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Biomed > week 10 > Flashcards

week 10 Flashcards

1
Q

Once Glucose is converted to Glucose-6-P (trapped glucose) it can
enter several pathways? what are they

A

Glycolysis
Pentose Phosphate Shunt
Glycogenesis

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2
Q

Which enzyme is needed to commit glucose-6-P to
glycolysis? (key controlling enzyme)

A

PFK1

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3
Q

The enzymes of the three irreversible reactions are
also the main regulated enzymes of glycolysis

A

PFK1
hexokinase/ glucokinase
pyruvate kinase

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4
Q

What reaction does Hexokinase catalyze?

A
  • glucose - glucose 6 phosphate
  • Reversibly regulated by glucose-6-phosphate

product inhibition

it is sensitive to need for glucose

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5
Q

When cellular concentrations of glucose-6-P rise above normal, what happens to hexokinase

A

it is temporarily inhibited to bring rate of glucose 6 P into balance with its rate of utilization

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6
Q

…. inhibits PFK1 by binding to an allosteric site. This lowers …… and …. and …. relieve the inhibition of PFK-1

A

ATP

Lowers the affinity of the enzyme for fructose-6-P

AMP and ADP relieve the inhibition of PFK-1

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7
Q

…. is a key intermediate in CAC . High levels of …… inhibit PKF-1.

A

citrate
citrate

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8
Q

Fructose 2,6-bisphosphate is the ……….. and activates …… it also enhances the affinity of ….. for …. stimulating glycolysis. Then inhibits ….. slowing gluconeogenisis

A

allosteric regulator

PFK-1

PFK-1 for fructose -6 -P

FBP-1

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9
Q

Fructose 2,6-bisphosphate is formed by phosphorylating ……….. by …..

A

Fructose-6-P, catalyzed by phosphofructokinase-2 (PFK-2)

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10
Q

What reaction does pyruvate kinase catalyze

A

the direct transfer of phosphate from phosphoenolpyruvate (PEP) to ADP to produce ATP and pyruvat

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11
Q

Pyruvate kinase is allosterically regulated by:

A

inhibition:
1. ATP
2. Acetyl-CoA
3. Fatty acids
Activation :
Fructose 1,6-bisphosphate

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12
Q

Glycolysis is regulated
hormonally by

A

insulin and
glucagon

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13
Q

insulin promotes the
transcription of (3)

Insulin also
promotes the activation of

A

Hexokinase,
phosphofructokinase-1, and
pyruvate kinase

PFK- 1 ( & inhibition FBP-2)

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14
Q

Glucagon reduces the expression of (3)

A

hexokinase, PFK-1, and pyruvate kinase

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15
Q

Glucagon promotes the
activation of

A

FBP-2 (& inhibition
PFK-2)

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16
Q

Fructose, Mannose, and galactose are converted into

A

glycolytic intermediates

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17
Q

Fructose metabolism primarily occurs in the

A

liver

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18
Q

Which monosaccharide is metabolized faster,
glucose or fructose, why?

A

glucose because it is absorbed by alot of cells in the body, where as fructose is not so it undergoes additional steps in the liver

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19
Q

The first two bypass reactions are the main
regulated reactions of gluconeogenesis
What were these bypass reactions?

A

Pyruvate Carboxylase (Bypass of Pyruvate Kinase)

Phosphoenolpyruvate Carboxykinase (PEPCK) (Bypass of Pyruvate Kinase):

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20
Q

Pyruvate can be converted either to:

A

acetyl CoA –> enter into CAC

Oxaloacetate —> enter into GNG

Lactate (Cori cycle)

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21
Q

What enzyme catalyzes conversion of pyruvate to oxaloacetate

A

pyruvate carboxylase

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22
Q

what is a allosteric activator of pyruvate carboxylase?

A

Acetyl CoA

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23
Q

What reaction does FBP-1 catalyze

A

catalyzes the hydrolysis of fructose-1,6-bisphosphate (FBP) to form fructose-6-phosphate and inorganic phosphate (Pi).

This reaction is a key regulatory step in both gluconeogenesis and glycolysis pathways.

