Lipids

What is the basis for all lipid?

Acetyl-CoA

How many carbons does acetyl-CoA have?

2 carbons

What are fatty acids used for in the body?

Metabolic fuel

What are sterols used for in the body?

They are a component of cell membranes, hormones, and vitamins

What are phospholipids used for in the body?

Comprise cell membranes

What are acylglycerols used for in the body?

The storage and transport of fatty acids

What type of acylglycerols are most commonly found in the diet?

Triacylglycerols

How long are acylglycerols generally?

≥14 carbons

What fatty acid chain length is considered “short”?

2-6 carbons

What fatty acid chain length is considered “medium”?

8-14 carbons

What fatty acid chain length is considered “long”?

16-20 carbons

What fatty acid chain length is considered “very long”?

22-26 carbons

What is different about short chain fatty acids?

Because they are short, they are able to overcome their hydrophobia and move through the circulatory system

What is the functional group at the end of fatty acids?

Carboxylic acid head groups

In what increments do fatty acid chains extend by?

They extend by 2 carbons at a time (due to acetyl-CoA having 2 carbons and it being the basis for all fatty acids)

What is the end opposite the functional group called?

The omega end or “N”-end

Saturated Fatty Acids Overview

Only contain single bonds, every carbon has the maximum number of hydrogens possible, they are typically solid at room temperature

Unsaturated Fatty Acids Overview

Have at least 1 double bond (are able to have up to 6 double bonds), typically liquid at room temperature

At what number carbon will the first double bond add on to?

The first double bond will add on to the 9th carbon

How can some fatty acids be named?

They can be named for whichever number carbon the first double bond is located at when counting from the omega end (e.g. omega-3 = first double bond is at the third carbon from the omega end)

Trans-Unsaturated Fatty Acids Overview

Have their hydrogens on opposite sides, more stable than the cis- conformation, generally considered to be more unhealthy

Which form of unsaturated fatty acids is healthier?

Cis-unsaturated fatty acids are generally healthier than trans-unsaturated fatty acids

When may trans-unsaturated fatty acids be considered “healthier”?

They are healthier when produced biologically (e.g. butter from cows milk) as opposed to produced chemically (e.g. margarine)

What does it mean if unsaturated fats are conjugated?

It means that there is no methyl group between groups of double bonded carbons, ruminants are able to conjugate fatty acids naturally

Acylglycerols Structure

Have a glycerol backbone, can have 1 (mono), 2 (di), or 3 (tri) fatty acids attached to the backbone

What kind of fatty acids are in milk?

Short-chained triacylglycerols, them being short is important because it means they can travel through the bloodstream and therefore be more easily absorbed by newborns

Phospholipids Structure

Have a phosphate head group that is polar and hydrophilic, a glycerol backbone is connected to the head group, 2 fatty acid chains are attached to the backbone, can also have a polar group attached to the head group assymetrically for the purpose of cell signaling and inflammation response

What is an example of a medium-chain saturated fat/oil(s)?

Coconut/palm oil

What is an example of a long-chain saturated fat/oil(s)?

Butter, lard, tallow, and palm

What is an example of a long-chain mono-saturated omega-9 fat/oil(s)?

Olive oil

What is an example of a long-chain polyunsaturated omega-6 fat/oil(s)?

Corn, soybean, safflower, and primrose oil

What is an example of a long-chain polyunsaturated omega-3 fat/oil(s)?

Linseed and fish oil

How many fatty acids do fat/oil(s) tend to have?

Most have 2 fatty acids, olive oil is one exception

How do the number of carbons and double bonds affect melting temperatures?

A higher number of carbons results in a higher melting temperature (for saturates fatty acids), and a lower number of double bonds results in a higher melting temperature (for unsaturated fatty acids)

Sphingolipids Structure

Has a sphingosine backbone, a head group attached to the backbone, an N group attached to the backbone, and one fatty acid attached to the N group

What are the 2 essential fatty acids for humans?

