1.5 - Lipids and Nucleic Acids

Question 1

What do lipids do?

Answer 1

Lipids are biological molecules which maintain the differences between what is outside and inside a cell

• They are the gatekeepers

Question 2

How do lipids react to water?

Answer 2

Lipids are insoluble in water (meaning they cannot be dissolved by water)

Question 3

Why are lipids insoluble?

Answer 3

Lipids are insoluble in water because they are nonpolar molecules. Water is a polar molecule, meaning it has a positive and a negative end. Lipids, being nonpolar, don’t interact well with the polar water molecules, causing them to repel each other. This property makes lipids hydrophobic, or “water-fearing,” and is why they tend to clump together and separate from water.

Question 4

What are the roles of lipids?

Answer 4

The roles for lipids in organisms include:
- Energy storage (fats and oils)
- Cell membranes (phospholipids)
- Capture of light energy (carotenoids; give colour to vegetables/leaves)
- Chemical messengers
- Hormones and vitamins (steroids and modified fatty acids)
- Thermal insulation
- Electrical insulation of nerves
- Water repellency (waxes and oils).

Question 5

T/F: Lipids share a common core structure

Answer 5

FALSE: Lipids do not share a common core structure

What is common to lipids is their hydrophobicity (they ALL avoid water)

Question 6

What are saturated fats?

Answer 6

A saturated fat is a type of fat in which the fatty acid chains have all single bonds

Question 7

What are unsaturated fats?

Answer 7

Unsaturated fats have at least one double bond between carbon atoms, creating a kink in the chain. This kink prevents the molecules from packing tightly, keeping the fat liquid at room temperature.

Unsaturated fats are usually liquid, come from plants, and are healthier for your heart.

Question 8

How do the structures of saturated and unsaturated fats differ?

Answer 8

Saturated fats have a straight structure, while unsaturated fats have bends in them

• Unsaturated fats also have double carbon bonds

Question 9

What is the state of fully saturated fats at room temperature?

Answer 9

At room temperature, fully saturated fats are solid (think butter). They have high-temperature stability (minimal changes to state over wide temperature range, no sudden changes)

Question 10

What is the state of unsaturated fats at room temperature?

Answer 10

At room temperature, unsaturated fats are liquid (think oil). They have low-temperature fluidity (meaning they are still fluid at low temperatures)

Question 11

What are triglycerides?

Answer 11

Triglycerides are the most abundant lipids and the most concentrated source of energy

Question 12

What are triglycerides made of?

Answer 12

The building blocks of triglycerides are glycerol (the same for each fat molecule) and fatty acids (different for each fat, they determine its chemical nature)

Question 13

What are the types of fatty acids?

Answer 13

• Saturated fatty acid (all available bonds are filled)
• Unsaturated fatty acid (has one or more double bonds)

Question 14

How are triglycerides formed?

Answer 14

Triglycerides are formed by a dehydration synthesis

Question 15

Why do fats possess more energy stored per unit mass/volume than carbohydrates?

Answer 15

Fats possess more energy per molecule and less hydration compared with carbohydrates because they have a higher number of CH bonds (LONG chain of molecules)

Question 16

What are the two kinds of unsaturated fats?

Answer 16

Monounsaturated and polyunsaturated

Question 17

What are the two kinds of hydrogenated fats?

Answer 17

Cis and trans fats

Question 18

Where are fats stored in animals?

Answer 18

In animals, fats are stored in adipose cells (connective-tissue cells designed to store fat)

Question 19

What are phospholipids?

Answer 19

Phospholipids are fat compounds similar to triglyceride

One end of the phospholipid is water-soluble (hydrophilic); the other end is fat-soluble (hydrophobic)

Question 20

What are phospholipids used for?

Answer 20

Phospholipids are used to join two different chemical environments

Question 21

What are bilayers?

Answer 21

Bilayers are double layers of phospholipids that make up cell membranes (also called biological membranes)

Question 22

What are steroids?

Answer 22

Steroids are signaling molecules. Steroids are organic compounds with a series of fused rings

Question 23

What is the structure of a steroid?

Answer 23

Steroids have a common 4-ring structure

Question 24

What do steroids do?

Answer 24

Steroids are involved in many structural and functional roles

Question 25

What is cholesterol?

Answer 25

Cholesterol is a common steroid in animal cell membranes. It is absorbed from food and synthesized in the liver. In addition to being a membrane constituent, it also is an initial substrate (layer) for synthesis of the hormones testosterone and estrogen (which are both also steroids)

Question 26

What properties do cholesterol have in the cell?

Answer 26

Cholesterol is a membrane temperature fluidity buffer, meaning it helps the cell regulate temperature and avoid extremes (too hot, too cold)

Question 27

What are vitamins?

Answer 27

Vitamins are small organic molecules essential to health

Question 28

What is Vitamin A good for?

Answer 28

It is important for normal development, maintenance of cells, and night vision

Question 29

What is Vitamin D good for?

Answer 29

It is important for absorption of calcium in the intestines.

Question 30

What is Vitamin E good for?

Answer 30

It is an antioxidant. It protects membranes from disease-causing agents.

Question 31

What is Vitamin K good for?

Answer 31

Vitamin K is a component required for normal blood clotting.

Question 32

What are waxes?

Answer 32

Waxes are saturated long fatty acids bonded to long fatty alcohols via an ester linkage (bond between oxygen and carbon atoms)

Question 33

What are waxes used for?

Answer 33

Waxes protect our hair, birds’ feathers, and insects’ eggs from both the damaging effects of excess water, and the damaging effects of water loss

Question 34

What are nucleic acids polymers?

Answer 34

Nucleic acid polymers are linearly arranged information molecules. They are composed of nucleotides (A, T, G, C)

Question 35

What are the two types of nucleic acid polymers? (aka Polynucleic acids)

Answer 35

The two types of nucleic acid polymers are DNA (deoxyribonucleic acid) and RNA (ribonucleic acid)

Question 36

What do DNA molecules do?

Answer 36

The DNA molecules of humans are enormous polymers that encode hereditary information bound in nucleotides

Question 37

What do RNA molecules do?

Answer 37

The RNA molecules carry out the instructions encoded in DNA

Question 38

What is the structure of DNA?

Answer 38

A double helix

Question 39

What are the 3 nitrogenous bases?

Answer 39

Cytosine, thymine, and uracil

• Uracil is only present in RNA (it replaces thymine in RNA molecules)

Question 40

What are the 2 purines?

Answer 40

Adenine and guanine

Question 41

What are the 2 pentose sugars?

Answer 41

Deoxyribose (in DNA)
Ribose (in RNA)

Question 42

What are the three main structural differences between DNA and RNA?

Answer 42

1. RNA has ribose, which has oxygen at carbon 2 of the sugar (two OH instead of one)
2. Instead of having thymine, RNA molecules have uracil
3. RNA is single stranded (single helix instead of double helix)

Question 43

When it comes to purine and pyrimidine bases, which is the small structure and which is the large structure?

Answer 43

Purine base = smaller word but BIGGER structure

Pyrimidine base = larger word but SMALLER structure

Question 44

What are the nucleotide pairings?

Answer 44

A pairs with T (or U), C pairs with G

• Every pairing needs 1 purine and 1 nitrogenous base