S1-L4: Lipids Flashcards
What are lipids?
- Large molecules formed from C/ H/ O & sometimes P
- are not polymers- just large
Describe the “non-polarity” feature of lipids
- largely non-polar–> mostly C-H/ C-C bonds
- ->largely insoluble in water
- soluble in non-polar solvents like hexane
- hydrophobic interactions caused by lipids grouping together in H2O
Outline examples of lipids
- Fats (solids)-a.r.t
- oils (liquid)- a.r.t
- waxes (solid v. hydrophobic)- a.r.t
- phospholipids (form membrane bilayers)
- steroids (derived from lanosterol)
What are triglycerides? (refer to figure 1)
-type of dietary fat
Outline the structure of triglycerides
-formed from 2 components:
1x Glycerol–> backbone AND 3x fatty acid chains
-fatty acid chains linked to glycerol backbone via ester bond
From which process are triglycerides formed?
-formed via dehydration synthesis–> condensation reaction
How are triglycerides broken down and what conditions are required for this process?
- broken down via hydrolysis
- requires intestinal enzyme–> triglyceride lipase + H2O
Why is the digestion for triglycerides beneficial?
-free fatty acids absorbed in to gut easier AND transported
Outline the two classes of fatty acids and give an example of each
1-saturated
2-unsaturated
1- contain single C-C bonds such as Palmitate
2- contain 1+ C=C double bond like Oleate
What are Omega-3 fatty acids? (figure 2)
-polyunsaturated fatty acids characterised by C=C presence 3 atoms away from terminal methyl group
How are Omega-3 fatty acids named?
- named by location of first C=C which counted from methyl end
- when not part of triglyceride–> Free Fatty Acids (FFA’s)
Are FFA’s important?
-some FFA’s essential–> can’t synthesis in body
Describe saturated (SFA’s) and unsaturated (UFA’s) fatty acids at room temperature
- SFA’s: from compact and closely packed triglycerides solid at room temp
- ->E.G: Palmitic acid (16 C) present in plant + animal fats
- UFA’s: form loosely packed triglycerides due to cis double bond which liquid at room temp
- ->like olive oil>80% oleic acid (18 C)
What are steroids?
-4 fused C ring with various side groups attached
What is lanosterol and how is it formed? (refer to figure 3)
- building blocks for all steroids
- formed by cyclization of squalene
Outline the following examples of steroids:
1-Cholesterol (figure 4) 2-Sex hormones (figure 5-oestrogen) 3-Corticosteroids 4-Aldosterone (figure 6) 5-Cortisol 6-Vitamin D-cholecalciferol (figure 7)
1-diagram 2-oestrogen/ progesterone/ testosterone 3-many functions (inflammation/fluid balance) -->produced in adrenal cortex 4-mineralocorticoid 5-glucocorticoid 6- a secosteroid --> at least one of ring structure broken up
Outline and describe phospholipids (figure 8)
- lipid with phosphate group (PO4 2-) covalently bonded to glycerol backbone instead of fatty acid
- phosphate group: polar/water soluble (hydrophilic)/is head
- fatty acid groups: non-polar/water insoluble (hydrophobic)/ is tail
Phospholipid examples
- H–> phosphatic acids
- Ethanolamine–> phosphatidylethanolamine
- Serine–> phosphatidylserine
- choline–> phosphatidylcholine
- Inositol–> phosphatidylinositol
What are the following? :
1-Micelle
2-Bilayer
1-spherical arrangement of lipid molecule
2-composed of 2 layers of lipids organised in to sheets
How do phospholipids organise themselves in water?
-the phospholipids organise themselves to keep hydrophilic heads “wet” AND hydrophobic tails “dry”
Describe cell memebranes
- complex structure-physically separates cell interior from outside environment to confer protection from surrounding
- ->also provide role in anchoring extracellular structured AND other cells needed for tissue formation
Outline glycolipids and their use
- lipid covalently attached to oligosaccharide
- forms part of cell membrane AND glycocalyx
- determines ABO blood group
What are lipoproteins? (figure 9)
-soluble complexes which transport lipids AND synthesised in liver
Describe the structure of lipoproteins
- spherical compounds with central hydrophobic core:
- -> triglyceride
- ->esterified cholesterol (cholesteryl ester)
- -> small amounts of other lipids + fat soluble vitamins
- external hydrophobic layer:
- -> phospholipids
- ->cholesterol (OH functional group outermost)
- ->apoproteins- stabilise structure + regulate enzyme activity at lipoprotein interface
Analyse figure 10 showing lipoprotein classification
-figure 10- table
Outline each of the following lipoprotein classifications:
1-Chylomicron
2-VLDL
3-IDL/LDL
4-HDL
1- carry dietary fat from small intestine to liver
2- Very Low Density Lipoprotein
–> produced in liver from synthesised TG’s + CE & carry fat to target tissues
3-TG’s gradually removed from circulating VLDL whcih become IDL (Intermediate Density Lipoprotein) THEN LDL (Low Density Lipoprotein)
4-High Density Lipoprotein
–>carries cholesterol to liver (“good cholesterol” reducing atherosclerosis)
–>Atherosclerosis: arteries clogged with fatty material- sites of fatty deposition called plaques
What is the optimal lipoprotein profile in terms of HDL/LDL/TG’s/Total Cholesterol?
