Biochem for final+makeup #2

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The first step of glycolysis is…

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1

The first step of glycolysis is…

irreversible and driven in direction of G6P by ATP

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2

The second step of glycolysis is

reversible and has a positive deltaG

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3

How is Hexokinase IV different from the other three?

It has low affinity for glucose, higher hill number and no product inhibition

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4

In reaction 3 of glycolysis, ATP is the donor, this means….

this is an irreversible step and is the first committed step

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5

Why is it important to interconvert DHAP and G3P

only glyceraldehyde 3-phosphate is a substrate for the remaining reactions of glycolysis

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6

In the first stages of glycolysis, glucose is converted to…

two molecules of G3P

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7

Key intermediate for the first phase of glycolysis

ATP-dependant phosphorylation of fructose-6-phosphate to fructose-1,6-biphosphate

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8

Which step is the first energy yielding step in glycoysis

reaction 6, the foramtion of 1,3-Biphosphoglycerate

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9

net ATP yield of glycolysis up to reaction 7 is…

zero

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10

Sites of regulation in glycolysis

Hexokinase (reaction 1)

PFK-1 (reaction 3)

Pyruvate Kinase (reaction 10)

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11

Reaction 1 of glycolysis

the ATP-dependant phosphorylation of glucose

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12

Reaction 3 of glycolysis

The ATP-dependant phosphorylation of fructose 6 phosphate

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13

Reaction 4 of glycolysis

The cleavage of F-1,6-B into two different triose phosphates

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14

Reaction 5 of glycolysis

Interconversion of dihydroxyacetone phosphate (DHAP) and Glyceraldehyde 3-phosphate (G3P)

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15

Reaction 6 of glycolysis

Formation of 1,3-biphosphoglycerate

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16

Reaction 7 of glycolysis

substrate level phosphorylation of ADP and formation of 3-phosphoglycerate

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17

Reaction 8 of glycolysis

isomerization of 3-phosphoglycerate

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18

Reaction 9 of glycolysis

dehydration of 2-phosphoglycerate

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19

Reaction 10 of glycolysis

substrate level phosphorylation #2 and the conversion of PEP to pyruvate

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20

Pyruvate kinase is allosterically inhibited by

ATP and acetyl-CoA

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21

Pyruvate kinase is allosterically activated by

AMP and fructose-2,6-biphosphate

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22

NAD+ is required in the oxidation of…

glyceraldehyde-3-phosphate to 1,3-biphosphoglycerate

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23

If O2 is available in glycolysis,

NADH is re-oxidized by the electron trnasport chain

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24

If O2 is unavailable in glycolysis

NADH is re-oxidized by the reduction of pyruvate to either lactate or ethanol

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25

Pyruvate is converted to lactate in

anaerobic tissues (NAD+ is recycled in the process)

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26

In some organisms, pyruvate is converted to ethanol in a process requiring...

thiamine pyrophosphate as a coenzyme (NAD+ is recycled)

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27

Glycogen breakdown three steps

  1. release of glucose-1-phosphate from glycogen

  2. conversion of glucose 1-phosphate to glucose 6-phosphate

    1. “remodeling” of glycogen to facilitate further breakdown

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28

Glycogen breakdown step 1

No ATP involved, catalyzed by glycogen phosphorylase

  • product is Glucose-1-Phosphate

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29

Glycogen breakdown step 2

catalyzed by phosphoglucomutase

  • product is glucose-6-phosphate

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30

What additonal enzyme is required to completely convert glycogen to glucose

debranching enzyme

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31

The debranching enzyme catalyzes two reactions…

transferase activity and a-1,6-glucosidase activity

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32

Glucose units are added to the…

non-reducing end of glycogen

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33

What adds individual glucose molecules to the non-reducing end of glycogen

NDP-sugar pyrophosphorylase and glycogen synthase

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34

The enzyme glycogenin serves as

both the primer and the catalyst for synthesis of new glycogen molecule

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35

Phosphorylase exists in 4 forms…

Phosphorylase a:

  • inactive or less active: taut ot T-form

  • active (phosphorylated): relaxed or R-form

Phosphoylase b:

  • same as a

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36

glucose binding to the R-form of phosphorylated phos. a causes…

a conformational change exposing the phosphorylated Ser residues to phosphoprotein phosphatase

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37

High glucose decreases the need for….

the cell to breakdown glycogen into glucose

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38

Glycogen synthase exsits in two forms…

a: active form

b: inactive form

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39

On thermodynamic ground alone, gluconeogenesis cannot..

be a simple reversal of glycolysis

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40

Gluconeogenesis reaction 1

conversion of pyruvate to oxaloacetate

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41

Gluconeogenesis reaction 2

conversion of OAA to PEP

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42

Gluconeogenesis reactions 3 to 8

conversion of PEP to Fructose-1,6-biphosphate

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43

Gluconeogenesis reaction 9

conversion of fructose-1,6-biphosphate to fructose-6-phosphate

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44

Gluconeogenesis reaction 10

conversion of fructose-6-phosphate to glucose-6-phosphate

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45

Gluconeogenesis reaction 11

conversion of glucose-6-phosphate to glucose

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46

F26BP

signal in the cell for low energy

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47

F26BP allosterically activates

PFK-1 and allosterically inhibits FBPase-1

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48

Pyruvate can be converted t glucose and glycogen via gluconeogenesis or….

