BIOCHEM Chp.9 Glycolysis, PDH, Glycogenesis, Glycogenolysis, Gluconeogenesis, & PPP

Question 1

What is Km?

Answer 1

the concentration of substrate when an enzyme is active at half of its maximum velocity. the lower the Km, the higher the enzyme affinity for the substrate

Question 2

What is GLUT2?

Answer 2

a low-affinity, high Km transporter in hepatocytes and pancreatic cells that captures excess glucose for storage after a meal.

Question 3

What are the glucose sensors for insulin release?

Answer 3

B-islet cells in the pancreas, GLUT2, and glucokinase

Question 4

What is GLUT4?

Answer 4

a high affinity, low Km glucose transporter in adipose tissue and muscle that responds to [glucose] in peripheral blood

Question 5

What is glucose stored in muscles and the liver?

Answer 5

muscle - glycogen
liver - FA

Question 6

What is glycoslysis?

Answer 6

a pathway that converts glucose into 2 pyruvate molecules and 2 ATP. occurs in the cytoplasm and does not require oxygen

Question 7

How do kinases operate?

Answer 7

they attach a phosphate group from ATP to their substrates

Question 8

What is the function of Hexokinase?

Answer 8

glucose enters the cell by facilitated diffusion or active transport, then hexokinase phosphorylates the glucose to glucose 6-phosphate

Question 9

What inhibits Hexokinase?

Answer 9

glucose 6-phosphate

Question 10

What is the function of Glucokinase?

Answer 10

phosphorylates glucose to Glose-6-phosphate in the liver and pancreatic B-islet cells, works with GLUT2 as a glucose sensor

Question 11

What induces Glucokinase?

Answer 11

insulin in the liver

Question 12

What is the function of Phosphofrutokinase-1?

Answer 12

phosphorylates fructose 6-phosphate to fructose 1,6, biphosphate using ATP

Question 13

What is the function of Phosphofrutokinase-2?

Answer 13

produces F2,6-BP that activates PFK-1

Question 14

What inhibits and activates Phosphofrutokinase-2?

Answer 14

it is activated by insulin and inhibited by glucagon

Question 15

What is the function of Glycaldhyde-3-phosphate dehydrogenase?

Answer 15

produced NADH to feed into the mitochondrial ETC when oxygen is present.
also phosphorylates Glyceraldehyde-3-phosphate to 1,3,-bisphosphoglycerate

Question 16

What is the function of 3-phosphoglycerate kinase?

Answer 16

substrate-level phosphorylation transferring phosphate from 1,3, bisphosphoglycerate to ADP, forming ATP and 3-phosphoglycerate

Question 17

What is the function of pyruvate kinase?

Answer 17

substrate-level phosphorylation transferring from Phosphoenolpyruvate to ADP forming ATP and pyruvate

Question 18

What are the irreversible enzymes in glycolysis?

Answer 18

glucokinase or hexokinase, PFK-1, and pyruvate kinase

Question 19

What inhibits and activates Phosphofrutokinase-1?

Answer 19

it is inhibited by ATP, citrate, and activated by AMP, F26BP

Question 20

What activates and inhibits pyruvate kinase?

Answer 20

Fructose 1-6-Bisphosphatase activates, and acetyl-CoA inhibits pyruvate

Question 21

How is NADH oxidized when oxygen or mitochondria are absent?

Answer 21

by cytoplasmic lactate dehydrogenase

Question 22

Describe glycolysis in erythrocytes

Answer 22

1,3, BPG is converted to 2,3, BPG via BPG Mutase that the RBC can use to

Question 23

What are the rate-limiting enzymes of carbohydrate metabolism?

Answer 23

Glycolysis: phosphofructokinase-1
Fermentation: lactase dehydrogenase
Glycogeneiss: glycogen synthase
Glycogenolysis: glycogen synthase phosphorylase
Gluconeogenesis: Fructose-1,6, biphosphatase
Pentose Phosphate Pathway: Glucose 6-phosphate dehydrogenase

Question 24

What are the steps of glycolysis?

Answer 24

Glucose → Glucose 6-Phpspahte (G6P) via Hexokinase. Step is irreversible
G6P → Fructose 6-Pphopsate (F6P) via Isomerase
F6P → Fructose-1-6-Biphosphatase (F16BP) via phosphofructokinase 1 (PFK-1)
F-1-6-BP → DHA and GA3P via Aldose
GA-3P → 1-3-BPG via GA-3-PDH, facilitated with the reduction of NADH to NAD+ which can be used in the ETC or in Fermentation
1-3-BPG → 3PG via 3-PGK. The lost phosphate from 1-3 BPG is used to construct ATP
3-PG → 2-PG via Mutase
2PG → PEP via Enolase
PEP → Pyruvate via Pyruvate Kinase. Step is irreversible

Question 25

What is the role of galactokinase?

Answer 25

to store of galactose in the cell

Question 26

How is galactose converted to glucose-1-phosphate?

Answer 26

galactose is converted to glocose-1-phophate via galatcose-1-phosphate uridyltransferase and epimerase

Question 27

What are the 3 fates of pyruvate made from glycolysis?

Answer 27

1. converted to acetyl-CoA by pyruvate dehydrogenase to enter into the Citric Acid Cycle if ATP is needed 2. FA synthesis i B-oxidation if sufficient ATP is present. 3. converted to oxaloacetate by pyruvate carboxylate and enters into gluconeogenesis

Question 28

What physiological changes promote a right shift of the oxygen disassociation curve (Bohr Effect)?

