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Physiology > Lipid Metabolism > Flashcards

Lipid Metabolism Flashcards

1
Q

What are the 2 main types of plasma membrane lipids?

A
  • Phospholipids
  • Glycolipids
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2
Q

What are the components of glycerophospholipids?

A

Most abundant lipid in cell membranes

Glycerol (a 3C sugar alcohol)

Phosphate group

2 Fatty acid chains (unsaturated or saturated)

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3
Q

What are the components of sphingolipids or sphingomyelin?

A

Sphingomyelin:

Phospholipid

Sphingosine backbone (1 fatty acid chain included as part of structure)

2nd Fatty acid chain

Phosphate group + Choline

Sphingolipid:

Glycolipid

Sphingosine backbone (1 fatty acid chain included as part of structure)

2nd Fatty acid chain

Oligosaccharide

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4
Q

Describe the metabolism of omega-3 or omega-6 fatty acids to form eicosanoids.

A
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5
Q

Ceramide

A

Sphingosine + Fatty Acid

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6
Q

Sphingomyelin

A

Ceramide + Phosphocholine

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7
Q

Glycolipid

A

Ceramide (Sphingosine + Fatty Acid) + Carbohydrate

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8
Q

Describe the metabolism of omega-3 or omega-6 fatty acids to form eicosanoids.

A
  • 3 metabolic pathways
  • Cyclooxygenase
  • Lipoxygenase
  • Epoxygenase
  • Converted into eicosanoids (lipid signaling molecules)
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9
Q

What is the function of phospholipase enzyme?

A
  • Phospholipase 2
  • Releases fatty acids & hydrolyzes phospholipids from the membrane
  • Triggered with inflammatory response
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10
Q

What are the 3 main classes of eicosanoid synthesizing enzymes?

A
  • Cyclooxygenase
  • Lipoxygenase
  • Epoxygenase
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11
Q

What are cyclooxygenases?

What do they synthesize?

A

COX:

  • Target of NSAID’s
  • Cyclize lipids
  • Form prostaglandin’s (omega-3 or omega-6)
  • Prostaglandin’s = Pro-inflammation
  • Trigger to protect cells from further injury/inflammation
  • 2 isoforms

Chronic inflammation = bad

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12
Q

What are NSAIDS?

Which class of enzymes do they inhibit?

A
  • Nonsteroidal anti-inflammatory drugs
  • Block formation of prostaglandins via pro-inflammatory pathway
  • Inhibit COX-1 and COX-2 enzymes
  • Reduce production of prostaglandins and thromboxanes
  • Reduce pain, fever, and inflammation
  • Side effects bc they block the actions of the housekeeping enzymes too (COX-1)
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13
Q

What is the major difference between COX-1 and COX-2?

A

COX-1:

  • Constitutive, expressed in most tissues
  • Physiological & homeostatic role
  • Cell signaling
  • Housekeeping functions
  • Lots of COX-1 when you are in a healthy state

COX-2:

  • Inducible!
  • Expressed in inflammation & trauma
  • Found in immune cells
  • Induced by cytokines
  • Maintains inflammation
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14
Q

Explain how low dose aspirin works.

A
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15
Q

Describe VLDL, LDL, and HDL

A

VLDL:

  • Very low density lipoprotein
  • Contains a small amount of cholesterol

LDL:

  • Low density lipoprotein
  • Risky for organisms
  • Transmits much of cholesterol in the blood

HDL:

  • High density lipoprotein
  • Less cholesterol than LDL and more amounts of proteins
  • Indicator of good health
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16
Q

How are lipid metabolites generated? How do they elicit their action?

A
  • Generated from Omega-3 and Omega-6 fatty acids
  • Short-lived
  • Act locally on nearby cells
  • Activate specific GPCR’s and nuclear receptors
  • Control local inflammation to injury
17
Q

What is the function of the phospholipase enzyme?

A
  • Phospholipase 2
  • Breaks open fatty acid
  • Releases fatty acids & hydrolyzes phospholipids from the membrane
  • Allows for formation of eicosanoid
  • Triggers inflammatory response
18
Q

What are cyclooxygenases?

What do they synthesize?

A

They make prostaglandins

Target of NSAIDs

Cyclize lipids

Form Omega-3 or Omega-6 prostaglandins

Prostaglandins = PRO-INFLAMMATION

COX triggers pro-inflammatory response to prevent cells from further injury/inflammation

19
Q

What is the major difference between COX-1 and COX-2?

