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85 Cards in this Set

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  • Back

What 2 classes are lipids broken into?

1) Those based on fatty acid Structures


2) Those based on isoprenoid structures

What are the different types of fatty acids?

1) Cis - more fluid and low melting point


2) Trans - less fluid and higher melting point


3) Saturated - less fluid and higher melting point

What fatty acids are the worse for your health?

Saturated and Trans Fats

Where are saturated fats found?

Meat and dairy products

Where are trans fats found?

Most are made in the hydrogenation process

What is partial hydrogenation?

Removes many of the cis bonds, but in the process converts the remaining ones the trans configuration

Why would you want to partially hydrogenate fats?

Trying to make oils solid and make them easier to work with. Increases shelf life

Difference in fat content between butter and margarine

Margarine - increased trans fats


Butter - increased saturated fats

What are the essential fatty acids?

1) Omega-3 - alpha linoleic acid


High levels in fish






2) Omega-6 - linoleic acid


High in vegetable oils

What kind of problems occur with too much omega 6 intake?

Promote inflammation and increase the risk of heart disease

What are eicosanoids derived from?

Arachidonic acid or any 20 carbon fatty acid

What are examples of eicosanoids?

Prostaglandins, thromboxanes, and leukotrienes

Eicosanoids are physiological mediators of many processes such as:

Inflammation


Vasodilation/constriction


Bronchodilation/constriction


Vascular permeability


Platelet aggregation

What is the major component of waxes?


An ester of long-chain fatty acids and long-chain alcohol

What are some uses of waxes?

1) Protective coating on plants and fur and skin of animals


2) Wax esters are components of beeswax, carnauba wax, ear wax

What are the physiological roles of TG's?

Insulation


Energy Storage



Does glycogen or TG's store energy more effectively?

TG's - oxidation of fats = more ATP


more places to oxidize due to more hydrogens attached to the carbons vs glycogen some hydrogens are attached to oxygens instead


Glycogen is more polar - water will come along and fill empty space causing decreased glycogen in one given area. TG's are not polar and will not bring water leading to more storage capacity



What else can TG's participate in besides energy and insulation?

1) Saponification - creation of soap


2) Emulsification - dispersion of one liquid in another (i.e. oil out)

Saponification

Heating of an ester in the presence of a base to create a soap. Fatty acid salts create micelles around dirt.

Why are micelles not a bilayer?

These only have one fatty acid chain versus 2 fatty acid chains.

Where does Lipogenesis of TG's occur?

Cytosol of liver cells and adipocytes

What are the substrates for TG lipogenesis?

Fatty acyl CoA's - made by adding a fatty acid to CoA


Glycerol - 3 - phosphate - the backbone

Lipolysis

Releases fatty acids from TG's

Where does lipolysis occur?

Done in adipocytes when fatty acids are needed for energy ( i.e. fasting, exercise, stress, etc.)

How is lipolysis activated?

TG lipase which is hormone sensitive lipase (HSL)

What are the products of Beta oxidation?

3 fatty acids and glycerol backbone

What activates HSL?

Epinephrine - fight or flight - increased energy


Glucagon - low blood sugar - need more energy

What inactivates HSL

Insulin - when we already have lots of glucose for energy

How is glycerol processed after lipolysis

Released into blood and taken up by the liver


Liver contains Glycerol Kinase

What does Glycerol Kinase do in the liver?

- Glycerol to G3P


- TG's


- Phospholipids


- DHAP to go in reverse and make glucose



How are fatty acids processed after lipolysis?

Carried in blood and transported into tissues


Used for energy in various tissues



Where are fatty acids used heavily?

Cardiac Muscle



Where are fatty acids not used?

RBC's and brain

What two different types of backbones can phospholipids have?

1) Glycerophospholipids/ phosphoglycerides - glycerol backbone




2) Sphingomyelins - ceramide backbone

Both phosphoglycerides and sphingomyelins contain:

Hydrocarbon chains


Polar Phosphate-alcohol head group

Phosphtatidates

Both fatty acids are in an ester link


Example: membrane components such as phosphatidylcholine

Plasmalogens

One fatty acid is an ether link and one in an ester link


Example: Platelet activating Factor



Phosphoglyceride uses

Emulsifying agents


Surfactants - polar parts can disrupt H bonds and lower the surface tension of water


Membrane Components



Importance of Surfactants in infants

Lack of certain phospholipids that make up lung surfactant is a major cause of respiratory distress syndrome in premature babies

Why a phosphate alcohol head group in phospholipids? Doesn't look like an alcohol??

The alcohol is removed when attached to the phosphate

Varying phosphate head groups in phospholipids



How do you make membrane phospholipids i.e. phosphatiylcholine?

Start on the cytoplasmic side of the SER and add a phosphocholine head group to DAG

How does DAG become TAG?

Add an acyl CoA

What is another way to make phosphatidylcholine?

