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T1 - Integrated (Full Review) > Biochemistry - Musculoskeletal Block > Flashcards

Biochemistry - Musculoskeletal Block Flashcards

1
Q

What is the inheritance pattern of Duchenne’s muscular dystrophy?

What is the life expectancy of affected individuals?

A

X-linked recessive;

< 35

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2
Q

Duchenne’s muscular dystrophy affects which muscles first?

What muscles often appear hypertrophied?

What is the usual cause of death?

A

The pelvic girdle;

calf muscles;

loss of function of diaphragmatic and cardiac muscle

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3
Q

What type of muscle (voluntary/involuntary) is the principal type affected in Duchenne’s muscular dystrophy?

What is a common first sign?

A

Voluntary;

failure of child to walk normally or hold normal posture - may walk on toes due to muscle contractures

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4
Q

Dystrophin binds actin to ____________, which binds to extracellular laminin.

A

α,β-dystroglycan

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5
Q

What disease is similar to Duchenne’s muscular dystrophy but is less severe and results later in life?

A

Becker muscular dystrophy

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6
Q

G-actin must be bound to ___ to polymerize into F-actin.

α- and β-tubulin must be bound to ___ to polymerize into microtubule protofilaments.

A

ATP;

GTP

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7
Q

True/False.

Both the GTP associated with microtubules and the ATP associated with actin will hydrolyze relatively soon after polymerization?

A

True

(although the ATP-actin hydrolyzes much sooner)

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8
Q

What are the three cellular proteins regulating actin polymerization?

A

Cofilin,

profilin,

thymosin-β4

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9
Q

What type of filament is especially important in cell migration (e.g. chemotaxis)?

A

Actin (microfilaments)

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10
Q

What are the four steps of cell movement during chemotaxis?

A

1. Foot process (lamellipodium) formation

2. Adhesion at the front of the cell

3. Translocation as the cell shifts forwards

4. Deadhesion at the back of the cell

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11
Q

What type of protein cross-links the cytoskeleton to the ECM?

A

Integrins

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12
Q

What type of protein cross-links actin into a meshwork on the P-face?

A

Spectrin

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13
Q

Hereditary spherocytosis can be caused by defects in what three proteins?

A

Spectrin, protein 4.1, ankyrin.

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14
Q

What type(s) of intermediate filament are especially prevalent in epithelial tissues?

A

Cytokeratins (acidic and basic)

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15
Q

What type(s) of intermediate filament are especially prevalent in muscle?

A

Desmin

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16
Q

What type(s) of intermediate filament are especially prevalent in mesenchymal tissues?

A

Vimentin

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17
Q

What type(s) of intermediate filament are especially prevalent in glial cells?

A

GFAP

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18
Q

What type(s) of intermediate filament are especially prevalent in neural tissues?

A

Neurofilaments

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19
Q

What type(s) of intermediate filament is especially prevalent in the nucleus?

A

Lamins

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20
Q

What are some of the physical features commonly seen in type I osteogenesis imperfecta?

What are some other common occurrences?

A

Blue sclera, triangular shape;

frequent fractures, hearing loss (beginning in the twenties), scoliosis, thin skin, loose joints, low muscle tone, brittle teeth

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21
Q

What inheritance does type I osteogenesis imperfecta exhibit?

It is due to a defect in what?

A

Autosomal dominant;

type I collagen

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22
Q

What type of osteogenesis imperfecta frequently results in death during embryogenesis or birth?

A

Type II

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23
Q

What gene is associated with osteogenesis imperfecta type I?

A

COL1A1

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24
Q

How is osteogenesis imperfecta treated?

What is the mechanism of action?

A

Bisphosphonates;

osteoclast inhibition

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25
Q

_______________ are useful for treating osteoporosis and osteogenesis imperfecta by inhibiting osteoclasts because they mimic ______________, which is needed for normal osteoclastic activity.

A

Bisphosphonates;

pyrophosphates

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26
Q

How do individuals with type II osteogenesis imperfecta typically die?

A

Severe bone fracturing during the birthing process

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27
Q

What effect do bisphosphonates tend to have on apoptosis in bone cells?

A

Increased osteoclast apoptosis;

decreased osteoblast apoptosis

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28
Q

The basic structure of collagen that gives it its strength is a:

A

triple helix

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29
Q

What is the basic repeating amino acid code for collagen?

What amino acids make up the variable portions?

A

Gly - X - Y;

X,Y = proline or hydroxyproline

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30
Q

Is the collagen helix a right- or left-handed helix?

A

Left

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31
Q

What type of bonding is extremely prevalent in collagen, binding the strands together?

A

Hydrogen bonding

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32
Q

Describe collagen in terms of tensile strength and elasticity.

Describe elastin in terms of tensile strength and elasticity.

A

High tensile strength, low elasticity;

low tensile strength, high elasticity;

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33
Q

Vitamin C is needed for what step of collagen formation?

Why is this step important?

A

Proline hydroxylation;

it stabilizes the triple helix

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34
Q

True/False.

Without Vitamin C, collagen cannot be synthesized.

A

False.

Vitamin C is responsible for post-translational proline hydroxylation.

(without vitamin C, the collagen strands are simply less stable and more easily degraded)

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35
Q

Vitamin C is a cofactor of what enzyme involved in post-translational collagen modification?

A

4-prolyl-hydroxylase

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36
Q

What type of collagen is a higher order structure found in the basement membrane?

A

Type IV

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37
Q

What type of collagen is an anchoring type that connects the dermal and epidermal layers?

A

Type VII

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38
Q

What organ systems are most susceptible in Alport’s syndrome?

What is the main genetic defect in Alport’s syndrome?

A

Kidney, ears (ossicles), and eyes (cornea);

type IV collagen defects

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39
Q

What is the most common form of inheritance seen in Alport;s syndrome?

A

X-linked

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40
Q

Where is type I collagen found?

A

Most connective tissue

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41
Q

Where is type II collagen found?

A

Cartilage and vitreous humor

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42
Q

Where is type III collagen found?

A

Extensible connective tissue

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43
Q

Where is type IV collagen found?

What structure does it have?

A

Basal lamina;

sheet-like networks

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44
Q

Where are type V and XII collagen found?

A

Tissues containing type I collagen

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45
Q

Where is type VII collagen found?

A

Anchoring basal lamina to underlying connective tissue

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46
Q

What protein serves as a scaffold for tropoelastin?

Mutations in this protein lead to what disorder?

A

Fibrillin;

Marfan’s syndrome

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47
Q

What is a (typically present) symptom of homocystinuria that differentiates it from Marfan’s syndrome?

A

Intellectual disability

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48
Q

What are the first three steps of collagen synthesis?

(starting with a transcribed collagen mRNA)

A

1. mRNA is translated into pre-procollagen

2. Hydroxylation of select proline residues

3. Glycosylation of select lysine residues

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49
Q

What are the second three steps of collagen synthesis?

