ANS NUTRITION (EXAM 3)

What are lipids?

organic compounds that are relatively insoluble in water, relatively soluble in organic solvents

One gram of fat

9.5 calories

One gram of carb/protein

4.0 calories

How much energy do lipids store?

they store massive amounts of energy that is 2x more than carbs & proteins

What are simple lipids?

esters of fatty acids w/ various alcohols

ex: fats, oils, & waxes

Fats/oils

1. esters of fatty acids w/ glycerol

2. make up largest fraction of lipids in most food materials

3. simple lipids

Wax

1. esters of fatty acids w/ alcohol other than glycerol

2. simple lipids

What are compound lipids?

esters of fatty acids containing non-lipid substances

ex: phospholipids (phosphorus), glycolipids (carbs), lipoproteins (proteins)

Derived Lipids

substances derived from simple or compound lipids by hydrolysis

ex: fatty acids, glycerols, other alcohols

Sterols

lipids w/ complex phenanthrene-type ring structures

ex: cholesterol

derived lipids

Terpenes

compounds that usually have isoprene-type structures

ex: aromatic compounds

derived lipids

Which lipids are most found in nutrition & the most important?

1. fatty acids

2. glycerols

3. mono, di, & triacylglycerols (aka triglycerides)

4. phospholipids

5. lipoproteins

Triglycerides

1. main storage form of energy in animals

2. significant for nutrition

Lipoproteins

important for lipids transport in blood/lymph

important for nutrition

T or F

Are waxes/terpenes nutritionally important?

F

What structure are fatty acids made up of?

2 carbon chains

carboxyl group on end of each chain

RCOOH (carbon chain, carboxyl group)

each carbon within chain has 2 H

carbon at END of chain has 3 carbons (terminal end)

Saturated fatty acids (FA bond type)

no double bonds

Unsaturated fatty acids (FA bond type)

at least one double bond (usually 1-4 double bonds)

removed H

Cis

R-chains/hydrogens are on same side of double bond

Trans

R-chains/hydrogens are on opposite sides of double bond

What structure type in MOST FA do animals have?

straight-chained (trans) and/or saturated

What number of carbons will animals have in the FA’S?

almost always have an even # of carbons

What number & structure type will plants/microbes have in the FA’S?

1. branched chain

2. odd # carbon chains

2 primary naming systems for FA

⍵ system (omega)

Δ system (delta)

⍵ system (omega)

number from terminal end

Δ system (delta)

number from carboxyl end

Where are ⍵-3 & ⍵-6 (omega) FA typically found?

fish fats or made by microbes

What makes omega-3 and omega-6 fatty acids structurally unique?

position of double bonds

What is CLA?

they are isomers of linoleic acid

Why are CLAs considered important from a medical perspective?

they are beneficial

Why are dairy and meat products great sources of CLA?

the microbes in the animals gut make it

What are mono-, di-, & triglycerides

esters of glycerol & FA

How is ester formed through these glycerides?

by reaction of an alcohol w/ an organic acid

What does the chain length & unsaturation degree determine about triacylglycerides? (TAG)

physical & chemical properties

How does FA in triglycerides vary?

same or diff FA can be in various positions

What do longer chains, less unsaturation, & more trans bonds mean in room temp?

it will become more solid

What do shorter chain, more unsaturation, & more cis bonds mean in room temp?

it will become less solid

What can phospholipids be broken up to yield?

FA, phosphate, glycerol (typically) & nitrogenous base (typically)

Where are phospholipids more widely distributed in?

body fluids

How does the fatty acid composition of phospholipids in animal tissues compare to other lipids?

higher in unsaturated FA in animal tissues

What is the most abundant sterol in animal tissues?

cholesterol

Which sterol yields vitamin D2?

ergosterol

What hormones is cholesterol based on?

sex hormones (most)

What are the main functions of lipids?

1. energy supply for normal maintenance & productive functions

2. essential fatty acids source

3. carrier of fat-soluble vitamins

4. integral constituent of cell membranes

What does a triglyceride (TG) break down into?

glycerol & fatty acids

By what type of reaction are triglycerides broken down?

hydrolysis reaction

If carbohydrates meet energy needs, what is the only dietary need for fat?

EFA

Which acids are the EFAS?

Linoleic acid and α-linolenic acid

What are the functions of EFAS?