oxidized to acetyl-CoA for energy production

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49

Acetyl-CoA activates/inhibits…

activates: pyruvate carboxylase

inhibits: pyruvate dehydrogenase

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50

Metabolic fates of G6P

substrate for glycolysis, glycogen synthesis, and PPP

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51

Cellualr respiration produces

CO2 from O2

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52

cellular respiration occurs in three stages…

acetyl-CoA production, acetyl-CoA oxidation via the citric acid cycle, electron transfer and oxidative phosphorylation

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53

Three processes that play central role in aerobic metabolism

citric acid cycle, electron transport, and oxidative phosphorylation

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54

Catabolism

oxidative breakdown of nutrients A

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55

Anabolism

reductive synthesis of biomolecules

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56

The citric cycle is amphibolic, meaning….

it plays a role in catabolism and anabolism

(CENTRAL METABOLIC PATHWAY)

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57

In Euk., the Citric acid cycle occurs in

the mitochondria

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58

In Euk., glycolysis occurs in

cytoplasm

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59

In Euk., oxidative phosphorylation occurs in

the inner membrane

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60

Stage 1 of citric acid cycle

Acetyl-CoA production

  • oxidation of fatty acids, glucose, and some AA. Yields some ATP NADH and FADH2

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61

oxidative decarboxylation of puyruvate

remaining 2 carbon atoms of pyruvate enter the citric acid cycle as acetyl-CoA and yield energy

  • catalyzed by pyruvate decarboxylase complex

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62

Channeling minimizes

side reactions

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63

Stage 2 of citric acid cycle

oxidation of Acetyl-CoA

  • generates NADH, FADH2, and one GTP

    • catalyzed by citrate synthase

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64

Conformational change occurs upon…

the binding oxaloacetate

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65

Open conformation

free enzyme does not have a binding site for acetyl-CoA

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66

Closed conformation

binding of oxaloacetate creates site for binding of acetyl-CoA

  • reactive baranion is protected in the closed conformation

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67

Citrate

poor substrate for oxidation

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68

elimaination of H2O from citrate gives

a cis C=C bond

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69

Isocitrate

a good substrate for oxidation

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70

Isocitrate dehydrogenase catalyzes…

the oxidative decarboxylation of D-isocitrate to a-ketoglutarate

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71

a-ketoglutarate dehydrogenase complex catalyzes the…

oxidative decarboxylation of a-ketoglutarate to succinyl-CoA

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72

The conversion of pyruvate to succinyl-CoA has resulted in

introduction of 2 carbon atoms as acetyl-CoA, loss of two carbon atoms as CO2

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73

Reaction 5 of citric acid cycle

substrate level phosphorylation of GDP as succinyl-CoA is converted to succinate

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74

Reaction 6 of citric acid cycle

FAD-dependent oxidation of succinate to fumarate

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75

Reaction 7 of citric acid cycle

stereospecific trans hydration of the double bond to form an alcohol

  • it is very specific for fumarate and L-malate

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76

Reaction 8 of citric acid cycle

dehydrogenation to give NADH

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77

The most important anaplerotic reaction

the reaction catalyzed by pyruvate carboxylase

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78

pyruvate carboxylase is allosterically activated by

acetyl-CoA

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79

The two major regulatory points of the citric acid cycle

production of acetyl-CoA by the pyruvate dehydrogenous complex

entry of acetly-CoA into the citric acid cycle as catalyzed by citrate synthase

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80

Regulation of pyruvate dehydrogenase complex occurs at tow levels…

allosteric inhibitors and activators (ATP, AMOP, NADH, NAD+…)

phosphorylation

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81

Pyruvate dehydrogenase complex activity is off when

fuel energy is high

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82

pyruvate dehydrogenase complex activity is on when

fuel energy is low

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83

citrate synthase is inhibited by

NADH, Succ-CoA citrate and ATP

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84

citrate synthase is activated by

ADP

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85

isocitrate dehydrogenase is inhibited by

ATP

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86

Isocitrate dehydrogenase is activated by

ADP

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87

Citric acid cycle makes…

GTP and reduced cofactors that could yield ATP

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88

What converts pyruvate into acetly-CoA

pyruvate dehydrogenase complex

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89

Cristae

convolutions of the inner membrane and serve to increase the surface area

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90

Ubiquinone

lipid-soluble conjugated dicarbonyl compound that readily accepts electrons

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91

cytochromes

small, water-soluable, colored, proteins that have important roles in biological redox reactions C

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92

Cytochromes are classified as a, b, or c based on

spectral characteristics

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93

All cytochromes undergo…

one electron reduction/oxidation at heme-based iron

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94

How many redox reactions are involved in transferring electrons from NADH to O2

about 12

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95

The electron transport chain can be divided into discrete segements…

Complex I, II, III, IV, and ATP synthases

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96

Complexes I, III, IV can drive…

ATP synthesis

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97

Complex IV is the link to

O2

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98

Uncouplers inhibit the

phosphorylation of ADP without affecting electron transport

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99

F0 protein

hydrophobic proton channel buried in the inner mitchondrial membrane

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100

F1 protein

projects into the mitochondrial matrix

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