(starting here with hydroxylated and glycosylated procollagen chains)

A
  1. Three pro-alpha-chains come together into an alpha-helix
  2. Procollagen secreted from cell
  3. Procollagen ends cleaved off by procollagen peptidase

(This is now tropocollagen)

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50
Q

Following secretion of procollagen from the cell and cleavage of its ends to form tropocollagen, what happens?

A

Lysyl oxidase cross-links mature collagen fibrils

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51
Q

A deficiency of lysyl oxidase leads to what disorder?

Lysyl oxidase is used to cross-link what together?

What element is necessary for its function?

A

Menke’s syndrome;

collagen fibrils;

copper

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52
Q

Ehrlos-Danlos syndrome is caused by a mutation in the ADAMTS2 gene. This leads to a deficiency in what enzyme?

What does this enzyme do?

A

Procollagen peptidase;

cleaves procollagen ends to form tropocollagen

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53
Q

What are three of the few enzymes in the body that require copper (Cu2+) as a cofactor?

A

Tyrosinase,

dopamine β-hydroxylase,

lysyl oxidase

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54
Q

How does the ECM serve as a source of growth and chemotactic factors?

A

Growth factors are bound to (sequestered in) proteoglycans until metalloproteases release them

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55
Q

What is the basic makeup of ECM?

(3 main players)

A

Hydrated gel

+

reinforcing fibers throughout

+

multiadhesive signaling proteins

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56
Q

What proteoglycan is associated with the basement membrane?

What collagen type is associated with the basement membrane?

What multiadhesive proteins are associated with the basement membrane?

A

Perlecan;

type IV;

fibronectin, laminin

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57
Q

What proteoglycan is associated with the basement membrane?

A

Perlecan

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58
Q

What collagen type is associated with the basement membrane?

A

Type IV

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59
Q

What multiadhesive proteins are associated with the basement membrane?

A

Fibronectin, laminin

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60
Q

What is a glycosaminoglycan (GAG) in terms of structure?

Are they osmotically active?

A

An unbranched polysaccharide made of repeating disaccharide units (often a uronic acid + an amino sugar);

yes, they keep tissues hydrated by storing water

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61
Q

Are glycosaminoglycans eosinophilic or basophilic?

Why?

A

Basophilic;

lots of SO4- and COO- groups

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62
Q

What is a proteoglycan (found in the ECM)?

A

A core protein with tons of attached glycosaminoglycans

(basically a protein with tons of sugars sticking off of it)

(one branch of the ‘Christmas tree’ seen in the attached illustration)

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63
Q

What is the major core protein of proteoglycans found on articular cartilage?

True/false.

It can absorb and release synovial fluid as needed (according to pressures).

A

Aggrecan;

true

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64
Q

What are the two main cartilaginous proteins that are often degraded in osteoarthritis?

A

Type II collagen;

aggrecan

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65
Q

Is hyaluronic acid a proteoglycan?

A

No;

it is a glycosaminoglycan forming the ‘trunk’ to which proteoglycan ‘branches’ attach

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66
Q

What type of proteoglycan is primarily found in cartilage?

What type of proteoglycan is primarily found in basal lamina?

What type of proteoglycan binds type I collagen and is widespread in ECM?

A

Aggrecan;

perlecan;

decorin

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67
Q

What two proteoglycans and one protein sequester TGF-β?

A

Aggrecan, decorin

(storing it until the tissue is damaged and growth is needed);

fibrillin

(that’s why Marfan’s syndrome patients have such long bones)

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68
Q

Why do individuals with Marfan’s syndrome grow such long bones?

A

Fibrillin (which is missing or defective in these patients) sequesters TGF-β

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69
Q

What is a super-abundant protein of the ECM that binds type I collagen, fibrin, and proteoglycans to integrins on cell membranes, essentially binding cells to ECM?

A

Fibronectin

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70
Q

What is fibronectin’s main function?

A

Connecting cells to ECM

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71
Q

Multiadhesive proteins are ECM proteins such as fibronectin and laminin. What is another protein in this family that is essential to proper blood coagulation?

A

von Willebrand’s factor

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72
Q

What is the principal multiadhesive protein of the basal lamina?

What cell membrane protein does it bind?

What particular basal lamina protein does it bind?

A

Laminin-1;

α,β-dystroglycan;

type IV collagen

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73
Q

What are the two main families of protein involved in cell-to-cell adhesion?

A

Cadherins (found in desmosomes);

CAMs (cell adhesion molecules)

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74
Q

Inflammatory molecules induce endothelial cells to express what protein that loosely interacts with leukocytes?

After that initial velcro-like contact, what stronger protein binds the leukocyte and helps is extravasate?

A

P-selectins;

integrins

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75
Q

Are collagen chains stabilized by interchain or intrachain hydrogen bonds?

A

Interchain

(there are no intrachain H-bonds)

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76
Q

What are enzymes?

How do they accomplish their function?

A

Biological catalysts (mostly proteins, but some are RNA);

by lowering activation energy

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78
Q

Do enzymes change the overall thermodynamics of a reaction?

(I.e., can they change equilibrium states?)

A

No; equilibrium is not changed but the reactions reach equilibrium more quickly

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79
Q

Under what conditions do human enzymes operate?

A

Very mild conditions

(aqueous environment, fairly neutral pH, body temperature)

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80
Q

How many types of reaction can a single enzyme produce?

With how many substrates can a single enzyme produce its specified product?

A

One

(reaction specificity);

one, or one class of structurally similar substrates

(substrate specificity)

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81
Q

If a reaction is thermodynamically stable, the product will always have a ________ ground state than the substrate.

A

Lower

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82
Q

What is the name of the peak point of the activation energy for a particular reaction?

A

Transition state energy

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83
Q

What is ΔG in terms of enzymatic reactions and activation energy?

A

The change in free energy

(i.e. the energy required to reach the transition state energy, aka the peak of the activation energy)

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84
Q

True/False.

Enzymes lower ΔG.

A

True.

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85
Q

What type of chemical interactions do enzymes typically use to bring substrates together in favorable ways towards the product of the reaction?

A

Weak bonds (I.e., not covalent bonds)

these can be hydrogen bonds, hydrophobic bonds, ionic bonds, or van der Waals (London forces) interactions

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90
Q

What is ΔG’°?

A favorable reaction will have a __ ΔG’°.

An unfavorable reaction will have a __ ΔG’°.

A

The total change in free energy for a reaction

(from the transition state energy [peak activation energy] to the product energy);

-

+

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91
Q

Why are transition state analogues useful in binding enzymes?

A

They tend to bind more forcefully than substrate or product analogues would

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92
Q

What type of analogue tends to bind enzymes more forcefully than either substrate or product analogues?

