Lipid Metabolism

Pt. 1

Proteins

made from amino acids

found in meat, eggs, nuts, seeds

used in growth, repair, defense, and signaling

Carbohydrates

Made from simple sugars

found in bread, pasta, and grains

used as energy source

Lipids (fats)

made from fatty acids & glycerol

found in oils, butter, cheese, and cream

used as energy source, insulation, signaling, and structure components

Minerals

general term for iron, calcium, etc. 

found in milk and meat

Vitamins

A,B,C,D,E,K

found in fruits & vegetables

used in co-ezymes and antioxidants

Fiber

made from carbs that cannot be digested in mammalian systems

used to keep the GI “regular”

Lipids are - in water

insoluble; high proportion of C-H bones makes them hydrophobic

Lipids consist primarily of

hydrocarbon chains and rings

Lipids are divided into 2 categories

Simple and complexS

Simple lipids

saturated and unsaturated fatty acids and their esters with alcohols i.e. glycerol

ex. mono-, di-, or triglycerides

Complex lipids

contains other residues with esterifies FAs

ex. phospholipids

Glycophospholipids are characterized as

amphipathic

Triglycerides compose 

the bulk of body lipids; gets deposited into cytoplasm of adipocytes

Metabolic use of simple lipids

Fuels and used as component in other classes of lipids

Triglyceride composition

1 glycerol + 3 FA

Triglyceride metabolic function

main storage of fatty acids & utilized as chemical energy

Unsaturated fatty acids

chains bonded via 1 or more double bond

Saturated fatty acids

chained bonded via 1 covalent bond

How many types of fatty acids are there?

>100

Short-chain fatty acids are utilized during what metabolic process?

Fermentation

Short-chain fatty acids

Acetate, Propionate, Butyrate, Valerate

Medium-chain fatty acids

Caproate, Caprylate (Octanoate), Laurate

Long-chain fatty acids

Myristate, Palmiate, Sterate, Arachidare, Behenate, Lignocerate

FA most commonly found in fats

palmitoleate

FA most commonly found in natural fats

Oleate

Fish oil is AKA…

alpha-linolenate

omega-3

How are fatty acids named

IUPAC or omega-reference

Where are trans USFA found?

partially hydrogenated vegetable oils - margarine

How are Trans USFA similar to SFA?

promote cholesterol absorption, but more linear

Trans USFA’s are associated with

hypercholesterolemia

Cis USFA metabolic function

increase cellular membrane fluidity

How does temperature effect the fluidity of the cell membrane?

with increased temperature, the fluidity of the membrane increases

How much energy is stored in triglyerides?

twice as much as carbohydrates

9cal/g v 4cal/g

Animal fats are typically?

SFA, solid at room temperature

Plant fats are typically?

USFA, liquid at room temperature

What type of bone is formed between glycerol and the FA when forming a triglyceride?

Ester bond

What type of reaction forms triglycerides?

condensation, releasing 3H2O into the body

Phospholipids are used

as a source of IP3 & DAG for signal transduction, & source of arachidonic acid for membrane components

Sphingolipids are found where?

As a component of the membrane

Cholesterol is found where

As a component of the membrane

Metabolic use of cholesterol

precursor of bile salts and steoid hormones

Metabolic use of bile salts

lipid digestion & absorption; main product of cholesterol metabolism

What component makes phospholipids water solubule?

phosphate group

When in solution, what happens to phospholipids?

spontaneously form micelles/lipid bilaters

Micelle

cluster of hydrophobic regions of the phospholipid face inwards, hydrophilic regions exposed to water

metabolic function of micelle

act as surfactant by reducing surface tension

Surfactant

traps dirt and oils

Derived lipids

steroid hormones, eicosanoids, vitamins, ketone bodies, & prostaglandins

Steroid hormone

intracellular signals that regulate gene expression in target cells

Eicosanoids

regulate physiological functions

Metabolic function of vitamins

vision, Ca+ metabolism, antioxidants, blood coagulation

Ketone bodies

metabolic fuels

Prostaglandins

produces by and active in most tissues

What is the normal LDL in canines?

1.019-1.087

What is the normal LDL in felines?

1.030-1.043

How are lipoproteins classified?

based on density

How is the density of lipoproteins obtained?

flotation-ultracentrifugation analysis

What is the largest lipoprotein?

Chylomicrons - <0.95g/mL

What is the smallest lipoprotein?

HDL - 1.063-1.21g/mL

Total lipid count in chylomicrons

99%

Total lipid count in HDL

50%

Lipoprotein classes (Smallest - Largest)

HDL, LDL, IDL, VLDL, Chylomicron

FA in adipose tissue are sent where?

muscle tissue & liver

What happens to FA when in the liver

TG > Oxidation > returned as VLDL

What happens to FA in the muscle

TG > Oxidation

T/F

Triglycerides must be broken down into free FA before entering the capillary

True

How are free FA transported in the capillary?

albumin

Pathway of FA

Chylomicron > VLDL > free FA > adipocyte > triglyceride droplet