1. Primary source of fuel for cells 2. Provides cell membrane stability 3. Allows transmembrane transport

CC2 Flashcards by LEDESMA, Anne Gelika

aka lipids

fats

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Lipid composition

mostly carbon-hydrogen (C-H) bonds

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Lipids are insoluble to:

blood (thus, requires transporter)

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Lipids are soluble to:

organic solvents

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Lipid transporter

Lipoproteins (VLDL, LDL, HDL)

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Lipid classifications

Fatty acids
Triglycerides
Cholesterol
Phospholipids
Fat soluble vitamins (A, D, E, K)

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Lipid functions

Primary source of fuel for cells
Provides cell membrane stability
Allows transmembrane transport

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Linear chains of C-H bonds that terminates with -COOH (carboxyl grp)

Fatty Acids

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Mostly found as constituent of phospholipids or TAG

Fatty Acids

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Mainly derived from TAG hydrolysis in the adipose tissue

Fatty Acids

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Important source of fuel/energy for cells

Fatty Acids

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Provides a substance for lipid → glucose conversion (gluconeogenesis)

Fatty Acids

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FA composition

Linear chains of C-H bonds that terminates with -COOH (carboxyl grp)

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FA are mostly found as constituent of

phospholipids or TAG

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FA is derived from

TAG hydrolysis in the adipose tissue

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FA 3 classifications

BASED ON:
Presence of ester bonds
Length/no.
No. of double bonds

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FA classification based on presence of ester bonds

Unesterified
Esterified

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FA classification based on length/no.

Short
Medium
Long

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FA classification based on no. of double bonds

Saturated
Monounsaturated
Polyunsaturated

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Bound to albumin in the plasma

Unesterified fatty acids

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Constituent of TAG or phospholipids

Esterified fatty acids

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Length/no. of short fatty acids

4-6

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Length/no. of medium fatty acids

8-12

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Length/no. of long fatty acids

> 12

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Fatty acid with no double bonds

Saturated

Fatty acid with 1 double bond

Monounsaturated

Fatty acid with 2 or more double bonds

Polyunsaturated

Examples of saturated fatty acids

Butyric acid Stearic acid Palmitic acid

Example of monounsaturated fatty acid

Oleic acid

Examples of polyunsaturated fatty acid

Linoleic acid Arachidonic acid

3 fatty acids + 1 glycerol

Triglyceride

aka Triglyceride

Triacylglycerol, Neutral fat

Contain saturated FA or unsaturated FA

Triglyceride

Hydrophobic, water insoluble: No charged or hydrophilic groups

Triglyceride

Predominant TAG form in plasma

Glyceryl ester

Main storage form of lipid in man

TAG

95% of storage fat; present in adipose tissue

TAG

Provide excellent insulation

TAG

TAG composition

3 fatty acids (saturated or unsaturated) + 1 glycerol

TAG hydrolysis

3 FA are released to the cells → FA is converted to energy

These 3 facilitates TAG hydrolysis:

* Lipoprotein lipase (LPL) * Epinephrine * Cortisol

2 fatty acids + glycerol

Phospholipids

aka Phospholipids

Conjugated lipid

3rd position of phospholipid structure

phospholipid head groups (PHOSPHORYLATION) Formed from conjugation of 2 FA and phosphorylated glycerol

Amphipathic: hydrophilic (outer) and hydrophobic (inner) head groups

Phospholipids

Most abundant lipid in the body

Phospholipids

derived from phosphatidic acid

Phospholipids

Site of origin of phospholipids

liver intestine

Lipid NOT routinely measured in the lab (low dx value)

Phospholipids

Participates in cell metabolism and blood coagulation

Phospholipids

Significant lipid in Amniotic fluid measurement

Phospholipids

Act as surfactants (alter fluid surface tension) during pregnancy

Phospholipids

Determines fetal lung maturity during 3rd trimester

Sphingomyelin / lecithin ratio

3 FORMS OF PHOSPHOLIPIDS

Lecithin (phosphatidylcholine) Sphingomyelin Cephalin

% IN TOTAL BODY PHOSPHOLIPID OF LECITHIN (PHOSPHATIDYLCHOLINE)