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24
Q

what does F26BP inhibit and stimulate (fructose 2,6 bisphosphate)

A

inhibits glycolysis and stimulates gluconeogensis

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25
Q

Gluconeogenesis is regulated hormonally by

A

insulin and glucagon

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26
Q

Glucagon promotes activation of ….., lowering levels of ……….

A

FBP-2

fructose 2,6 bisP

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27
Q

Glucagon can also induce the transcription of

A

PEP carboxykinase

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28
Q

what is this pentose phosphate shunt? what is its purpose?

A

Alternative metabolic pathway for glucose that
“shunts” molecules into and out of glycolysis

purpose:

Generates two main products:
- NADPH
- Ribose-5-Phosphate (“pentose phosphates)

Also generates Fructose-6-Phosphate and glyceraldehyde3-Phosphate, which can feed back into glycolysis

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29
Q

where does the pentose phosphate shunt happen

A

cytoplasm

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30
Q

why is it called a shunt?

A

“shunts” or diverts some of the glucose-6-phosphate away from the usual glycolytic pathway, where it would continue to be metabolized to produce ATP through glycolysis. Instead, the glucose-6-phosphate is directed into the PPP to serve different purposes, such as generating NADPH or ribose-5-phosphate.

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31
Q

what are the two phases of the pentose phosphate shunt

A

oxidative (irreversible) and non oxidative(reversible)

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32
Q

describe the oxidative phase of the pentose phosphate shunt. what are its functions?

A

Glucose-6-phosphate -> Ribulose-5-Phosphate

generates 2 NADPH

functions:
- fatty acid synthesis
- reduces glutathione

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33
Q

what is glutathione? what role does NADPH play with glutathione?

A

a 3 amino acid peptide (glycine-cystine glutamate)

  • neutralizes and reduces hydrogen peroxide to water by donating electrons
  • NADPH regenerates glutathione by replacing the donated Hs
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34
Q

what is the oxidative phase regulation in PPP

A

Rate-limiting step:
Glucose-6-P –> 6-phosphoglucono-�-lactone

Enzyme: glucose-6-Phosphate dehydrogenase (G6PD)

Regulated by ratio of NADPH:NADP+

inhibited by high levels of Acyl CoAs

upregulated by insulin

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35
Q

High NADPH:NADP+ ratio inhibits

A

G6PD

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36
Q

G6PD deficiency is an …..linked trait and results in …..

A

X
Results in hemolytic anemia when an individual is
exposed to oxidant stress

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37
Q

in the non oxidative phase of the PPP …

A

Riboluse-5-P is converted to
Ribose-5-P OR into
glycolytic intermediates

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38
Q

Glucose is stored in polymeric form as glycogen
mostly in the

A

liver and skeletal muscle

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39
Q

High glucose/energy levels will triggers

A

glycogen synthesis (glycogensis)

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40
Q

Glucose can be rapidly delivered to the blood
stream when needed by

A

degradation of glycogen in
the liver
- Glycogenolysis

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41
Q

Glucose is transferred onto a growing chain of glycogen as

A

UDP-glucose

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42
Q

UDP-glucose is added to an existing strand of
glycogen by the enzyme

A

glycogen synthase

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43
Q

Glucose is added to the
non-reducing end in what
type of link?

A

glycosidic linkage

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44
Q

Branching enzyme catalyzes the transfer of ……. to ……

A

4-8 glucose residues to a branch point

Branching enzyme is also called amylo-α(1,4 —–> 1,6)
glucosyl transferase

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45
Q

Glycogen synthase cannot initiate a new glycogen
chain de novo, it requires a primer. what does the primer contain?

A

pre-formed (alpha1 —> 4) polyglucose chain with at least 4-8 glucose residues

  • Found within glycogenin (contains both the enzyme and the primer to create the primer)
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46
Q

in glycogenolysis …… is removed from ….. ends of glycogen by enzyme …. Sequentially cleaves Sequentially cleaves ……..from the non-reducing
ends until ……units away from a branch point. Then glucose is released as ….. Once all chains degraded to
within 4 units of a branch point, the molecule is called a …..

