3.6 energy stores: glycogen and lipids

Question 1

where is glycogen stored

Answer 1

liver and muscles

Question 2

what is the glycogen stored in liver used for

Answer 2

buffering blood glucose level

Question 3

what is the glycogen stored in muscles used for

Answer 3

To provide glucose to generate energy during exercise

Question 4

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

Answer 4

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

Question 5

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

Answer 5

To breakdown a glucose from glycogen, we use phosphorylase

Question 6

why is glycogen metabolism controlled reciprocally

Answer 6

• It is controlled reciprocally to prevent futile cycle

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

Question 7

2 methods of glycogen metabolism

Answer 7

allosterically and by hormones

Question 8

3 molecules of allosteric control in glycogen metabolism

Answer 8

a. AMP (signals low enrgy levels)

b. Calcium (signals increased activity in muscles)

c. Glucose (signals enough energy)

Question 9

2 hormones in glycogen metabolsim

Answer 9

insulin
glucagon

Question 10

how does insulin work in glycogen metabolism

Answer 10

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

○ Glycogenesis (glycogen synthesis).

○ Inhibition of glycogenolysis (glycogen breakdown)

Question 11

how does glucagon work in glycogen metabolism

Answer 11

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

○ Glycogenolysis (glycogen breakdown).

○ Inhibition of glycogenesis (glycogen synthesis).

Question 12

how does glucagon function

Answer 12

• 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

Question 13

how does insulin function

Answer 13

• 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

Question 14

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

Answer 14

obesity - all animals

pregnancy toxaemia - cows, sheep

hepatic lipidosis - cats, horses

diabetes - dogs, cats

Question 15

what is the primary form of lipid storage

Answer 15

triacylglycerols (TAGS)

Question 16

where is lipids stored (3)

Answer 16

• adipose tissues
• small amount in liver and muscles

Question 17

properties of TAGS

Answer 17

non-polar
non toxic
highly energy dense

Question 18

2 types of adipose tissue

Answer 18

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

Question 19

properties of WAT (5)

Answer 19

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

Question 20

properties of BAT

Answer 20

• 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

Question 21

which 2 forms are lipids transported in blood as

Answer 21

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

Question 22

which organ is used for lipid metabolism

Answer 22

liver

Question 23

what happens to the chylomicrons after transporting lipids to the liver

Answer 23

they become chylomicron remnants

Question 24

what happens to chylomicron remnants

Answer 24

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

Question 25

what are VLDL used for

Answer 25

Transport newly synthesized TAG from the liver to adipose tissue

Question 26

what are LDL used for

Answer 26

carry a mixture of lipids around the body

Question 27

what are HDL used for

Answer 27

Return lipid to liver from other tissues

Question 28

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

Answer 28

- pancreatic lipase - lipoprotein lipase - adipose triglyceride lipase - adipose hormone sensitive lipase - adipose monoacyglycerol lipase

Question 29

what are the uses of the 5 types of lipase

Question 30

process of lipolysis

Answer 30

- 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

Question 31

where does fatty acid synthesis occurs mostly

Answer 31

liver and adipose tissues

Question 32

process of fatty acid synthesis

Answer 32

- 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

Question 33

what enzyme is involved in fatty acid synthesis

Answer 33

acetyl CoA carboxylase (ACC)

Question 34

how is ACC inhibited and activated

Answer 34

inhibit: glucagon and adrenaline activate: insulin

Question 35

what does malonyl CoA do

Answer 35

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

Question 36

what is the 16 C lipid called

Answer 36

palamitate

Question 37

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

Answer 37

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

Question 38

what is lipogenesis

Answer 38

Lipogenesis = building fats

Question 39

what is adipogenesis

Answer 39

Adipogenesis = expansion of adipose tissue