70% (highest)

% IN TOTAL BODY PHOSPHOLIPID OF SPHINGOMYELIN

20%

% IN TOTAL BODY PHOSPHOLIPID OF CEPHALIN

10% (lowest)

Other examples of phospholipids

Phosphatidylserine Phosphatidylethanolamine Phosphatidylcholine (lecithin)

Unsaturated steroid alcohol contains 4 rings, component of steroids

Cholesterol

Phospholipid composition

2 fatty acids + glycerol 3rd position: phospholipid head groups

Single C-H side chain tail, similar to FA

Cholesterol

aka Cholesterol

3-hydroxy-5,6-cholestene

T/F Cholesterol is amphipathic

Precursor for the assembly of cell membrane and bile acids

Cholesterol

NOT metabolized by most cells (not a fuel source)

Cholesterol

What happens to unmetabolized cholesterol?

recycled back to the liver

Cholesterol is converted to:

Bile salts Steroid hormones Vitamin D (Ca absorption) and cell membrane

Production of bile salts

liver

Storage of bile salts

gallbladder

Promote fat absorption in the intestine

Bile salts

Examples of steroid hormones from conversion of cholesterol

glucocorticoids mineralocorticoid estrogen

Cholesterol classification

Unesterified (Free cholesterol) Esterified (Cholesterol ester)

Unesterified type of cholesterol

Free cholesterol (amphipathic)

Esterified type of cholesterol

Cholesterol ester (neutral lipid)

% in total chole of Free cholesterol

30%

% in total chole of Cholesterol ester

70%

Location of Free cholesterol

Plasma, Serum, RBC

Location of Cholesterol ester

Plasma, Serum

Polar form (hydrophilic) cholesterol

Free cholesterol (unesterified)

Nonpolar form (hydrophobic) cholesterol

Cholesterol ester

T/F Cholesterol types are measured individually in the laboratory.

F Both are measured in the laboratory as TOTAL CHOLESTEROL

Enzyme for esterification

Lecithin Cholesterol Acyl Transferase (LCAT)

T/F Lecithin Cholesterol Acyl Transferase (LCAT) is not normally present

F Normally present

Site of synthesis of LCAT

Liver

Promotes FA transfer from lecithin to chole → products: lysolecithin + cholesterol esters

Lecithin Cholesterol Acyl Transferase (LCAT)

Activator of Lecithin Cholesterol Acyl Transferase (LCAT)

Apo A1

Products when LCAT promotes FA transfer from lecithin to chole

lysolecithin + cholesterol esters

Used to transport lipids

LIPOPROTEIN

Composed of both lipids and proteins

LIPOPROTEIN

Protein part of LPP

apolipoprotein

T/F In lipoproteins, density depends on the protein constituent

APOLIPOPROTEIN FUNCTIONS

✓ Maintain structural integrity ✓ Ligands for cell receptor ✓ Activators and inhibitors of enzymes

T/F Apolipoproteins are amphipathic

Composition of lipoprotein

Free cholesterol (surface) Phospholipids (surface) TAG (core) Cholesteryl esters (core)

Found on the SURFACE of apolipoprotein

Free cholesterol Phospholipids

Found on the CORE of apolipoprotein

TAG Cholesteryl esters

MAJOR LIPOPROTEIN TYPES

Chylomicrons VLDL LDL HDL

Largest to smallest lipoproteins

Chylomicrons (largest) VLDL LDL HDL (smallest)

Least dense (↓ protein) to Most dense (↑ protein)