What are two examples of this?

A

Transition state analogue;

most HIV protease inhibitors,

Oseltamivir (TAMIFLU) - binds neuraminidase

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93
Q

True/False.

Initial velocity (vi or v0) will remain unchanged even if enzyme concentration increases.

A

False.

Left graph: different initial velocities (dashed line) for different enzyme concentrations

Right graph: linear relationship between initial velocity and enzyme concentration

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94
Q

What enzymatic class transfers electrons from donors to acceptors?

A

Oxidoreductases

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95
Q

Redox reactions mostly involve what atoms (elemental types) in our cells?

A

Carbon, nitrogen, sulfur

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96
Q

What two mnemonics can be used to remember which molecule is reduced and which is oxidized in a reaction based on the movement of electrons?

A

LEO the lion says GER;

OIL RIG

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97
Q

What is velocity in terms of enzyme kinetics?

A

The rate of appearance of P (product)

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98
Q

State the Michaelis-Menten equation.

A
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99
Q

What is initial velocity (vi or v<span>0</span>) in terms of enzyme kinetics?

A

The rate of product appearance at t = 0

(before any loss of substrate or other change in conditions)

(basically, peak velocity for the enzyme in question)

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101
Q

True/False.

A high concentration of enzyme will reach reaction equillibrium faster than a low concentration of enzyme?

A

True.

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102
Q

The Y-axis of a Michealis-Menten graph shows:

The X-axis of a Michealis-Menten graph shows:

A

Velocity (rate of product formation; often mmoles/sec)

Substrate concentration [S]

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103
Q

In Michaelis-Menten enzyme kinetics, the value for Km is __ Vmax.

A

1/2

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104
Q

Km is:

Vmax is:

A

the substrate concentration [S] at 1/2 Vmax

the velocity at an infinte amount of [S]

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106
Q

What is the general hypothesis of enzyme kinetics on which the Michaelis-Menten equation builds?

A

E + S -> ES* -> E + P

OR

E + S

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107
Q

At infinitely large [S], V0 = ?

At small [S], V0 = ___________ proportional to ____

A

Vmax;

linearly, [S]

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108
Q

Will enzymes with a high affinity for a particular substrate have a low or high Km?

A

Low

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109
Q

What type of inhibitor is shown in this Lineweaver-Burke plot?

A

Competitive

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110
Q

What type of inhibitor is shown in this Lineweaver-Burke plot?

A

Mixed

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111
Q

What type of inhibitor is shown in this Lineweaver-Burke plot?

A

Noncompetitive

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112
Q

What type of inhibitor is shown in this Lineweaver-Burke plot?

A

Uncompetitive

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113
Q

A high Km indicates what relationship between enzyme and substrate?

A

Low affinity

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114
Q

True/False.

Km is the velocity at half of Vmax.

A

False.

Km is the substrate concentration at Vmax/2

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115
Q

Hexokinase I has a much lower Km [glucose] than glucokinase (hexokinase IV).

Which has a lower affinity for glucose?

A

Glucokinase (hexokinase IV)

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116
Q

The Km values for Hexokinase for Glucose and fructose are Km = 0.05 mM and Km = 1.5 mM, respectively.

Hexokinase has a higher affinity for which substrate?

A

Glucose

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117
Q

What is Kcat in terms of enzyme kinetics?

How is it expressed?

A

The speed one enzyme has in turning out product when saturated with substrate;

products / sec

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118
Q

What are the four main types of enzyme inhibition?

(Note: one of these types is a subset of another)

A

Competitive

Mixed (subset: noncompetitive)

Uncompetitive

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119
Q

Noncompetitive inhibitors are a subset of ___________ inhibitors.

A

Mixed

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121
Q

Describe competitive inhibition effects in regards to the following:

Km

Vmax

Binding location on the enzyme

Can it be overcome by increasing substrate concentration?

A

Increase;

no change;

at the active site;

yes

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122
Q

Describe mixed inhibition effects in regards to the following:

Km

Vmax

Binding location on the enzyme

Can it be overcome by increasing substrate concentration?

A

Increase;

decrease;

distant from the active site (binds either E or ES)

no

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123
Q

Describe noncompetitive inhibition effects in regards to the following:

Km

Vmax

Binding location on the enzyme

Can it be overcome by increasing substrate concentration?

A

No change;

decrease;

distant to active site;

no

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124
Q

Describe uncompetitive inhibition effects in regards to the following:

Km

Vmax

Binding location on the enzyme

Can it be overcome by increasing substrate concentration?

A

Decrease;

decrease;

distant to active site (only to ES);

no

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128
Q

What formula works out the Y = mX + b for Lineweaver-Burke plots?

A

1/V0 = (Km/Vmax) * (1/[S]) + (1/Vmax)

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129
Q

What is the Y in Y=mX+b for a Lineweaver-Burke plot?

A

1 / V0

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130
Q

What is the m in Y=mX+b for a Lineweaver-Burke plot?

A

(Km / Vmax)

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131
Q

What is the X in Y=mX+b for a Lineweaver-Burke plot?

A

(1 / [S])

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132
Q

Describe the Lineweaver-Burke plot of an enzyme with uncompetitive inhibition (especially in regards to Km and Vmax).

A

Decrease in both

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133
Q

Describe the Lineweaver-Burke plot of an enzyme with noncompetitive (a type of mixed) inhibition (especially in regards to Km and Vmax​).

A

Decrease in Km;

no change in Vmax

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134
Q

Describe the Lineweaver-Burke plot of an enzyme with competitive inhibition (especially in regards to Km and Vmax​).

A

Increase in Km;

no change in Vmax

135
Q

Describe the Lineweaver-Burke plot of an enzyme with mixed inhibition (especially in regards to Km and Vmax​).

A

Increase in Km;

decrease in Vmax

136
Q

What is the b in Y=mX+b for a Lineweaver-Burke plot?

A

(1 / Vmax)

(the Y-intercept)

137
Q

The Y coordinate for a Lineweaver-Burke plot is:

The X coordinate for a Lineweaver-Burke plot is:

A

1 / V0

1 / [S]

138
Q

The slope for a Lineweaver-Burke plot is:

The Y-intercept (b) for a Lineweaver-Burke plot is:

The X-intercept for a Lineweaver-Burke plot is:

A

Km / Vmax

1 / Vmax

- 1 / Km

143
Q

Describe the effect of each of the following types of inhibitor on Km:

Competitive

Mixed

Noncompetitive

Uncompetititve

A

Increase

increase

No change

Decrease

144
Q

Describe the effect of each of the following types of inhibitor on Vmax:

Competitive

Mixed

Noncompetitive

Uncompetititve

A

No change;

decrease;

decrease;

decrease

145
Q

What type(s) of inhibitor can bind either the enzyme (E) or the enzyme-substrate (ES) complex?

