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alimentary > 3.6 energy stores: glycogen and lipids > Flashcards

3.6 energy stores: glycogen and lipids Flashcards

1
Q

where is glycogen stored

A

liver and muscles

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2
Q

what is the glycogen stored in liver used for

A

buffering blood glucose level

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3
Q

what is the glycogen stored in muscles used for

A

To provide glucose to generate energy during exercise

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4
Q

how does glucose form glycogen (simple details) (inclu. enzyme)

A

Moving the phosphate around, then adding the glucose to an existing glycogen chain using glycogen synthase

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5
Q

how does glycogen form glucose (simple details) (inc. enzyme)

A

To breakdown a glucose from glycogen, we use phosphorylase

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6
Q

why is glycogen metabolism controlled reciprocally

A
  • It is controlled reciprocally to prevent futile cycle

So only one side of the cycle is on at each time for energy efficient

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7
Q

2 methods of glycogen metabolism

A

allosterically and by hormones

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8
Q

3 molecules of allosteric control in glycogen metabolism

A

a. AMP (signals low enrgy levels)

b. Calcium (signals increased activity in muscles)

c. Glucose (signals enough energy)

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9
Q

2 hormones in glycogen metabolsim

A

insulin
glucagon

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10
Q

how does insulin work in glycogen metabolism

A
  • Released after a meal when blood glucose is high.
  • Activates phosphatases, promoting:

○ Glycogenesis (glycogen synthesis).

○ Inhibition of glycogenolysis (glycogen breakdown)

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11
Q

how does glucagon work in glycogen metabolism

A
  • Released during fasting or low blood glucose.
  • Activates kinases, promoting:

○ Glycogenolysis (glycogen breakdown).

○ Inhibition of glycogenesis (glycogen synthesis).

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12
Q

how does glucagon function

A
  • Glucagon act on a cell surface receptor of liver cells for:
  • Intracellular signal
  • Activation of a protein kinase which activates phosphorylase to breakdown glycogen into glucose
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13
Q

how does insulin function

A
  • Insulin opposes this effect by acting on its own cell surface receptors for:
  • A different intracellular signal that ultimately activates a protein that opposes kinases - phosphatase which activates glycogen synthase
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14
Q

diseases involved in aberrant fat handling/metabolism (and what species are affected)

A

obesity - all animals

pregnancy toxaemia - cows, sheep

hepatic lipidosis - cats, horses

diabetes - dogs, cats

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15
Q

what is the primary form of lipid storage

A

triacylglycerols (TAGS)

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16
Q

where is lipids stored (3)

A
  • adipose tissues
  • small amount in liver and muscles
17
Q

properties of TAGS

A

non-polar
non toxic
highly energy dense

18
Q

2 types of adipose tissue

A

white adipose tissue (WAT)
brown adipose tissue (BAT)

19
Q

properties of WAT (5)

A
  • Single fat droplet
  • Few mitochondria
  • Specialized to store triacylglycerol
  • Secretes multiple adipokines
  • Multiple anatomical depots
20
Q

properties of BAT

A
  • Multiple small fat droplets
  • Many mitochondria
  • Highly oxidative
  • Non-shivering thermogenesis for heat production (regulated by uncoupling proteins)
  • Smaller quantities of depots (e.g. periscapular depot)
  • Mostly observed in neonates (new born), smaller animals
21
Q

which 2 forms are lipids transported in blood as

A
  1. fatty acids (mostly bound to albumin)
  2. lipoproteins
22
Q

which organ is used for lipid metabolism

A

liver

23
Q

what happens to the chylomicrons after transporting lipids to the liver

A

they become chylomicron remnants

24
Q

what happens to chylomicron remnants

A

they are processed in the liver to form VLDL, LDL, HDL

25
Q

what are VLDL used for

A

Transport newly synthesized TAG from the liver to adipose tissue

26
Q

what are LDL used for

A

carry a mixture of lipids around the body

27
Q

what are HDL used for

A

Return lipid to liver from other tissues

28
Q

what are the 5 types of lipase involved in hydrolyses of TAGS

A
  • pancreatic lipase
  • lipoprotein lipase
  • adipose triglyceride lipase
  • adipose hormone sensitive lipase
  • adipose monoacyglycerol lipase
29
Q

what are the uses of the 5 types of lipase

A
30
Q

process of lipolysis

A
  • Fatty acids are oxidized in the mitochondria of active tissues to produce ATP (requires oxygen)
    • Important in active tissues
      ○ e.g. skeletal muscle
    • Oxidation occurs in the mitochondrial matrix
    • Requires transport of activated fatty acids molecules across the mitochondrial membrane, which is a controlled process (acyl carnitine via CPT1 transporter)
      ○ It is inhibited by malonyl-CoA which is intermediate in fatty acid synthesis - the use reciprocal regulation
    • Activated fatty acids = fatty acyl CoA
    • Once in the mitochondrial matrix, fatty acyl CoA is broken down by the repeated removal of 2-carbon fragments as acetyl CoA
      ○ This process is beta-oxidation

Palmitate (a fatty acid with 16 carbons), it undergoes 7 cycles, each cycle removing 2 carbons as acetyl CoA, this results in 8 acetyl CoA

31
Q

where does fatty acid synthesis occurs mostly

A

liver and adipose tissues

32
Q

process of fatty acid synthesis

A
  • Fatty acids are synthesized from acetyl CoA when energy is abundant
    • Synthesis occurs by repeated condensation of 2 carbon units to build up an even numbered long chain of fatty acids
    • Synthesis cannot occur by reversing the B-oxidation breakdown pathway○ It uses unique path with some unique enzymes and occurs in cytosol
      Thus reciprocal regulation
33
Q

what enzyme is involved in fatty acid synthesis

A

acetyl CoA carboxylase (ACC)

34
Q

how is ACC inhibited and activated

A

inhibit: glucagon and adrenaline

activate: insulin

35
Q

what does malonyl CoA do

A

inhibit CPT 1 and thus transport of acyl CoA into mitochondria for breakdown

36
Q

what is the 16 C lipid called

A

palamitate

37
Q

why would ACC release the lipid when it gets to 16C

A

When the chain is 16 C long (palmitic acid), it becomes too big for the enzymes and is released

38
Q

what is lipogenesis

A

Lipogenesis = building fats

39
Q

what is adipogenesis

A

Adipogenesis = expansion of adipose tissue

alimentary (14 decks)

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