Chylomicrons VLDL LDL HDL

Major LPP Location: Apo A-1

HDL

Major LPP Location: Apo A-II

HDL

Major LPP Location: Apo A-IV

CM, VLDL, HDL

Major LPP Location: Apo B-100

LDL, VLDL

Major LPP Location: Apo B-48

Major LPP Location: Apo C-I

CM, VLDL, HDL

Major LPP Location: Apo C-II

CM, VLDL, HDL

Major LPP Location: Apo C-III

CM, VLDL, HDL

Major LPP Location: Apo E

VLDL, HDL

Major LPP Location: Apo(a)

Lp (a)

Apolipoprotein with major location is HDL

Apo A-I Apo A-II Apo A-IV Apo C-I Apo C-II Apo C-III Apo E

Apolipoprotein with major location is Chylomicron

Apo A-IV Apo B-48 Apo C-I Apo C-II Apo C-III

Apolipoprotein with major location is VLDL

Apo A-IV Apo B-100 Apo C-I Apo C-II Apo C-III Apo E

LCAT activator, ABCA1 lipid acceptor

Apo A-I

LCAT inactivator

Apo A-II

LDL receptor ligand

Apo B-100 Apo E

Remnant receptor ligand

Apo B-48

LPL cofactor

Apo C-II

LPL inhibitor

Apo C-III

Plasminogen inhibitor

Apo(a)

Least dense (2% protein) lipoprotein

Chylomicrons

Most dense (50% protein) lipoprotein

HDL

Largest lipoprotein

Chylomicron

Smallest lipoprotein

HDL

Lipoprotein with highest lipid content

Chylomicrons

Lipoprotein with smallest lipid content

HDL

Most TAG rich lipoprotein

Chylomicron

Lipoprotein with least TAG content

HDL

Most cholesterol rich lipoprotein

LDL

Lipoprotein with least cholesterol content

Chylomicrons

Conversion Factor (mmol/L) for TOTAL CHOLESTEROL

0.026

Conversion Factor (mmol/L) for TAG

0.011

Reference range (mg/dL) Total cholesterol = HDL cholesterol = LDL cholesterol = TAG =

Total cholesterol = 140-200 HDL cholesterol = 40-75 LDL cholesterol = 50-130 TAG = 60-150

aka Pre-β lipoprotein

VLDL

aka β lipoprotein

LDL

aka Bad cholesterol

LDL

aka α lipoprotein

HDL

aka good cholesterol

HDL

Largest, least dense lipoprotein

Chylomicrons

Lipoprotein completely cleared in the circulation within 6-9 hrs after eating

CHYLOMICRONS

Float in the middle of serum → homogenous turbidity (before and after overnight standing)

VLDL

Most atherogenic lipoprotein (initiates formation of fatty plaque in BV)

LDL

Cardioprotective lipoprotein

HDL

Site of CHYLOMICRON production

Intestine

Site of VLDL production

Liver

Production of LDL

VLDL lipolysis to IDL → LDL

Site of HDL production

Liver Intestine

Delivers dietary lipids (exogenous TAG) to hepatic and peripheral cells

CHYLOMICRONS

Transfers endogenous TAG from the liver to peripheral tissue

VLDL

Transfers dietary cholesterol to peripheral tissue

LDL

Transfer excess cholesterol from peripheral cells back to the liver

HDL

MINOR LIPOPROTEIN TYPES

LIPOPROTEIN(a) INTERMEDIATE DENSITY LPP (IDL)

ABNORMAL LIPOPROTEINS

LIPOPROTEIN X B-VLDL (floating β lipoprotein)

aka Sinking pre-β lipoprotein

LIPOPROTEIN(a)

LDL lipoprotein-like particle

LIPOPROTEIN(a)

Has similar structure to plasminogen

LIPOPROTEIN(a)

↑ Lp(a) confers ↑ risk for:

o Premature CHD o Stroke

Competes with plasminogen for fibrin

Lp(a)

Mechanism of premature CHD

MECHANISM: Competition with plasminogen for fibrin Clot formation will prevent further blood loss. When bleeding is controlled due to clot → damaged BV undergoes repair → clot removed through fibrinolysis. Plasminogen promotes fibrinolysis. In presence of Lp(a), it will compete with plasminogen (Lp(a) – acts as inhibitor of plasminogen). Fibrin clot will not be dissolved, accumulates and adds up in the fatty flakes in the blood vessels → early manifestation of CHD