Linoleic acid and alpha-linolenic acid

Linoleic Acid Structure

It is an omega- 6 fatty acid with 2 double bonds

Alpha-Linolenic Acid

It is an omega-3 fatty acid and has 3 double bonds

Arachidonic Acid

Essential for obloigatory carnivores, 20:4, derived from linoleic acid

Docosahexaenoic Acid

NOT essential but important for newborns, 22:6, derived from a-linolenic acid

Butyric Formula

C4:0

Caprylic Formula

C8:0

Capric Formula

C10:0

Lauric Formula

C12:0

Palmitic Formula

C16:0

Stearic Formula

C18:0

Oleic Formula

C18:1

Linoleic Formula

C18:2

a-Linolenic Formula

C18:3

Arachidonic Formula

C20:4

Docosahexaenoic Formula

C22:6

Polyunsaturated Fatty Acids (PUFAs)

Unsaturated fats with 2+ double bonds, unable to stack due to kinked shape, leads to lower melting point as a result of weak intermolecular forces, typically liquid @ room temperature

Lipid Partitioning: Poikilotherms

Store fat in the mesentery (tissue holding organs together), liver, and muscle, fish can store fat within muscle cells

Lipid Partitioning: Homeotherms

Store fat viscerally (around organs), subcutaneously (blubber), and in muscle, perform behavioral modifications to support increased lipid stores (hibernation/migration)

Where do most lipids get broken down?

Duodenum of the small intestine

Pre-Gastric Esterase

Comes from saliva but only takes effect once in the stomach, starts the process of breaking food down

Gastric Lipase

Comes from the stomach, works at the outsides of the fat globule cleaving off diglycerides and FFA’s

What is bile’s role in lipid digestion?

It holds the fat globule in place so that digestive enzymes can break it down

Pancreatic Lipase

Activated by colipase, comes from the pancreas, responsible for majority of triglyceride digestion and for breaking down the rest of the diglycerides into monoglycerides and FFA’s

Mixed Micelle

Monoglycerides and FFA’s interact with water to form this, delivers them to enterocyte where fat will be dropped off and absorbed

What happens after the monoglycerides and FFA’s are absorbed by the enterocytes?

They are used to rebuild triglycerides

Chylomicron

Comprised of triglycerides, cholesterol, and vitamins, too large for the circulatory system so it travels via the lymphatic system until it reaches the vena cava at which point it is able to enter the circulatory system, once in the circulatory system it will travel to various adipose tissues

What happens to fat in ruminants?

Microbes act on the fat first and will perform biohydrogenation to get rid of double bonds (saturate the FA), microbes utilize most of the glucose there leaving ruminants to rely on acetate and butyrate

VLDL

Very-low density lipoprotein, comprised of synthesized tryiglycerides and cholesterol, made by the liver, leads to IDL and LDL

LDL

Low-density lipoprotein, formed in circulation from the VLDL/IDL, deposits cholesterol throughout the body, too much cholesterol results in plaques in the arteries, considered to be “bad” cholesterol

HDL

High-density lipoprotein, made in circulation and entirely out of cholesterol, circulates throughout body picking up extra cholesterol and taking it back to the liver, considered to be “good” cholesterol

What does the liver do with excess cholesterol?

The liver will put the excess cholesterol back into bile/the GI tract so that it can get filtered out and excreted with urine/feces

Lipoprotein: LDL

Consists of a cholesterol core, outer layer of amphipathic lipds, and an integral aprotein, Apo B

Lipoprotein: HDL

Consists of a cholesterol core, outer layer of amphipathic lipids, and a peripheral apoprotein, Apo A, C, D, and E

Apoprotein

Lipids wrapped around a protein, help identify other lipoproteins, tell molecules where to go

What tissues use FA’s?

Liver, renal cortex, skeletal muscle (except during severe exercise), and cardiac muscle