A

non reducing
glucose
glycogen phosphorylase

α (1 –> 4) linkages

4

Glucose is released as
glucose-1-P

limit dextrin

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47
Q

the glycogenolysis de-branching enzyme has
two functions:

A
  1. transfers the outer 3 glucose
    residues from the branch to
    another non-reducing end
    (leaving only 1 reside behind at the branch point)
    * Aka Oligo-α(1,4)-α(1,4)-
    glucotransferase
  2. Removes the final glucose
    residue in the alpha(1–> 6) linkage
    * Aka Amylo-α(1,6) glucosidase
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48
Q

in glycogenolysis Glucose-1-P is converted to ….. by enzyme ….

A

glucose-6-P

phosphoglucomutase

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49
Q

The liver can then convert glucose-6-P into glucose
with the enzyme …..

A

Glucose-6-Phosphatase (G6Pase)

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50
Q

what muscles do not have Glucose-6-Phosphatase (G6Pase)

A

Muscles, on the other hand, do not release glucose into the bloodstream as a primary function. Instead, muscles use G6P for their own energy needs and store it as glycogen.

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51
Q

what are the two regulated enzymes in glycogen metabolism

A

Glycogen synthase
glycogen phosphorylase

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52
Q

Glycogen synthase regulation is Allosterically activated by

A

glucose-6-P

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53
Q

Glycogen phosphorylase regulation is Allosterically inhibited by:

A

Glucose-6-P
* ATP
* Free glucose (in the liver only)
- Allosterically activated by AMP (muscle only)

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54
Q

Glycogen synthase and glycogen phosphorylase can
also be regulated by

A

covalent modification

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55
Q

Glycogen synthase is de-activated by

A

phosphorylation

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56
Q

Glycogen phosphorylase is activated by

A

phosphorylation

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57
Q

Phosphorylation is catalyzed initially by the same protein,

A

protein kinase A (PKA)

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58
Q

How is PKA activated?

A

system involving cyclic AMP

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59
Q

Covalent modification of glycogen
metabolism is under

A

hormonal control

60
Q

In the presence of glucagon (and
epinephrine):

A

Glucagon binds to its GCPR
* G⍺s activates adenylyl cyclase —>
cAMP levels rise
* PKA phosphorylates glycogen synthase, rendering it INACTIVE
- Glycogenesis is inhibited

  • PKA phosphorylates
    glycogen phosphorylase
    kinase, rendering it
    ACTIVE
  • Glycogen phosphorylase
    kinase phosphorylates
    glycogen phosphorylase,
    rendering it ACTIVE
  • Glycogenolysis is
    promoted
61
Q

glycogen metabolism In the presence of Insulin

A
  • Insulin promotes the breakdown
    of cAMP and thus inactivation of PKA
  • Insulin activates protein
    phosphatase 1, which removes the phosphate group from glycogen synthase, rendering it ACTIVE

glycogenesis is promoted

  • Insulin promotes the
    breakdown of cAMP and
    thus inactivation of PKA
  • Insulin activates protein
    phosphatase 1, which
    removes the phosphate
    group from:
  • Glycogen
    phosphorylase
    kinase & Glycogen
    phosphorylase,
    rendering them both
    INACTIVE
  • Glycogenolysis is inhibited
62
Q

somatic sensory, non cranial

A

touch, pain, pressure , vibration, temperature

spinal nerves
TO spinal cord

63
Q

somatic motor non cranial

A

non cranial skeletal muscles

FROM spinal cord
spinal nerves

64
Q

visceral motor

A

autonomic NS all the SNS and sacral PaNS

Spinal nerves
FROM spinal cord

65
Q

somatic motor cranial

A

cranial skeletal muscles
cranial nerves

66
Q

visceral motor

A

parasympathetic nervous system
cranial nerves

67
Q

white matter

A

collections of mylienated axons in the CNS

68
Q

mylien is

A

a multi layer lipid coat that insulates axons formed by specialized glial in the peripheral and CNS

increases conduction velocity

69
Q

only ….. has white matter

A

CNS

70
Q

grey matter is

A

areas of the central nervous system that have relatively few myelinated axons

71
Q

tract

A

a collection of axons in the CNS

large tracts are usually white matter

72
Q

a nerve is a

A

collection of grey matter in the PNS

73
Q

what are the sites of integration of the neuron

A

cell body and axon hillock

74
Q

dorsal columns in the spinal cord are examples of

A

tracts

75
Q

much of the volume of the cerebral cortex is ……
……. forms a relatively thin layer superficially

A

white
grey

76
Q

How does the peripheral nervous
system (PNS) differ from the central
nervous system (CNS)?

