lipids Flashcards
1
Q
Functions of lipids?
A
Store energy
Water repellent
Buoyancy control and acoustics in marine animals
Cofactors for enzymes
Protect organs
Insulation from environment
Pigments
Digestion
Membrane structure
Signalling molecules
Antioxidants
2
Q
What is a FFA?
A
Free fatty acid
Not a component of another lipid
3
Q
Describe fatty acid structure
A
Fatty -hydrocarbon chain
Acid - carboxyl group
4
Q
How long can the fatty acid hydrocarbon chain be?
A
2-24 carbons
5
Q
Why is the hydrocarbon chain hydrophobic?
A
can’t form hydrogen bonds with H2O
6
Q
What are SFAs?
A
Saturated fatty acids
no double bonds in hydrocarbon chain
7
Q
What are MUFAs?
A
Mono unsaturated fatty acids
Have 1 C=C in hydrocarbon chain
Usually has a kink
8
Q
What are PUFAs?
A
Polyunsaturated fatty acids
Multiple C=C in hydrocarbon chain
9
Q
How does the number of C=C in the hydrocarbon chain affect fatty acid boiling point?
A
More C=C lowers the boiling point
e.g
olive oil - oleic acid - PUFA - liquid at room temp
butter - mostly SFAs - solid at room temp
10
Q
Naming fatty acids, which is carbon 1?
A
carbon of carboxyl group
11
Q
What is the second carbon in fatty acids called?
A
α carbon or carbon 2
12
Q
If the name of a fatty acid has 14:3 included, what does this mean?
A
14 - number of carbons
3 - number of C=C
13
Q
What is the Δ used for when naming fatty acids?
A
Shows position of double bond
E.g Δ 5,9 shows there are double bonds on carbons 5 and 9
14
Q
What does it mean if a double bond is:
Cis
Trans
A
Cis - H atoms on same side of double bond
Trans - H atoms on opposite sides of double bond
15
Q
All natural fatty acids are cis or trans?
A
cis
16
Q
What is the last carbon in the hydrocarbon chain called?
A
Omega ( ω ) carbon
17
Q
What does it mean if a FA is an:
omega 3 FA
omega 6 FA
A
omega 3 - first C=C is on the 3rd carbon counting from the ω carbon
omega 6 - first C=C is on the 6th carbon counting from the ω carbon
18
Q
Omega-3 fatty acids are considered…
A
Anti-inflammatory
19
Q
Omega-6 fatty acids are considered…
A
Pro-inflammatory
20
Q
Example of an omega-6 fatty acid?
A
Arachidonic acid
21
Q
example of an omega-3 fatty acid?
A
Eicosapentaenoic acid (EPA)
22
Q
3 derivatives of arachidonic acid and their functions
A
Prostaglandins
fever, renal blood flow, mucosal protection, inflammation
Thromboxanes
formation of blood clots
Leukotrienes
inflammation, smooth muscle contraction in lungs
23
Q
What is arachidonic acid made from?
what enzyme does it use?
A
Cell membrane phospholipids
uses phospholipase enzyme
24
Q
what are the 3 arachidonic acid derivates?
A
- leukotrienes
- prostoglandins
- thromboxane and prostaglandins
25
what pathway is leukotrienes produced by?
lipoxygenase pathway
26
what pathway are prostaglandins and thromboxane produced by?
cyclooxygenase pathway
27
what is needed to produce (prostaglandins and thromboxane)
cox-1
28
what is needed to produce just prostaglandin
cox-2
29
is cox 1 physiological or inducible?
physiological
30
is cox 2 physiological or inducible?
inducible
31
What will inhibit the production of arachidonic acid?
Corticosteroids
32
What will inhibit the production of both thromboxane and prostaglandins?
NSAIDS - non-steroidal anti-inflammatory drugs
33
Examples of NSAIDS?
Ibuprofen
Phenylbutazone
Diclofenac
34
Describe COX-2 preferential NSAIDs and examples of them
Affect COX-2 more than COX-1
Meloxicam
Carprofen
35
Example of COX-2 specific NSAID
coxibs
36
Why shouldn't you use steroids and NSAIDs together?