VLDL remnant: 1st product of VLDL catabolism

INTERMEDIATE DENSITY LPP (IDL) VLDL → IDL → LDL

Subclass of LDL

INTERMEDIATE DENSITY LPP (IDL)

Migration of Lp(a)

Variable * pre-β * between LDL & albumin (Migrates with VLDL)

Minor lipoprotein that migrates with VLDL

LIPOPROTEIN(a)

Migration is either pre-β or β region

INTERMEDIATE DENSITY LPP (IDL)

Minor lipoprotein with a density similar to LDL

LIPOPROTEIN(a)

Specific and sensitive indicator of cholestasis

LIPOPROTEIN X

Abnormal lipoprotein found in obstructive jaundice and LCAT deficiency

LIPOPROTEIN X

MAJOR LIPID CONTENT OF LIPOPROTEIN X

Phospholipid & Free cholesterol (90%)

PROTEIN FRACTION OF LIPOPROTEIN X

Apo C Albumin

aka Abnormally migrating β-VLDL

B-VLDL (floating β lipoprotein)

Lipoprotein found in type 3 hyperlipoproteinemia or dysbetalipoproteinemia

B-VLDL (floating β lipoprotein)

Rich in cholesterol than VLDL

B-VLDL (floating β lipoprotein)

Has a defective VLDL catabolism (failure to convert VLDL to LDL causing IDL accumulation)

B-VLDL (floating β lipoprotein)

Migration of LIPOPROTEIN X

Towards cathode (unique, since all LPP migrates toward anode)

Migration of B-VLDL (floating β lipoprotein)

β region (Migrates with LDL)

LIPOPROTEIN(a) migration

Variable: * pre-β * between LDL & albumin (Migrates with VLDL)

IDL migration

Either pre-β or β region

Density is similar to VLDL by ultracentrifugation

B-VLDL (floating β lipoprotein)

Lipoprotein metabolism

1. Lipid Absorption 2. Exogenous Pathway 3. Endogenous Pathway 4. Reverse Cholesterol Transport Pathway

Conversion of dietary lipids into more polar/absorbable (amphipathic) compounds by PANCREATIC LIPASE

LIPID ABSORPTION

Enhanced by emulsifying agents (bile salts)

LIPID ABSORPTION

Site of occurrence of LIPID ABSORPTION

Small intestine

Converted in LIPID ABSORPTION

Dietary lipids

ENZYME in LIPID ABSORPTION

Pancreatic lipase

Products in LIPID ABSORPTION

More polar/absorbable (amphipathic) compound Triglyceride → Monoglycerides Cholesterol esters → Free cholesterol Phospholipids → Lysophospholipids

Chylomicrons transports exogenous dietary lipids (TAG) from the intestine to the liver and circulation (peripheral cells) In the liver: LPL hydrolyzes TAG in CM into FA & glycerol or re-esterified for long term storage Converts CM → CM remnant particles

EXOGENOUS PATHWAY

MEDIATOR in EXOGENOUS PATHWAY

Chylomicrons (synthesized in the intestine) Absorbed dietary lipids are transported by CM from intestine to the circulation which makes lipemic plasma

SITE OF OCCURRENCE OF . EXOGENOUS PATHWAY

Intestine ↓ Liver & Circulation (peripheral cells)

CONVERTED IN EXOGENOUS PATHWAY

Dietary lipids (TAG) (exogenous)

ENZYME IN EXOGENOUS PATHWAY

Lipoprotein lipase (LPL)

PRODUCTS IN EXOGENOUS PATHWAY

TAG in CM → Fatty acids & glycerol or → Re-esterified for long term storage in hepatic cells CM → CM remnant particles

TAG in the liver (endogenous) is packaged into VLDL, carrying lipids to the circulation

