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Biochem Concepts Review
Main review cards for Biochem Final
105
Biochemistry
Professional
12/09/2011

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Cards

Term
What are the common chain lengths for fatty acids found in milk?
Definition
4-10 C
Term
What are the two essential fatty acids?
Definition
Linoleic and Linolenic Acid
Term
What protein is used to transport free fatty acids?
Definition
Albumin
Term
What enzyme is responsible for hydrolysis of ester linkages in dietary TGs prior to absorption into the circulation?
Definition
Pancreatic Lipase
Term
What stimulates release of bile salts from the gall bladder and where do they end up?
Definition
Cholecystokinin; small intestine
Term
Where are chylomicrons synthesized, and where do they end up?
Definition
Intestinal cells; lymph for transport to blood via thoracic duct
Term
What is the ultimate fate of bile salts?
Definition
Reabsorbed in the ileum and recycled to liver
Term
What is the main function of colipase?
Definition
To relieve bile acid inhibition of lipase
Term
What effect does bicarbonate have on lipase activity?
Definition
By raising the intestinal pH it increases lipase activity
Term
What is the main clinical use of Oral Lipase Inhibitors?
Definition
Decrease formation of chylomicrons; decrease levels of TG in blood; useful in patients that cannot utilize chylomicron
Term
Where are TGs reassembled in the intestinal cells, and what enzyme activates fatty acids for TG synthesis?
Definition
Reassembly occurs in the smooth ER; fatty acyl CoA synthase activates fatty acids
Term
What structural scaffolding protein is the core of chylomicron synthesis?
Definition
Apo B-48 (added in rough ER)
Term
Where are chylomicrons assembled?
Definition
Rough ER
Term
What is the fate of short and medium chain fatty acids?
Definition
Instead of being packaged into chylomicrons they diffuse across cell membranes of intestinal cells directly into the portal vein
TRANSPORTED BOUND TO SERUM ALBUMIN IN BLOOD
Term
What is the consequence of a deficiency in LPL (lipoprotein lipase)?
Definition
Decreased ability to deliver LONG CHAIN fatty acids to cells via chylomicrons and VLDLs
Term
What is the function of LDLs?
Definition
Deliver cholesterol to liver and tissues that have large cholesterol needs
Term
What is the function of HDLs?
Definition
To transport cholesterol from membranes of tissues BACK TO THE LIVER
Term
What is the structural scaffolding protein of VLDLs?
Definition
Apo B-100
Term
What process makes Apo B-48 from the Apo B-100 gene?
Definition
RNA Editing via a STOP CODON in intestinal cells
Term
What effect does insulin have on LPL synthesis?
Definition
Stimulatory
Term
What is required on the lipoprotein particle to activate Lipoprotein Lipase (LPL)?
Definition
Apo CII
Term
What is the function of Apo E?
Definition
Apo E is the ligand for the chylomicron REMNANT receptor in the liver, which allows remnants to be taken up after lipid cargo is delivered to tissues
Term
What happens if ApoC II is defective?
Definition
Hyperlipidemia (no triggering of LPL, cannot get chylomicron/VLDL fatty acids out of blood and into tissue)
Term
Why is gastric lipase more important in lipid digestion in neonates than in adults?
Definition
Lipase is more active at a higher pH; adults have a more acidic pH
Term
Where do chylomicrons acquire Apo CII?
Definition
From HDL
Term
What is the carbon source for most fatty acid synthesis?
Definition
Main source is carbohydrate
Term
Where is acetyl CoA synthesized to eventually build fatty acids?
Definition
Liver Mitochondria
Term
What essential intermediate allows Acetyl CoA to leave the mitochondria and enter the cytosol?
Definition
Citrate
Term
What is the immediate donor of the 2 carbon acetyl units of fatty acids?
Definition
Malonyl CoA
Term
What enzyme makes malonyl CoA?
Definition
Acetyl CoA Carboxylase
Term
What is the rate limiting step of fatty acid synthesis?
Definition
The synthesis of Malonly CoA by Acetyl CoA Carboxylase
Term
What is the reducing factor used by fatty acid synthase?
Definition
NADPH
Term
Where are fatty acids synthesized?
Definition
In the cytosol by fatty acid synthase
Term
What two molecules are condensed to build fatty acids, and what is the final product?
Definition
Malonyl CoA + Acetyl Co A to make PALMITIC ACID
Term
What two molecules are condensed to form citrate?
Definition
Acetyl CoA and Oxaloacetate
Term
What enzyme breaks citrate into its component parts, and what are those parts?
Definition
Citrate Lyase; Oxaloacetate and Acetyl CoA
Term
How many NADPH are required per acetate unit added to a fatty acid during synthesis?
Definition
TWO
Term
Where does the NADPH used in fatty acid synthesis come from?