A

COX-1:

  • Constitutive, expressed in most tissues
  • Physiological & homeostatic role
  • Cell signaling
  • Housekeeping functions
  • Lots of COX-1 when you are in a healthy state

COX-2:

  • Inducible!
  • Expressed in inflammation & trauma
  • Found in immune cells
  • Induced by cytokines
  • Maintains inflammation
20
Q

What are NSAIDS?

Which class of enzymes do they inhibit?

A
  • Nonsteroidal anti-inflammatory drugs
  • Block formation of prostaglandins via pro-inflammatory pathway
  • Inhibit COX-1 and COX-2 enzymes
  • Reduce production of prostaglandins and thromboxanes
  • Reduce pain, fever, and inflammation
  • Side effects (gastric/ulcers/bleeding) bc they remove the housekeeping enzymes too
21
Q

Explain how low dose aspirin works.

A
  • Aspirin is an irreversible inhibitor of COX
  • Blocks COX-1 in the platelets
  • Short ½ life
  • Reduces the ability of blood to clot→ doesn’t eliminate it!
  • Makes platelets less sticky
  • Decreases heart attacks and stroke in people with already narrowed blood vessels
22
Q

What are COX-2 inhibitors?

What are their advantages over COX-1 inhibitors?

A

COX-2 Inhibitors:

Target inflammation and pain response

Freedom from GI side effects and doesn’t take away housekeeping functions

Can cause cardiovascular problems due to imbalance of good/bad prostaglandins

23
Q

What class of lipid mediator does lipooxygenase synthesize?

A

Leukotrienes

24
Q

What are leukotrienes?

A
  • Produced via lipoxygenase pathway from arachidonic acid
  • Pro-inflammatory pathway
  • Originated in leuklpcytes but now seen in mast cells, platelets and macrophages in response to immunologic stimuli
  • 100X stronger than prostaglandins
  • Responsible for inflammation and mucous secretion in later stages of allergic response
25
Q

What are dual pathway NSAIDS?

A
  • Block the first step
  • Block arachidonic acid cycle via both cyclooxygenase and lipoxygenase pathways
  • Strong analgesic (pain reliever) and strong anti-inflammatory
26
Q

What are epoxygenases?

What do they synthesize?

A
  • Epoxygenase highly expressed in endothelium & heart
  • Converts omega-6 fatty acids into epoxides
  • Anti-inflammatory pathway in the body
  • Lower blood pressure
  • Prevent arrhythmia
  • Cerebrovascular health
  • Released in the endothelium
27
Q

How do steroidal anti-inflammatory drugs function? Which enzyme do they block?

A
  • Block the action of phospholipase 2
  • 2 types of corticosteroids: glucocorticoids & mineralocorticoids
  • Corticosteroids stimulate the production of a glycoprotein called lipocortin
  • Lipocortin inhibits the activity of phospholipase A2
  • Inhibit phospholipase 2 = no generation of arachidonic acid
28
Q

Which lipids are steroid hormones derived from?

A

Cholesterol

29
Q

Structure and function of cholesterol

A
  • Polar head group
  • Steroid nucleus
  • Alkyl side chain (hydrocarbon tail)
  • Precursor of steroid hormones
  • Forms bile acids
  • Generates vitamin D
30
Q

What are the primary sources of cholesterol?

A
  • Stored as part of the lipid membrane as an ester
  • Diet
  • Local synthesis in liver
  • Liver excretes cholesterol in bile by converting it to bile salts→ high cholesterol = problem with cholesterol synthesis
31
Q

How is cholesterol transported in the blood?

A
  • Via lipoprotein lipase (LPL) formation from liver
  • High LPL levels = cholesterol is not well bound
32
Q

Describe how cholesterol is converted to bile.

A
  • Turned into a hydrophilic molecule
  • Cholesterol → Cholic Acid (now can dissolve in aqueous solution)
  • Bile salts that form mixed micelles to solubilize cholesterol and reduce bile acid toxicity
33
Q

What is the primary function of bile?

A
  • Fluid that is made and released in the liver
  • Stored in the gallbladder
  • Breaks down fats into fatty acids
34
Q

What are the five different classes of steroid hormones that are formed from cholesterol?

A
  • Glucocorticoids→ cortisol
  • Mineralocorticoids→ aldosterone
  • Androgens → testosterone
  • Estrogen → estradiol
  • Progestogens→ progesterone
35
Q

What are the functions of steroid hormones?

A
  • Carbohydrate regulation
  • Lipid Soluable
  • Mineral balance
  • Reproductive functions
  • Inflammatory response → production of glucocorticoids
  • Stress response
  • Bone metabolism
  • Cardiovascular fitness

Physiology (11 decks)

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