Concepts to understand

LIPIDS

Lipid molecules contain relatively large ___ fragments

____: do not dissolve in water but do dissolve in non-polar solvents

•Do ___ form polymers but held together by hydrophobic forces

Lipids Major FUNCTIONS

Cell membrane:
-____ components
-Regulation of membrane _____
- Membrane ____ (cholesterol, saturation of fatty acids)
-Membrane flexibility

Energy storage:
Fuel RESERVES of a typical 70-kg man

Triacylglycerols (adipose tissue): 100'000 kcal (30-40 days)
Glycogen (liver): 600 kcal (1 day)
Glucose (blood): 40 kcal
Protein (muscle): 25,000 kcal

Lipids Major FUNCTIONS

Protection:
-Protection of internal organs
-____ insulation
-Electric insulation (____ in myelin cells)
-Skin oil

Cell signaling:
There is a wide spectrum of signal molecules (e.g., steroid hormones)

Storage and transport:
-Fat-soluble ___
-____ transport fats in blood plasma

And it tastes good too ...

Overview of all types of Lipids

These types are formed from a few rearranged functional units, like in a LEGO game.

Simplest building block: FATTY ACIDS (FA)

FA: R-COO(-)

Acyl group: RCO-

Hydrocarbon tail: R

>100 FAs that vary in:
-Length
-# of double bonds
-position of double bonds
-branching
-Mostly hydrophobic
-Polar carboxyl group --> acid

SATURATED FAT

-__ double bonds in the hydrocarbon tail

-FAs that are saturated have the ____ number of H atoms.

UNSaturated Fat

Fatty acids that have ___ ___ in their hydrocarbon tails (R) are UNsaturated.

-One double bond = ____ FA
-Many double bonds = _____ FA

Melting point = temperature at which solid fat becomes ___

Cis = 13 degrees Celsius

Trans: 45 degrees Celsius

Linear molecules pack ___

*This concept is important for membrane fluidity (need Cis b/c fats stay liquid under physiological conditions.)

Rotation is ___ around the double bond with cis and trans configurations

__ conformation is prevalent in FA
(even though ___ is often more stable)

*Trans fat may occur at ___ concentrations

The problem of dietary trans fats:

-UNsaturated fat (vegetable oil) can be ____ to become partially saturated, and therefore solid --> longer shelf life, spreadable "butter."

A certain fraction of trans molecules is inevitably produced.

Trans fats are known to be ____ : increase "bad" cholesterol

Melting Point in FA's

-___ with carbon chain length

-Decreases with addition if a __ ___

GLYCEROL

-is the backbone of many fat molecules

-The three hydroxyl groups can form up to ___ linkages

Glycerol + ester linkages with FAs give _______

Come from vegetable oils, milk products, meat

Body-produced from ___ calories we consume.

ROLE: energy depot
-However, high levels may cause ___

When glucose levels are poorly controlled in diabetes, ___ levels may increase indicating the problem.

Glycerophopholipids are ___ molecules

They have both hydrophobic and hydrophilic groups.

The lipid composition of different membranes __ throughout the cell.

Sphingosine (another backbone)

-is similar in structure to glycerol but has a derivative (___ group)

-However, it is a backbone for a new lipid class:

______

Sphingomyelin is abundant in the ___ ___ system.

______ : glycosphingolipid in which one monosaccharide residue is attached toa ceramide

Compare:

Phospholipid versus Glycosphingolipid

___ = oligosaccharide chain is attached to a to a cerebroside

(a cerebroside + more sugars)

Cholesterol

-precursor to ___

Membrane fluidity:
-At WARM temperatures cholesterol ___ movement of phospholipids

-At COOL temperatures it maintains ___ by preventing tight packing

-Can be both made & consumed

Steroids are derivatives of ___ including:

-Steroid ___, such as androgens (m) & estrogens (f), cortisol

-Bile ___ (facilitate absorption of lipids in the intestine)

Reconnecting to Lecture 10

A, D, E, and K are the lipid vitamins; contain long ___ chains. They belong to the ___ class.

These fat-soluble vitamins are stored in fat tissues and the ___.

Vitamin A deficiency is the leading cause of preventable childhood ___ in developing countries.

Vitamin A is the precursor for a light-sensitive pigment in rhodopsin.

___ are esters of long-chain fatty acids and long-chain alcohols

Lipids summary:

• Largely hydrophobic

-May have a polar group => amphiphilic

-3 Fatty Acids + glycerol => ____

{2 Fatty Acids + phosphate-X}+ glycerol => ______

Glycerophospholipids are major components of cell membranes

Sphingolipids have a different (____, not glycerol) backbone
Sphingolipids are also part of the cell membrane

Steroids.

Cholesterol modulates membrane ___

Terpenes

Waxes

Eicosanoids: signal molecules that are locally formed near membranes

Vitamins