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NME > Liver & Glucose Homeostasis > Flashcards

Liver & Glucose Homeostasis Flashcards

1
Q

Biomolecules as energy stores

A
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2
Q

Fuel Metabolism: Energy for ATP synthesis derived from the oxidation of 3 main body fuels:

A
  • glucose stored as glycogen
  • long chain fatty acids stored as
    triacylglycerol
  • amino acids
  • obtained intermittently from meals yet
    required continuously
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3
Q

What kind of proteins can enter the citric acid cycle?

A

Deaminated (remove nitrogen)

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4
Q

2 requirements of fuel metabolism:

A

1) store fuels when abundant
2) release fuels in a controlled way during
the post-absorptive period, during
exercise or starvation

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5
Q

Phases of assimilation:

A

1) immediate absorptive events
2) post-absorptive events

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6
Q

Phases of assimilation: Immediate absorptive state:

A
  • liver and adipose tissue mainly take up
    materials
  • glycogen
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7
Q

Phases of assimilation: Post-absorptive state:

A
  • mobilisation of reserves of glycogen built up during feeding
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8
Q

Functions of the liver (9):

A
  • store glycogen
  • break down glycogen
  • deaminates surplus amino acids and
    converts amino groups into ammonia and
    then urea
  • synthesise glucose from non-carb
    precursors
  • synthesise ketone bodies and secrete for
    fuel for other tissues
  • aid elimination of cholesterol from the
    body and synthesises bile salts from
    cholesterol
  • stores fat soluble vitamins ADEK
  • metabolism and elimination of drugs
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9
Q

Ketone bodies:

A
  • produced from fatty acid breakdown
  • acetoacetate
  • beta-hydroxybutyrate
  • acetone
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10
Q

Liver and Ketone Bodies:

A
  • selfless
  • synthesise ketone bodies but can not
    utilise them as an energy source
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11
Q

hypoglycaemia

A

low plasma glucose concentration

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12
Q

Glucose metabolism

A
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13
Q

Glucose metabolism and the Brain:

A
  • the brain is most vulnerable to
    hypoglycaemia as cerebral cells derive their
    energy predominantly from aerobic
    metabolism
  • Brain can not (3):
    • store glucose in significant amounts or
      synthesise glucose
    • metabolise substrates other than glucose
      or ketone bodies
    • extract sufficient glucose for their needs
      from extracellular fluids at low concs
      because glucose entry into the brain is
      not facilitated by hormones
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14
Q

Why does RBCs need so much glucose?

A
  • no mitochondria present
  • can only use glycolysis no oxidative
    phosphorylation
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15
Q

Glycogenolysis

A

mobilisation of liver glycogen stores

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16
Q

Gluconeogensis

A

glucose syntehsis in liver and kidneys from non-carb precursors eg amino acids, glycerol, lactate

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17
Q

Glycolysis

A

Oxidation of glucose by peripheral tissues

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18
Q

Mechanisms controlling blood glucose:

A
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19
Q

Insulin primary mechanism

A

increase absorption of cells to glucose

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20
Q

Pancreas and Insulin Secretion:

A
  • blood glucose high -> high ATP in beta cells
    in the Islets of Langerhans
  • Closes K+ channels and depolarises
    membranes
  • Voltage gated Ca2+ channels open in
    response allowing Ca2+ to flow into the cell
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21
Q

Alpha cells in the Islets of Langerhans (pancreas) secrete

A

glucagon (alphabetical both first)

22
Q

Beta cells in the Islets of Langerhans (pancreas) secrete

A

insulin (alphabetical both second)

23
Q

Blood glucose varies a lot throught the day and night due to changes in food intake.

True or False?

A

False
varies relatively little
controlled by fluctuations in circulating levels of insulin or glucose

24
Q

When dietary glucose intake is low,

A

glycogenolysis is high
gluconeogenesis is high before eating (mainly night)

25
Q

Glucose is absorbed from the intestine for how many hours following a meal?

A

2-3 hours

26
Q

Glycogen is degraded between meals and lasts for

A

12-24 hours

27
Q

Glucose homeostasis

A
28
Q

insulin stimulates

A

the entry of glucose into cells is the major and most important metabolic effect of insulin

29
Q

How do polar molecules such as glucose enter cells, across a lipid membrane?

