Lipids

Question 1

what are lipids and provide examples

Answer 1

1. uncharged nonpolar molecules
2. fats & oils

Question 2

Name four of the major types of lipids

Answer 2

1. Fatty acids
2. Triacylglycerols
3. Phospholipids
4. Steroids

Question 3

Describe the components of a fatty acid.

Answer 3

1. Fatty acids are hydrocarbon
   (alkyl) chains with a carboxyl group at one end.
2. The alkyl chain makes it a fat and the carboxyl group makes it an acid.

Question 4

Explain the difference between a saturated fatty acid and an unsaturated fatty acid.

Answer 4

1. saturated = no double bonds between carbons in the alkyl chain
2. unsaturated = 1 or more double bond between carbons

Question 5

Explain what the term “unsaturated” refers to in a fatty acid chain.

Answer 5

1. that a fatty
   acid is not saturated with hydrogen.
2. Notice that with a double bond, there are fewer H atoms than with a single bond not equal saturated

Question 6

Describe what fatty acids are categorized by

Answer 6

1. The number of carbons in the chain
2. The number of double bonds in the chain

Question 7

Describe features that can determine whether a fat will be liquid or solid at room temperature and explain why

Answer 7

1. Fatty acids with longer and/or
   more saturated carbon chains are more solid
2. Fatty acids with shorter and/or less saturated chains are more liquid.

Question 8

Describe the general organization of a triglyceride (a ___ and three ___).

Answer 8

a glycerol and three fatty acids

Question 9

State the role of triglycerides and where are they stored.

Answer 9

Triglycerides are the common form of lipid storage molecule and they are typically found in fat cells (adipocytes).

Question 10

State the other name for triglycerides.

Answer 10

Triacylglycerols

Question 11

Describe the general features and components of a phospholipid.

Answer 11

General features:
1. amphipathic, with a polar
(hydrophilic) “head group” and a set of non-
polar (hydrophobic) lipid (acyl) chains.
Components:
1. A diacylglycerol (which is like a
triglyceride, but with two acyl chains instead of three)
2. A phosphate group (remember it’s in the
name – phospholipid).
3. A further group designated R here, which
is also called the “headgroup”. It is always
polar.

Question 12

Name two common phospholipids.

Answer 12

Phosphatidylcholine and phosphatidylserine are abundant phospholipids in our cell membranes.

Question 13

Explain how phospholipids form a bilayer and the molecular effect that keeps the acyl chains buried at the centre.

Answer 13

1. Since phospholipids are amphipathic, they can form lipid bilayers.
2. The lipid chains align side by side in the interior of the bilayer and the head groups face the aqueous environment = the hydrophobic effect.

Question 14

Give three examples of common steroids.

Answer 14

1. Cholesterol
2. Estrogen/ testosterone
3. Bile acids

Question 15

Generally describe the structure that steroids share.

Answer 15

contain a specific 4- ringed structure, called the steroid nucleus. ( 3 6 carbon rings and 1 5 carbon ring)

Question 16

List four roles of cholesterol and the disease with which it is associated.

Answer 16

Four roles of cholesterol:
1. Maintains membrane fluidity in cell membranes
2. Precursor for bile acids (important for fat digestion)
3. Precursor for steroid hormones (such as estrogen and testosterone)
4.Precursor for vitamin D
Disease associated with cholesterol:
1. Cardiovascular disease (e.g., atherosclerosis)

Question 17

Explain where lipids are synthesized in the cell and what kind of electron carrier is used for these reactions.

Answer 17

1. Lipid synthesis takes place in the smooth endoplasmic reticulum in the cytosol
2. NADPH = builds molecules

Question 18

Explain what 18:0 and 18:1 means

Answer 18

1. 18 = 18 carbons 0 = no double bound
2. 18 = 18 carbons 1 = 1 double bond

Question 19

Describe why fatty acids can be more liquid then others

Answer 19

1. The higher melting points of more
   saturated fatty acids and of longer fatty
   acids results from more regular packing
   and greater interaction between adjacent
   fatty acid chains.
2. Longer chains allow more interaction.
3. Chains that are more saturated take up
   less space and interact more than
   unsaturated chains do