Steroids reduces arachidonic acid formation
no need for NSAIDs too
more side effects
37
What are TAGs?
Triacylglycerols/ triglycerides
38
Describe the structure of TAGs
- 3 fatty acids
* can be different
- 1 glycerol
- Fatty acids joined to glycerol by ester bonds ( C=O-O-C) : each of the 3 OH groups in glycerol forms an ester bond with the carboxyl group of a fatty acid
39
How are the ester bonds in TAGs broken?
hydrolysed by lipases or esterases
40
Can TAGs cross the cell membrane?
no
41
What are the main lipid components of dietary fats?
TAGs
42
how are TAGs digested
* TAGs are digested into FA and monoacylglycerol components in the small intestine.
* Re-constituted into TAGs within enterocytes.
* Packaged in the ER of enterocytes into
chylomicrons.
* Enter the lymphatic system via the lacteal where they join lymph fluid to become chyle fluid.
Chyle returns to vascular system through venous return and then supplies tissues with TAGs.
43
what are chylomicrons?
* lipoproteins: composed of phospholipids and
apolipoproteins
- transport fat from small intestine (where absorbed) to liver and adipose tissues
44
Where are lacteals found?
In small intestine villi
45
What is chyle fluid?
Lymph fluid containing many chylomicrons
46
When are fatty acids used for energy?
Fasting/starvation
47
Where are TAGs stored?
adipocytes
48
What is excess glucose converted to?
Fatty acids
Glycerol
stored in apodicytes
49
Is storage of TAGs in apodicytes short or long term?
long term
50
When would there be an excess glucose?
Energy requirements met
Glycogen store full
51
When does lipogenesis occur?
Glucose surplus + glycogen store full
Transported to liver in blood
Converted to fatty acids and glycerol in the liver
52
Describe the pathway of lipogenesis
Glucose synthesises glycerol
Glycolysis of glucose produces pyruvate
Pyruvate forms acetyl coA
Provides 2C at a time
NADPH needed to form fatty acids from acetyl coA
53
What are lipoproteins transported from hepatocytes as?
VLDL - very low density lipoprotien
54
Describe lipoproteins
Same structure as chylomicrons
Transport TAGs and cholesterol
Higher cholesterol than chylomicrons
Named according to density
less cholesterol = higher density
VLDL, IDL, LDL, HDL
Transport fats around the body
55
How are fatty acids freed from lipoproteins?
Lipoprotein lipases
56
What is lipolysis?
Breakdown of stored TAGs in apodicytes to fatty acids and glycerol
57
What induces lipolysis?
Several hormones:
glucagon
cortisol
adrenaline
58
When does lipolysis occur?
After 24 hour fasting
Endurance exercise - 'going through the wall' switch from glucose metabolism to lipid metabolism
59
Why can FFAs exist in the blood freely?
How do they usually travel in the blood?
Have carboxyl group - hydrophilic
Bound to albumin
60
What can use FFAs freely?
What can't and why?
Muscle + the liver
Brain:
FA too large to cross blood brain barrier
61
How are fatty acids metabolised?
Β-oxidation
In mitochondria
62
Can fatty acids cross the mitochondrial double membrane?
No
Transported in by carnitine shuttle
63
Where can large FA be oxidised?
Peroxisomes
64
Steps of the carnitine shuttle
1. Fatty acid binds to coA ⇒ fatty acyl coA via fatty acyl CoA synthase (FACS) in cytoplasm
2. CoA exchanged for carnitine ⇒ acyl carnitine using CPT 1 (carnitine palmitoyltransferase I)
3. Acyl carnitine translocated by facilitated diffusion using an unbound carnitine via CAT (Acylcarnitine translocate)
4. Carnitine of the acyl carnitine exhanged for coA via CTP 2 ( carnitine palmotoyltransferase II)⇒ fatty acyl coA reformed - B-oxidation can now occur
64
Steps of the carnitine shuttle
1. Fatty acid binds to coA ⇒ fatty acyl coA
2. CoA exchanged for carnitine ⇒ acyl carnitine
3. Acyl carnitine translocated by facilitated diffusion using an unbound carnitine
4. Carnitine of the acyl carnitine exhanged for coA ⇒ fatty acyl coA reformed - B-oxidation can now occur
65
Describe B-oxidation
2 carbons removed from fatty acid chain at a time
produces acetyl coA
produces NADH and FADH2
Acetyl coA then used for krebs/TCA cycle
NADH and FADH2 used in oxidative phosphorylation (ETC)
66
What happens when there is excess acetyl coA?
