8. intergrated metabolism

Question 1

define anabolic pathways

Answer 1

synthesis of large molecules

uses ATP and NADH

Question 2

define catabolic pathway

Answer 2

breakdown of large molecules

fuel oxidation

exergonic, makes ATP, waste products made

Question 3

Metabolic homeostasis

Answer 3

control of balance between substrate availability and need by anabolic vs catabolic pathways

Question 4

four basic types of metabolic pathways

Answer 4

fuel oxidation: glycolysis and TCA

fuel storage and mobilisation: glycogenesis and glycogenoylsis

Biosynthetic pathways

Detoxification/waste disposal pathways urea cycle

Question 5

what are the normal levels of blood glucose

what happens if there is a significant decrease in blood glucose levels <60mg/dl

why does this occur

what happens if there is too much glucose

Answer 5

80-100 mg/dl

hypoglycemia, can enter coma

glucose influx lowers due to low Km of BBB transporters- need a lot of glucose to get past it

hyperosmolar effects= neurological defects and coma

• Concentration rises above renal tubular threshold
• Non-enzymatic glycosylation of proteins, sticking glucose to proteins which don’t need it- changes structure and function

Question 6

3 ways the balance between use, release, storage by different tissues is achieved

Answer 6

1. Blood [nutrient]: Fatty acids, Conc. determines whether skeletal muscle uses fatty acids or glucose.
2. Hormones
3. Central Nervous System: controls via pituitary gland with hormones or sympathetic

Question 7

The two major hormones that regulate fuel storage & mobilization:

Answer 7

• Insulin: promotes storage of fuels (& use for growth)
• Glucagon: promotes mobilization of fuels

Question 8

what tissues do insulin act on?

Answer 8

liver, muscle & adipose

Question 9

what does insulin promote?

Answer 9

• Glycogen formation in liver & muscle
• Conversion of glucose to triacylglycerols (liver)
• Protein synthesis (e.g. albumin) in liver
• Storage of triacylglycerols (adipose)
• Increases glucose uptake by muscle & adipose
• Amino acid uptake & protein synthesis in skeletal muscle

Question 10

what tissues do glucagon act on?

Answer 10

liver and adipose (muscles dont have receptors)

Question 11

what does glucagon promote?

Answer 11

• Increased Glycogenolysis, reduced glycogen synthesis in liver
• Stimulates gluconeogenesis & ketogenesis
• Mobilises fatty acids from adipose triacylglycerols

Question 12

which cells secrete insulin and glucagon?

Answer 12

• α cells secrete glucagon: ↓ Plasma [glucose] & ↑ [adrenaline]
• β cells secrete insulin: ↑ Plasma [glucose]

Question 13

what is insulin synthesised as

insulin release:

insulin release modulation

Answer 13

preprohormone- C peptide is cleaved

• 80 mg/dL threshold
• Proportional release up to 300 mg/dL
• Rapidly degraded by liver

autonomic nervous system and vagus nerve

Question 14

glucagon: what is it synthesised as

where is it degraded

regulation

what promotes release

Answer 14

preprohormone

degraded by liver and kidneys

seceretion regulated by [insulin] and [glucose]

released promoted by

• catecholamines (e.g. epinephrine)
• amino acids (so, meal composition is important)

Question 15

Intracellular Events: Insulin

Answer 15

•Insulin autophosphorylates cell receptor

-receptor’s tyrosine kinase domain phosphorylates enzymes

•Basic cellular responses:

1) Reverses glucagon-stimulated phosphorylation
2) Kicks off a phosphorylation cascade
3) Induction/repression of enzyme
4) Stimulate protein synthesis
5) Stimulate glucose & amino acid intake

Question 16

Intracellular Events: Glucagon

Answer 16

•Glucagon binding causes 2nd’ry messenger formation:

• G protein dissociation activates Adenylate cyclase
• Creates cAMP
• Activates cAMP-dependent protein kinase
• Phosphorylates regulatory enzymes
• Controls carbohydrate & lipid metabolism

amplification cascade

Question 17

Answer 17