A

Mixed

(and noncompetitive, a subtype of mixed)

146
Q

What type(s) of inhibitor can be overcome by increasing substrate concentration?

A

Competitive only

147
Q

What type of inhibitor can only bind the enzyme-substrate (ES) complex?

A

Uncompetitive

148
Q

What type(s) of inhibitor bind(s) enzymes distant to the active site?

A

Mixed (and the noncompetitive subtype);

uncompetitive

153
Q

Which ring structure is found in microtubules during interphase or mitosis?

A

Singlets

154
Q

Which ring structure is found in microtubules in cilia and flagella?

A

Doublets

155
Q

Which ring structure is found in microtubules in basal bodies and centrioles?

A

Triplets

156
Q

What is the most common type of enzyme inhibitor in the body?

How does it typically work?

A

Mixed;

allosteric regulation

157
Q

Describe allosteric inhibition.

A

A ligand binds an enzyme (distant to its active site) and decreases its affinity for its substrate

158
Q

What type of inhibition occurs when a ligand binds an enzyme (distant to its active site) and decreases its affinity for its substrate?

A

Allosteric regulation

159
Q

A product of glycolysis inhibits (provides negative feedback to) an early enzyme of glycolysis.

This is an example of what type of inhibition?

A

Allosteric regulation

160
Q

How do irreversible inhibitors work?

A

They covalently bind active sites

161
Q

What are mechanism-based (suicide) inhibitors?

What is an example class?

(Name two examples of this class.)

A

Irreversible inhibitors (they covalently bind active sites) that are activated by the enzyme they inhibit;

serpins

(α 1-antitrypsin, antithrombin III)

162
Q

What type of inhibitor is here described:

an irreversible enzyme that is activated by the enzyme it inhibits

What is are two examples?

A

Mechanism-based (suicide) inhibitors;

α 1-antitrypsin, antithrombin III

(both serpins)

163
Q

True/False.

Allosteric regulation can be used to both increase and decrease enzymatic activity.

A

True.

164
Q

Hemoglobin is an example of an allosterically regulated protein that shows a ___________ curve when plotted against [S].

True/False.

Many allosterically regulated enzymes show this curve.

A

Sigmoidal;

true

165
Q

When substrate concentration is much greater than Km, this is a ____ order reaction.

A

Zero

166
Q

When substrate concentration is less than Km, this is a ____ order reaction.

A

First

167
Q

When [S] = Km, V0 =

A

1/2 Vmax

168
Q

Enzymes stabilize what to decrease activation energy?

A

The transition state

169
Q

What molecule is bound to both α- and β-tubulin monomers?

A

GTP

170
Q

The GTP attached to which tubulin monomer in microtubules becomes hydrolyzed over time and has effects on microtubule stability?

A

β-tubulin

171
Q

How does taxol exert an effect on cancer cells?

A

It stabilizes microtubules, halting mitosis

172
Q

Which types of cytoskeleton are polarized?

A

Microfilaments;

microtubules

174
Q

What are the three types of microtubule present in the spindle apparatus?

A

Aster,

kinetochore,

polar

176
Q

What are aster microtubules?

A

Extend from the spindle poles towards the cell cortex and orient the spindle poles with respect to the axis of cell division

177
Q

What do kinetochore microtubules do?

A

Bind the kinetochore of the chromosome centromere and pull apart the sister chromatids during early anaphase

178
Q

What are the three main functions of polar microtubules?

A
  1. Push duplicated centrosomes apart in Prometaphase
  2. Help orient the central spindle
  3. Push the spindle poles further apart in late anaphase
179
Q

What protein walks down aster microtubules, pulling the spindle apparatus towards the cell cortex?

What protein walks down polar microtubules, pushing the spindle apparatus apart?

A

Aster dynein;

kinesin

181
Q

How are the spindle apparatuses pulled apart during mitosis?

A

Dyneins attach to the cortex and motor towards the (-) end of aster MTs

(green circle in image)

182
Q

Which end of the microtubule polymerizes most rapidly?

Which end of the microtubule depolymerizes most rapidly?

A

The + end;

the + end

183
Q

Which end of the microtubule protofilament is least stable?

Why?

A

The - end;

due to treadmilling (older monomers with more hydrolyzed GTP are found at the - end)

184
Q

Why is the process of treadmilling important to microtubule protofilaments?

A

Older β-tubulin monomers are sent towards the back

(higher concentrations of GDP = less stability)

185
Q

What provides an especially important aspect of stability to the + end of microtubules that must be present for new tubulin dimers to be added?

A

GTP caps

186
Q

What is microtubule treadmilling?

A

Polymerization at the + end & depolymerization at the - end

187
Q

Name three microtubule associated (stabilizing) proteins (MAPs).

A

Tau,

MAP2,

MAP4

188
Q

Name three microtubule destabilizing proteins.

A

Kinesin-13,

stathmin,

katanin

189
Q

What chemical reaction inactivates Tau protein and causes tau aggregations (neurofibrillary tangles) to form?

What is Tau’s normal function?

A

Hyperphosphorylation;

microtubule stabilization

190
Q

What molecule is hydrolyzed to allow for kinesin ‘walking’ and dynein stalk power strokes?

A

ATP

191
Q

When does the centrosome (MTOC) replicate?

When do the two spindle poles migrate to either end of the cell?

A

In late interphase (just before mitosis);

prophase

200
Q

What is the cell cortex?

A

The actin layer covering the P-face of the plasma membrane

201
Q

When do kinetochore microtubules bind to kinetochores?

A

Prometaphase

203
Q

What amino acid on Tau protein can occur in the cis- or trans-conformation and is relevant to Tau tangle formation?

Which form is normal?

Which form leads to tangles?

What enzyme tries to correct the issue?

A

Proline (part of a phosphothreonine-proline motif);

trans;

cis;

proline isomerase 1 (PIN1)

205
Q

What region of a transport kinesin interacts with the microtubule?

What region of a transport kinesin interacts with the cargo?

A

The head domains;

the tail domain

206
Q

True/False.

A defect in spectrin can result in small and fragile red blood cells.

A

True.

207
Q

How does vitamin C help in collagen synthesis in terms of iron control?

A

It maintains iron in the Fe3+ form (oxidized)

208
Q

What happens during anaphase A?

What happens during anaphase B?

A

Chromosomes are pulled apart (kinetochore microtubules shorten);

the spindle apparatuses are pulled apart (kinesins travel down polar microtubules)

209
Q

How many reactions occur in glycolysis?

What phase are the first 5 known as?

What phase are the second 5 known as?

A

10;

the investment/preparatory phase;

the payoff phase

210
Q

What are the two goals of the investing/preparatory phase of glycolysis?

How many ATP are invested at this point?

