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Biochemistry > Metabolic Control L18 > Flashcards

Metabolic Control L18 Flashcards

(59 cards)

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1
Q

what are the main biochemical pathways in the cell

A 
Carbohydrates
Amino Acids 
Lipids
Purines and Pyrimidines
Vitamins and coenzymes, hormones
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2
Q

why must the cell regulate biochemical pathways

A

provide products in pathway at the rate they are needed

maintain the steady state concentrations of metabolites within a narrow range (homeostasis)

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3
Q

why must the cell regulate homeostasis

A

Large changes in metabolites may have deleterious effects on cells
Intermediates needed for several pathways need a delicate control
Need for rapid response to changes in supply or demand (e.g. response to hormones)

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4
Q

what are the four different levels of regulation in the cell

A

modulation
interconversion
changes in enzyme biosynthesis
compartmentalisation

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5
Q

what is the regulation of modulation

A

Rapid but modest changes in enzyme activity in response to fluctuating levels of metabolites

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6
Q

what is the regulation of interconversion

A

Slower but larger scale activation of suppression of pre–formed enzyme ‘pools’

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7
Q

what is the regulation of changes in enzyme biosynthesis

A

Slow but major changes in gene expression via

  • Transcription of DNA into mRNA
  • Translation of mRNA into protein
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8
Q

what is the regulation of compartmentalisation

A

Restricting the access of enzymes to substrates via regulating transport in and out of mitochondria, nuclei, endosomes, membranes etc

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9
Q

what are all the cell regulations related to

A

enzyme activity

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10
Q

how long does enzyme synthesis/degradation take

A

hours

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11
Q

how long does enzyme modification take

A

mins to seconds

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12
Q

how long does enzyme activity take

A

milliseconds

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13
Q

what is modulation

A

control of enzyme activity by inhibitors/activators

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14
Q

which enzymes act as control points

A

enzymes catalysing irreversible reactions

enzymes at the start of the pathway

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15
Q

what is feedback inhibition

A

Decrease the activity of the enzyme, decrease the rate of the products made – less ATP production
When need more ATP the inhibition is removed

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16
Q

what is branch point inhibition

A

enzymes in bacterial amino acid metabolism are subject to a range of feedback inhibition strategies
If one amino acid is low, will feedback and stimulation production of that particular part of the pathway
Some branch point enzymes have several isoforms, each with different feedback regulators

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17
Q

what is interconversion

A

reversible transformation of one enzyme form into another, typically with an alteration in the enzyme activity
modification either activates or inhibits enzyme activity

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18
Q

what is used to convert glucose to glucose-6-phosphate

A

hexokinase

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19
Q

what is used to convert glucose-6-phosphate to glucose-1-phosphate

A

using phosphoglucomutase

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20
Q

what is used to convert glycogen-1-phosphate to glycogen

A

glycogen synthase

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21
Q

what is used to convert glycogen to glucose-1-phosphate

A

glycogen phosphorylase

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22
Q

what glucose is released to be used

A

glucose-1-phosphate

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23
Q

which glycogen phosphorylase is inactive, why

A

Glycogen phosphorylase b as no phosphate group

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24
Q

what causes glycogen phosphorylase to be converted to phosphorylase a isoform, effect

Study These Flashcards
A

response to a hormonal signal glycogen phosphorylase b is converted to the phosphorylase a ISOFORM and permanently activated

25
what happens in glycogen metabolism to make G-1-P
glycogen synthesase inactive due to the adrenaline | adrenaline activates glycogen phosphorylase
26
what regulates these enzymes in glucose metabolism
Adrenaline
27
what does phosphorylase b use to be converted to a
phosphorylation step requires ATP + the enzyme phosphorylase kinase
28
how many protein kinases are there
~520 protein kinases
29
what is needed to remove phosphate by hydrolysis
specific protein phosphatases
30
what bond is stable even during protein isolation
covalent phospho-serine, -threonine and -tyrosine bond
31
what transfers the terminal phosphate of ATP to the hydroxyl groups of ser, thr, tyr
specific protein kinases
32
what happens in signal transduction cascade
Hormone can stimulate production and release of protein kinase A Protein kinase A converts phosphorylase b kinase to hav a phosphate phosphorylase b kinase with phosphate converts phosphorylase b to phosphorylase a
33
what happens in signal transduction
set of chemical reactions in a cell that occurs when a molecule, e.g. hormone, attaches to cell membrane receptor pathway is a cascade of biochemical reactions inside cell that eventually reach target molecule or reaction
34
where is glycogen stored
muscles
35
what happens in signalling transduction pathway
1. Adrenaline cannot enter the cell need to bind to receptors on the membrane, when bind they have to stimulate a secondary hormone cAMP 2. when adrenalin binds to receptor adenylate cyclase is activated cAMP stimulated by adenylate cyclase 3. Activates Protein Kinase A 4. Cascade to activate glycogen phosphorylase
36
how can protein kinase a affect gene expression
by phosphorylating a transcription factor
37
how can other hormones or growth factors affect gene expression
other hormones or growth factors can affect gene expression via Ca++ and/or Protein Kinase C
38
what is the control of gene expression
transcription and translation
39
what is the control of gene expression in a eukaryotic cell
DNA to RNA first level of control (transcriptional control) RNA transcript to mRNA (RNA processing control) mRNA to protein (translation control) protein to inactive protein (protein activity control) Can intervene at these points of control
40
how is control of gene expression mainly controlled
through initiation of transcription - Structure of gene - Interaction with RNA polymerase (form pre initiation complex PIC)
41
how are totipotent genes controlled in gene expression
Majority of cells contain full complement of DNA Different tissues express different genes, due to the transcription factor they originally express, it determines the function of the cell
42
what are the RNA polymerases needed to initiate transcription
Poly I Poly II Poly III
43
what does Poly I used in
rRNA
44
what is Poly II used in
mRNA
45
what is Poly III used in
tRNA and 5rRNA
46
what is the role of polymerase in gene expression
binds to the promoter of the gene, which impact on what genes are expressed and what proteins are made
47
what are the consensus sequences in prokaryotes
TATA box
48
what are the consensus sequences in polymerase II dependent promoters of eukaryotes
TATA box CAAT box GC box
49
what is the TATA box
TATAAAA
50
what is the CAAT box
GGNCAACT
51
what is the GC box
GGGCGG
52
what are the transcription factors that polymerase requires for transcription initiation
TFIIA TFIIB D E
53
what is the order that polymerase and the four other factors bind
1. TFIID, binds directly to the TATA box promoter region 2. TFIIA binds with TFIID that is already bound to the TATA box 3. TFIIB then binds and facilitates RNA polymerase II to bind 4. TFIIE binds to form the preiniation complex and trigger the beginning of transcription at the initiation point (start point
54
why can't polymerase initiate transcription without the other four factors
does not recognise the promoter and it requires four other factors to initiate transcription from a TATA box promoter region
55
what is formed in initiation of transcription
basal transcription complex
56
what are enhancers
sequences far from the promoter that proteins can bind to
57
what effect do proteins binding to DNA sequence have
can activate or repress transcription
58
what is the structure of transcription factors
often homo- or hetero-dimers | they can also have several domains
59
what may the activation domain have
can include ligand binding sites – interaction with signal molecules

Biochemistry (13 decks)

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