Answer 28

high 2,3-BPG, low pH, high [H+] protons, high CO2, all of which occur during exercise

Question 29

What is the role of mutases?

Answer 29

they move functional groups from one place in a molecular to another

Question 30

What are the effects of 2,3-BPG on hemoglobin?

Answer 30

it binds allosterically to the B-chains of HbA and decreases its affinity for oxygen

Question 31

What is glycogenesis?

Answer 31

the synthesis of glycogen using glycogen synthase and branching enzymes

Question 32

What is the function of glycogen synthase?

Answer 32

it attached glucose molecules from UDP-glucose to the growing glycogen chain, forming a-1,4 glycosidic links b/w glucose molecules

Question 33

What is the function of branching enzymes?

Answer 33

moves a block of oligoglucose from one branch and adds it to the growing glycogens in a new branch using a-1,6 glycosidic links

Question 34

What stimulates and inhibits Glycogen synthase?

Answer 34

Insulin and ATP stimulate glycogen synthase, and Epinephrine, glucagon, and AMP inhibit it

Question 35

What is gluconeogensis?

Answer 35

done in the cytoplasm and mitochondria of liver cells

Question 36

What is glycogenolysis?

Answer 36

the breakdown of glycogen to glucose-1-phosphate using glycogen phosphorylase and debranching enzyme

Question 37

What is the role of the debranching enzyme?

Answer 37

moves a block of oligosaccharides from one branch and connects it to the chain using a-1,4 glycosidic links. it also removes branching points connected via a-1,6 glycosidic links, freeing up glucose molecules

Question 38

What is the function of Glycogen phosphorylase?

Answer 38

serves as the rate-limiting step in glycogenolysis. It removes glucose molecules from glycogen using phosphorylation, breaking the alpha-1-4 glycosidic linkages, and releasing glucose monomers but stops at branch points.

Question 39

What inhibits and activates Glycogen phosphorylase?

Answer 39

Insulin and ATP inhibit glycogen phosphorylase Epinephrine, glucagon, and AMP stimulate it (opposite of glycogen synthase)

Question 40

Where do Glycolysis, the TCA, PPP/HMP shunt, and Oxidative phosphorylation occur?

Answer 40

Glycolysis occurs in the cytoplasm. The citric acid cycle occurs in the mitochondrial matrix (Except succinate dehydrogenase, which is located in the inner membrane) pentose phosphate pathway/hexone monophosphate shunt occurs in the cytoplasm Oxidative phosphorylation occurs in the inner membrane.

Question 41

What is the function of glucosidase?

Answer 41

it hydrolyzes the leftover alpha-1-6 linkages the debranching enzyme may not catch, releasing individual glucose molecules

Question 42

What is the purpose of the pentose phosphate pathway/hexone monophosphate shunt?

Answer 42

ribose 5-phosphate and NADPH

Question 43

What is the rate-limiting step of the Pentose Phosphate pathway/Hexone Monophosphate shunt?

Answer 43

glucose-6-phosphate dehydrogenase

Question 44

What activates and inhibits Glucose-6-phosphate Dehydrogenase?

Answer 44

activated by NADP+ and insulin and inhibited by NADPH

Question 45

What is the function of Pyruvate Carboxylate?

Answer 45

converts pyruvate into oxaloacetate in gluconeogenesis

Question 46

What activates Pyruvate Carboxylate?

Answer 46

aCoA form B-oxidation

Question 47

What is the function of Phosphoenolpyruvate Carboxykinase (PEPCK)?

Answer 47

converts Oxaloacetate to Phosphoenolpyruvate in gluconeogenesis

Question 48

What activates Phosphoenolpyruvate Carboxykinase (PEPCK)?

Answer 48

glucagon and cortisol

Question 49

What is the function of Fructose-1,6,-biphosphate?

Answer 49

Converts 1,6-biphosphate to fructose 6-phosphate bypassing phosphofructokinase-1

Question 50

What activates and inhibites Fructose-1,6,-biphosphate?

Answer 50

ATP directly and glucagon indirectly (by decreasing levels of F-2,6-BP) activate, and AMP directly and insulin indirectly (bia increase levels of F-2,6-BP)

Question 51

What is generated during fermentation?

Answer 51

coenzymes needed in glycolysis - no energy is generated

Question 52

What is the function of fructokinase?

Answer 52

fructose is phosphorylated by fructokinase, trapping it in the cells

Question 53

What does aldolase B produce?

Answer 53

dihydroxyacetone phosphate (DHAP) and glyceraldehyde (which can be phosphorylated to form glyceraldehyde 3-phosphate)

Question 54

What are the reactants and products of the PDH complex?

Answer 54

Pyruvate, NAD+, and CoA are the reactants, and aCoA, NADH, and CO2 are the products.

Question 55

What inhibits the PDH complex?

Answer 55

a build-up of the product, aCoA from either TCA or fatty acid b-oxidation signals the cell is energetically satisfied and the production of aCoA should be stopped

Question 56

What is the function of NADPH?

Answer 56

antimicrobial resistance via bacterial destruction by bleach within lysosomes, and functional carriage of energy across organelle membranes for use within the mitochondria