A
  1. To make the process irreversible
  2. To split the 6-carbon sugar into two 3-carbon sugars

2

211
Q

By the end of the glycolytic investing/preparatory phase, glucose has been split into two molecules known as:

A

Glyceraldehyde-3-phosphate

212
Q

In the second five glycolytic reactions, the payoff phase, what high energy molecules are produced?

What is the net gain of glycolysis?

A

4 ATP, 2 NADH;

2 ATP, 2 NADH

213
Q

The GLUT transporters work via what type of transport?

A

Facilitated diffusion

214
Q

What GLUT transporters are found in virtually all mammalian tissues and maintain basal glucose levels?

A

GLUT1, GLUT3

215
Q

What GLUT transporter is found in liver and pancreatic cells (as well as the basolateral portion of epithelium in the small intestine) and removes excess glucose from the blood / controls insulin secretion?

A

GLUT2

216
Q

What GLUT transporter is found in muscle and fat cells and is insulin sensitive?

A

GLUT4

217
Q

What GLUT transporter is found in mucosal membranes and spermatozoa for fructose transport?

A

GLUT5

218
Q

GLUT1 and GLUT3 are found in what tissues?

What is their purpose?

A

Virtually all mammalian tissues - maintain cellular basal glucose needs

219
Q

GLUT2 is found in what tissues?

What is its purpose?

A

Pancreatic tissues - control insulin secretion;

Liver and small intestinal tissues - removes excess glucose from blood

220
Q

GLUT4 is found in what tissue(s)?

It is ________-sensitive.

A

Muscle and adipose;

insulin

221
Q

GLUT5 transporters move what substance?

A

Fructose

222
Q

For GLUT1, GLUT2, GLUT3, GLUT4, and GLUT5, state the relative Km for each.

(place them in order of increasing Km)

A

GLUT3 - 1 mM

GLUT1 - 1 - 2 mM

GLUT4 - 5 mM

GLUT5 - 10 mM

GLUT2 - 15 - 20 mM

223
Q

Normal physiological glucose levels are around: ____mM.

A

5.5

(100 mg/dl)

224
Q

Which GLUT transporters are transporting glucose almost all the time?

Which GLUT transporters are transporting glucose in the well-fed state only?

A

GLUT1, GLUT3, GLUT4;

GLUT2

(note: GLUT5 transports fructose)

225
Q

Describe the basic steps of insulin secretion.

A

1. Glucose levels rise (GLUT2 Km = 15 - 20 mM)

2. GLUT2 transporters allow glucose into pancreatic β cells

3. ATP is formed via glycolysis

4. ATP turns off K+ leak channels

5. The cell depolarizes

6. Calcium floods the cell and insulin is released

227
Q

How do anti-hyperglycemic drugs such as sulfonylureas or meglitinides work?

What drug does the opposite?

A

They close ATP-sensitive K+ channels in pancreatic β cells

(note: these are channels that were pumping K+ into the cell);

diazoxide (treats insulinoma-induced hypoglycemia)

228
Q

What is the 3-carbon end product of glycolysis?

A

Pyruvate

230
Q

What is the first step of glycolysis?

Why is this step important (3 reasons)?

A

Hexokinase adds a phosphate to glucose (making G6P).

  1. Energy investment
  2. Traps glucose in cell
  3. Ionic charges increase favorability of subsequent interactions
231
Q

What are substrates and product of the first step of glycolysis/

A

Glucose (+ hexokinase + ATP + Mg2+) –> Glucose-6-phosphate

232
Q

Why is the first step of glycolysis (shown below) a favorable reaction (- ΔG)?

A

ATP coupling

233
Q

Should type I diabetics be given sulfonylureas and/or meglitinides?

Should type II diabetics be given sulfonylureas and/or meglitinides?

A

They shouldn’t. They don’t have β cells;

Yes

234
Q

Where are GLUT4 transporters when glucose levels are low?

Where are GLUT4 transporters when glucose levels are high?

A

Endocytosed;

on the plasma membrane (exocytosed)

236
Q

When GLUT2 transports glucose into liver cells, what effect does this have on glucokinase?

A

It draws it out of the nucleus

237
Q

Which of the following would inactive liver glucokinase by shuttling it into the nucleus, incoming glucose or liver gluconeogenesis?

A

Liver gluconeogenesis

239
Q

What is the commitment step of glycolysis?

Via what enzyme?

A

Step 3;

phosphfructokinase-1 (PFK-1)

241
Q

What are the substrates and main product of the 3rd step of glycolysis?

A

F6P (+ PFK-1 + ATP + Mg2+) –> F1,6BP

242
Q

What are some allosteric activators of the third step of glycolysis (shown below)?

A

AMP, ADP, F2,6BP

243
Q

What are some allosteric inhibitors of the third step of glycolysis (shown below)?

A

ATP, citrate

244
Q

What effect does F2,6BP have on the third step of glycolysis (shown below)?

What effect does citrate have on the third step of glycolysis (shown below)?

A

Allosteric activation;

allosteric inhibition

245
Q

What enzyme catalyzes the formation of F2,6BP?

What enzyme catalyzes the breakdown of F2,6BP?

A

PFK-2;

F2,6BPase -2

246
Q

Why is the hexokinase found in the liver (hexokinase IV) called glucokinase?

Does it have any inhibitors?

A

It only acts on glucose;

yes, F6P

247
Q

Which is allosterically inhibited by G6P, hexokinase I or glucokinase?

A

Hexokinase I

250
Q

What happens in step two of glycolysis?

What enzyme is responsible?

A

G6P is turned into F6P;

phosphohexose isomerase

251
Q

Describe glucagon’s overall effects on the following:

PKA or PPP

F2,6BPase-2 or PFK-2

F2,6BP

Glycolysis

Gluconeogenesis

A

PKA activity increased

F2,6BPase-2 activity increased

F2,6BP decreased

Glycolysis inhibited

Gluconeogenesis stimulated

252
Q

Describe insulin’s overall effects on the following:

PKA or PPP

F2,6BPase-2 or PFK-2

F2,6BP

Glycolysis

Gluconeogenesis

A

PPP activity increased

PFK-2 activity increased

F2,6BP increased

Glycolysis stimulated

Gluconeogenesis inhibited

254
Q

What are the two investment steps of the preparatory phase (1st five steps) of glycolysis?

A

Steps 1 and 3

255
Q

What occurs in step 6 of glycolysis?

Why is this important?

A

Inorganic phosphate is added to glyceraldehyde-3-phosphate to form 1,3-bisphosphoglycerate;

there are now two phosphates on each molecule, yielding four ATP total in the payoff phase (2 ATP net)

256
Q

In step 6 of glycolysis, inorganic phosphate is added to glyceraldehyde-3-phosphate to form 1,3-bisphosphoglycerate.

What enzyme accomplishes this and what electron acceptor is needed?

