Carbohydrate Metabolism

Question 1

Glucokinase

Answer 1

present in the pancreatic beta-islet cells as part of the glucose sensor and is responsive to insulin in the liver

Question 2

Hexokinase

Answer 2

traps glucose

Question 3

Phosphofructokinase-1 (PFK 1)

Answer 3

rate limiting step

Question 4

Phosphofructokinase-2 (PFK 2)

Answer 4

produces F2,6-BP, which activakes PFK-1

Question 5

Glyceraldehyde-3-phosphate dehydrogenase

Answer 5

produces NADH

Question 6

3-phosphoglycerate kinase and Pyruvate Kinase

Answer 6

perform substrate level phosphorylation

Question 7

Irreversible reactions catalyzed by

Answer 7

Glucokinase, PFK-1, pyruvate Kinase

Question 8

Aerobic Oxidation of NADH

Answer 8

occurs via electron transport chain

Question 9

Anaerobic Oxidation of NADH

Answer 9

occurs via cytoplasmic lactate dehydrogenase

Question 10

Pyruvate Dehydrogensare

Answer 10

converts pyruvate to acetyl-CoA and is stimulated by insulin and inhibited by acetyl-CoA

Question 11

Citric Acid Cycle Main Substrates

Answer 11

Pyruvate 
Citrate
Isocitrate
Ketogluterate
Succinyl-CoA
Succinate
Fumarate
Malate
Oxaloacetate

Question 12

Location of CAC

Answer 12

mitochondrial matrix

Question 13

Main Goal of CAC

Answer 13

to oxidize acetyl-CoA to CO2 and generate NADH, FADH and GTP

Question 14

Location of ETC

Answer 14

matrix facing surface of the inner mitochondrial membrane

Question 15

General Steps of ETC

Answer 15

NADH donates electrons to the chain, which are passed from one complex to the next. Reduction potentials increase down the chain until the electrons end up on oxygen, which has the highest reduction potential

Question 16

How does NADH cross the inner mitochondrial membrane?

Answer 16

2 shuttle mechanisms
glycerol 3-phosphate shuttle
malate-aspartate shuttle

Question 17

Proton-Motive Force

Answer 17

The electrochemical gradient generated by the ETC across the inner mitochondrial membrane. The intermembrane space has a higher concentration of protons than the matrix; this gradient stores energy, which can be used to form ATP vie chemiosmotic coupling.

Question 18

ATP Synthase

Answer 18

enzyme responsible for generating ATP from ADP and an inorganic phosphate (Pi)

Question 19

Summary of the Energy Yield of Metabolic Processes:
Glycolysis:
Pyruvate Dehydrogenase:
CAC:

Answer 19

2 NADH and 2 ATP
1 NADH
3 NADH, 1 FADH2, 1 GTP

Question 20

NADH Produces:

Answer 20

2.5 ATP

Question 21

FADH Produces:

Answer 21

1.5 ATP

Question 22

GTP Produces:

Answer 22

1 ATP

Question 23

Total Energy Yield from 1 Glucose

Answer 23

30-32

2 ATP from glycolysis + 2 ATP (GTP) from CAC + 25 ATP from NADH + 3 ATP from FADH2

Question 24

Glycogenesis

Answer 24

the building of glycogen using glycogen synthase and branching enzyme

Question 25

Glycogen Synthase

Answer 25

Creates alpha-1,4-glycosidic links between glucose molecules. Activated by insulin in liver and muscles.

Question 26

Branching Enzyme

Answer 26

Moves a block of oligoglucose from one chain and connects it as a branch using an alpha-1,6-glycosidic link

Question 27

Glycogenolysis

Answer 27

The breakdown of glycogen using glycogen phosphorylase and debranching enzyme

Question 28

Glycogen Phosphorylase

Answer 28

removes single glucose 1-phosphate molecules by breaking alpha-1,4 glycosidic links. In the liver is is activated by glucagon to prevent low blood sugar In exercising skeletal muscle it is activated by epinephrnie and AMP to provide glucose fo the muscle itself

Question 29

Debranching Enzyme

Answer 29

moves a block of oligoglucose from one branch and connects it to the chain using an alpha-1,4 glycosidic link

Question 30

Gluconeogenesis

Answer 30

Occurs in the cytoplasm and the mitochondria, of primarily the liver. Mostly the reverse of glycolysis with the same enzymes but some exceptions.

Question 31

Three Irreversible Steps of Glycolysis Needed Different Enzymes in Gluconeogenesis

Answer 31

Pyruvate Carboxylase and PEP Carboxykinase bypass Pyruvate Kinase Fructose-1,6-bisphosphatase bypasses phosphofructokinase-1 (PFK-1) Glucose-6-phosphatase bypasses hexokinase/glucokinase

Question 32

Pentose Phosphate Pathway

Answer 32

Occurs in the cytoplasm and generates NADPH and sugars for biosynthesis.

Question 33

Rate Limiting Enzyme for Pentose Phosphate Pathway

Answer 33

glucose-6-phosphate dehydrogenase activated by NADP+ and insulin inhibited by NADPH

Question 34

Fermentation

Answer 34

occurs in the absence of oxygen, lactate dehydrogenase oxidizes NADH to NAD+ therefore replenishing the oxidized coenzyme for glyceraldehyde-3-phosphate dehydrogenase, reduces pyruvate to lactate

Question 35

Functions of NADPH

Answer 35

primarily acts as an electron donor, potent reducing agent for many functions

Question 36

Pathways that form acetyl-CoA

Answer 36

``` Glycolysis Fatty Acid Oxidation (beta-oxidation) Amino Acid Catabolism Ketones Alcohol ```

Question 37

Complex 1 in ETC

Answer 37

NADH donates elections here

Question 38

Complex 2 in ETC

Answer 38

FADH2 donates electrons here

Question 39

Complex 3 in ETC

Answer 39

Q-cycle occurs, which is the main contributor to the proton motive force

Question 40

Complex 4 in ETC

Answer 40

final transfer of electrons to oxygen and water is formed