1. creates cell membrane structure

2. eicosanoids foundation

3. precursor to prostaglandins

What does the eicosanoids foundation function do for EFAS?

it regulates & releases pituitary hormones

What does the precursor to prostaglandins do for EFAS?

Vasodilators, stimulate smooth muscle contraction, inhibit release of FA release from adipose, regulate immune function

What vitamins are fat-soluble?

A, D, E, & K

Where are the fat-soluble vitamins incorporated in?

micelles

What are micelles important for?

lipid absorption

Where do lipids start preparing for absorption?

Duodenum & Jejunum (upper mostly)

What do bile acids do in absorption?

They aid in break down of large to small molecules & increases surface area

What do the pancreatic & intestinal lipases break down during digestion?

TG (triaglycerides)

What positions do pancreatic & intestinal lipases get digested at?

1 & 3 positions

T or F

TG are soluble in micelles

F, they ARE NOT SOLUBLE

T or F

Monoglycerides & FA are soluble in micelles

T

What does bile promote the activity of?

pancreatic lipase activity

What do bile salts facilitate?

absorption

What is the base of bile acids?

cholesterol

What is the main function of bile acids?

aid in lipid absorption

T or F

Bile acids are amphipathic

T

What happens to bile acids after they aid in lipid absorption?

they can be reabsorbed & recycled

What are the 4 bile acids?

Cholate

Deoxycholate

Taurocholate

Glycocholate

Which lipid products can be absorbed passively?

Glycerol & SCFA (short chain fatty acids)

How many carbons do short-chain fatty acids (SCFA) have?

2-10

How do monoglycerides and long-chain fatty acids (LCFA) enter the enterocyte?

by diffusion across the apical side

Other lipids are hydrolyzed to what in the intestinal lumen?

FFA (free fatty acids)

Which enzymes hydrolyze these lipids?

Pancreatic & intestinal lipases

What happens to parts that are not broken down to FFA?

they are absorbed intact

In what form must cholesterol be absorbed?

non-esterified form (free form)

How well are dietary sterols absorbed?

not well, poorly absorbed

Where are FA and monoglycerides transported to inside the epithelial cell?

ER (endoplasmic reticulum)

What is resynthesized in the ER from FA and monoglycerides?

triglycerides

After TG resynthesis, where are the lipids transferred?

from the ER to the Golgi

What is packaged together with TG in the Golgi?

Cholesterol, lipoproteins, and other lipid particles (which is called chylomicron)

How does the chylomicron leave the epithelial cell?

Transported to the basolateral side and exocytosed (exocytosis, pinocytosis)

What are LCFA converted to inside the epithelial cell?

Fatty acetyl-CoA with ATP

Fatty acyl-CoA can be re-esterified to reform what?

Diglycerides (DG) or triglycerides (TG)

What is the minimum carbon length of fatty acids that can enter chylomicrons?

12 or more carbons

T or F

Can short-chain fatty acids (2-10 carbons) enter chylomicrons?

No, only w/ FA or 12 or more carbons

Where do chylomicrons go after exiting the cell?

the lacteal

The lacteal leads to which system?

lymphatic system

Through which structure does the lymphatic system carry chylomicrons to the blood?

thoracic duct

What is the correct order of chylomicron transport?

Exocytosis → lacteal → lymphatics → thoracic duct → blood

Where do avians transfer chylomicrons?

directly to portal blood

What is the key difference between avian and nonruminant chylomicron transport?

Avians use portal blood; nonruminants use the lacteal and lymphatics

In what form are lipids carried in blood and lymph after digestion or a meal?

as chylomicrons

Can free lipids move through the blood?

Yes, free lipids can move thru blood as mobilized deposits

In what form are blood lipids transported?

lipoproteins

What range of lipoproteins carries blood lipids?

Very low to high density lipoproteins

What happens to lipoprotein density as the proportion of protein increases?

density increases

As protein proportion increases in a lipoprotein, what happens to the proportion of lipids?

the proportion of lipids decreases

What are the 4 major classes of lipoproteins?

1. Chylomicrons - lowest density

2. Very low density lipoprotein (VLDL)

3. Low density lipoprotein (LDL)

4. high density lipoprotein - greatest density (HDL)

What chemical nature do apolipoproteins have?

Amphipathic

What is the structural role of apolipoproteins?

Structural component of lipoproteins

Besides structure, what else do apolipoproteins do?

they help w/ recognition by cells