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What fructose intermediate is found only in the liver?
What is the major dietary source of Fructose?
Fructose control is..?
- Intestinal Sucrase which yields both glucose and fructose
- Not under Insulin control
The Km of Hexokinase for Fructose is?
What does this mean?
- is high (low affinity)
- That very little F-6-P will be made with fructose. Fructose is a poor substrate competitor.
F-1-P Km is ____ compared to F16BP Km.
- High (lower affinity)
- Can at times lead to backup of F-1-P. Lack of Aldolase B leads to fructose poisoning
In order for Glyceraldahyde to enter glycolysis, what needs to happen?
Need to add a Phosphate via ATP.
A disease that is the lack of Fructokinase is called?
A disease that is the lack of Aldolase B is called?
- "Essential Fructosuria"- Fructose accumulation in the urine
- "Hereditary Fructose Intolerance" - Buildup of F-1-P, leads to phosphates sequestered--> low ATP production.
Other routes for F-6-P other than glycolysis include?
- Production of Glycoconjugates.
- F-6-P + Glutamine --> Glucosamine-6-phosphate + Glutamate
- This is a irreversible reaction
- N/O linkage. N(asparagine), O (threonine or serine)
- Create Mannose-6-P via isomerization
What is the role of Dolichol-pyrophosphate?
It is a very long lipid molecule that acts as an oligosaccharide carrier in the ER.
What is the Polyol Pathway and its function?
- Trapping sugars into a cell by adding Pi Group by NADPH based reduction.
- Example: in the seminal vessicals (remember fructose is broken down faster).
Hyperglycemic effects on sorbitol
Increased glucose amounts leads to more sorbitol and the high amounts of intracellular glucose causes water retention and damages the cells. Seen in Diabetes patients.
- Galactokinase Galactose--> galactose-1-P
- Aldose reductase Falactose--> galactitol
- Uridyltransferase Galactose-1-P --> UDP-Galactose
Functions of UDP-Galactose?
- Production of lactose. (in mammary tissue)
- uses the enzyme Lactose synthase that has 2 parts (A & B)
- A= Galactosyltransferase and B= lactalbumin)
- Inhibits protein B of Lactose Synthase
- Promotes Protein B of Lactose Synthase
Acid Glucose synthesis
- UDP-Glucose --> UDP-Glucouronate--> can lead to Vit C or Proteoglycan production
- Enzyme is UDP-glucose Dehydrogenase
Glucuronidation. What is it?
A process that creates polar compounds that can be more easily cleared in the urine.
Name some hormones that simulate lipolysis
Norepinephine, Glucocorticoids, GH, TH
What is Cushings disease?
Excess Glucocorticoids- Fat tissue reduced in the extremities.
Effects of :
- - Insulin- Inhibits lipolysis ( the breakdown of lipids) by inhibiting HSL via Dephosphorylation
- - Glucagon and Epinephrine- Promotes Lipolysis
Albumines role with Free Fatty acids?
How do TAG travel through the blood?
- Albumine acts as a plasma carrier of FFA's
- Triacylglycerols travel through the blood via Chylomicrons
Before the FA can enter the Mitochonria to be oxidized, what must occur?
(addition of CoA) of the FA must occur.
- Fatty Acyl + ATP + CoASH--> Fatty Acyl-CoA
- * done with the Enzyme Acyl-CoA synthetase
What is the role of Carnitine? What is it made of?
- Carnitine transports Long Chain Fatty Acids through membranes into and out of the matrix (its the shuttle).
- It is made of 2 Essential Amino Acids. Lysine and 3 methionine (CH3) groups.
- The cell has 2 Carnitine-palmitoyl transferases
What are the 4 steps of B-Oxidation?
What is produced?
1. Oxidation 2. Hydration 3. Oxidation 4. Thiolytic cleavage
1FADH2 and 1NADH per cycle
What is the Respiratory Quotient?
How to compare energy efficiencies?
RQ = CO2 released/ O2 consumed
Efficiency= ATP produced/ per carbon
Three points of regulation of fatty acid utilization.
- 1. HS-lipase
- 2. Malonyl-CoA inhibites Carnitine Tranferase I. causes FA buildup.
- 3. Caritine transferase I- activity increases in prolonged fast.
Degradation of Very Long Chained Fatty Acids
- Takes place in the Peroxisomes.
- Peroxide needed.
What is Zellwegers Syndrome?
- Patients have non-functioning peroxisomes. Cannot break down VLCFA due to defective ladelling(M6P) of new proteins.
- Broad nose, and widely spaced eyes.
What is Refsums disease?
- When FA's B-carbon has a CH3 and the Alpha carbon cannot be oxidized. B-oxidation is stymied and cannot proceed. leads to the accumulation of Phytanic acid.
- The Hydroxylation step is prevented in this disorder.
- Phytanic acid (high in green plants).
Degradation of unsaturated FA
Proper oxidation of unsaturated FA requires isomerization to an intermediate trans shape.
Oxidation of Odd chain FA
- Need to add a carbon to make it a even number. This is done with CO2 addition.
- Total process requires 3 steps.
- Process requires Cobalamin (B12) and Biotin.
The most comon denzyme difficiency in B-Oxidation
- Medium chain acyl-CoA dehydrogenase (From the 1st step).
- Gets confused with SIDS
Since there is an increase in Acyl-CoA that cannot get into the mitochondria, they are diverted to TAG synthesis. Will see lipid droplets in muscle cells.
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