LIPIDS 1 Flashcards
(69 cards)
1
Q
- is an organic compound found in living organisms that is insoluble (or only sparingly soluble) in water but soluble in non-polar organic solvents.
- Unlike other biomolecules, lipids do not have a common structural features that serves as the basis for defining such compounds.
A
Lipid
2
Q
Five categories of lipids
A
- Energy-storage lipids
- Membrane lipids
- Emulsification lipids
- Chemical messenger lipids
- Protective-coating lipids
3
Q
o Triacylglycerols
A
Energy-storage lipids
4
Q
o Phospholipids
o Sphingoglycolipids
o cholesterol
A
Membrane lipids
4
Q
o obile acids
A
Emulsification lipids
5
Q
o steroid hormones
o eicosanoids
A
Chemical messenger lipids
6
Q
o Biological waxes
A
Protective-coating lipids
6
Q
- _________ exhibit structural diversity
- Some are esters, some are amides, and some are alcohols (acyclic and cyclic) and some are polycyclic.
A
Lipids
7
Q
Types of fatty acids
A
Saturated and unsaturated fatty acids
Polyunsaturated fatty acids (pufas)
7
Q
- Carboxylic acids with linear (unbranched) carbon chain - Fatty acids are naturally occurring monocarboxylic acids
- Even number of Carbon atoms:
o Long chain fatty acids: C12 - C26
o Medium chain fatty acids: C6 – C11
o Short-chain fatty acids: C4 – C5
A
Saturated and unsaturated fatty acids
8
Q
- Numbering starts from the end of -COOH group
- See structural notation: it indicates number of C atoms
o Lauric acid has 12 C atoms and no double bonds so it is (12:0)
A
Saturated fatty acids
9
Q
- A monounsaturated fatty acid is a fatty acid with a carbon chain in which one carbon–carbon double bond is present.
- Different ways of depicting the structure
A
Unsaturated fatty acids
9
Q
- A ________________ is a fatty acid with a carbon chain in which two or more carbon–carbon double bonds are present.
- Up to six double bonds are found in biochemically important PUFAs.
- Two types of unsaturated fatty acids:
o Omega (ω)-3 fatty acids:
o Omega(ω)-6 fatty acid:
A
Polyunsaturated fatty acids (pufas)
10
Q
An unsaturated fatty acid with its endmost double bond three carbon atoms away from its methyl end.
A
o Omega (ω)-3 fatty acids:
10
Q
is an unsaturated fatty acid with its endmost double bond six carbon atoms away from its methyl end.
A
o Omega(ω)-6 fatty acid
11
Q
Selected unsaturated fatty acids of biological importance
* Numbering starts from the other end of COOH
* See structural notation: it indicates number of C atoms
o 18:2 - 18 carbons, 2 double bonds
A
Selected unsaturated fatty acids of biological importance
* Numbering starts from the other end of COOH
* See structural notation: it indicates number of C atoms
o 18:2 - 18 carbons, 2 double bonds
12
Q
Essential fatty acids
* Must be part of diet
* Nutritionally important Omega-3 and Omega-6 fatty acids
o Linolenic acid – Omega-3
o Linoleic acid – Omega-6
* Linoleic Acid Deficiency:
o Skin redness - becomes irritated
o Infections and dehydration
o Liver abnormalities
o Children need it the most
o Human milk has more than cow’s milk
A
American diet
* Sufficient in omega 6 fatty acids
* Deficient in omega 3 fatty acids
o Fish: good source for omega 3 fatty acids
* High rate of heart disease may be due to imbalance in omega 3 and 6 fatty acids
o Ideal ratio – Omega 6 : Omega 3 (4-10 g: 1g)
13
Q
- Short chain fatty acids have some solubility whereas long chain fatty acids are insoluble
- Short chain fatty acids are sparingly soluble because of carboxylic acid polar group
- Physical properties such as melting point depends on the number of C atoms and degree unsaturation
A
Water solubility
14
Q
- Length of carbon chain
- Degree of unsaturation (number of double bonds in a molecule)
A
The melting point
15
Q
- The number of bends in a fatty acid chain increase as the number of double bonds increase
o Less packing occurs
o Melting point is lower
o Tend to be liquid at room temperature
A
Space-filling molecules
16
Q
- With the notable exception of nerve cells, human cells store small amounts of energy providing materials:
o The most widespread energy storage material - carbohydrate glycogen
o Present in small amounts - Storage material is the triacylglycerols:
o Triacylglycerols are concentrated primarily in special cells (adipocytes)
o Nearly filled with the material.