Goes into ketogenesis cycle
67
What happens in ketogenesis?
Excess acetyl coA converted into ketones
68
What can be smelled on the breath of an animal suffering from ketoacidosis?
Acetone - sweet smelling/ pear drops
e.g milk fever, uncontrolled diabetes
69
what can be produced from ketogenesis?
- acetoacetate
- b- hydroxbutyrate
- acetone
70
What is pregnancy toxaemia in sheep also known as?
twin lamb disease
71
Describe twin lamb disease
- affects ewes in late gestation
- often those with more than one lamb
- inadequate nutrition during late gestation/ anorexia
- foetal glucose demands can't be met by the ewe/gluconeogenesis
- adipose stores are mobilised and fatty acids are b-oxidised
- excess fatty acid metabolism results in ketone formation and ketoacidosis- pregnancy toxaemia
72
Describe milk fever
Bovine toxosis
Usually affects dairy cow in early lactation
Caused by inadequate nutrition in last gestation + early lactation
Glucose requirements for milk production not met by gluconeogenesis
Adipose stores mobilised
B-oxidation of fatty acids
Excess metabolism causes ketone formation
excess acetone= ketoacidosis
73
What are phospholipids also called?
Glycerophospholipids
74
Components of phospholipds
- 2 fatty acids
*usually one saturated, one unsaturated
- Phosphate group
*bound to 3' C of glycerol
- Glycerol
*Polar head group can vary
75
Why are phospholipid heads hydrophilic?
Phosphate group is negatively charged
76
Describe the most common phospholipid in the plasma membrane
Phosphoatidylcholine
has choline polar head group
77
Which glycerophospholipid is involved in cell-signalling processes?
Phosphoatidylinositol 4,5 -biphosphate
78
Describe cardiolipin
Phospholipid
Found in cardiac tissue and mitochondria
Biomarker for apoptosis
Head group is another phospholipid
4 fatty acids in the molecule overall
79
What are sphingolipids? How do they relate and differ to phospholipids (structure)
Lipids found in plasma membrane
Both have hydrophilic/phobic parts
Sphingolipids only have one fatty acid
80
Sphingolipid structure
Fatty acid linked to sphingosine
no glycerol
Head group attached to sphingosine
head group + sphingosine = sphingoid base
81
Structure of sphingomyelin?
Fatty acid
Sphingosine
Phosphocholine head group
82
3 functions of sphingomyelin
Myelin sheath surrounding + insulating nerve cell axons
Role in action potential transduction
Involved in apoptosis
83
What are glycosphingolipids?
Example?
Sphingolipids with carbohydrate head group
Blood group
diff carb head group = diff blood group
84
What is cholesterol the starting point for?
Many sterols
85
Why are sterols very hydrophobic?
High carbon content
86
How can you tell a sterol apart from other lipids?
Conserved ring structure
4 carbon rings
3 hexagonal
1 pentagonal
87
What is cholesterol needed for?
Proper membrane function
Steroid hormone synthesis
88
How do animals obtain cholesterol?
Dietary source
Synthesise from acetyl coA
89
2 examples of sex hormones
Testosterone
Oestrogen
90
What is cortisol?
Importance?
Excessive amounts can cause?
Stress response steroid hormone
Induce gluconeogenesis when starvation
Cushing's disease
91
Importance of aldosterone?
Causes Na retention and K excretion in kidneys
This causes water retention
92
Which disease results in reduced/no production of aldosterone?
