| What are fatty acids? | They are amphipathic molecules (CH chains ending with COOH) CH3-(CH)n-COOH 2<n<20 they occur as esterified molecules by other components like glycerol or sphingosine. |
| Is the CH tail of the fatty acids saturated or not? | It can be and can not be, if there is a double bond it is unsaturated (up to 6). |
| How is the physical state of saturated and unsaturated fatty acids? | Staurated (solids in room temp)
unsaturated (liquid at room temp)
Unsaturation degree (nb of double bonds) determines the fluidity of the fatty lipid. |
| List the most common saturated fatty acids. | butyric acides , myristic acids stearic acids |
| List most common unsaturated fatty acids | oleic acid, linoleic acid, and arachidonic acid |
| are all fatty acids amphipathic molecules? | yes, because they all have a polar (hydrophilic) side (COOH) and a non polar (hydrophobic) tail. |
| What are triglycerides? | triacylglycerols are nuetral fats since they lack the hydrophilic side. |
| How are triglycerides formed? where are they found? | By ester bonds with glycerol (Three fatty acids are ester bonded to glycerol in the OH releasing water. They are mainly stored in cells (adipose, seeds) as energy reserve. |
| What is the main role of phospholipids? | They form the main structure of cell membrane |
| Describe the phospholipids | large hydrophillic head and large hydrophobic tail, diverse. |
| What are the groups of phospholipids? | glycerol derived, sphingosine derived. |
| How is the glycerol derived phospholipids? | Same as glycerol triglycerides however the third OH group of glycerol is attached to a phosphate group, conferring the amphipathic . |
| What is the importance of the hydrophilic head of the phospholipids? | Linking to polar molecules such as choline, serine, ethanoamine and inositol, to the phosphate group. |
| How is the noemclature of phospholipids ? | according to the added molecules phosphatidylcholine, phosphatidylinositol, phosphodylicethanolamine... |
| How are sphingosine derived lipids? | have a global structure (hydrophilic head with hydrophobic tail) but contain sphigosine instead of glycerol (NH-CH-CH-CH2) (amino alcohol) and phosphate is added at the OH group |
| What is the sphingosine linked to a fatty acid named? | ceramide |
| What are the roles of sphingosine derived phospholipids? | Structure of membrane (myelin sheath of nerve cells- sphingomyelin (phosphatidylcholine) . |
| What are the roles glycolipids? | They cover the outermost shells of most cells, play a crucial role in immunity, blood grop detemination and cell-cell recognition.. |
| Describe the structure of glycolipids. | presence of sugar motif instead of phosphate in phospolipids. Two types glycerol derived and sphigosine derived. |
| How are glycerol derived glycolipids? | Same as glycerol derived phospholipids but instead of a phosphate group the third HO group attaches to carbs , in bacteria and plant cells |
| How are sphingosine derived glyclipids? | are in animal cells , cerebrosides (simplest glycolipids) galactocerebroside contains galactose and abundant in myelin sheath of brain and nerves. carbs linked to the sphingosine may be olgisaccharides containing modified oses, forming the gangliosides |
| What is the difference between cerebrosides and gangliosides? | cerebro->simple carb
ganglio->modified olgicarbs |
| What are cerides? | fatty acids linked to fatty alcohol. esterifies forming a ceride, abundant in bee wax, cork and leaf cuticle.
example cetylic alcohol (CH3-(CH2)15-OH) fatty acid (CH3-(CH2)14-COOH) |
| How do triglycerides form soap molecules? | (after hydrolysis of ester bonds) ionic bonds between COO- and fatty acid molecules and metal ions supplied, usually Na+. |
| How is hydrolysis of triglycerides achieved? | lipases, alkaline medium+heat |
| How do cyclic structures of carbohydrates occur? | OH group (4' or 5' carbon) linked to carboxyl group (1') |
| What are non-saponifiable lipids? | do not contain fatty acids and are mainly steroids or terpenes |
| How do terpenes form? | polymerization of several propene molecules, with certain rearrangement and molecular modification such as cyclisation (cycles) |
| Give examples on terpenes? | fat-soluble vitamins (A, E and K), carotenoids (carrots) or other pigments like lycopene (red tomato), abundant in roots, petals, fruits and leaves. |
| What are the structural characteristics of terpenes? | cyclic structure at one pole of the molecule, resulting from intramolecular interactions, at the opposite pole they have a hydrophilic group (OH) providing them with slight amphipathic characteristic. |
| What does the cyclic structure of terpenes result in? | intramolecular reactions |
| What are steroids? | lipids of complex cyclic molecules on which diverse chemical groups are branched. They are derivatives of (non linear arrangement of 3 cyclohexanes and 1 cyclopentane) |
| How do steroids vary physiologically? | according to nature of chemical groups attached to the cyclohexane and cyclopentane.
Hormones (estrogen, progesterone, testosterone and other adrenal hormones) involved in cell-cell communication (vital roles)
Vitamins (D) indespensible for normal growth and bone developement, it is produced from a precursor (cholesterol) under the effect of UV sun light.
Structural roles: cholesterol cell membrane structure, OH of first cyclohexane gives it hydrophilic head responsible for amphipathy in cholesterol that forms 50% of cell membrane og animal cells.
Fluidity: OH group ensures fluidity
Bidirectional regulation: cholesterol stabilizes melting point at high temperatures, and prevents hardening the cell at lower temperatures. |
| Talk briefly about cholesterol? | abundant in most animal products (eggs, butter, meat, cheese) excess cholesterol cause cardiovascular issues but crucial as precursor of vitamin D for growth and developement, synthesis of sex, bile salts and adrenal hormones. |
| How can we understand the structural organization of lipids? | Through seeing their interaction with water |
| What does water dissolve? | it is a universal solvent, it can dissolve nonionic polar molecules such as alcohols, aldehydes and ketones containing OH group |
| What can water do to amphipathic molecules? | they form micelles and/or lipid layers when they are vigorously mixed they form a suspension or heterogenous solution, so that amphipathic molecules form bilayers, monolayers, liposomes and micelles. |
| How are amphipathic molecules structures interacting with water? | hydrophobic tails are close to one another directed away from water avoiding contact with it, hydrophobic interaction keeps the tails together, hydrophobic interaction stabilizes the sturctures (micelles and lipid layers) and they form the cell membrane. |
| Describe micelle lipid structure. | microscopic spherical structure polar heads are arranged at the surface of the sphere interacting with water forming ionic and H bonds, and hydrophobic tails are towards the inside. |
| Describe bilayers. | exclude hydrophobic tails from water molecules, when large enough, it may fold back and form an artificial spherical vesicle named liposome that encloses a hydrophilic lumen, the central layer is hydrophobic and forms a barrier against hydrophilic compounds, it is not completely impermeable since it allows flow of some hydrophilic molecules among lipid molecules. |