A

Different cells populate the PNS

Axons/nerves in the PNS can
sometimes regenerate after damage

The PNS is much less “isolated” than
the CNS – cells of the immune system
are allowed to enter and exit the PNS
more freely

Fewer neuronal cell bodies in the PNS
versus the CNS

77
Q

Ganglia

A

collections of neuronal cell
bodies in the peripheral nervous system

78
Q

Nuclei

A

collections of neuronal cell
bodies in the central nervous system

79
Q

basal nuclei are often known as

A

basal ganglia – widely accepted
misnomer

80
Q

Both nuclei and ganglia will contain
axons, but more of the volume of these
structures is devoted to

A

neuronal and
glial cell bodies

81
Q

Glial cell types:

A

Astrocytes
Oligodendrocytes
Microglia

82
Q

Fluid spaces within the CNS

A

Ventricles, ependymal cells, choroid plexus, Interstitial fluid

83
Q

functions of the astrocyte

A

forms a part of the blood brain barrier

regulates interstitial fluid composition

provides structural support and organization to the central nervous system

assists with neuronal development

replicates to occupy space of dying neurons

84
Q

functions of the ependymal cell

A

lines ventricles of brain and central canal of spinal cord

assists in production and circulation of cerebrospinal fluid

85
Q

functions of microglial

A

phagocytic cells that move through the CNS

protects the CNS by engulfing infectious agents and other potential harmful substances

86
Q

functions of the oligodendrocyte

A

myelinated and insulates axons

allows faster action potential propagation along axons in the CNS

87
Q

what are the most numeral cells in the CNS

A

astrocytes
- highest in grey matter

88
Q

what is the critical role of astrocytes in the CNS

A

Facilitate the formation and strengthening of synapses (neuroplasticity)

Regulate the concentration of ions in the interstitial fluid
* K+, Na+, Cl-, HCO3-, Ca+2

Structural support for the brain
* Intermediate filament – GFAP (glial fibrillary acidic protein)

Barrier functions – induce the formation of the BBB at the brain microvasculature, form a “limiting membrane” at the external CNS surface

“Feed” neurons – help extract nutrients from the blood, provide nutrients to neurons to support energy metabolism

89
Q

astrocytes are connected to eachother via

A

gap junctions

Small “tunnels” that connect the
intracellular fluid of astrocytes to
each other (span the cell
membranes and connect cell to
cell) in a network known as a
syncytium

90
Q

waves” of calcium increases
and general ……that
move through the brain,
astrocyte-to-astrocyte have been observed

A

depolarization

91
Q

what are the processes of oligodendrocytes

A

Each process wraps around the axon of
a CNS neuron many times, “sheathing”
the axon in myelin

Myelin sheath = compacted layers of
cell membrane rich in sphingolipids
that have very little cytosol

92
Q

what is the function of mylien

A

Increases the speed with which an
action potential moves down an axon

Reduces the energy consumed by
movement of an action potential down
an axon – more efficient signaling

93
Q

roughly …. as many oligodendrocytes as neurons in the CNS

A

twice

94
Q

what are the functions of microglial cells

A

Remove (phagocytosis) cellular debris

Monitor the environment and fight pathogens

If the pathogen cannot be eliminated by resident
microglia, they “call in” other white blood cells through secretion of soluble factors (cytokines) and can present antigen to other immune cells

95
Q

what are microglial cells derived from?

A

blood borne immune cells that migrate into the CNS

96
Q

subarachnoid space

A

Around the periphery of the brain

97
Q

where is the cerebrospinal fluid found

A

subarachnoid space
Within particular compartments
of the brain (4 ventricles - third ventricle, lateral ventricle, 4th ventricle and cistern)

98
Q

where does the CSF circulate

A

moves from lateral ventricles to 3rd then 4th ventricles

circulated into the subarachnoid space and down the spinal cord

eventually absorbed by specialized structures known as arachnoid granulations (transport CSF into venous structures)

98
Q

where is the CSF formed from?

