L32 - fuel homeostasis

Question 1

why is fuel homeostasis needed?

Answer 1

tissues constantly require nutrients but food consumption isnt constant

Question 2

where is glycogen stored

Answer 2

liver mainly

muscles in small amounts

Question 3

define absorptive state

Answer 3

food in gut

when nutrients are entering blood from GI tract

Question 4

define post-absorptive state

Answer 4

empty GI tract
energy supplied by body stores
eg sleeping

Question 5

(in absorptive state) how is absorbed glucose stored short term by the liver

Answer 5

converted to glycogen for storage

Question 6

(in absorptive state) how is absorbed glucose stored long term by the liver when glycogen stores full

Answer 6

converted to glycerol and FAs and transported to adipose to form TGs (when glycogen stores full)

Question 7

(in absorptive state) what happens to glucose in muscles

Answer 7

used for energy

some stored as glycogen

Question 8

(in absorptive state) what happens to absorbed AAs in liver

Answer 8

converted to keto acids which either:
enter TCA cycle
get converted into FAs then TGs

Question 9

(in absorptive state) what happens to absorbed AAs in muscle

Answer 9

used to replace proteins lost by catabolism

Question 10

(in absorptive state) what happens to absorbed fats in adipose tissue

Answer 10

converted to TGs (with glycerol from glucose) and stored in adipose tissue

Question 11

(in absorptive state) how are absorbed fats utilised by other organs

Answer 11

oxidised to provide energy

Question 12

in absorptive state what happens to excess
sugars
fat
AAs

Answer 12

sugars - stored as glycogen / converted to
FA&glycerol and stored as TGs in adipose
tissue
Fat - oxidised for energy / stored in adipose as TGs
AAs - used for protein synthesis/ converted to
ketoacids and oxidised or converted to FA and
stored as TGs in adipose

Question 13

how is plasma [glucose] maintained in post-absorptive state

Answer 13

1. gylcogenolysis
2. gluconeogenesis (converting protein/fat to glucose)
3. glucose sparing ( using FA / KA as fuel) to spare glucose for CNS

Question 14

short term glucose store

Answer 14

glycogen (liver and muscles)

Question 15

long term glucose store

Answer 15

breakdown of TGs in adipose tissue

Question 16

(postabsorptive state) how is glucose generated from protein

Answer 16

skeletal muscle protein catabolised to AAs

AAs converted to glucose in liver

Question 17

(post-absorptive state) how is glucose generated from adipose tissue)

Answer 17

TG converted to Glycerol and FAs

liver then converts glycerol to glucose

Question 18

how are states controlled

Answer 18

SNS

endocrine - pancreatic H’s and thyroid H’s

Question 19

what cells secrete insulin

Answer 19

pancreatic B cells

Question 20

what cells secrete glucagon

Answer 20

pancreatic a cells

Question 21

is insulin anabolic or catabolic?

Answer 21

anabolic

Question 22

is glucagon anabolic or catabolic

Answer 22

catabolic

Question 23

how does insulin increase glucose uptake in muscles and adipose

Answer 23

1. increases glucose uptake in muscles and adipose by moving transporters to membrane
2. increases glucokinase activity (involved in glycolysis1 so more glucose uptake to produce energy)
3. promotes synthesis of FA and glycerol from glucose which can then be stored as TG in adipose

Question 24

how does insulin increase glycogen production in liver and muscle

Answer 24

activates glygogen synthase

Question 25

how does insulin increase AA uptake in muscle

Answer 25

by increasing transporter activity and protein synthesis

Question 26

list ways insulin stimulates anabolism (5 ways)

Answer 26

1. increases glucose uptake in muscles and adipose by moving transporters to membrane
2. increases glucokinase activity (involved in glycolysis 1 so more glucose uptake)
3. activates glycogen synthase increasing glycogen production in liver and muscle
4. increases AA uptake in muscle by increasing transporter activity and protein synthesis
5. promotes synthesis of FA and glycerol which can then be stored as TG in adipose

Question 27

how does insulin reduce glycogenolysis in muscle and liver

Answer 27

inhibits glycogen phosphorylase

Question 28

how does insulin inhibit adipocyte lipolysis

Answer 28

by inhibiting lipoprotein lipase

Question 29

in what ways does insulin inhibit catabolic activity

Answer 29

1. inhibits glycogen phosphorylase - reducing glycogenolysis in muscle and liver
2. inhibits gluconeogenesis in liver
3. inhibits keto-acid production in liver
4. inhibits adipocyte lipolysis by inhibiting lipoprotein lipase

Question 30

what are the actions of glucagon

Answer 30

targets liver to generate glucose by

1. glycogenolysis
2. gluconeogenesis

Question 31

what influence do the thyroid hormones have on fuel homeostasis (3 things)

Answer 31

1. they set the basal metabolic rate
2. increase mitochondrial metabolism
3. regulate expression of many enzymes involved in metabolic processes)

Question 32

what effect does NA and adrenaline have on insulin and glucagon

Answer 32

inhibit insulin
stimulate glucagon
(stimulate breakdown of stores)

Question 33

what organs involved in fuel homeostasis are affected by NA

Answer 33

liver and adipose tissue as they are under autonomic control, skeletal muscle isnt so only affected by Adrenaline

Question 34

how does an insulin deficiency affect catabolism

Answer 34

1. increased catabolism (glycogenolysis/gluconeogenesis/lipolysis/protein breakdown)
2. cant stop breaking down stores leads to weight loss

Question 35

in an insulin deficiency, what energy source does the body try to replace glucose with and what does this lead to

Answer 35

ketoacids

diabetic ketoacidosis

Question 36

how does insulin deficiency affect anabolism

Answer 36

1. anabolism decrease
2. leads to hyperglycaemia ( high plasma [glucose] that cant be utilised as no insulin)
3. glucose lost in urine
4. osmotic diuresis (water retention in urine due to high [glucose])
5. water & ssalt loss & polydipsia (thirst)