A

Glyceraldehyde-3-phosphate dehydrogenase;

NAD+

260
Q

What happens in step 7 of glycolysis?

Via what enzyme?

A

1,3-Bisphosphoglycerate is turned into 3-phosphoglycerate and ATP is formed;

phosphoglycerate kinase

262
Q

Which must have a higher energy state, 1,3-bisphosphoglycerate or ATP?

(reaction 7 of glycolysis shown below)

A

1,3-Bisphosphoglycerate

(used for substrate-level phosphorylation)

264
Q

What happens in step 10 of glycolysis?

Via what enzyme?

A

Phosphoenolpyruvate is turned into pyruvate and ATP;

(substrate-level phosphorylation)

pyruvate kinase

265
Q

True/False.

PFK-2 and F2,6BPase-2 are two separate domains of the same enzyme and both can be active at the same time.

A

False.

They are two separate domains of the same enzyme, but only one is active at any one point in time

266
Q

Which must have a higher energy state, phosphoenolpyruvate or ATP?

(reaction 10 of glycolysis shown below)

A

Phosphoenolpyruvate

(used for substrate-level phosphorylation)

267
Q

What effect does glucagon have on FBPase-2 activity?

How?

A

Increased;

phosphorylation of the enzyme via PKA

268
Q

What effect does insulin have on PFK-2 activity?

How?

A

Increased;

dephosphorylation of the enzyme via phosphoprotein phosphatase

269
Q

Does glucagon activate the F2,6BPase-2 or PFK-2 domain?

How?

Does insulin activate the F2,6BPase-2 or PFK-2 domain?

How?

A

F2,6BPase-2, phosphorylation via PKA;

PFK-2, dephosphorylation via PPP

270
Q

What effect does glucagon have on F2,6BP levels? How?

What effect does insulin have on F2,6BP levels? How?

A

Decreased, via PKA –> F2,6BPase-2 activity;

increased, via PPP –> PFK-2 activity

271
Q

Does F2,6BP allosterically activate or inhibit glycolysis?

A

Activate

274
Q

During the 7th step of glycolysis (shown below), 1,3-BPG can be isomerized to become what substance?

What effect will this have on the blood?

What effect will this have had on glycolytic ATP production?

A

2,3-BPG;

causes oxygen release from hemoglobin;

one less ATP (because step 7 was skipped)

275
Q

What happens in step 4 of glycolysis (starting with F1,6BP)?

What happens in step 5 of glycolysis?

A

The F1,6BP is chopped into DHAP and glyceraldehyde-3-phosphate;

the DHAP is isomerized into glyceraldehyde-3-phosphate

276
Q

Name an allosteric inhibitor of hexokinase I.

A

G6P

278
Q

What is the purpose of anerobic acidosis?

A

To regenerate NAD+

by turning pyruvate into lactate

280
Q

What steps of glycolysis involve ATP hydrolysis?

What steps of glycolysis involve NADH production?

What steps of glycolysis involve ATP production?

A

Steps 1 and 3;

step 6;

steps 7 and 10

281
Q

How many irreversible steps are there in glycolysis?

So how does gluconeogenesis get around this?

A

3;

with alternate enzymes (4 of them)

282
Q

What is the term that describes the fact that reactions with fairly neutral ΔGs with occur rapidly if very thermodynamically stable reactions occur later in the flow?

(E.g. the less favorable steps 2 and 5 of glycolysis happen readily because steps 1, 3, and 10 occur?)

A

Substrate flux

284
Q

With key exceptions in three steps, gluconeogenesis is basically just ___________ in reverse.

A

Glycolysis

285
Q

What are the four unique gluconeogenic enzymes?

A

Pyruvate carboxylase

Phosphoenolpyruvate carboxykinase

Fructose 1,6-bisphosphatase

Glucose 6-phosphatase

286
Q

What gluconeogenic enzymes allow the body to skip backwards past the ‘irreversible’ step 10 of glycolysis (shown below)?

A

Pyruvate carboxylase

Phosphoenolpyruvate carboxykinase

287
Q

What gluconeogenic enzymes allow the body to skip backwards past the ‘irreversible’ step 3 of glycolysis?

Where is this enzyme found?

A

Fructose 1,6-bisphosphatase;

the cytosol

288
Q

What gluconeogenic enzymes allow the body to skip backwards past the ‘irreversible’ step 1 of glycolysis?

Where is this enzyme found?

A

Glucose 6-phosphatase;

the ER

289
Q

What are the first two steps of gluconeogenesis?

What step of glycolysis and enzyme has this allowed us to reverse?

A

1. Pyruvate carboxylase combines CO2 + biotin + ATP + pyruvate to make oxaloacetate

2. Phosphoenolpyruvate carboxykinase adds GTP to oxaloacetate to release that same CO2 and make phosphoenolpyruvate (PEP);

Step 10, pyruvate kinase

290
Q

The ATP production in glycolysis is termed ___________-_____ phosphorylation.

This in contrast with __________ phosphorylation.

A

Substrate, level;

oxidative

292
Q

What happens in step 8 of glycolysis (starting with 3-phosphoglycerate)?

What happens in step 9 of glycolysis?

A

3-PG is isomerized to 2-PG by PG mutase;

2-PG is dehydrated to phosphoenolpyruvatase by enolase

293
Q

How can G6P access the ER to be acted upon by glucose 6-phosphatase in gluconeogensis?

A

G6P transporter 1 is found on the ER membrane

295
Q

What glycolytic intermediate is one of the highest energy compounds that we know of?

A

Phosphoenolpyruvate

(much higher than ATP or 1,3-BPG)

297
Q

What are the three important products of glycolysis?

A

2 Pyruvate

2 NADH

2 ATP

298
Q

What are the glucose-derived substrates and intermediates of glycolysis (starting at glucose and ending at pyruvate)?

Bold each one that is used for substrate-level phosphorylation to form ATP.

Place an asterisk next to each one that is used for glycolytic NADH production.

A

[1 Glucose] –>

G6P –>

F6P –>

F1,6BP –>

GAP* + DHAP (DHAP –> GAP*) –>

1,3-BPG –>

3-PG –>

2-PG –>

PEP –>

[2 Pyruvate]

299
Q

In the liver, what hormone serves to inactivate pyruvate kinase?

Via what enzyme?

A

Glucagon;

PKA

300
Q

What are some allosteric activators of pyruvate kinase?

What are some allosteric inhibitors of pyruvate kinase?

A

ADP, phosphoenolpyruvate, F1,6BP;

ATP, alanine, acetyl-CoA, long-chain fatty acids

301
Q

In the liver, what hormone serves to activate pyruvate kinase?

Via what enzyme?

A

Insulin;

PPP

302
Q

How many fatty acids can be attached to one glycerol molecule?

A

Three

(to make a triglyceride)

304
Q

What are the two most common genetic causes of hemolytic anemia?