A

choroid plexus (a complex of capillaries and epithelial cells)

99
Q

the choroid plexus …

A

Selectively transports water, electrolytes,
nutrients from blood to CSF

Tight junctions prevent unwanted substances
from entering the CSF

100
Q

The interstitial fluid (extracellular fluid) of the brain and spinal cord is formed by

A

Filtration of CSF from the ventricles through
the ependymal cells

Regulated filtration of fluid through capillaries
deeper in the CNS tissue

101
Q

The central nervous system is
isolated/protected from a number of
factors that can circulate through the
bloodstream such as

A

Immune cells
* White blood cells attack pathogens and
remove cellular debris
* The CNS structure is delicate, and its
function depends on its precise architecture – usually white blood cells aren’t allowed into the CNS

Exception – microglial cells
Noxious wastes and toxins
Pathogens

102
Q

Most capillaries in the body are quite …. they have few…

A

leaky
Nutrients, electrolytes, water,
metabolites filter through easily – few
tight junctions

103
Q

Astrocytes contact capillaries in the CSF
via structures known as

A

endfeet

104
Q

Endfeet cause

A

increased tight junction
expression in capillary endothelial cells

Endfeet also “tell” capillaries what to
transport into the CNS tissue

105
Q

what are the three structures in a nerve

A

Epineurium
Perineurium
Endoneurium

106
Q

what is the epineurium

A

strong, fibrous connective tissue covering that surrounds each nerve

Blood vessels run within this layer – known as the vasa
nervorum

107
Q

what is the perineurium

A

surrounds bundles of axons (some myelinated, some not) known as fascicles

formed by fibroblast-like cells arranged in
sheets 2-6 cells thick

Tight junctions are found between these cells – therefore the
perineural layer can regulate what moves into the fascicle

108
Q

what is the Endoneurium

A

delicate connective tissue layer that surrounds individual axons

109
Q

what is in barrier 1 of the BNB

A

the cells of the perineurium and the tight junctions between them

110
Q

what is in barrier 2 of the BNB

A

the endothelial cells that line the capillaries
within the fascicles also express many tight junctions

111
Q

what do both BNB actively regulate

A

movement of ions
and immune cells into the fascicles

112
Q

which is more permissive to the entrance of white blood cells? BNB or BBB?

A

BNB

113
Q

Schwann cells

A

provide the myelin
sheath for axons
within fascicles

114
Q

how do schwann cells differ from oligodendrocytes

A

in that one cell only
myelinates one axon

  • Each oligodendrocyte
    myelinates multiple
    nearby axons
  • Schwann cells can
    extend as far as 1
    mm along an axon
115
Q

Satellite cells surround,

A

protect, and nourish
neuronal cell bodies located
in ganglia

  • do not establish blood ganglion barrier
116
Q

Multiple satellite cells are closely apposed to

A

neuronal
cell bodies

117
Q

The morphologic relationship of the dendritic spine to
the axon terminal can influence the

A

effectiveness of the
synapse

118
Q

Spine maturation makes the synapse more

A

effective

119
Q

what is the flopodia

A

dendritic spine immature and
“looking for a connection” with an axon terminal

The “mushroom” and “branched” spines were shown to elicit
more effective neuronal responses when they are stimulated

120
Q

the soma is a

A

Site of protein synthesis for the rest of the neuron

121
Q

Nissl substance

A

basophilic area nearby the nucleus of a neuron composed of lots of free ribosomes and rER

122
Q

Microtubules, actin microfilaments, and
neurofilaments found in the body and in the

A

processes of neurons

123
Q

Neurofilaments =

A

intermediate filaments that are
more concentrated in axons – provide structural
stability for neuronal processes

124
Q

Microtubules have

A

opposite orientation in dendrites
vs. axons – this is arranged in the cell body

125
Q

Pseudo-unipolar neurons

A

These neurons have a distal process that
either interacts with a sensory receptor or
serves as a sensory receptor (A)

The proximal process synapses in the CNS
(B)