Definition
Malic Enzyme and the Pentose Phosphate Pathway
Term
What are the two actions of malic enzyme?
Definition
GENERATE NADPH FOR FATTY ACID SYNTHESIS
-convert malate to pyruvate for shuttling back into mitochondria
Term
What are the 3 things required for the function of Acetyl CoA Carboxylase, and what is the final product of this enzyme?
Definition
1)ATP
2)BIOTIN BIOTIN BIOTIN BIOTIN
3)CO2
Final Product= Malonyl CoA
Term
What is the effect of each of the following on the action of Acetly CoA Carboxylase?
-Citrate
-Palmitoyl CoA
-Insulin
-Glucagon
-Epinephrine
Definition
-Citrate-INCREASE ACTIVITY
-Palmitoyl CoA- DECREASE ACTIVITY
-Insulin- ACTIVATES
-Glucagon- DEACTIVATES
-Epinephrine- DEACTIVATES
Term
What are the two important amino acid residues used by Fatty Acid Synthase, and what do they do?
Definition
Phosphopantethine and Cysteine
-form thioesters with developing fatty acyl chain
-the chain moves between these 2 sulfhydryl residues as it elongates
Term
Where does elongation of fatty acids occur and what does it require?
Definition
Smooth ER; NADPH and Malonyl CoA

(most often Palmitate (C16) to Stearate (C18)
Term
Where does desaturation of Fatty Acids occur, and what is required?
Definition
Endoplasmic Reticulum; O2, NADH, and cyt b5 (using Fe)
Term
What is the restriction on human desaturase enzymes, and what does it mean for dietary fatty acid intake?
Definition
Human desaturases cannot introduce double bonds between Carbon 9 and the methyl end of a FA chain, so LINOLEIC and LINOLENIC ACIDS ARE ESSENTIAL
Term
What are the two essential elements of Triglyceride Synthesis, and what do they form?
Definition
Glycerol-3-phosphate and Fatty Acyl CoA; they form Phosphatidic Acid
Term
What liver enzyme catalyzes the formation of Glycerol-3-phosphate from glucose?
Definition
Glycerol Kinase
Term
From what does adipose tissue make glycerol-3-phosphate?
Definition
Glycolysis
Term
What enzyme in adipose tissue that breaks down Triglycerides is activated by low levels of insulin?
Definition
Hormone Sensitive Lipase
Term
What is the backbone of glycerophospholipids?
Definition
Glycerol
Term
What is the backbone of sphingolipids?
Definition
Sphingomyelin
Term
What is the fatty-acid like component of sphingomyelin?
Definition
Sphingosine (contains a nitrogenous portion)
Term
What family of compounds makes lung surfactant?
Definition
Phospholipids
Term
What is the building block for phospholipids?
Definition
Phosphatidic Acid
Term
What class of compounds is important in antigenic determinants of blood group substances?
Definition
Sphingolipids
Term
What is the main function of sphingomyelin?
Definition
Structural component of the outer leaflet of nerve and the myelin sheath
Term
What is Zellwegers Syndrome?
Definition
A state of non-functioning peroxisomes
-INABILITY TO SYNTHESIZE PLASMALOGENS
Term
What is the action of Phospholipase A1?
Definition
To cleave the first fatty acid (1-acyl) from backbone
Term
What is the action of Phospholipase A2?
Definition
To cleave the second fatty acid (2-acyl) from backbone (as in release of Arachidonic Acid)
Term
What is the action of Phospholipase C?
Definition
To cleave the phosphate group, with its head group, off of the backbone
Term
What is the action of Phospholipase D?
Definition
To cleave JUST THE HEAD GROUP (not phosphate) from the backbone, leaving Phosphatidic Acid
Term
What enzyme is deficient in Tay Sachs disease?
Definition
Hexosaminidase A
Term
What enzyme is deficient in Gauchers Disease?
Definition
Beta Glucosidase
Term
What enzyme is deficient in Neimann-Pick disease?
Definition
Sphingomyelinase
Term
What enzyme catalyzes the hydrolysis of PIP2 to produce IP3 and DAG (stimulating PKC)?
Definition
Phospholipase C
Term
What major lung surfactant is deficient in respiratory distress syndrome?
Definition
Phosphatidylcholine
Term
Why does a lack of surfactant cause respiratory distress?
Definition
Surface tension causing sac collapse
Term
What ratio do we use as a measure of lung maturity in neonates?
Definition
Lecithin to Sphingomyelin Ratio
Term
How do you treat respiratory distress syndrome?
Definition
Administer CORTICOSTERIODS within 48-72 hours before delivery to stimulate surfactant production
-administer oxygen
Term
What is the MOST DIRECT source of Acetyl CoA for biosynthesis of fatty acids?