A
  1. G6PD deficiency
  2. Pyruvate kinase deficiency
305
Q

What is the main sign of pyruvate kinase deficiency that is often first seen at high altitudes?

Why does it occur?

A

Hemolytic anemia;

step 7 of glycolysis is circumvented by 2,3BPG formation

(step 10 is already inhibited by the PK deficiency:

subtrate-level ATP synthesis is stopped, and that’s all erythrocytes have for energy production)

306
Q

Why would an individual with COPD have a resultant acidosis?

(2 reasons)

A

Increase in carbonic acid due to trapped CO2

(respiratory acidosis)

Lack of O2 = pause in oxidative phosphorylation; switch to anerobic glycolysis for energy production –> lactic acid production

(lactic acidosis)

308
Q

True/False.

A patient with severe COPD may present with simultaneous respiratory and metabolic acidosis.

A

True

(O2 deficiency / lactic acidosis –> metabolic cause;

CO2 buildup –> respiratory cause)

309
Q

During the day (from about breakfast to midnight) blood sugar comes mostly from what two sources?

During the night (midnight to breakfast), it comes mostly from what source?

A

Diet, glycogenolysis;

gluconeogenesis

311
Q

Why are the effects of hexokinase, PFK-1, and pyruvate kinase deemed ‘irreversible?’

A

They have such negative ΔGs and are hugely thermodynamically favorable

312
Q

For the most part, gluconeogenesis is just glycolysis in the reverse direction.

How many unique gluconeogenic enzymes are there?

What tissues contain them?

A

Only 4;

hepatic, kidney, and intestinal epithelial tissues

313
Q

What are normal glucose physiological levels?

(in both mg/dl and mM)

A

100 mg/dl;

5.5 mM

320
Q

What step of gluconeogenesis occurs in the mitochondria and requires biotin as a cofactor?

A

Step 1

(Pyruvate carboxylase combines CO2 + biotin + ATP + pyruvate to make oxaloacetate)

321
Q

Identify the cellular compartment where each of the following gluconeogenic enzymes are found:

Pyruvate carboxylase

Phosphoenolpyruvate carboxykinase

Fructose 1,6-bisphosphatase

Glucose 6-phosphatase

A

Mitochondria

Mitochondria, cytosol

Cytosol

Endoplasmic reticulum

322
Q

What tissues have all of the following enzymes?

Pyruvate carboxylase

Phosphoenolpyruvate carboxykinase

Fructose 1,6-bisphosphatase

Glucose 6-phosphatase

A

Liver, kidney, intestinal epithelium

(Note: adipose tissue has PC and PEP-CK for glyceroneogenesis)

324
Q

How many steps does it typically take to convert alanine to pyruvate?

A

1

325
Q

What is an example of a substrate that can be turned into DHAP and then GAP, a gluconeogenic/glycolytic intermediate?

What is an example of a substrate that can be turned into oxaloacetate, a gluconeogenic intermediate?

What is an example of a substrate that can be turned into pyruvate, a gluconeogenic intermediate?

A

Glycerol;

some amino acids;

lactate, alanine

326
Q

Most of the glucose made in gluconeogenesis is made from the starting substrate:

A

Alanine

327
Q

What is the main allosteric activator of PFK-1 and allosteric inhibitor of F1,6BPase?

A

F2,6BP

328
Q

What hormone does the pancreas release in the starved state?

What hormone does the pancreas release in the fed state?

A

Glucagon (islet α cells)

Insulin (islet β cells)

329
Q

What effect does glucagon have on pyruvate kinase?

A

Inactivation

(through phosphorylation via PKA)

330
Q

What effect does acetyl-CoA have on pyruvate carboxylase?

A

Activation

(for increased oxaloacetate to be available in gluconeogenesis or the TCA)

331
Q

A high glucagon : insulin ratio stimulates the synthesis of what energy-controlling enzymes?

A high insulin : glucagon ratio stimulates the synthesis of what energy-controlling enzymes?

A

Pyruvate carboxykinase, F1,6BPase, G6Pase

(gluconeogenic enzymes)

glucokinase, PFK-1, pyruvate kinase

(main glycolytic enzymes)

332
Q

Although adipose tissue cannot perform gluconeogenesis, it still has the first two enzymes of gluconeogenesis (pyruvate carboxylase and PEP carboxykinase).

Why is that?

A

They are used to synthesize glycerol 3-phosphate from pyruvate

(glyceroneogenesis)

333
Q

Describe the two steps of glycogen debranching during glycogenolysis.

Name the two enzymes involved

A

1. 3 G1P residues are transfered from the branch, leaving just one at the branch point (enzyme: glucosyl 4,4-transglycosidase)

  1. α-1,6 glucosidase cleaves the remaining G1P
335
Q

What effect does glucagon have on serum fatty acid levels?

A

They increase dramatically

336
Q

In which organs does glyceroneogenesis occur?

A

The liver and adipose tissue

337
Q

In what tissues is glycogen synthesized and stored?

A

The liver and skeletal muscle

338
Q

What enzyme is found in hepatic tissues but not skeletal tissues and explains why muscle does not break down glycogen to maintain blood sugar levels as the liver does?

A

Glucose 6-phosphatase

(the muscle cannot release its sugar as the liver can)

339
Q

What bond is found in linear glycogen chains?

What bond is found in glycogen branch points?

A

α-1,4 glycosidic linkages

α-1,6 glycosidic linkages

340
Q

Although glucose is quickly phosphorylated by hexokinase when it enters the muscle (creating glucose 6-phosphate), why is this not yet useful to glycogen synthesis?

So, what is the first step of glycogen synthesis?

A

Glycogen synthesis starts with glucose 1-phosphate;

G6P is converted to G1P by phosphoglucomutase

341
Q

What are the first two steps of glycogen synthesis?

(Let’s assume a glucose molecule has entered the myocyte through a GLUT4 transporter and just been phosphorylated to G6P by hexokinase I)

A

1. G6P –> G1P (via phosphoglucomutase)

2. G1P –> UDP - glucose (via UDP-glucose pyrophosphorylase*)

(Note*: 2 phosphate groups were hydrolyzed from UTP and UMP was attached to G1P to form UDP-glucose)

342
Q

What are the first two enzymes of glycogenesis?

What is the third step?

A

Phosphoglucomutase;

UDP-glucose pyrophosphorylase;

UDP-glucose –> added to glycogen (α-1,4 glycosidic bond)

343
Q

A deficiency of what enzyme causes type 0 glycogen storage disease? (state the alternate name if there is one)

Identify any majorly affected organs.

What are the main signs/symptoms?

A

Glycogen synthase;

the liver;

hypoglycemia, elevated ketones,

early death

344
Q

A deficiency of what enzyme causes type I glycogen storage disease? (state the alternate name if there is one)

Identify any majorly affected organs.