The process that connects A to B behaves
as an axon

Typical of dorsal root ganglion cells –
somatic sensation

126
Q

Bipolar neurons

A

These neurons have a distal process (A)
that acts as a dendrite – it either serves as
a sensory receptor or interacts with a
sensory receptor

The proximal process synapses in the CNS
– it is an axon and conducts action
potentials (B)

Typical of neurons that detect the special
senses – vision, hearing, smell

127
Q

Multipolar neurons

A

The most common neurons

Dendrites receive information from
other neurons via synaptic terminals

The cell body summates and
integrates this information

The axon carries action potentials to:

  • Other neurons
  • Glands
  • Muscle tissue

Typical of all interneurons and
somatic motor neurons

128
Q

Cranial nerve afferents:

A

Special Senses
* CN I, II, VII, VIII, IX, X
* Somatic Senses
* Mostly CN V

129
Q

Visceral Sensory

A

CN IX and X
* Baroreceptors
* Visceral sensation
from most of the
alimentary tract,
lungs, heart

130
Q

Sensation is composed of a number of distinct steps
(not all need to be present):

A

Detection of a physical/chemical stimulus by some type of
receptor

Transduction – transforming the physical stimulus into an
electrical impulse that can be carried along an axon

Other neurons at various levels of the central nervous system can detect the electrical impulse and modify its intensity and route the signal to various CNS locations

Perception – conscious awareness of the sensation – this occurs at the level of the cortex

131
Q

Afferents that ascend through the spinal cord:

A

Somatic sensation below the neck
Visceral Sensation

132
Q

Examples of effectors

A
  • Skeletal muscle (voluntary movements)
  • Smooth muscle (blood vessels, GI tract,
    genitourinary tract, respiratory tract)
  • Glands (endocrine or exocrine)
133
Q

Somatic Motor
efferents

A

control of skeletal muscles

  • Usually voluntary
  • Some we don’t have conscious control over (i.e.
    middle ear muscles)
134
Q

Major cranial nerves –
somatic motor:

A
  • CN VII, V, XI
  • CN IX, X, XII
  • CN III, IV, VI
135
Q

Efferents for skeletal
muscles below the neck
are part of the
corticospinal tract

A

Axons from neurons in
the pre-central gyrus
decussate and descend
down the spinal cord

Synapse on anterior
horn motor neuron

Axon of anterior horn
motor neuron exits the
central nervous system
as a spinal nerve

136
Q

Visceral motor
efferents – cranial
nerve PaNS

A

CN X – PaNS control
for the heart, lungs,
majority of the GI
system

CN III – PaNS
control over
pupillary muscles

CN VII, IX – PaNS
control over
salivary, tear glands

137
Q

Visceral motor
efferents – spinal
nerve ANS & PaNS

A

SNS control for the
heart, lungs,
proximal GI tract

SNS control for
pupillary muscles,
salivary glands, tear
glands

SNS and PaNS
control for distal GI
tract, reproductive
structures, bladder

138
Q

Sympathetic Nervous System

A

“Fight or Flight”
- Increases heart rate and cardiac output
- improves ventilation
- Decreases digestive function
- Increases glucose availability (gluconeogenesis,
glycogenolysis)
- Increases blood flow to skeletal muscles, heart
- Decreases blood flow to GI tract, skin, kidneys
- Major hormones/neurotransmitters: epinephrine and
norepinephrine

139
Q

paravertebral ganglia

A

adjacent to the vertebral column

140
Q

prevertebral ganglia

A

Anterior to vertebral
column

141
Q

Parasympathetic Nervous System

A

Rest and digest
- Decreases heart rate and cardiac output
- Bronchoconstriction and increased mucous secretion
- Increases digestive function and GI motility
- Increases blood flow to digestive tract

142
Q

what is the major neurotransmitter in the parasympathetic NS

A

acetylcholine

143
Q

what are the two paths of the PaNS

A

Vagus nerve – all of
the visceral
efferents up to the
proximal large bowel

Sacral nerves – all of
the visceral
efferents to the rest
of the large bowel,
kidney, reproductive
organs

Ganglia are located
closer to target
organs

144
Q
A

Biomed (9 decks)

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