Lipids And Membranes Flashcards
The cellular oxidation of fatty acids to CO2 and H2O is
Highly exergonic (energy releasing)
Fatty acids properties and functions (6)
- Major structural units of lipids
- aliphatic
- long chain
- mono carboxylic acids
- terminal carboxyl group
- 4- 36 carbons
Saturated fatty acids naming
-anoic
Unsaturated fatty acids with double bonds naming
-enoic
Unsaturated fatty acids with triple bonds naming:
- ienoic
Delta defines what?
The position of any double bond with a superscript numeral describing the location.
cis-delta9 defines what?
There is a cis double bond between carbons 9 and 10.
The quantitatively most common saturated fats in most organisms are: (2)
Palmitoleic and oleic.
What organism contains more polyunsaturated fats than animals?
plants
fat is solid at
at room temp
oil is liquid at
room temp
Lipids are generally ___ in water
insoluble
some lipids have a part of which is hydrophobic and a part of the molecule which is hydrophilic; what is this called?
Amphipathic
Lipids are classified as such (3)
- Energy storage
- membrane lipids cell structure
- Bilogically active lipids (hormones)
What are Triglycerides?
Glycerol and the 3 fatty acids attached to the Glycerol.
typical chain length of a fatty acid?
4-36 carbons
palmitic acid
palm oil
stearic acid
cow fat
16:1 delta9 defines
16 carbon fat with one double bond at the 9 carbon position (palmitoleic acid)
The more double bonds in a fatty acid the lower the
melting point
EFA
Essential Fatty Acids
TAGs
Triacylglycerols (TAG) are the simplest lipids. Note the other names for these: triglycerides, triacylglyceride fats, neutral fats.
oxidation of unsaturated fats =
rancidity
An ester is formed when
a fatty acid is oxidised into a resin or wax
a lipid is classed a phospholipid if….
it contains a phosphate
a lipid is classed a glycolipid if…..
it contains a glucose or a galactose
if the poly-functional backbone group is glycerol, these are called
glycerophospholipids
if the poly-functional backbone group is the long chain amino alcohol sphingosine, they are called
sphingolipids
Sphingolipids structure and function
can be phospho- or glyco-lipids. They also have a polar head and two non-polar tails, but they contain sphingosine instead of glycerol. Firstly, sphingosine is the backbone of sphingolipids and it is made up of unbranched C18 alcohol with double bonds between C4 and C5, an amino group at C2 and hydroxyl groups at C1 and C3. Sphingolipids are involved with recognition events at the cell surface. They are responsible for our different blood groups
Cholesterol structure/function (4)
- is the major sterol in animal tissue.
- It has a long hydrophobic side chain
- amphipathic
- has an important role as a component of cell membranes
bi-layer structure of membranes are composed of
phospholipids
Cholesterol or derivatives are molecules that do what in membranes?
rigid molecules that restrict the freedom of rotation of the hydrocarbon tails in their vicinity hence decreasing fluidity while they also prevent close packing that would restrict movement within the bilayer. By stopping too much movement or too little movement of the bilayer by the amount of sterol present these substances are able to regulate the fluid nature of the lipid portion
integral or intrinsic proteins
proteins that are wholly within the membrane and are bound very tightly. They have both polar and nonpolar groups on their surfaces so they can bond with the hydrophobic tails and the polar heads of the phospholipids.
Peripheral or extrinsic proteins
are exposed on only one surface of the membrane and are generally weakly held by hydrophilic interaction with the polar surface of the membrane. These proteins often serve a regulatory role. Hydrophillic portions.
Simple diffusion through a membrane
the process by which substances pass from areas of high concentration to areas of low concentration. resonably difficult ecause of the change in character from polar to nonpolar to polar again as the membrane is crossed.
Passive transport (facilitated diffusion) through a membrane
The movement of polar compounds and ions across membranes is made possible by protein carriers. These proteins act in a similar way to enzymes but the ‘substrate’ is only relocated; it is not converted into a ‘product’. called transporters or permeases.
Active transport -
when a substance needs to be moved against a concentration gradient. To achieve this potassium ions are pumped into the cell and sodium ions are pumped out. Energy is needed to drive the pump and this is provided directly from ATP.
Gated ion channels
They are like gates that open in the membrane and allow the unrestricted passage of selected ions for a very short time. They are used in transmission of electrical impulses in nerves. Require a electromagnestic gradient.
the human diet is derived from what percentage of triglycerides?
30%
Three different types of lipases have been identified in mammals that hydolyse triglycerides into glycerol and there constituent fatty acids.
- Pancreatic lipase
- Lipoprotein lipase
- Hormone sensitive lipase
an enzyme secreted by the pancreas into the duodenum, which hydrolyses dietary triacylglycerols into di- and mono- acylglycerols and free fatty acids.
Pancreatic lipase
an enzyme attached to the outer surface of cells lining capillaries adjacent to adipose tissue or skeletal muscle. These lipases catalyse the hydrolysis of triacylglycerols associated in lipoproteins (multimolecular aggregates of lipid and protein, designed to stabilise water-insoluble lipids in an aqueous environment, the bloodstream) to form glycerol and free fatty acids.
Lipoprotein lipase
an enzyme found inside adipose tissue cells, which catalyses the hydrolysis of storage triacylglycerols to form free fatty acids and glycerol This enzyme is activated by hormones such as glucagon and adrenaline. Such hormone activation plays an important physiological role in fasting, to mobilise energy stores for use as a fuel.
Hormone-sensitive lipase
β- oxidation and where it occurs
a three stage process of fatty acid metabolisation. The first of these stages is β- oxidation leading to the formation of acetyl-CoA. Through reactions involving dehydrogenation, hydration, and oxidation to a ketone we cleave two carbon units from the fatty acid chain.
- mitochondtion and peroxisomes.
Lipid catabolism
enzymes break down triglycerides to fatty acids with lipases,