A

Antelded

30
Q

Glucose enters cells by:
- passive diffusion
- facilitated diffusion
- active transport

A

facilitated diffusion (down conc grad)

31
Q

Family of glucose transporter proteins are structurally related but

A

encoded by different genes that are expressed in a tissue specific manner

32
Q

Glucose transport into tissues: Glut 1:

A
  • many tissues
  • erythorocytes
  • muscle
  • brain
  • kidney
  • placenta etc
33
Q

Glucose transport into tissues: Glut 2:

A
  • liver
  • pancreatic beta cells
34
Q

Glucose transport into tissues:: Glut 3:

A
  • brain
35
Q

Glucose transport into tissues: Glut 4:

A
  • skeletal muscle
  • adipose tissue
    **insulin sensitive
36
Q

Glucose transport into tissues: Glut 5:

A
  • small intestine
  • (fructose not glucose transporter)
37
Q

All cells express at least on isoform of glucose transporter proteins (Gluts).

True or False?

A

True
a certain level of glucose uptake is an absolute necessity

38
Q

Glucose transporters

A
39
Q

Insulin Regulation of Glucose Entry into Tissues:

A
  • insulin binds to insulin receptor
  • causing auto-phosphorylation
  • changing conformation of insulin receptor
    on the inside of the cell
  • through cascade reactions results in the
    inhibition of lipolysis
40
Q

Cellular effects of insulin:

A

Immediate effects:
- increase in the rate of glucose uptake in
muscle and adipocytes
- modulation of activity of enzymes involved
in glucose metabolism

(occur in minutes, does not require protein synthesis, occurs at insulin 10-9 or -10 mols/L)

Long lasting effects:
- increased expression of liver enzymes that
synthesize glycogen
- increased expression of adipocyte
enzymes that synthesize triacylglycerols
- inhibits lipolysis in adipose tissues by
inactivating hormon-sensitive lipase which
mobilises fatty acids from TG stores
- functions as a growth factor for some cells
eg fibroblasts

(occur over several hours, require continous exposure to insulin at 10-8 mol/L)

41
Q

Pentose Phosphate Pathway

A
  • cytosolic pathway in all cells
  • branches from glycolysis at G6P
  • Products:
    • ribose phosphate: synthesizes RNA/DNA
    • NADPH: biosynthesis, maintain redox
      balance of cell
42
Q

Tissues involved in biosynthesis (liver, adipose) are rich in

A

PPP enzymes (pentose phosphate pathway)

43
Q

in cells where biosynthetic processes are less active, PPP intermediates are

A

recycled back into glycolysis

44
Q

Fate of glucose in muscle and heart

A
45
Q

Fate of glucose in Liver

A
  • Glut2
  • stored as glycogen, glycolysis to form
    pyruvate and then acetyl CoA
  • some to produce ATP, excess acetyl CoA
    used for fat synthesis
  • some goes through PPP pentose
    phosphate pathway to form NADPH to
    support fat biosynthesis
46
Q

Fate of Glucose in the Liver

A
47
Q

Fate of glucose in the brain:

A
  • Glut1 & Glut3
  • aerobic metabolism to produce energy
  • some used in pentose phosphate pathway
    to provide NADPH for lipid synthesis
48
Q

Fate of Glucose in Brain

A
49
Q

Fate of Glucose in Adipose Tissue:

A
  • Glut 4
  • glycolysis to produce acetyl CoA to produce
    ATP or synthesise fats
  • some used for pentose phsophate
    pathway to produce NADPH also required
    for fatty acid synthesis
50
Q

Fate of Glucose in Adipose tissue

A
51
Q

Fate of Glucose in Main Body Tissues:

A

RBCs: Glut 1: glycolysis to lactate to produce energy

  • some used in pentose phosphate pathway
    to produce NADPH for the maintenance of
    reduce glutathione
  • RBCs do not have mitochondria and
    therefore can not oxidise glucose fully via
    the TCA cycle and the ETC
  • must rely on glycolysis of glucose alone for
    energy requirements
52
Q

Fate of Glucose in Main Body Tissues

A

NME (52 decks)

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