Carbohydrate Metabolism

Front 1

What is the term for the anaerobic catabolism of glucose?

Back 1

Glycolysis

Front 2

What is the main fuel source for the brain?

Back 2

Glucose

Front 3

What two tissues do not contain mitochondia?

Back 3

Red blood cells, cornea and lens regions of retina do not contain mitochondria and therefore depend on glycolysis as the major mechanism for ATP production

Front 4

What human cells does glycolysis occur in?

Back 4

All human cells

Front 5

Anaerobic degradation of glucose produces what and how many ATP?

Back 5

Lactate and 2 ATP

Front 6

Aerobic complete oxidation of glucose produces what and how many ATP?

Back 6

CO2 and H20. 32 ATP

Front 7

How is glucose transported into a cell?

Back 7

by a glucose transporter or GLUT

Front 8

How does insulin affect glucose uptake?

Back 8

The hormone insulin increases insulin receptor enzymatic activity which causes GLUT4 to be placed on the cell membrane's surface where it transports glucose inside the cell

Front 9

What tissues used GLUT4?

Back 9

Muscle, heart, and adipose tissue

Front 10

What are the three stages of glycolysis?

Back 10

Priming stage, splitting stage, oxidoreduction-phosphorylation stage

Front 11

Where does the priming stage of glycolysis occur?

Back 11

the priming stage of glycolysis occurs in the cytosol

Front 12

What are the irreversible reactions in the priming stage of glycolysis?

Back 12

conversion of glucose to glucose 6-phosphate by hexokinase (uses atp to get the phosphate) and conversion of fructose 6-phosphate to fructose 1,6 biphosphate by 6-phosphofucto-1-kinase

Front 13

What happens in the splitting stage of glycolysis?

Back 13

Fructose 1,6-biphosphate is split by fructose-bisphophate aldolase into dihydroxyacetone phosphate (DHAP) and Glyceraldehyde 3-phosphate (GAP). DHAP is converted by triosephosphate isomerase into GAP thus forming two GAPs from one glucose

Front 14

What happens in the oxidoreduction-phosphorylation stage of glycolysis?

Back 14

GAP eventually becomes Pyruvate which can be converted to L-lactate.

Front 15

What stages of glycolysis use ATP, which produce, and which are ATP neutral?

Back 15

priming stage uses 2 ATP, splitting stage is ATP neutral, oxidoreduction-phosphyrlation stage produces 2 ATP

Front 16

What is the overall rxn for aerobic metabolism in glycolysis?

Back 16

D-Glc + 6 O2 + 32 ADP + 32Pi +32H --> 6 CO2 + 6 H2O + 32 ATP

Front 17

What is the overall reaction for anaerobic metabolism?

Back 17

D-Glc + 2 ADP + 2 Pi --> 2 L-lactate + 2 ATP + H20

Front 18

What are the three major regulatory enzymes of glycolysis?

Back 18

Hexokinase, 6-phosphofructo-1-kinase, and pyruvate kinase

Front 19

What happens when you decrease ATP in the cell?

Back 19

It will increase AMP which is a positive effector to increase glycolysis (ATP+ADP+AMP = constant)

Front 20

What happens if an accumulation of glucose-6-phosphate occurs?

Back 20

It will slow glycolysis allowing G6P to be used by the pentose phosphate pathway or used for glycogen synthesis

Front 21

Hydrogen cations act upon glycolysis how after being formed from the ionization of lactic acid?

Back 21

Hydrogen cations are negative effectors of glycolysis

Front 22

What acts as both a positive effector of 6-phosphofructo-1-kinase and also as a negative effector of fructose 1,6-bisphosphatase?

Back 22

fructose 2,6 bisphosphate

Front 23

How is the bifunctional enzyme 6-phosphofucto-2-kinase / fructose 2,6 - bisphosphatase regulated?

Back 23

via phosphorylation

Front 24

Where is the hormone glucagon released from?

Back 24

alpha cells of pancreas which release it into the blood stream

Front 25

Where does glucagon bind on liver cells? what does this activate?

Back 25

g-protein; activateds adenylate cyclase

Front 26

What hormone has the same effect as glucagon in hepatic cells?

Back 26

epinephrine

Front 27

What is the role of glucagon in hepatic cells?

Back 27

Down regulates glycolysis to conserve glucose for other cells

Front 28

What does adenylate cyclase do when activated by glucagon (indirectly) or epinephrine in hepatic cells?

Back 28

synthesizes cAMP which decreases fructose 2,6-bisphosphate which in turn decreases glycolysis

Front 29

How do heart cells respond to epinephrine binding?

Back 29

opposite to hepatic cells: The heart contains a different isoenzyme of 6-phosphofructo-2-kinase / fructose 2,6-bishphosphatase which activates 6-phosphofructo-2-kinase when phosphorylated.

This increases glycolysis to supply energy to the heart.

Front 30

What term describes the formation of glucose from noncarbohydrate substances?

Back 30

gluconeogenesis

Front 31

What is the overall rxn of gluconeogenesis?