1) Make phosphatidylethanolamine first - add phosphoethanolamine from CDP-ethanolamine to a DAG backbone


2) Methylate the PE to create PC



Where do methyl groups come from?

SAM - S-adenosyl methionine

What vitamins help SAM function?

B9 and B12 (Cobalamin)

How do you get some of the newly made phospholipids to the other side of the bilayer membrane?

A special flippase enzyme will translocate various phospholipids across the membrane

How do you get the newly made phospholipids from the SER membrane to the cell membrane?

Pieces of SER contain the new phospholipid bud off as little vesicles and re-insert into the plasma membrane

Fatty Acid Functions

1) Broken down for energy via beta oxidation


2) Can be used to make membranes


3) Form various derivatives - Sphingolipids, waxes, TG's, Eicosanoids

Sphingomyelin Structure

Ceramide Backbone


Phosphocholine Polar head group


Hydrocarbon Chains (palmitate)



What makes up ceramide?

Sphingosine and a fatty acid

Cerebrosides

Ceramide backbone


Monosaccharide head group


Common in neuronal membranes

Sulfatides

Ceramide backbone


Sulfated monosaccharide head group


Common in neuronal membranes

Glycosphingolipid examples

Neutral : Cerebrosides


Acidic: Gangliosides and Sulfatides

Gangliosides

Ceramide Backbone


Head group: 1 or more sialic acid residues plus one ore more monosaccharides


Common in neuronal cell membranes



GM2

G = Ganglioside


M = Number of sialic acids - mono = 1


2 = Pattern of monosaccharide attachment

Tay-Sachs Disease

The accumulation of GM2 in lysosomes due to an enzyme deficiency


The most sever excess if in the brain and that build up leads to neuronal cell damage


Death early as 5 years of age

How many carbons are in an isoprene unit?

5 carbon unit

What is an example of an isoprenoid?

Terpenes - lipids comprised of various numbers of isoprene units

Examples of terpenes:

Beta carotene


Squalene - makes cholesterol


Citronella

T/F


The smallest isoprenoid is made up of 2 isoprene units

True - So monoterpene actually has 2 units instead of 1

What is a mixed terpenoids?

Mixed terpenes are non-terpene molecules with terpenes attached

3 examples of mixed terpenoids

Vit. K


Coenzyme Q


Amino acids with isoprene attached - Prenylated protein

Steroids

Isoprenoids


Complex molecule made of 6 isoprene units

How can you identify Sterols?

Steroid with a hydroxy group at C3

T/F


All steroid hormones are derived from terpenes

False, all steroid hormones are derived from cholesterol



How can you tell if it's testosterone or progesterone

There will be a double bonded O at C-3 instead of the OH like in sterols

Synthesis of Isoprenoids

Isoprene units are donated from isopentyl pyrophosphate - you need a carrier molecule

What are the three main steps of cholesterol synthesis?

1) Formation of isopentenyl pyrophosphate


2) Creation of squalene


3) Cyclization of squalene into cholesterol and addition of hydroxy group

Step 1 of Cholesterol Synthesis:

3X Acetyl CoA to


HMG CoA (can also go to ketogenesis) to


Mevalonate to


Isopentenyl pyrophosphate <-> Dimethylallyl pyrophosphate



What is the rate limiting step in Step 1 of cholesterol synthesis

HMG CoA is catalyzed by HMG CoA reductase


This enzyme is blocked at high cholesterol levels and the cholesterol-lowering drugs "statin" and you do not form mevalonate

3 Uses of Acetyl CoA



CAC


Ketogenesis


Cholesterol formation

Step 2 of cholesterol synthesis

Formation of squalene


Uses 6 isopentyl pyrophosphates to donate isoprenes

Where does cholesterol synthesis occur?

In the liver

What does the liver use cholesterol for?

Make Bile


Make lipoproteins - Tissues take in LDL and release its components

Familial hypercholesteremia

Inherited defect in LDL receptors


Leads to an increase in circulating LDL and therefore an increase in cholesterol in the blood and increased risk of MI

What is the molecule used as a precursor to form steroids?

Cholesterol

What is cholesterol converted to first?

Progesterone and other steroid hormones form there.



Aldosterone

Made in the adrenal cortex


Promotes sodium reabsorption that leads to salt and water retention and increased BP

Cortisol

Made in the adrenal cortex


Stress hormone that promotes gluconeogenesis, glycogenolysis

Testosterone

Some made in adrenal cortex but most is made in testes


Responsible for male characteristics



Estrogen

Some made in adrenal cortex - Most made in ovaries and placenta


Responsible for female characterisitics

What are most plant steroids?

Sterols



How can plants sterols be used therapeutically?

Can mimic cholesterol in the intestine and partially block cholesterol absorption

Cardiac Glycosides

Function to increase the force of contraction of the heart


i.e. Digoxin (medicinal) Ouabain (toxic)