What are the main signs/symptoms?

A

(von Gierke’s) glucose 6-phosphatase;

the liver;

hepatomegaly, kidney failure

345
Q

True/False.

von Gierke’s disease affects skeletal muscle and hepatic tissues.

A

False.

Skeletal muscle lacks glucose 6-phosphatase;

type I glycogen storage disease affects the liver and kidney

346
Q

A deficiency of what enzyme causes type II glycogen storage disease? (state the alternate name if there is one)

Identify any majorly affected organs.

What are the main signs/symptoms?

(Note: has infantile, juvenile, and adult presentations)

A

(Pompe’s) lyosomal glucosidase;

skeletal and cardiac muscle;

  • infantile form* - death by age 2
  • juvenile form* - muscle defects
  • adult form* - as a muscular dystrophy
347
Q

A deficiency of what enzyme causes type IIIa glycogen storage disease? (state the alternate name if there is one)

Identify any majorly affected organs.

What are the main signs/symptoms?

A

(Cori’s or Forbe’s) Debranching enzyme;

the liver, skeletal muscle, cardiac muscle;

myopathy, infantile hepatomegaly

348
Q

Type IIIb glycogen storage disease is similar to type IIIa (Cori’s or Forbe’s) with what key exception?

A

It is a deficiency of debranching enzyme in the liver only

(presents only as infantile hepatomegaly)

349
Q

A deficiency of what enzyme causes type IV glycogen storage disease? (state the alternate name if there is one)

Identify any majorly affected organs.

What are the main signs/symptoms?

A

(Anderson’s) Branching enzyme;

the liver, skeletal muscle;

hepatosplenomegaly, myoglobinuria

350
Q

A deficiency of what enzyme causes type V glycogen storage disease? (state the alternate name if there is one)

Identify any majorly affected organs.

What are the main signs/symptoms?

A

(McArdle’s) Glycogen phosphorylase [in muscle];

skeletal muscle;

exercise-induced cramps, myoglobinuria

351
Q

A deficiency of what enzyme causes type VI glycogen storage disease? (state the alternate name if there is one)

Identify any majorly affected organs.

What are the main signs/symptoms?

A

(Hers’s) glycogen phosphorylase [in the liver];

the liver;

hepatomegaly

352
Q

What differentiates McArdle’s disease from Hers’s disease?

A

Location;

McArdle’s - glycogen phosphorylase in skeletal muscle is deficient

Hers’s - glycogen phosphorylase in the liver is deficient

353
Q

Name the alternate name (if applicable) and missing enzyme for each of the following glycogen storage diseases:

Type 0

Type Ia

Type II

A

Glycogen synthase;

(von Gierke’s) glucose 6-phosphatase

(Pompe’s) lysosomal glucosidase

354
Q

Name the alternate name (if applicable) and missing enzyme for each of the following glycogen storage diseases:

Type IIIa

Type IIIb

Type IV

A

(Cori’s or Forbe’s) Debranching enzyme

Liver debranching enzyme

(Anderson’s) Branching enzyme

355
Q

Name the alternate name (if applicable) and missing enzyme for each of the following glycogen storage diseases:

Type V

Type VI

A

(McArdles’s) Muscle glycogen phosphorylase

(Hers’s) Liver glycogen phosphorylase

356
Q

Name the alternate name (if applicable) and missing enzyme for each of the following glycogen storage diseases:

Type VII

Type XI

A

(Tarui’s) Muscle PFK-1

(Fanconi-Bickel) GLUT2

357
Q

True/False. (for each of the following)

The branching of glycogen (A) increases storage space, (B) increases the number of ends and thus the speed with which it can be stored or broken down, and (C) decreases its solubility.

A

A. True

B. True

C. False; branching increases solubility

358
Q

De novo glycogenesis needs a starting point and can’t just start as free-floating UDP-glucose molecules.

What is the primer protein that serves as this initialization point?

A

Glycogenin

359
Q

Anderson’s disease affects what organ tissues?

A

(type IV glycogen storage disease)

hepatic tissue and skeletal muscle

360
Q

What enzyme chops single G1P molecules from glycogen in a linear manner?

What is this enzyme’s cofactor?

A

Glycogen phosphorylase;

Pyridoxal phosphate (vitamin B6)

361
Q

What are the four primary enzymes of glycogenesis?

In de novo glycogenesis, they build off what primer?

A

Phosphoglucomutase;

UDP-glucose pyrophosphorylase;

glycogen synthase;

Glycosyl 4,6 transferase (branching enzyme)

glycogenin

363
Q

Lysosomal acidic α-glucosidase is the equivalent of what other enzyme (but found in the lysosome instead)?

Similar to this other enzyme, it cleaves what type of bond?

A

Glycogen phosphorylase;

α-1,4 glycosidic linkages

364
Q

Name all four enzymes of glycogenolysis that take branched glycogen and turn it into G6P molecules.

A

Glycogen phosphorylase;

*glucosyl 4,4 transglycosidase;

*α-1,6 Glucosidase;

phosphoglucomutase

(*both part of debranching enzyme)

365
Q

What cofactor does glycogen phosphorylase require?

It is basically the active form of vitamin __.

A

Pyridoxal phosphate;

B6

366
Q

Which of the following is activated by phosphorylation and which is deactivated by phosphorylation?

Glycogen synthase

Glycogen phosphorylase

A

Activated: glycogen phosphorylase

Inactivated: glycogen synthase

367
Q

Via what covalent modification is glycogen synthase activated?

What hormone would likely result in this effect?

A

Dephosphorylation;

insulin (and PP1 –> inactivating glycogen synthase kinase 3)

368
Q

Via what covalent modification is glycogen phosphorylase activated?

What hormone would likely result in this effect?

A

Phosphorylation;

glucagon/epinephrine (and PKA –> activating phosphorylase kinase)

369
Q

Why do individuals with pyruvate kinase deficiency often manifest with hemolytic anemia at high altitudes?

(Hint: steps 7 and 10 of glycolysis are the only ATP-producing mechanisms that RBCs have)

A

As 1,3-BPG is isomerized to 2,3-BPG (because of the altitude), the afflicted individual loses their only remaining ATP-production step of glycolysis (step 7)

(step 10 is already compromised by the pyruvate kinase deficiency)

370
Q

True/False.

Erythrocytes in patients with pyruvate kinase deficiency are getting all their ATP from only step 10 of glycolysis.

A

False.

The RBCs are getting all their ATP from only step 7

(step 10 is compromised by the PK deficiency)

371
Q

Which is allosterically inhibited by F6P, hexokinase I or glucokinase?

A

Glucokinase

372
Q

Which amino acid is the most common substrate for kinase modification of the proteins that control the rates of glucose catabolism and glycogen formation?

A

Serine

T1 - Integrated (Full Review) (29 decks)

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