Lipid Metabolism Flashcards

Flashcards on Lipid Metabolism

What are the most abundant dietary lipids?

Triglycerides

What are the two essential fatty acids that must be ingested?

Linoleic and linolenic acid

Name three functions of fatty deposits in adipose tissue.

Protective cushion, insulating layer, energy source

How do dietary fats help the body?

Absorb vitamins

What are the major energy fuels for hepatocytes and skeletal muscle?

Dietary fats

What part of the neuron contains lipids?

Myelin Sheaths

Name three functions of prostaglandins.

Smooth muscle contraction, control of blood pressure, inflammation

What does cholesterol stabilize?

Membranes

What are two things cholesterol is a precursor of?

Bile salts and steroid hormones

Name three functions of the liver related to lipids.

Synthesizes lipoproteins, makes tissue factor, synthesizes cholesterol

What does the liver use cholesterol for?

To form bile salts

What do certain endocrine organs use cholesterol for?

Synthesize steroid hormones

What are the storage lipids (neutral)?

Triacylglycerols

What are the two components of triacylglycerols?

Glycerol and Fatty Acids

Name 2 types of Membrane lipids (polar)

Phospholipids and Glycolipids

Name 2 types of Phospholipids

Glycerophospholipids and Sphingolipids

Name 2 types of Glycolipids

Sphingolipids and Galactolipids (sulfolipids)

What is another lipid in the membrane?

Archaebacterial ether lipids

What type of bond links fatty acids to glycerol in triglycerides?

Ester bonds

Where does glycolysis take place?

Cytosol

Name 3 process that occur in the mitochondrial matrix

Citric acid cycle, oxidative phosphorylation, B-Oxidation of fatty acids

Where Does Fatty acid synthesis take place?

Cytosol

Where does gluconeogenesis take place?

Interplay of both Cytosol and Mitochondrial matrix

Where does the urea synthesis occur?

Interplay of both Cytosol and Mitochondrial matrix

What molecules can be broken down into Acetyl CoA?

Amino acids, Glucose and other sugars, and Fatty acids

What are the three stages of FA metabolism?

Digestion in GI tract lumen, Anabolism formation, Oxidative breakdown in mitochondria

Name 3 sources cells obtain fatty acid fuel from?

Fats consumed, Fats stored, or Fats synthesized

How are waste products of fat metabolism transported?

Lymph as chylomicrons

What type of fats are routinely oxidized for energy?

Neutral Fats

What are the two separate pathways for catabolism of fats?

Glycerol pathway and Fatty acids pathway

What emulsifies dietary fats in the small intestine?

Bile salts

What degrades triacylglycerols?

Intestinal lipases

Where does triacylglycerols incorporation take place?

Chylomicrons

In the capillary, what converts triacylglycerols to fatty acids and glycerol?

Lipoprotein lipase

What is the main component of the interior of Chylomicrons?

Triglycerols

What percentage of mass do Triglycerols make up in Chylomicrons?

Greater than 80%

What is found on the exterior part of Chylomicrons?

Apolipoproteins

What do Apolipoproteins serve as?

Signals for chylomicron uptake & metabolism

What is glycerol converted to?

Glyceraldehyde 3-phosphate (GAP)

What is GAP converted to?

Acetyl CoA

What cycle does Acetyl CoA enter?

Krebs Cycle

What is produced during beta oxidation of fatty acids?

Two-carbon acetic acid fragments

What happens to glycerol after lipases hydrolyze triacylglycerols?

Glycerol is phosphorylated

DHAP converted to what?

GAP

What phase does GAP enter in glycolysis?

Payoff phase

What are the three steps for fatty acid breakdown (catabolism)?

Mobilization, Activation and transportation, Step-by-step breakdown in mito matrix

When lipids must be mobilized, what are triglycerols degraded into?

Fatty acids & glycerol

When lipids must be mobilized, where are they released from?

Adipose tissue

Where must fatty acids be transported for degradation?

Mitochondria

Where are fatty acids broken down step-by-step?

Mitochondrial matrix

What system does Glucagon activate during Mobilization of Triglycerols?

Receptor-G protein-adenylate cyclase system

What is activated during Mobilization of Triglycerols?