Definition
CITRATE
Term
Where are the primary sites of cholesterol synthesis?
Definition
LIVER, adrenals, gonads, intestine, placenta
Term
What effect does cholesterol have on cell membranes?
Definition
Promotes FLUIDITY
Term
In what form can most plasma cholesterol be found?
Definition
In its ESTERIFIED form
Term
Where does cholesterol synthesis occur?
Definition
In the CYTOPLASM, with enzymes in the cytosol and in the membrane of the ER
Term
What is the rate limiting step of cholesterol synthesis?
Definition
HMG-CoA Reductase converting Acetyl CoA to Mevalonate
Term
What enzyme is the target of cholesterol drug therapy, and what class of drugs are these?
Definition
HMG CoA Reductase; STATINS
Term
How do the following effect the action of HMG-CoA Reductase?
-Cholesterol
-Mevalonate
-Statin Drugs
Definition
-Cholesterol- inhibits
-Mevalonate- inhibits
-Statins- inhibit
Term
What enzyme is the key regulatory point in cholesterol biosynthesis and where is it located?
Definition
HMG CoA Reductase; ER Membrane
Term
What are isoprenoids precursors to?
Definition
(activated 5 carbon units) precursors to cholesterol, dolichol, heme, and CoQ
Term
What effect does insulin have on cholesterol synthesis?
Definition
Stimulatory
Term
What effect does glucagon have on cholesterol synthesis?
Definition
Inhibitory
Term
What is the major lipoprotein on HDLs?
Definition
ApoA-1
Term
What is ACAT? (Acyl:cholesterol acyltransferase)
Definition
The enzyme that synthesizes cholesterol esters in TISSUES
Term
What is LCAT? (Lecithin:cholesterol acyltransferase)
Definition
The enzyme that synthesizes cholesterol esters in BLOOD
Term
What are 3 effects of high cholesterol on cellular regulation of cholesterol?
Definition
-LDL receptors decrease
-HMG CoA Reductase activity decreases
-ACAT storage of cholesterol esters INCREASES
Term
What are the 2 functions of HDL?
Definition
-transfer ApoCII and ApoE to chylomicrons and VLDL
-scavenge cholesterol from tissues and transfer it to LDLs
Term
What stimulates LCAT (and PCAT)?
Definition
ApoA-1 on the HDL particle
Term
What is the function of Cholesterol Ester Transfer Protein (CETP)?
Definition
To transfer cholesterol esters to VLDLs from HDLs and to transfer TGs from VLDLs to HDLs
Term
What problem can arise with phagocytosis of oxidized LDL particles?
Definition
Atherosclerosis- Oxidized LDLs are recognized as foreign- the result is FOAM CELLS- fatty streaks on the tunica interna
Term
What is a possible cause of familial hypercholesterolemia?
Definition
Defective LDL receptor- LDLs hang around and get attacked by macrophages
Term
Name 3 types of Eicosanoids:
Definition
Prostaglandins, leukotrienes, thromboxanes
Term
Define autocoid:
Definition
A substance produced in one cell type that alters its own activity or the activity of cells of the same type
Term
Define paracoid:
Definition
A substance released from one cell type that alters the function of neighboring cells of a different type
Term
What enzyme releases arachidonic acid from membrane phospholipids?
Definition
Phospholipase A2
Term
From what fatty acid is arachidonic acid synthesized?
Definition
Linoleic Acid (Essential Fatty Acid)
Term
What compounds are produced by Cyclooxygenase?
Definition
Prostaglandins and Thromboxanes
Term
What compounds are produced by Lipoxygenase?
Definition
HPETE, leukotrienes, HETE, lipoxins
Term
What compounds are produced by Cytochrome P450?
Definition
Epoxides (diHETE and HETE)
Term
What inhibits Cyclooxygenase?
Definition
Aspirin and NSAIDS
Term
What do thromboxanes do?
Definition
Stimulate platelet aggregation, cause vasoconstriction
Term
What are 2 Cox-2 inhibitors and what do they target?
Definition
Vioxx and Celebrex; Target inflammatory cells
Term
What is one IRREVERSIBLE inhibitor of cyclooxygenase?
Definition
Salicylate (Aspirin)
Term
What are some functions of leukotrienes?
Definition
Vascular permeability, T-cell proliferation, interferon gamma, IL-1, IL-2
Term
What do lipoxins stimulate?
Definition
Production of SUPEROXIDE for respiratory burst in leukocytes
Term
What line of treatment should be used for asthma attacks?
Definition
Glucocorticoids- suppress transcription and translatoin of Cyclooxygenase; induce the synthesis of proteins that inhibit the activity of Phospholipase A2; decrease synthesis of inflammatory mediators in bronchial tissues
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