Additional GI Notes

Question 1

describe the events in glycogenesis

Answer 1

glucose phosphorylated to glucose-6-phosphate (uses ATP and hexokinase catalyst)

G6P then stores as glycogen or broekn down by glycolysis

G6P converted to glucose-1-phosphate

G1P converted to UDP-glucose by UDP glucose phosphorylase

Glycogen synthase adds the new UDP-glucose to the end of the existing glycogen chain

Question 2

describe the events in glycogenolysis

Answer 2

catalysed by glycogen phosphorylase

glycogen has one glucose cleaved

glucose is combined with a phosphate

G1P then converts to G6P by phosphoglucomutase

G6P is phosphorylated in the liver and released into the blood by glucose-6-phosphatase

Question 3

what bonds link glucose molecules

Answer 3

alpha-1,4-glycosidic bonds

Question 4

what is glycogenin and where is it found

Answer 4

found at the centre of a glycogen molecule

it allows for a glycogen starting point as glycogen synthase cant make glycogen from scratch

Question 5

what does transglycosylase allow

Answer 5

branches to be added to a glycogen molecule

Question 6

what GLUT transported transports glucose produced by glycogen to the blood

Answer 6

2

Question 7

what are the three classic precursors of gluconeogenesis

Answer 7

Lactate
Glucogenic Amino acids (not ketogenic)
Glycerol

Question 8

what is rewuired to start gluconeogenesis

Answer 8

4ATP and 2 GTP

Question 9

what stimulates glycolysis

what inhibits glycolysis

Answer 9

high AMP, ADP or ATP

High citrate, alanine, acetyl-CoA (these also promote gluconeogenesis)

Question 10

how many carbons can the body synthesise into its fatty acids - after which the others are essential fatty acids

Answer 10

9

Question 11

what must fatty acids be broken down into to join the TCA cycle

Answer 11

CoA derivatives
fatty acid + CoA –> acyl-CoA
NOT ACETYL

Question 12

how is acyl-CoA transferred into the mitochondria

Answer 12

carnitine shuttle

Question 13

what is the P/O ratio

Answer 13

the amount of ATP produced from the movement of 2 electrons through the transport chain donated by the reduction of oxygen to water

Question 14

what are the three ketone bodies

Answer 14

acetoacetate
acetone
hydroxy-butyrate

Question 15

what happens during periods of starvation

Answer 15

lots of oxaloacetate is used up for gluconeogenesis and so ketone bodies are produced from excess acetyl-CoA and ketone levels rise leading to acidosis

Question 16

describe lipogenesis

Answer 16

occurs in the liver
acetyl-CoA produced in matric
acetyl-CoA carboxylase regulates how much fatty acid is synthesised at once
fatty acid synthesis requires acetyl-CoA, manolyl-CoA and NADPH
palmitoyl-CoA can antagonise acteyl-CoA carboxylase if the levels get too high

Question 17

steps in urea synthesis

Answer 17

transamination - amino group transferres to a keto acid
deamination - amino group is removed from the glutamic acid and reforms the keto acid - the free ammonium ion can now enter the urea cycle which needs 3ATP –> produces urea, 2 phosphate, 2 ADP, AMP and fumarate
urea cycle - ammonium ions converted to urea along with aspartic acid

Question 18

what are ketogenic vs glucognic amino acids broken down into

Answer 18

K = acetyl-CoA
G = pyruvate

Question 19

what do alpha4-beta7 integrin on T cells and MADCAM-1 on the endothelium do

Answer 19

aid the transport of T cells out of the gut

Question 20

what do paneth cells secrete and where are they from

Answer 20

defensins and they are found in the small intestine

Question 21

what Ig is present in bile

Answer 21

IgA

Question 22

what analgesia cant be given in gallstones and why

Answer 22

morphine because it constricts the sphincter of Oddi and increases intrabiliary pressure

Question 23

what substances act on the CTZ to enduce vomiting

Answer 23

substance P 
opiates
dopamine
ACh
5-HT
Histamine

Question 24

what are the side effects of severe vomiting

Answer 24

excessive acid loss
leading to hypochloraemic metabolic alkalosis
loss of K - hypokalaemia

Question 25

what layer of the bowel is most affected by ischaemia

Answer 25

mucosa - most metabolically active part

Question 26

raised AST

Answer 26

alcohol and MI 10x

viral/autoimmune hepatitis and drugs 20x

Question 27

raised ALT

Answer 27

liver damage

50x viral or drug hepatitis

Question 28

raised ALP

Answer 28

raised bone turnover rate

blockage in the bile duct

Question 29

raised GGT

Answer 29

obstructive jaundice
cholecystitis
alcohol abuse
helps to inform if the raised ALP is to do with the liver or not

Question 30

what factors give an automatic MUST score of 2

Answer 30

BMI <18.5
>10% weight loss (not planned)
acutely unwell and starving for more than 5 days

Question 31

RDA for fibre, red meat and salt

Answer 31

F = 24g/day
RM = 70g/day
S= 6g/day