L4 - Lipids Flashcards
Describe the properties of lipids. (x7)
- Large biomolecules
- Formed from C, H, O and sometimes, P
- Not polymers
- Largely non-polar (as there are mostly C-H and C-C bonds)
- Largely insoluble in water
- Soluble in non-polar solvents
- Hydrophobic interactions cause lipids to group together in water
What are triglycerides made up of?
- 1 Glycerol
- 3 Fatty Acids
What bond is formed between fatty acids and glycerol?
Ester bond
Describe the digestion of triglycerides.
- Broken down by hydrolysis
- Requires intestinal enzyme, triglyceride lipase + H2O
= FFAs more easily absorbed in the gut and transported
What are the 2 classes of fatty acids?
- Saturated
- Unsaturated
What are saturated fatty acids?
Fatty acids that contain only single C-C bonds.
What are unsaturated fatty acids?
Fatty acids that contain one or more double bonds (C=C).
What are Free Fatty Acids (FFAs)
Fatty acids that are not part of a triglyceride.
Name the 2 fatty acids that are essential and cannot be synthesised in the body.
- Omega 3
- Omega 6
How are omega FFAs named?
By the location of the first double bond, counted from the methyl end (= omega end).
What types of triglycerides do saturated and unsaturated fatty acids form, and what state are they in at room temperature?
- SFAs form compact, closely packed triglycerides = solid at RTP
- UFAs form loosely packed triglycerides (due to cis double bonds) = liquid at RTP
Describe the properties of steroids.
- Steroids are lipids
- Basic structure is 4 fused carbon rings with various side groups attached
- Lanosterol is the building block for all steroids
What is the building block for all steroids?
Lanosterol
How is lanosterol formed?
By the cyclisation of squalene.
Name 4 examples of steroids.
- Cholesterol
- Sex Hormones
- Corticosteroids
- Vitamin D (Cholecalciferol) = a secosteroid
What are 2 functions of corticosteroids?
- Anti-Inflammation
- Fluid balance
Where are corticosteroids produced?
In the adrenal cortex
Name 2 examples of corticosteroids, and classify what type of steroids they are.
- Aldosterone (mineralocorticoid)
- Cortisol (glucocorticoid)
Name 3 sex hormones that classify as steroids.
- Oestrogen
- Progesterone
- Testosterone
What are phospholipids?
Lipids with a phosphate group (PO42-) covalently bonded to the glycerol backbone, instead of a fatty acid.
Describe the properties of the phosphate group in a phospholipid.
- Acts as a ‘head’
- Polar
- Soluble in water (hydrophilic)
Describe the properties of the fatty acid groups in a phospholipid.
- Acts as a ‘tail’
- Non-Polar
- Insoluble in water (hydrophobic)
Name the 5 different substances that the group ‘X’ on phosphate can be, and describe what product is formed as a result.
- Hydrogen = Phosphatidic Acid
- Ethanolamine = Phosphatidylethanolamine
- Serine = Phosphatidylserine
- Choline = Phosphatidylcholine
- Inositol = Phosphatidylinositol
How do phospholipids organise themselves in water?
- Hydrophilic heads point outwards
- Hydrophobic tails point inwards
What are micelles?
Spherical arrangement of lipid molecules
What is a bilayer?
Composed of 2 layers of lipids organised as a sheet
What is the purpose of the cell membrane?
Complex structure that physically separates the interior of the cell from the outside environment to confer protection from the surroundings.