Lipids!

Question 1

What is the general structure of a fatty acid? Which parts are polar and non-polar?

Answer 1

A hydrocarbon tail (nonpolar) with a carboxylic acid group (COOH) at one end (polar)

Question 2

What determines the melting point of a fatty acid?

Answer 2

Chain length and degree of saturation (more saturation = higher melting point)

Question 3

What is the pKa of a fatty acid?

Answer 3

usually 4.7-5.0

Question 4

What is a saturated fatty acid?

Answer 4

A fatty acid with no double bonds

Question 5

What is an unsaturated fatty acid?

Answer 5

A fatty acid with one or more double bonds (usually in the cis form)

Question 6

What is the difference between omega (ω) and systematic fatty acid numbering?

Answer 6

Omega starts from the methyl end; systematic starts from the carboxylic acid end

Question 7

What is a PUFA?

Answer 7

A polyunsaturated fatty acid
- more than 1 double bound but has to be at least 3 carbons apart!!!!!!!!

Question 8

Where is the double bond in omega 3? and where does this fat come from?

Answer 8

Double bond is on 3rd carbon from the methyl end

From animals

Question 9

Where is the double bond in omega 6? and where does this fat come from?

Answer 9

6 carbons in from methyl end

From plants

Question 10

What does “18:1(n-9)” indicate?

Answer 10

18 carbon atoms, 1 double bond, first double bond 9 carbons from the methyl end
- Oleic acid - most common monounsaturated FA

Question 11

Describe stearic acid/ Octadecanoic acid

Answer 11

Octadecanoic acid (18:0)
- 18C, no double bonds

Question 12

Describe palmitic acid/ Hexadecanoic acid

Answer 12

(16:0) = 16 carbons long, no double bonds
Comes from palm plants
Forms palmitate when goes to COO-

Question 13

Name two essential fatty acids.

Answer 13

Linoleic acid (omega-6) and alpha-linolenic acid (omega-3)

Question 14

Describe alpha linolenic acid/Octadecatrienoic acid

Answer 14

• Octadecatrienoic acid
• 18 carbons long
• Trienoic acid = 3 double bonds
• So would be 18:3(n-3)
• omega 3 or cis-9,12,15 – octadecatrienoic acid

Question 15

Describe linoleic acid/ Octadecadienoic acid

Answer 15

• Octadecadienoic acid so would be 18:2 (n-6) or 18:2 cis cis – 9,12

Question 16

Why are some fatty acids essential in the human diet?

Answer 16

Humans cannot introduce double bonds beyond the 9th carbon from the carboxyl end and can’t survive without eating them

Question 17

What is the role of arachidonic acid?

Answer 17

It is a precursor to eicosanoids (inflammatory signaling molecules)
CAN REPLACE linoleic acid if deficient

Question 18

What is a triacylglycerol (TAG)?

Answer 18

A lipid made of 3 fatty acids esterified to a glycerol backbone
- is non polar

Question 19

Difference between simple and mixed TAGs?

Answer 19

Simple = identical fatty acid chains; Mixed = different fatty acid chains and are named according to the position on glycerol
e.g. 1-palmitoleoyl-2-linoyl-3-stearoyl-glycerol

Question 20

Should we have more omega 6 or omega 3?

Answer 20

Omega 6

Question 21

Why are fats more efficient for energy storage than carbohydrates?

Answer 21

Fats store complete oxidation is ~38 kJ/g which is more than carbs ~ 17kJ/g, are anhydrous, and take up less space so easier to store

• if whole body was made of carbs it would be too heavy

Question 22

What is the structure of a phospholipid?

Answer 22

Glycerol + 2 fatty acids + phosphate group with a polar head group
- also called glycerophospholipids/ phosphoglycerides

Question 23

Where is the phosphate on a glycerol?

Answer 23

• 3rd position point on glycerol

Question 24

If the R group on a phosphate is just H what is it called?

Answer 24

Phosphatic acid

Question 25

What does amphiphilic mean?

Answer 25

Has both hydrophilic (polar) and hydrophobic (nonpolar) parts

Question 26

What are the most common head groups on a phospholipid?

Answer 26

Phosphatidylinositol Phosphatidylserine Phosphatidylcholine Ethanolamine - need to know these sadly

Question 27

What are sphingolipids?

Answer 27

Membrane lipids which have sphingosine instead of glycerol

Question 28

What is the backbone of sphingolipids?

Answer 28

Sphingosine (an amino alcohol)

Question 29

What are 2 sphingolipids where the amino alcohol is attached to the phosphate?