ENDOGENOUS PATHWAY

MEDIATOR OF ENDOGENOUS PATHWAY

VLDL LDL

SITE OF OCCURRENCE OF ENDOGENOUS PATHWAY

Circulation (peripheral cells)

CONVERTED/CARRIED IN ENDOGENOUS PATHWAY

TAG in the liver (endogenous)

ENZYME IN ENDOGENOUS PATHWAY

Lipoprotein lipase (LPL)

PRODUCTS IN ENDOGENOUS PATHWAY

VLDL carrying endogenous TAG: → 50%: VLDL remnants by LPL → taken up by liver → 50%: LDL → delivers of exogenous cholesterol to peripheral cells

HDL remove excess cholesterol in circulation → liver

REVERSE CHOLESTEROL TRANSPORT PATHWAY

MEDIATOR IN REVERSE CHOLESTEROL TRANSPORT PATHWAY

HDL

SITE OF OCCURENCE OF REVERSE CHOLESTEROL TRANSPORT PATHWAY

Circulation (peripheral cells) ↓ Liver (for excretion)

CONVERTED/CARRIED IN REVERSE CHOLESTEROL TRANSPORT PATHWAY

Excess cholesterol

LIPID DISORDERS

1. Arteriosclerosis 2. Hyperlipoproteinemia o Hypercholesterolenemia o Hypertriglyceridemia o Combined hyperlipidemia 3. Hypolipoproteinemia 4. Lp(a) elevation

Deposition of esterified cholesterol (hydrophobic), in artery walls

ARTERIOSCLEROSIS

lipoprotein indicator of inc. esterified chole in the blood

LDL

Increased fats + insoluble components → smooth muscle cells, extracellular lipid, calcification, fibrous tissue, macrophages, lymphocytes and platelets (fatty plaque)

ARTERIOSCLEROSIS

Thrombosis (blocks circulation): caused by rupture/erosion

ARTERIOSCLEROSIS

Conditions under ARTERIOSCLEROSIS and their affected sites

Coronary artery disease (CAD): heart (angina, MI) Peripheral vascular disease (PVD): arteries in arms or legs Cerebrovascular disease (CVD): brain vessels (stroke)

Under HYPERLIPOPROTEINEMIA

Hypercholesterolenemia Hypertriglyceridemia Combined Hyperlipoproteinemia

↑ Cholesterol ↑ LDL, ↓ receptors

Hypercholesterolenemia

↑ TAG ↓ LPL or APO C-II VLDL → VLDL remnants CM → CM remnants

Hypertriglyceridemia

↑ TAG, Cholesterol ↑ VLDL and CM remnants APO E2/2

Combined Hyperlipoproteinemia

OTHER LIPID DISORDERS

1. Familial Hypercholesterolemia (Type 2a) 2. Familial Dysbetalipoproteinemia (Type 3 hyperlipoproteinemia) 3. Abetalipoproteinemia (Basses-Kornzweig Syndrome) 4. Hypobetalipoproteinemia 5. Niemann-Pick Disease (Lipid Storage Disease) 6. Tangier’s Disease 7. Lipoprotein Lipase (LPL) Deficiency 8. LCAT Deficiency 9. Tay-Sachs Disease

Contained when a tube of turbid plasma is left overnight in a refrigerator at 4ºC and became lipemic

CHYLOMICRONS VLDL

Phospholipids are derived from

Phosphatidic acid

What is determined in Sphingomyelin / lecithin ratio?

Fetal lung maturity during 3rd trimester

B-VLDL (floating β lipoprotein) is found in these conditions

Type 3 hyperlipoproteinemia Dysbetalipoproteinemia

aka Familial Hypercholesterolemia

Type 2a

aka Familial Dysbetalipoproteinemia

Type 3 hyperlipoproteinemia

aka Abetalipoproteinemia

Basses-Kornzweig Syndrome

aka Niemann-Pick Disease

Lipid Storage Disease