Back 31

2 L-lactate + 6 ATP + 6 H20 --> glc + 6 ADP + 6 P + 4 H

Front 32

How many ATPs does glycolysis produce?

Back 32

2 ATP

Front 33

How many ATP does gluconeogenesis consume?

Back 33

6 ATP

Front 34

Signal transduction through the insulin receptor is regulated by autophophorylation of what?

Back 34

Tyrosine

Front 35

In a liver cell, increasing cAMP will do what?

Back 35

increase fructose 2,6-bisphosphatase activity

Front 36

Where are most triglycerides in the serum contained?

Back 36

in VLDLs and chylomicrons

Front 37

Cell to cell signlaing that requires the two cells to be in contact is called?

Back 37

juxtacrine

Front 38

What does succinyl CoA sythetase convert succinyl CoA into in the TCA cycle?

Back 38

succinate

Front 39

What is the immediate trigger for the disassociation of the alpha subunit from the beta and gamma subunit of a G-protein couple receptor?

Back 39

binding of GTP

Front 40

As pyruvate kinase is non involved in gluconeogenesis, what two rxns conver pyruvate to phosphoenolpyruvate (PEP)?

Back 40

Pyruvate to Oxaloacetate via Pyruvate carboxylases and Oxaloacetate to PEP via PEP carboxykinase; this requires two ATP

Front 41

What enzyme is used during gluconeogenesis to produce fructose 6-phosphate from fructose 1,6-biphosphate as 6-phosphofructo-1-kinase is not reversible?

Back 41

fructose 1,6-bisphosphatase

Front 42

What enzyme is used to bypass the step between glucose and glucose-6-phosphate during gluconeogenesis as hexokinase is not reversible?

Back 42

glucose-6-phosphatase

Front 43

What does increasing epinephrine binding to cardiac cell cause?

Back 43

fructose 2,6-bisphosphatase activity to increase

Front 44

Do glycolysis and gluconeogenesis ever occur at the same time?

Back 44

no, anything that down regulates glycolysis up regulates gluconeogenesis

Front 45

During gluconeogenesis, fatt acid oxidation does what to mitochandrial Acetyl Coa and NADH?

Back 45

increases mt Acetyl Coa and NADH

Front 46

What is insulin level during fed state?

Back 46

high

Front 47

What is glucagon level in a fasting state?

Back 47

high

Front 48

When glucagon activates adenylate cyclase which activates cAMP, protein kinase A is activated which then does what?

Back 48

Phosphorylates (activates) cAMP-response element binding protein (CREB). CREB promotes transcription of the PEP carboxykinase gene and other gluconeogenic genes

Front 49

What is the storage form of glucose?

Back 49

glycogen

Front 50

Where is glycogen found?

Back 50

liver (used to regulate blood glucose level) and in muscle (used as fuel for that muscle)

Front 51

What kind of linkages occur between glucose residues?

Back 51

alpha-1,4-glyocsidic linkages and branches that occur from alpha-1,6-glycosidic linkages

Front 52

How often do branches occur on glycogen?

Back 52

about every 4th residue

Front 53

What initiates glycogenolysis?

Back 53

glycogen phosphorylase (converts glycogen to cut off into glycogen plus glucose 1 -phosphate)

Front 54

How does the liver utilize glycogen?

Back 54

Breaks it down into glucose to circulate it in the blood

Front 55

How does muscle tissue utilize glycogen?

Back 55

White muscle uses it anaerobically to become lactate white red muscle uses it aerobically to become CO2 and H20

Front 56

At what point does glycogen phosphorylase stop removing glucose 1 phosphate residues?

Back 56

within 4 residues of a branch point

Front 57

What takes the 4 residue branch point during glycogenolysis and continues the breakdown?

Back 57

Debranching enzyme transfers 3 residues and then cleaves the alpha-1,6-glycosidic linkage. Glycogen phosphorylase then continues cleaving the alpha-1,4-glycosidic linkages

Front 58

Does glycogenesis require energy and if so in what form?

Back 58

yes and uridine triphosphate

Front 59

What is the process of glucose addition using glycogen synthase?

Back 59

glucose carbon 1 (reducing end) is always added to the existing carbon 4 of the glycogen chain (in the alppha linakge) by glycogen synthase

Front 60

What kind of chains does glycogen synthase make?

Back 60

straigh chains (amylose)

Front 61

When does the branching enzyme transfer 7 residues in glycogen synthesis?

Back 61

when it locates a chain of glycogen longer than 11 residues

Front 62

What is the advantage of storing glucose as glycogen?

Back 62

Glucose is osmotically active (dissolves in aqueous solution). It would cost a lot of ATP to maintain the glucose gradient across the cell membrane.

Glucose would cause osmotic uptake of water into the cell and lyse the cell.

Glycogen is not very soluble in aqueous solution and thus not very osmotically active.

Front 63

Why store energy as glycogen rather than storing all energy as fat?

Back 63

Glycogen can be mobilized more quickly than fat.

Fat can not be used as energy in the absence of oxygen.

Glycogen can be easily converted to glucose for the brain, fat can not.