Metabolism of Carbohydrates and Proteins Flashcards Preview

Block 3 ALS > Metabolism of Carbohydrates and Proteins > Flashcards

Flashcards in Metabolism of Carbohydrates and Proteins Deck (41):
1

efficiency of nutrient absorption of proteins

92

2

efficiency of nutrient absorption of fat

95

3

efficiency of nutrient absorption of carbs

99

4

efficiency of nutrient absorption of alcohol

100

5

what are the guts adaptations

The gut is adapted to absorb almost the whole of the
macronutrients in a meal, irrespective of meal size

Has abundant reserve capacity

6

what level is control energy intake

Control of energy intake is at the level of the mouth

7

phases of gastric secretion

Cephalic: sight/smell/taste
of food – vagus nerve

Gastric: food in stomach: gastrin

Intestinal: chyme in duodenum

8

what are the principal stimulants of acid secretion at the level of the parietal cells

histamine, gastrin
and acetycholine (ACh; neurocrine).

9

CCK(2) receptors recognise
Gastrin and CCK: they have
some amino acid sequence
in common. what is this different to?

note this is
different to the effect of
duodenal CCK which stimulates
pancreatic secretion.

10

action of Histamine

Histamine, released from enterochromaffin-like (ECL) cells, binds to H2 receptors that activate
adenylate cyclase (AC) and generate cAMP. Gastrin, released from G cells, binds to CCK2
receptors that activate phospholipase C to induce release of cytosolic calcium (Ca++).

11

action of Gastrin

Gastrin stimulates the parietal cell directly and, more importantly, indirectly by releasing histamine
from ECL cells. ACh, released from intramural neurons, binds to M3 receptors that are coupled to
an increase in intracellular calcium. The intracellular cAMP- and calcium-dependent signaling
systems activate downstream protein kinases ultimately leading to fusion and activation of
H+K+-ATPase, the proton pump.

12

true or false, stomach distension also inhibits gastric secretion

true

13

Gastric Inhibitory Polypeptide secreted by the duodenum was formerly thought to do just that : inhibit gastric acid secretion. However what is actually the case?

this
is not the case and it was renamed Glucose-dependent Insulinotropic Polypeptide when it was discovered it stimulates insulin secretion in response to glucose in the duodenum. It is now one of the ‘Incretins’ – used to treat diabetes.

14

when and where is this released. and what does it do? gastrin

Secreted by the stomach in response to food, especially, protein
Stimulates acid and pepsinogen secretion and gastric motility: inhibits gastric emptying

15

when and where is this released. and what does it do? secretin

Secreted by the duodenum in response to acid
Inhibits gastric acid production; increases pancreatic and biliary bicarbonate secretion

16

when and where is this released. and what does it do? CCK

Secreted by duodenum in response to food (especially fat). Inhibits gastric secretion and motility: stimulates pancreatic bicarbonate and enzyme secretion and bile secretion

17

when and where is this released. and what does it do? somatostatin

Released from D-cells in stomach and duodenum in response to acid : inhibits gastric secretion

18

first line treatment for inhibiting parietal cell acid secretion

Proton Pump Inhibitors
(PPIs)

19

what are the strategies for inhibiting parietal cell acid secretion

gastrin agonists
prostagladine agonist
h2 agonist
muscarininic antagonist

20

Cimetidine trade name
use

Trade Name: Tagamet
Use: H2-receptor antagonist
Use: Treat heartburn, Gastroesophageal reflux disease (GERD)

21

treatment of H.pylori

Amoxicillin + clarithromycin
Amoxicillin + metronidazole
Combined therapy

22

size of villi and total absorptive surface of the small intestinal mucosa

Each villus is 0.5 – 1.5 mm long
20 – 40 villi / mm2
total absorptive surface = 300 m2

23

how does venous drainage work in the small intestinal mucosa

venous drainage enters the
hepatic portal vein; the liver
controls entry of nutrients
into the peripheral circulation

24

how does lymphatics work in the small intestinal mucosa

The lacteal drains into the lymphatic system,
which enters the circulation at the thoracic duct
– the liver clears remnants after other tissues

25

when are villi cells damaged and what is the lifetime

Lifetime (~2-3 days)
Damaged in coeliac disease
and following anti-cancer
drugs/radiotherapy leads to
flattened mucosa and
malabsorption

26

ileum digestion

: continuing digestion: absorption of
monosaccharides
amino acids
fatty acids, glycerol, other lipids
many drugs
water

27

jejunum digestion

continuing digestion
start of absorption

28

what is the end-products of salivary, gastric and pancreatic enzyme digestion. carbs

disaccharides (maltose, sucrose, lactose)

29

what is the end-products of salivary, gastric and pancreatic enzyme digestion protein

short peptides, mainly dipeptides (60%)
free amino acids (40%)

30

what is the end-products of salivary, gastric and pancreatic enzyme digestion fat

monoglycerides
long chain free fatty acids
glycerol

31

what is interesting about glucose active transport

this mechanism remains intact in diarrhoea/cholera and provides
the scientific basis for oral rehydration supplements: NaCl: glucose: KCl

32

how is Active transport mechanism remains intact in cholera/diarrhoea

SGLT not affected
byVibrio cholera: basis of oral rehydration fluids: contain Na+, K+ and glucose

33

true or false Luminal digestion yields 40% free amino acids and 60% peptides consisting primarily
of 2 to 6 amino acid residues.

true

34

what are Short chain fatty acids: acetate, propionate and butryate formed

fermentation of starch and dietary fibre in the colon (large intestine))

35

what is dietary fibre

Remains of plant cell walls, resistant to digestion

Includes (some) resistant starch
and a variety of miscellaneous compounds

36

uk remended intake of fibre

18g

37

what is glycemic index?

the relative ability of carbohydrate food to increase blood glucose levels.

38

what is the effect of Carbohydrates with a low GI value (55 or less)

are more slowly digested, absorbed and metabolised and cause a lower and slower rise in blood glucose and, therefore insulin levels.

39

what is butyrate

thought
to protect against
colorectal cancer
anti-proliferative (anti-cancer) action

40

what is propionate thought to do?

may
Inhibit food intake
anorectic effect

41

Benefits of non-starch polysaccharides

adsorb bile acids and cholesterol
increased clearance of cholesterol from the body
bile acids may have tumor-promoting action
adsorb potential carcinogens in the colon
increase viscosity of gut contents
slower absorption - may be beneficial in diabetes
bacterial fermentation  mainly acetate, propionate and butyrate
butyrate may have anti-proliferative (anti-cancer) action
propionate may have an anorectic effect (reduce food intake