry 1 species of ions in either directions based on the concentration of the species on either side of the membrane.