A
Energy-storage materials
17
Q
Two types of triacylglycerols
A
a. Simple Triacylglycerols
b. Mixed Triacylglycerols
18
Q
o Three identical fatty acids are esterified
o Naturally occurring simple triacylglycerols are rare
A
Simple Triacylglycerols
18
Q
- Chemical Properties due to two functional groups: esters and alkenes
o Hydrolysis: Partial hydrolysis of triacylglycerols
o Breaking of 1-2 ester bonds to give rise to mono - or diacylglycerol and fatty
acid(s)
o Carried out by enzymes produced by the pancreas
A
Partial hydrolysis
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o A triester formed from the esterification of glycerol with more than one kind of fatty acid
o In nature mostly mixed triacylglycerols are found and are different even from the same source depending on the feed
corn
peanut
wheat -fed cows have different triacylglycerols
Mixed Triacylglycerols
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* Numerous studies now indicate that eating nuts can have a strong protective effect against coronary heart disease:
o Low amounts of saturated fatty acids
o Nuts also contain valuable antioxidant vitamins, minerals, and plant fiber
protein
Fat and fatty acid composition of nuts
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* Addition of hydrogen across double (=) bond - increases degree of saturation
* Many food products are produced by partial hydrogenation of oils and fats
* Peanut oil + H2 Peanut Butter
* Vegetable oil + H2 Margerine
Hydrogenation
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* Hydrolysis in basic solution: Produce salt of fatty acid and glycerol
Saponification
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* Double bonds in triacylglycerols are subject to oxidation with oxygen in air (an
oxidizing agent) –Leads to C=C breakage
* Remember that oxidation of alkenes may result into two short chain molecules –
an aldehydes or a carboxylic acid:
Oxidation
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* contains one or more fatty acids, a phosphate group, a platform molecule
(glycerol or sphingosine) to which the fatty acid(s) and the phosphate group are
attached, and an alcohol that is attached to the phosphate group.
Phospolipids
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* is a lipid that contains two fatty acids and a phosphate group esterified to a
glycerol molecule and an alcohol esterified to the phosphate group.
* All attachments (bonds) between groups in a glycerophospholipid are ester
linkages
Glycerophospholipids
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* Structures based on the 18-carbon monounsaturated aminodialcohol sphingosine
* contains one fatty acid and one phosphate group attached to a sphingosine
molecule and an alcohol attached to the phosphate group
* Saponifiable lipids
Sphingophospholipids
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* are called cerebrosides
* contains a single monosaccharide unit – either glucose or galactose
o they occur primarily in brain (7% of dry mass)
Simple sphingoglycolipids
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* Contains both a fatty acid and carbohydrate
sphingoglycolipids
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* Complex sphingoglycolipids are called Gangliosides
o contain a branched chain of up to seven monosaccharide residues.
* Occur in the gray matter of the brain as well as in the myelin sheath.
Gangliosides
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* Lipids: Fused Rings
* Cholesterol: C27 steroid molecule
* A steroid is a lipid whose structure is based on a fused ring system of three 6
carbon rings and one 5 carbon ring.
* Important in human cell membranes, nerve tissue and brain tissue
o Important in chemical synthesis: Hormones, vitamins essential for life
Cholesterol: third major type of membrane lipid
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* Liver synthesizes cholesterol: ~ 1g everyday; so it is not necessary to consume in the form of diet
* Cholesterol synthesis decrease if it is ingested but reduction is not sufficient:
Leads to cardiovascular disease
o Animal Food: Lot of cholesterol
o Plant Food: No cholesterol
Cholesterol in food
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o Separates aqueous interior of a cell from the aqueous environment surrounding the cell
o Up to 80% of plasma membrane is lipid material
o The membranes are lipid bilayer made up of phospholipids
Cells
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o Cholesterol helps regulate membrane fluidity – The fused ring system does nor
allow rotation of fatty acid tails in the vicinity
o Fits between fatty acid chains of the lipid bilayer: Make it rigid
o Cholesterol thus acts a membrane plasticizer
Cholestral
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o To maintain cellular processes various molecules transported across the cell membranes.