- HDL: >60 mg/dL
- LDL: 60-130 mg/dL
- TG’s: <150 mg/dL
- Total Cholesterol: <200 MG/dL
Describe the key feature of TG’s and how it alongside FFA’s are useful
- TG’s largely non-polar AND relatively compact
- TG’s + FFA’s have energy-rich C-H bonds available for chemical reactions within cells
Outline the storage of TG’s
-stored as lipid droplets in cytoplasm of adipocyte cells in adipose tissue
What is White adipose tissue and what is it used for?
- cushions internal organs like shock-absorber
- give insulation-protecting internal organs from temp change AND reducing heat loss
Similarly, outline what Brown adipose tissue is
- used to generate body heat
- ->brown adipocytes contain numerous fat vacuoles AND mitochondria
Where is white adipose tissue located?
-analyse figure 11
How can having excess adipose in the body increase the risk of disease? (figure 12)
- exerts undue pressure on organs
- is major endocrine organ–> produces pro-inflammatory hormones like Leptin/ cytokine TNFa
- diseases which could get are atherosclerosis/stenosis. AND aneurysms
What are the three diseases which can form as stated previously from excess adipose?
- Thrombosis: clotting of circulating blood
- Stenosis: abnormal narrowing of body passage such as blood vessel
- Aneurysms: blood-filled bulge in blood vessel
Explain how phospholipids are involved in electrical insulation inside the body
- phospholipids from myelin insulation around nerve fibers
- myelin–> increases speed of nervous impulses
- Schwann cell produce myelin peripherally
- ->oligodendrocytes produce myelin centrally
What is the link between Vitamins A/D/E/K and fats, lipids and steroids?
- fat soluble
- some are also lipid/steroid derived
Briefly explain what each of the following Vitamins
1-A
2-D
3-E
4-K
1- retinol/ retinoic acid/ carotenoids + healthy teeth/skin/sight
2-cholecalciferol + derivatives AND helps body absorb Ca2+ for healthy bones
3-tocopherol (antioxidant) found in oils AND anit-oxidant protects cell from damage
4-phylloquine + menaquinone AND important for coagulation of blood
What are hormones? (refer to figure 13)
- chemical messengers
- ->steroidal hormones derived from cholesterol
What is Eicosanoids?
-derived from w-3 AND w-6 fatty acids
Outline what 1-postaglandins/2-leukotrienes and 3-thromboxane’s are used for
1-inflammation/vascular tone
2-asthma/allergy
3-vascualr tone/platelet aggregation (platelets clumping together)
With reference to figure 14 and 15 how do lipids prevent moisture loss?
- lipid layer able to inhibit water evaporation
- skin moisture loss reduced by lipid layers
- lipid layer on tear film reduces moisture loss from cornea
- so lipids control what goes in and out of body
- lipids prevent tears drying out so eyes not dry out
Summary of lecture
1-lipids–>non-polar macromolecules (mostly C-H + C-C bonds)
–> C/ H/ O & P atoms
2-triglycerides main dietary fat source
–>3 fatty acid chains esterified to glycerol backbone
3-saturated VS mono-/poly-unsaturated fatty acids impact on fluidity
4-steroids have key functional roles
–>cholesterol/hormones/Vitamin D
5-phospholipids able to form membrane bilayers
–>glycocalyx/glycosphingolipids
6-Lipoprotein profile influence susceptibility to cardiovascular disease
–>HDL Vs LDS
7-white VS brown adipose tissue
–>different location + functions
8-phospholipids form myelin sheath around nerve fibres
9-lipids prevent water loss skin AND eye