Answer 29

choline, ethanolamine

Question 30

What is a ceramide?

Answer 30

A sphingosine + fatty acid attached via an amide bond

Question 31

What is sphingomyelin?

Answer 31

A sphingolipid with phosphorylcholine head group; found in myelin sheath

Question 32

What % of lipids do sphingomyelins take up in the human body?

Answer 32

25% of all lipid in humans

Question 33

What is the structure of sphingomyelin and why?

Answer 33

Usually 2 straight chains, gives tighter packing and stabilises the membrane. Also alters fluidity

Question 34

What are glycolipids?

Answer 34

Lipids with a carbohydrate group instead of phosphate e.g galatose or glucose - they are amphipathic specialised membrane components

Question 35

3 examples of glycolipids?

Answer 35

Cerebrosides, sphingoglycolipids, glycosphingolipids

Question 36

Where are glycolipids commonly found?

Answer 36

Plant cells and nerve cells

Question 37

What is the biological role of glycolipids?

Answer 37

Cell recognition and signaling (e.g. blood group antigens)

Question 38

What defines the structure of a steroid?

Answer 38

4 fused rings (3 six-membered, 1 five-membered) Relatively non-polar

Question 39

Which organism are steroids found?

Answer 39

- Only found in eukaryotes but similar found in prokaryotes is called hopanoids

Question 40

What is cholesterol?

Answer 40

Most common steroid - rigid and flat, important in membranes; amphipathic; precursor to hormones and vitamins

Question 41

How does cholesterol affect membrane fluidity?

Answer 41

Stabilizes membrane by decreasing fluidity at high temp and increasing at low temp - reduces entropy - prevents FA associated so kept apart and can't crystallise

Question 42

List 3 steroid hormones derived from cholesterol.

Answer 42

Testosterone, cortisol, aldosterone - also for Vit D and bile salts

Question 43

What is a medicine used to treat high cholesterol?

Answer 43

Simvastatin

Question 44

What is a terpenoid (isoprenoid)?

Answer 44

A molecule derived from isoprene units

Question 45

Name 3 important molecules derived from terpenoids.

Answer 45

Fat soluble vitamins: Vitamin A, Vitamin K, and Ubiquinone (CoQ10)

Question 46

What are lipoproteins?

Answer 46

Complexes of lipids and proteins that transport fats in the bloodstream

Question 47

What are lipopolysaccharides (LPS)?

Answer 47

Complexes of lipids and carbohydrates found in bacterial outer membranes

Question 48

What are waxes made of?

Answer 48

Long-chain fatty acids and long-chain alcohols joined by ester bond - long saturated chain so pack and form induced dipole dipoles

Question 49

Where does a fatty acid with omega-6 come from?

Answer 49

Plants

Question 50

How does the systematic numbering system begin in fatty acids?

Answer 50

Carbon 1 is the carboxylic acid

Question 51

What is the alternative method to systematic numbering in fatty acids?

Answer 51

Omega to reference carbon other end of carboxyl carbon. Next one in from carboxyl is alpha, then beta, then end one is always omega

Question 52

What does it mean if something is a phosphosphingolipid?

Answer 52

It contains sphingosine (not glycerol like phospholipids) Has a phosphate group And often includes a choline head group (just like phosphatidylcholine

Question 53

What is the cis form of a biological fatty acid?

Answer 53

Both hydrogens on the same side

Question 54

What is the primary oxidation in bodies?

Answer 54

Beta oxidation

Question 55

What is the most common saturated fatty acid?

Answer 55

Palmitic acid

Question 56

What does trienoic mean?

Answer 56

3 double bonds

Question 57

What are the 3 essential fatty acids?

Answer 57

Alpha linoleic acid Linoleic acid Arachidonic acid - only essential if deficient in linoleic acid

Question 58

What is a TAG with 3 steroid acid chains called?

Answer 58

Tristearolyglycerol

Question 59

What is a TAG with 3 oleic acid residues called?

Answer 59

Trioeoylglycerol

Question 60

What are the 3 components of a sphingosine?

Answer 60

A long hydrocarbon tail (like fatty acids) A hydroxyl group (-OH) An amino group (-NH₂)

Question 61

What are terpenoids?

Answer 61

Lipid-based molecules built from repeating units of a simple 5-carbon molecule called isoprene (C₅H₈)

Question 62

What state would you find a saturated TAG in at room temperature?

Answer 62

Solid

Question 63

Name the 3 TAG functions

Answer 63

1. Insulation 2. Protection 3. Store energy