o Three types of transport:
Passive transport
Facilitated transport
Active transport
* ____________ wherein a substance moves across a cell membrane by diffusion from a region of higher concentration to a region of lower concentration.
o Only a few types of molecules, including
o O2, N2, H2O, urea, and ethanol, can cross membranes by passive transport
Passive transport
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o Responsible for moving substance such as nutrients and electrolytes across
the membrane
o Receptors for hormones and neurotransmitters
o Act as markers: process by which different cells recognize each other
Proteins
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* a substance moves across a cell membrane with the aid of a membrane protein from a region of higher concentration to a region of lower concentration.
o The specific protein carriers or transporters are involved in the process
Facilitated transport
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* a substance moves across a cell membrane, with the aid of membrane proteins, against a concentration gradient with the expenditure of cellular energy.
o Proteins involved in active transport are called “pumps.” The needed energy is
supplied by molecules such as ATP.
Active transport
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* An __________ is a substance that can disperse and stabilize water-insoluble substances as colloidal particles in an aqueous solution.
emulsifier
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* ___________ are tri- or dihydroxy cholesterol derivatives
* The carbon 17 side chain of cholesterol has been oxidized to a carboxylic acid
* The oxidized acid side chain is bonded to an amino acid (either glycine or taurine)
through an amide linkage
* Bile is a fluid containing emulsifying agents (Bile acids) secreted by the liver,
stored in the gallbladder, and released into the small intestine during digestion
Bile acids
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* A ___________is a biochemical substance produced by a ductless gland that has a
messenger function.
* ____________ serve as a means of communication between various tissues.
o Some hormones are lipids.
Hormones
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: derivatives of cholesterol
Steroid hormones
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: derivatives of arachidonic acid
Eicosanoids
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: control reproduction and secondary sex characteristics
Sex hormones
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: control numerous biochemical processes in the body
Adrenocorticoid hormones
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* Classified into three major groups:
o Estrogens
o Androgens
o Progestins
Sex hormones
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the female sex hormones
Estrogens
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the male sex hormones
Androgens
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the pregnancy hormones
Progestins
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* Produced by the adrenal glands - small organs located on top of each kidney
* 28 Different hormones have been isolated from the adrenal cortex
* Two types of adrenocorticoid hormones:
o Mineralocorticoids
o Glucocorticoids
Adrenocorticoid hormones
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control glucose metabolism and counteract inflammation
Glucocorticoids
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control the balance of Na and K ions in cells
Mineralocorticoids
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o Have profound physiological effects at extremely low concentrations.
o Eicosanoids are hormone-like molecules
o Exert their effects in the tissues where they are synthesized.
o Eicosanoids usually have a very short “life.”
* Eicosanoids Arachidonic acid
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* C20-fatty-acid derivative containing cyclopentane ring and oxygen-containing functional groups
o Involved in raising body temperature,
o Inhibiting the secretion of gastric juices,
o Increasing the secretion of a protective mucus layer into the stomach,
o Relaxing and contracting smooth muscle, directing water and electrolyte
balance, intensifying pain, and enhancing inflammation responses.
Prostaglandins
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o Inflammatory response
o Production of pain and fever
o Regulation of blood pressure
o Induction of blood clotting
o Control of reproductive functions, such as induction of labor
o Regulation of the sleep/wake cycle
* Physiological effects of eicosanoids:
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* C20-fatty-acid derivative containing a cyclic ether ring and oxygen-containing functional groups
o Promote platelet aggregation
Thromboxanes
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* C20-fatty-acid derivative containing three conjugated double bonds and hydroxy groups
o Promote inflammatory and hypersensitivity (allergy) responses
Leukotrienes
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: a monoester of a long-chain fatty acid and a long-chain alcohol.
biological wax
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Water-insoluble and water-repellent because of
long nonpolar hydrocarbon chains.
Properties of Biological waxes
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Cholesterol derivatives that functions as emulsifying agents that make
dietary lipids soluble in aqueous environment of the digestive tract:
o Approximately one third of cholesterol produced by liver is converted to bile
acids.
o Action similar to soap in washing
Bile Acids
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Monounsaturated Fats
Omega 3 and 6
Good Fats
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saturated fat
Trans-monounsaturated fats
Bad Fats
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Predominantly Saturated
Solids or semisolids at room temperature
Animal source and tasteless
Fats
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Predominantly unsaturated
Liquids at room temperature
Plants and fish oil
Oils