What does this cause?
Addison's disease - destroys aldosterone producing cells
Electrolyte imbalance, dehydration, death
93
2 steroid drugs used in practice
Prednisone
Prednisolone
94
Steroid hormone found in cabbages?
Brassinolide
95
Cholesterol is the starting point for the synthesis of...
Bile acids
96
Why are bile acids important?
Detergents
Emulsify lipids
allow lipase to break lipid down
Cholesterol homeostasis
too much cholesterol = make more bile acids
97
Describe the path from primary bile acids to secondary to conjugated
Primary bile acid dehydoxylated
hydroxyl group removed
Secondary bile acid made
then conjugated by glycine or taurine
Makes conjugated bile acid
now hydrophilic
98
How do bile acids aid in fat digestion?
Break fats into smaller droplets/micelles
Allows pancreatic lipases to break lipid down
99
Hydrophobic/philic parts of the bile acid?
Phobic- sterol
Philic - conjugated amino acid
100
what are the fat soluble and water soluble vitamins?
fat soluble- K A D E
water soluble- B C
101
How is vitamin D3 manufactured?
Cholesterol in skin
Presence of sunlight
uv-b radiation
processes in skin, liver, kidney
102
What is vit D3 needed for?
What happens if deficient?
Calcium absorption in small intestine
Rickets - bones not developed properly
103
What is retinol?
vitamin A
104
Is vitamin A derived from cholesterol?
No - doesn't have 4 ring structure
105
Is retinol hydrophilic or hydrophobic?
Hydrophobic
106
What is retinol produced from?
B-carotene
found in carrots
Split into 2 identical molecules - retinol
107
How is retinal converted to retinoic acid? What is this important for?
11-cis- retinal oxidised
forms retinoic acid
108
Why is vitamin E hydrophobic?
Large carbon chain
109
Role of vitamin E
antioxidant properties
- the important antioxidant in hydrophobic environments such as within cell membranes
- protects fatty acids within cell membranes from oxidation
110
Differences and similarities of vitamins C and E
Similarities - both antioxidant
Diff - vit C is hydrophilic
Vit C works in aqueous environments - not hydrophobic
111
Importance of vitamin K
Cofactor in blood coagulation pathway
112
Is vitamin K hydrophobic or hydrophilic?
hydrophobic
113
Describe the blood coagulation pathway
Vit K is a cofactor for Vit-K dependent carboxylase enzyme
Enzyme adds carboxyl group to glutamate residues in certain clotting factors
makes carboxyglutamate residues
CG residues chelate Ca ions
enables clotting factors to bind to cell membranes and form a clot
114
What happens to vitamin K in the blood coagulation process?
What must be done to maintain balance?
oxidised in process so needs to be reduced
115
How does warfarin work?
Inhibits enzyme that oxidises reduced Vitamin K
Vitamin K is not active whilst it is reduced
Means that blood cannot clot
116
How can you treat a dog that has eaten rat poison?
Make them sick
If late , oversupply with vitamin K
117
Which vitamin is the liver very rich in?
Vitamin A
118
3 things vitamin A is needed for
Vision
Gene regulation
Appropriate bone turnover
119
Excess of vitamin A causes.. (bones)
Excessive breakdown of bone
by osteoclasts
Causes loss of bone from general skeleton
High Ca released from lost bone in skeleton
Circulates and deposits in inappropriate locations
New bone formed in inappropriate locations
120
Why is vitamin A toxic at high doses but vitamin C isn't?
Vit C water soluble - can be excreted
Vit A hydrophobic
needs to be converted to hydrophilic in order to be secreted
Vit A stored in adipose tissue
not accessible to drug metabolism enzymes
121
Structure of waxes
Long chain fatty acid
Long chain alcohol
Joined by ester bond
122
Functions of waxes
Plankton use as energy store
Waterproofing feathers
Protection + pliability of hair and skin
Beeswax
123
Who makes polyketides?
What do we used them for?
Plants and fungi
Drugs
124
Many pigments are ___ - based
fat
