Chapter 11: Introduction to the course and Lipids

Question 1

Lipids

Answer 1

defined as water-insoluble molecules that are highly soluble in organic solvents

Question 1

lipids do not form

Answer 1

polymers

Question 2

Biochemical roles of lipids (3)

Answer 2

• key components of membranes
• play a variety of roles in signal transduction pathways
• used to store energy

Question 3

Free Fatty Acids (4)

What it is+commonly used as+structure

Answer 3

• simplest type of lipid
• most commonly used as a fuel
• building blocks for membrane lipids
• chains of hydrogen-bearing carbon atoms, called hydrocarbons, that terminate with carboxylic acid groups

Question 4

Triacylglycerols (2)

WHat it is+the structure

Answer 4

• This class of lipid is the storage form of
  fatty acids
• formed by linking 3 fatty acids chains with an ester linkage to three alcohol groups in glycerol

Question 5

Phospholipids

Answer 5

• consist of fatty acids attached to a scaffold that also bears a charged phosphoryl group, creating a macromolecule with a polar head and
  nonpolar tail

Question 6

Glycolipids

Answer 6

• lipids bound to carbohydrates

Question 7

Steroids

Answer 7

• polycyclic hydrocarbons

Question 8

Fats Vs Carbohydrates

Answer 8

Fats are good fuels because they are more reduced than carbohydrates; that is, the carbon atoms are bonded to hydrogen atoms and other carbon atoms rather than to oxygen atoms, as is the case for carbohydrates. Because of this greater reduction, fats yield more energy than
carbohydrates do when undergoing combustion to carbon dioxide and water, they have more hydrogen-carbon bonds, which release more energy when broken.

Question 9

Oleic acid

Answer 9

a C18 fatty acid

Question 10

The notation 18:0 denotes a C18 fatty acid with

Answer 10

no double bonds

Question 11

ionized forms of fatty acids

Answer 11

Loses the H

Question 12

Palmitate is a

Answer 12

16-carbon saturated fatty acid

Question 13

oleate is a

Answer 13

18-carbon fatty acid with a single cis double bond.

Question 14

The configuration of the double bonds in most unsaturated fatty acids is —-.

Answer 14

cis

Question 15

The double bonds in polyunsaturated fatty acids are separated by at least one

Answer 15

methylene group

Question 16

The properties of fatty acids and of lipids derived from them are markedly dependent on (2)

Answer 16

chain length and degree of saturation

Question 17

Unsaturated fatty acids have — melting points
than those of saturated fatty acids of the same length

Answer 17

lower

Question 18

Explain why cis double bonds lower melting temp in lipids

Answer 18

The presence of a cis double bond introduces a kink in the fatty acid and makes tight packing between the chains impossible. The lack of tight packing limits the van der Waals interactions between chains, lowering the melting temperature.

Question 19

The fat that accumulates in the pan as bacon is fried is composed primarily of —- fatty acids and solidifies soon after the burner is turned off.

Answer 19

saturated

Question 20

Olive oil, on the other hand, is composed of high concentrations of oleic acid and some —- fatty acids and remains liquid at room temperature.

Answer 20

polyunsaturated

Question 21

Thus, —– and —— enhance the fluidity of fatty acids and of their derivatives.

Answer 21

• short chain length
• cis unsaturation

Question 22

Despite the fact that fatty acids are our principal energy source, the concentration of free fatty acids in cells or the blood is —- because free fatty acids are —-. High concentrations of free fatty acids would ——.

Answer 22

• low
• strong acids
• disrupt the pH balance of the cells

Question 23

How are triacylglycerols used?

Answer 23

When energy is required during a fast (for instance, while
sleeping), the fatty acids are cleaved from the triacylglycerol and carried to the cells. The ingestion of food replenishes the triacylglycerol stores.

Question 24

triacylglycerols are stored in a

Answer 24

• anhydrous form

containing no water

Question 25

adipose tissue

Answer 25

• ## the major site of accumulation of triacylglycerols

Question 26

adipose cells (Fat cell) (2)

What happens inside cell+what they do

Answer 26

• droplets of triacylglycerol coalesce to form a large
  globule in the cytoplasm
• specialized for the synthesis and storage of triacylglycerols and for their mobilization into fuel molecules that are transported to other tissues by the blood.

Question 27

Three major kinds of membrane lipids, be specific

Answer 27

Phospholipids, sphingolipids (of which glycolipids are a subclass), and cholesterol.

Question 28

Phospholipid molecule is constructed from four components:

Answer 28

• one or more fatty acids
• a platform to which the fatty acids are attached
• a phosphate
• an alcohol attached to the phosphate

Question 29

Phosphoglycerides (2)

Answer 29

• Phospholipids derived from glycerol
• composed of a glycerol backbone to which are attached to fatty acid chains and a phosphorylated alcohol

Question 30

In phosphoglycerides, the hydroxyl groups at C-1 and C-2 of glycerol are ——. The C-3 hydroxyl group of the glycerol backbone is —–

Answer 30

• esterified to the carboxyl groups of the two fatty acid chains
• esterified to phosphoric acid

Question 31

The simplest phosphoglyceride

Answer 31

phosphatidate

Question 32

Sphingosine (2)

What it is+what its used as

Answer 32

• an amino alcohol that contains a long, unsaturated hydrocarbon chain
• backbone for sphingolipids

Question 33

Sphingomyelin (3)

What it is+ structure (2)

Answer 33

• a common sphingolipid and phospholipid found in membranes
• the amino group of the sphingosine backbone is linked to a fatty acid by an amide bond.
• the primary hydroxyl group of sphingosine is attached to phosphorylcholine through an ester linkage.

Question 34

Sphingolipids

what it is+ where it is found

Answer 34

A lipid having sphingosine rather than glycerol as its backbone. Sphingolipids are found in the plasma membranes of all eukaryotic cells, although the concentration is highest in the cells of the central nervous system.

Question 35

Glycolipids

Answer 35

• play a role in cell–cell interactions
• glycolipids in animal cells are derived from sphingosine.

Question 36

Difference between Glycolipid and sphingomyelin

Answer 36

Glycolipids differ from sphingomyelin in the identity of the unit that is linked to the primary hydroxyl group of the sphingosine backbone. In glycolipids, one or more sugars (rather than phosphorylcholine) are attached to this group.

Question 37

The simplest glycolipid, called a —-, contains a single sugar residue, either glucose or galactose

Answer 37

• cerebroside

Question 38

How are glycolipids orientated?

Answer 38

Glycolipids are oriented in an asymmetric fashion in membranes with the sugar residues always on the extracellular side of the membrane

Question 39

All steroids have a

Answer 39

• tetracyclic ring structure called the steroid nucleus
• The steroid nucleus consists of three cyclohexane rings and a cyclopentane ring joined together

Question 40

Where are cholesterol stored?

Answer 40

• Free cholesterol does not exist outside of membranes. Rather, it is esterified to a fatty acid for storage and transport.

Question 41

Membrane anchors

Answer 41

hydrophobic groups that are covalently attached to proteins (in blue) and tether the proteins to the membrane