Hormone-sensitive lipases (HSL)

Permits access of HSL to triglycerols in fat droplets?

PKA phosphorylation of perilipin

What happens after Fatty acids released from adipocyte into bloodstream?

bind to serum proteins, transported to other cells

What stimulates glucagon release?

Low blood glucose

hormone sensitive lipase is stimulated by what?

Glucagon → cAMP → PKA → HSL (perillipin)

What inhibits hormone sensitive lipase?

Insulin

What needs to be activated for transportation into mitochondria for degradation?

Fatty acids

What transports Acyl carnitine across the Cytostolic side?

Carnitine Translocase

What is the overall reaction for Activation of Fatty Acids?

Fatty acid + CoA + ATP → fatty acyl-CoA + AMP + 2Pi

Where does Carnitine acyltransferase I reside?

Outer mitochondrial membrane

Where does Carnitine acyltransferase II reside?

Inner mitochondrial membrane

What are the three stages of fatty acid oxidation?

b-oxidation of fatty acids, Acetyl-CoA oxidized to CO2, electrons transferred

What is the first stage of fatty acid oxidation?

b-oxidation of fatty acids

What is the second stage of fatty acid oxidation?

Acetyl-CoA oxidized to CO2

What is the third stage of fatty acid oxidation?

electrons transferred

Name the repetitive sequence of in Degradation of even- numbered, saturated fatty acids?

Oxidation, Hydration, Oxidation, Thiolysis

What does the oxidation of palmitate produce?

8 molecules of acetyl-CoA

How many ATP are ultimately formed from Acyl-CoA dehydrogenase?

10.5

How many ATP are ultimately formed from B-Hydroxyacyl-CoA dehydrogenase?

17.5

How many ATP are ultimately formed from Isocitrate dehydrogenase?

20

How many ATP are ultimately formed from a-Ketoglutarate dehydrogenase?

20

How many ATP are ultimately formed from Succinate dehydrogenase?

12

How many ATP are ultimately formed from Malate dehydrogenase?

20

What is the total ATP yield from Oxidation of One Molecule of Palmitoyl-CoA to CO2 and H₂O?

108

What enzyme is required for b-Oxidation of Monounsaturated Fatty Acids?

Enoyl-CoA isomerase

How much ATP is lost per double bond in b-Oxidation of Monounsaturated Fatty Acids?

2 ATP

What enzyme is required for b-Oxidation of Polyunsaturated Fatty Acids?

2,4- dienoyl-CoA reductase

How much ATP is lost per additional double bond in b-Oxidation of Polyunsaturated Fatty Acids?

3 ATP

What is the final product in b-Oxidation of Odd- Chain Length Fatty Acids?

Succinyl CoA

What is lipogenesis?

Excess dietary glycerol and fatty acids form triglycerides

Why is glucose easily converted into fat?

Acetyl CoA is an intermediate

What is lipolysis?

Breakdown of stored fat

What is necessary for the complete oxidation of fat?

Oxaloacetate

What are fats converted into without Oxaloacetate?

Ketones

Where does Ketogenesis take place?

Liver

Two enzymes key for coordinated regulation of lipolysis and lipogenesis

ACC & CAT 1

What is ACC

First enzyme in FA synthesis

ACC = acetyl-CoA carboxylase

What molecule drives reactions in Anabolic?

Glucose

What are the two enzymes key for coordinated regulation?

Acetyl-CoA carboxylase (ACC) and carnitine acyl transferase I

What is the first enzyme in FA synthesis pathway?

ACC

What regulates transport of FA into mitochondrial matrix for b-oxidation?

Carnitine acyl transferase I

What happens to Insulin levels, When diet provides carbohydrate?

High blood glucose

What happens to Glucagon levels, When diet provides carbohydrate?

Low blood glucose

What happens to ACC when protein phosphatase is activated?

Activation as ACC is dephosphorylated

What happens to ACC when phosphatase is deactivated?

Deactivation as ACC is phosphorylated

What is the produced from Acetyl-CoA when ACC is active under high blood glucose conditions?

Malonyl-CoA

What stimulates insulin release?

High carb meal

What does Insulin-dependent protein phosphatase do?

Dephosphorylates ACC (activates enzyme)

What does ACC catalyze?

Formation of malonyl-CoA