Lipids & Biomembranes

Question 1

3 biological functions of lipids

Answer 1

1. energy storage
2. structural
3. signalling

Question 2

Energy storage

Answer 2

• fatty acids = carboxylic acids + hydrocarbon chains
• primary energy storage molecule
• usually an even number of carbons

Question 3

Types of fatty acids:

Answer 3

Saturated = all single bonds
Unsaturated = some double bonds
Monosaturated = 1 double bond only
Polyunsaturated = multiple double bonds

Question 4

Nomeclature of Fatty Acids

Answer 4

• specify length followed by number of bonds seperated by colon
  e. g. 18 carbons with 2 double bonds = 18:2
• carbons numbred from carboxyl end (COOH)
• triangle denotes double bond

Question 5

Essential Fatty Acids

Answer 5

• essential but cannot be produced in body as we lack the ezyme required
  e. g. omega-3 & omega-6
• must be obtained via: cold water fatty fish, nuts, seeds, plant oils

Question 6

Storage Lipids: Tricylaglyserols (TAGs)

Answer 6

• glycerol esterified with 3 fatty acid chains
• energy storage molecules (oxidation of fatty acids produces ATP, TAGs are stored in adipocytes)
• important for heat insulation
• non polar

Question 7

Saturated TAGs

Answer 7

• straight tails
• can pakc tightly
• hard fats e.g. butter
• unhealthy
• fat tails are in cis configuration

Question 8

Unsaturated TAGs

Answer 8

• tails have kinks
• cannot pack tightly
• liquid at room temp
• healthier than saturated fats

Question 9

Trans Fats

Answer 9

• isomer of cis configuration
• not common in nature
• better for food prep due to longer shelf life
• more resistance to high temps
• solid at room temp
• can b made by hydrogenation of natural unsaturated fats
• not healthy, increases risk of cardiovascular disease

Question 10

Waxes

Answer 10

• long chain of saturated fatty acids combines with long chain alcohol linked via ester bonds
• hydrophobic
• high melting point
  used in pharmeceuticals/cosmetics

Question 11

Three Types of Structural Lipids:

Answer 11

1. Glycerophospholipids (aka phospholipids)
2. Sphingolipids
3. Sterols

Glycolipids - type of phopholipid or sphingolipid

Question 12

Glycerophospholipid (aka phospholipid)

Answer 12

• most abundant in cell membranes
• amphipathic
• structure: (glycerol backbone, phosphate head, 2 fatty acid tails)
• form bilayers
• head dictates class of phospholipid
• fatty acid tails modulate fluidity depending on length and whether saurated/unsaturated

Question 13

Sphingolipids:

Answer 13

• structure: polar head, 2 hydrophobic tails. (no glycerol)
• linked by phosphodiester or glycosidic bonds
• amphipathic
• polar head defines class of sphingolipid

Question 14

Glycolipids:

Answer 14

• not a type on its own - is a type of phospholipid or sphingolipid
• occurs when phospho or sphingo are glycosylated (sugar group attached to head)
• found in outer face of plasma membrane
• roles in cell reprogramming

Question 15

Sterols:

Answer 15

e. g. most common: cholesterol
- structure: 4 fused rings, hydrocarbon side chain, hydroxyl group
- integral to biological membrane (rigidity, impermeability, integrity)
- seen in steroid hormones & bile acids

Question 16

Biological Membranes - Structure: Polarity

Answer 16

structural lipid are insoluble in water but amphipathic:

• hydophobic group inside away from water
• hydrophilic groups woutside exposed to water

Question 17

Biological Membranes - Function:

Answer 17

• exclusion of toxins and ions
• energy transduction
• cell movement
• interaction with other cells
• nutrient accumulation

Question 18

Biological Membrane - Structure: 3 Sections

Answer 18

• fluid mosiac model: coponents move laterally around membrane
• lipid content: neg charged lipid on intracellular side of membrane
• protein component embedded into bilayer: hydrophobic portions in bilayer; hydrophillic protions sit intra/extracellularly

Question 19

Biological membrane - Structure: Membrane Proteins

Answer 19

• integral proteins
• peripheral proteins
• lipid anchored proteins

Question 20

Signalling Lipids:

Answer 20

• phospholipids that sit inner face act as eserve of messenger molecules
• these are releases iin repinse to extracellular signals e.g. chemical signal,
• hormones can act as extracellular messengers

Question 21

Lipids:

Answer 21

• heterogenous class of organic compounds
• classified based on water solubility
• amphipahic

Question 22

Examples of Open Chain Forms of Lipids

Answer 22

fatty acids, glycolipid, vitamins

Question 23

Examples of Cyclic Forms of Lipids

Answer 23

cholesterol, steroid hormones, bile acids