Module 9: Lipids

lipids have chains of what?

carbon atoms

what are the major categories of lipids?

glycerides

waxes

phospholipids

steroids

prostaglandins

fat soluble vitamins

What are glycerides?

3 fatty acids combined with glycerol via ester bonds

What are glycerides also called?

acylglycerols

what are the 3 categories of acylglycerols?

monoacylglycerol, diacylglycerol, triacylglycerol

What is the structure of fatty acids?

long chained carboxylic acids that end in a methyl group (CH₃)

What are fatty acids a component of?

fats

Naturally occurring fats have…

an even number of carbons

How many carbons do human fats have?

12-24

What must be obtained from the diet?

essential fatty acids

Which fats have to be obtained from the diet?

linoleic acid (omega 6) and alpha-linoleic acid (omega 3)

what are polyunsaturated fats?

more than one double bond

What is cis isomer of fats?

the kink is on the same side of the double bond

what is trans isomer of fatty acids?

the kink is on the opposite side of the double bond

How do double bonds affect fatty acids?

by how well they fit together and the amount of london force that is present

What are the properties of a highly saturated fatty acid?

crystal lattice structure

high melting point (butter)

has straight chains

what are the properties of primarily unsaturated fatty acids?

lots of kinks and bends

fit together poorly

lower melting point (olive oil)

What is the structure of a phospholipid?

charge phosphate group

2 fatty acids combined with glycerol

What are phospholipids a major component of?

cell membranes

How do phospholipids form a bilayer?

the hydrophobic carbon tails dissolve in each other and the hydrophilic polar heads are pointed toward the water environment

structure of a phospholipid

what group does lecithin have?

a choline group

what group does cephalin have?

a serine amino acid group

what is lecithin used as?

an emulsifier

where can you find lecithin?

egg yolks

where can you find cephalin?

in the brain

how is propofol prepared?

the drug + soybean oil and the emulsifier egg lecithin

do people tend to have allergies to propofol?

no

can people who are allergic to eggs, soy, and legumes receive propofol?

yes, because they are allergic to the proteins of those substances

what is the structure of a steroid?

three 6-membered rings attached to a 5-membered ring

many drugs can have steroidal structure but not…

act like steroids

what are examples of steroidal medications?

rocuronium and vecuronium

what are the roles of lipids?

1. source of fuel

2. components of important biological molecules

the fatty acids in fats supply…?

energy

When do fatty acids supply energy?

between meal times and during increased demand (exercise)

Why are fats important?

they store energy

How can fatty acids create ATP?

through fatty acid oxidation in the beta oxidation pathway

What are examples of biological lipids?

phospholipids

cholesterol

eicosanoids

steroids

bile salts

What are the biological functions of lipids?

1. membrane components

2. signaling functions

3. structure

4. digestion

Which lipids are components of biological membranes?

phospholipids, cholesterol, sphingomyelin

what is sphingomyelin?

a structural component of cell membranes

what functions does sphingomyelin have?

participates in signaling pathways/insulation of myelin sheaths

What is a sphingomyelin a major component of?

myelin sheaths

how does sphingomyelin’s signaling functions work?

extracellular substrates bind to sphingomyelin → hydrolysis → release of ceramide

what is ceramide?

acts like a second messenger triggering other cellular activities

what are some functions of ceramide?

tells the cell to stop growing, respond to stress, or undergo cell death (apoptosis)

what are eicosanoids?

a group of signaling molecules

which molecules are eicosanoids?

prostaglandins

prostacyclins

thromboxanes

leukotrienes

what are the functions of eicosanoids?

signaling

inflammation

regulating immune response

regulate BP

control platelet functions

what are eicosanoids derived from?

arachidonic acid (20 carbon fatty acid)

what pathway is synthesizes thromboxane and prostaglandin?

cyclooxygenase pathway (COX)

what are the functions of the COX-1 pathway?

PG_{2 -} gastric protection

TXA_{2 -} platelet functions

what are the functions of the COX-2 pathway?

conversion of prostaglandins into chemical messengers for:

pain

bone formation

fever

What do NSAIDS do the COX pathway?

block the arachidonic pathway

traditional NSAIDs block…

the COX-1/COX-2 pathway

which NSAIDs block the COX-2 pathway?

COX-2 selective NSAIDs

what are steroids?

lipid molecules that have structural and hormonal roles

What is a major structural lipid?

cholesterol

what are examples of hormonal steroids?

androgens (testosterone) and estrogens

what do corticosteroids help control?

reabsorption of sodium which helps maintain volume and pressure

what are examples of corticosteroids?

aldosterone and ADH

what kind of corticosteroid is aldosterone?

a mineralcorticosteroid

what is another name for ADH?

vasopressin

what does aldosterone do?

regulates salts, water, and bp

what does ADH do?

regulate fluid balance and volume by controlling how much the kidneys reabsorb water

what is an example of a glucocorticosteroid?

cortisol

what are the functions of glucocorticosteroids?

fuel homeostasis

stress related production of metabolic energy

what are the functions of androgens and estrogens?

development of secondary se*ual characteristics

what do bile salts do?

help in the digestion and absorption of fats from the diet

how are bile salts derived?

from cholesterol

where are bile salts stored?

in the liver

what do bile salts act as?

an emulsifier

what do bile salts do to fats?

solubilize them in the small intestine

what is vitamin-D?

a fat soluble vitamin

why is vitamin D important?

it is required for calcium metabolism

how is vitamin-D produced?

from cholesterol and absorption of UV light

where is vitamin-D procesed?

in the liver and kidneys into the active form of calitriol

when are fatty acids a fuel source?

during fasting and high energy activities

how are fatty acids transported in the bloodstream?

they attach to the hydrophobic pockets on albumin

what are the most common dietary fatty acids?

palmitate and stearate (saturated long-chains)

oleate (monounsaturated)

linoleate (polyunsaturated)

short and medium chain fatty acids can …

cross membranes without assistance

long chain fatty acids require …

transport across membranes

what is impermeable to long chain FAs?

the inner and outer mitochondrial membranes

what must long chain fatty acids be to cross membranes?

activated and transported

long chain fatty acid transport involves and results in what?

involves carnitine and results in acyl-CoA in the mitochondrial matrix

what can long-chain even carbon fatty acids do?

proceed to oxidation and energy release without prior modification

which FA’s require modification/additional steps before metabolism?

very long chain FAs

unsaturated FAs

odd-chain-length FAs

what is beta oxidation of fatty acids?

process where body breaks down stored fats into smaller two-carbon units of Acetyl CoA

what is acyl CoA?

the starting molecule for beta-oxidation

what is the process to make acetyl CoA?

acyl-CoA undergoes a 4 step process of oxidation of the beta carbon → cleaving of 2 carbons off the fatty acid → acetyl CoA

where does beta oxidation occur?

in the mitochondrial matrix

Explain how beta oxidation is a repetitive process

process repeats on the diminishing chain of fatty until all carbons have been converted

What is produced during beta oxidation?

NADH and FADH₂ with each turn

what are the net products of beta oxidation?

1 NADH

1 FADH₂

_{1 Acetyl CoA}

what can happen to the products produced during beta oxidation?

they can undergo the TCA cycle

in order for the acetyl group to be cleaved, how many carbons does it need to have?

2

Does the FA have to have an even number of carbons to undergo beta oxidation?

yes

How many carbons does palmitic acid have?

16

How many times can palmitic acid be cleaved per 2-carbon groups?

7 times

what are the net products of cleaving palmitic acid?

7 NADH, 7 FADH2, and 8 Acetyl CoA molecules