Biochemistry of Digestion

Glycogen
A highly branched polymer of glucose with alpha 1,4 and alpha 1,6 glycosidic linkages. The structure allows for the easy removal of glucose upon request
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GLUT-2
The channel that allows glucose uptake into the liver
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Glycogenin
An enzyme involved in converting glucose to glycogen. It acts as a primer, by polymerizing the first 8 glucose molecules within a granule
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Glucokinase
The enzyme that phosphorylates glucose into glucose-6-P in the liver
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Hexokinase
The enzyme that phosphorylates glucose into glucose-6-p in the muscles
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Glucose-6-phosphatase
The enzyme that converts glucose-6-phosphate back into glucose in the liver
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Phosphoglucomutase
The enzyme that isomerises glucose-6-p into glucose-1-p during glycogen synthesis
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Glycogen synthase
Active when dephosphorylated by protein phosphatase-1-G (insulin initiates this). Inactive when phosphorylated by glycogen synthase kinase-3 (GSK-3)
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Glycogen phosphorylase
Active when phosphorylated by phosphorylase kinase. Inactive when dephosphorylated by protein phosphatase-1-G
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Insulin
A hormone that activates protein phosphatase-1-G which dephosphorylates glycogen synthase and glycogen phosphorylase during glycogen synthesis. It also phosphorylates GSK-3 to inactivate it
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ApoB
A signalling lipoprotein molecule used as identifying signatures on major lipid-containing proteins (e.g. CM, VLDL, LDL)
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LPL
The enzyme that breaks down apoproteins and triglycerides into free fatty acids. Its expression is stimulated by insulin
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Glycerol-3-phosphate
The enzyme used in fatty acid esterification within the peripheral tissues. It is generated after glucose uptake and glycolysis by insulin
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Immature
The chylomicron that leaves the digestive tract
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Mature
The chylomicron after receiving the apoproteins CII and E from HDL to increase the chylomicrons affinity for LPL
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VLDL
A lipoprotein produced by the liver, has the apoprotein B100. Has a very high concentration of TG and cholesterol. It also receives apoproteins CII and E from HDL to increase affinity for LPL. The remnant is LDL or IDL
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Transamination
First step in the breakdown of AAs to produce energy. The removal of the NH3+ group from an amino acid to be added on to a ketoacid (e.g. alpha ketoglutarate)
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Oxidative deamination
Second step in the breakdown of AAs to produce energy. Glutamate dehydrogenase breaks glutamate back down into the ketoacid and NH3+ to safely move within the body
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Glutamine synthetase
The enzyme that converts glutamate into glutamine. Glutamine can carry the nitrogen safely into the liver where it is disposed of via the urea cycle
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HSL
An enzyme that is inhibited by insulin
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GLUT-4
Glucose transporters that are found on skeletal muscle. Their expression is increased by insulin
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GSV
GLUT-4 storage vesicles. They are pre-formed vesicles that are moved from the cytoplasm to the plasma membrane, allowing more glucose uptake
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Adipocyte
Cells which have very little cytoplasm and the bulk of them is taken up by a huge lipid droplet. Their cytoplasm contains lipases
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Perilipin
A protein that coats triglycerides in adipocytes to prevent them from being attacked by lipases too early. Once phosphorylated, this protein folds back to expose the lipid for lipases to work on
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ATGL and HSL
The enzymes responsible for catalysing the first step in the breakdown of a triglyceride to release 1 fatty acid
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HSL
The enzyme responsible for catalysing the second step in the breakdown of TGs. It releases one more fatty acid
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MGL
The enzyme responsible for catalysing the final step in the breakdown of TGs. This step releases the last fatty acid
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Orlistat
The only drug on the market to combat obesity. It is a lipase inhibitor which prevents TG breakdown and reduces the absorption of dietary fat. This means that fat will be present in stool - steatorrhea
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Other cards in this set

Card 2

Front

The channel that allows glucose uptake into the liver

Back

GLUT-2

Card 3

Front

An enzyme involved in converting glucose to glycogen. It acts as a primer, by polymerizing the first 8 glucose molecules within a granule

Back

Preview of the back of card 3

Card 4

Front

The enzyme that phosphorylates glucose into glucose-6-P in the liver

Back

Preview of the back of card 4

Card 5

Front

The enzyme that phosphorylates glucose into glucose-6-p in the muscles

Back

Preview of the back of card 5
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