lipids lecture

Why are lipids largely hydrophobic?

Due to chains of carbon atoms

What are the major categories of lipids? (6)

1. Glycerides

2. Wax

3. Phospholipids

4. Steroids

5. Prostaglandins

6. Fat soluble vitamins

What are glycerides a combination of?

Up to three fatty acids combined with glycerol

What bonds do glycerides have within them?

Ester Bonds

What’s another name for glycerides?

Acylglycerols (mono, di, tri)

What are fatty acids?

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

Fatty acids are a component of what?

Fats (Along with glycerol)

Do you naturally occurring fatty acids have an even number of carbon atoms or an odd number of carbon atoms?

Even

How are essential fatty acids obtained?

Through diet

What is a saturated fatty acid?

A fatty acid composed of only single carbon-carbon bonds

What are unsaturated fatty acids?

Fatty acids having at least one double bond

What kind of isomers of fatty acids exist?

Cis (kinked, same side) and trans (straight, opposite side)

It should be noted that double bonds in fatty acids affect what?

How well they fit together and thus the amount of intermolecular London force present

A fat composed primarily of highly saturated fatty acids tends to form what structure more readily?

A crystal lattice

Does a saturated fat have a higher or lower melting point?

Higher

Are saturated fats Solid or liquid at room temperature?

Solid (ex. Butter)

What shape do unsaturated fats have in their structure?

Their shape is full of kinks and bends

Are unsaturated fats solid or liquid at room temperature?

Liquid

Do unsaturated fats have a higher or lower melting point?

Lower

What are phospholipids composed of?

A charged phosphate group with two fatty acids combined with glycerol

phospholipids are a major component of what cellular structure?

Cell membranes

How do phospholipids contribute to the structure of cell membranes?

Their hydrophobic carbon chains (tails) congregate together with polar heads pointed outward into the aqueous environment

A number of additional molecules may be added to phospholipids to form different distinct molecules. Give two examples of this.

1. A lecithin has a choline group added

2. A cephalin has a serine amino acid group added

What emulsifier is propofol made in?

Soybean oil, and egg lecithin (found in egg yolks)

Why can propofol still be given to patients with egg or soy allergies?

Because allergies to those substances are caused by proteins found in them and NOT by their lipid constituents

What is the steroid structure characterized by?

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

Fatty acids present in fats supply energy during what periods?

During periods of increased demand, such as exercise or fasting

What pathway is used to generate ATP via fatty acid oxidation?

Beta-oxidation pathway

Which lipids function as membrane components? (3)

1. Phospholipids

2. Cholesterol

3. Sphingomyelin

Which group of lipids function for signaling? And what are the lipids within that group? (4)

Eicosanoids

1. Prostaglandins

2. Prostacyclins

3. Thromboxanes

4. Leukotrienes

Which lipids function as structure and signaling? (1)

Steroids

Which lipids function in digestion? (1)

Biles salts

Although sphingomyelins primary function is cell membrane structure, is also participates in what?

1. Signaling functions that result from the binding of extracellular substrates to sphingomyelin

2. insulation for axonal myelin sheaths

What does the extracellular binding of substrates to sphingomyelin cause?

Hydrolysis of the molecule, and therefore the release of ceramide

Once ceramide is released, what does it act as?

A second messenger triggering other cellular activities

What does the signaling activity of the eicosanoid lipid group result in? (4 things)

1. Promoting inflammation

2. Regulating immune response

3. Regulation of blood pressure

4. Control of platelet function

Eicosanoid lipids are derived from fatty acids containing how many carbons?

These lipids are derived from 20-carbon fatty acids

Eicosanoid lipids Are most commonly derived from which specific fatty acid?

arachidonic acid

Which pathway mediates synthesis of prostaglandins and thromboxanes?

The cyclooxygenase pathway (COX)

What two body functions are controlled by the COX-1 pathway?

1. Gastric protection

2. Platelet function

What three body functions are controlled by the COX-2 Pathway?

1. Pain

2. Bone formation

3. Fever

Which lipid group plays a variety of important, structural and hormonal roles?

Steroids

Which steroid is a major structural lipid?

Cholesterol

What are the three sub groups of steroids?

1. Corticosteroids

2. Glucocorticoids

3. Androgens/estrogens

List two corticosteroids. What do corticosteroids help control?

1. Aldosterone

2. Anti-diuretic hormone (ADH)

They help control the reabsorption of sodium to help maintain blood volume and blood pressure

What’s an example of a Glucocorticoid and what do they play a role in?

1. Cortisol

They play a role in fuel, homeostasis, and stress related protection of metabolic energy

What do androgens and estrogens do?

Produce varied effects, such as development of secondary sexual characteristics

What is a fat-soluble vitamin that’s required for calcium metabolism?

Vitamin D

How is the majority of vitamin D produced?

From cholesterol and absorption of UV light in the skin

What does the active form of vitamin D become once it is processed by the liver and kidneys?

Calcitrol

How are fatty acids transported into the bloodstream?

Through being attached to hydrophobic pockets on albumin

What are the four most common dietary fatty acids?

1. Palmitate

2. Stearate

3. Oleate

4. Linoleate

There are short and medium-chain fatty acids, as well as long-chain fatty acids. Which ones require transport across membranes and which ones don’t?

Long-chained fatty acids require transport. Short/medium-chain does not

What is the first step of lipid metabolism?

The transportation of long-chain fatty acids into the mitochondria

How are long-chain fatty acids able to cross the mitochondrial membrane?

They must be activated and transported through a several step process involving carnitine, resulting in fatty acyl-CoA in the mitochondrial matrix

You have long-chain, even # of carbon saturated fatty acids and you have long-chain, odd # unsaturated fatty acids. Which ones can proceed to oxidation and energy release without prior modification?

Long-chain, even # carbon saturated fatty acids

Once fatty acyl-CoA is now in the mitochondrial matrix, what process/pathway begins?

Beta carbon oxidation

What happens during B-oxidation?

The beta carbon (2nd carbon from carboxyl end) is oxidized which effectively cleaves (cuts) 2 carbons off of the fatty acid. This creates an acetyl-CoA molecule

Which reduced molecules are produced during each turn of the beta oxidation “spiral”?

NADH

FADH2

What are the net products produced when each two carbon acetyl group is cleaved from an even # fatty acid?

1 NADH

1 FADH2

1 acetyl-CoA

When NADH, FADH2 and acetyl-CoA are produced what can then take place?

These products can take place in the TCA cycle

What happens to acetyl-CoA in the liver?

It becomes converted into Ketone bodies

Can the ketone bodies be converted back into acetyl-CoA?

Yes

Where does this happen? And why would the ketone bodies be converted back into acetyl-CoA?

In the skeletal muscles and other tissues. For energy production in the TCA cycle

In diabetic ketoacidosis, the body in a starved state resorts to what?

Excessive fatty acid metabolism

What does excessive fatty acid metabolism result in?

An overproduction of glucose and ketone bodies

What is responsible for the distinctive fruity breath in DKA patients?

The ketone body, acetoacetate, can spontaneously decarboxylate which produces acetone

If the 16-carbon fatty palmitic acid gets cleaved 7 times, what are the net products produced?

7 NADH

7 FADH2

8 acetyl-CoA

If the 16-carbon fatty palmitic acid gets cleaved 7 times, what are the net products produced?

7 NADH

7 FADH2

8 acetyl-CoA

Why does one fatty acid chain ultimately produce much more ATP than one glucose molecule?

Because it has many more C-C bonds available for breaking and releasing energy