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Biology Option D > Option D.2 Digestion > Flashcards

Option D.2 Digestion Flashcards

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1
Q

Where is food taken into in mammels?

A

alimentary canal (gut)

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2
Q

What is the alimentary canal?

A

long tube with muscular wall;

food is held in lumen and digested there

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3
Q

What are the glands called that release digestive enzymes?

A

exocrine glands; where secretory cells are arranged

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4
Q

What are major exocrine glands release?

A

gastric glands in stomach; exocrine glands in pancreas;

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5
Q

What fluid is secreted onto food to aid digestion in gut?

A

digestive juice (bunch of enzymes)

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6
Q

Is the secretion of digestive juice continuous?

A

No. Coordination regulated by nervous hormonal mechanisms that ensure secretion:

  • when/where required
  • volume and composition of juice is appropriate to food
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7
Q

What is an example of digestive juice secretion regulated by nervous/hormones?

A
  • sight/smell of food causes brain to send nerve impulses via vagus nerve from medulla;
  • gastric gland cells in stomach wall are stimulated;
  • Gastric juice from gastric glands
  • if receptors in stomach wall detects peptides/distension of stomach, impulses to brain
  • brain responds by sending impulse to secrete gastrin in nearest duodenum;
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8
Q

What is chyme?

A

when food is mixed with gastric juice and churned by muscle action

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9
Q

Describe the mechanism of secretion control in the stomach

A
  • sight/smell of food causes brain to send nerve impulses via vagus nerve from medulla;
  • gastric gland cells in stomach wall are stimulated;
  • Gastric juice from gastric glands
  • includes HCl;
  • makes optimum pH for protease enzymes (pepsin)
  • if receptors in stomach wall detects peptides/distension of stomach, impulses to brain
  • brain responds by sending impulse to secrete gastrin in nearest duodenum;
  • gastrin stimulates secretion of acid and pepsinogen
  • when stomach pH falls to 3.5 gastrin secretion slows (at pH 1.5 it stops);
  • protein acts as buffer so when protein present pH falls more slowly
  • chyme starts entering duodenum only if low in protein, contains glucose and fatty acids
  • if chyme not low in protein, it stimulates lining of duodenum to secrete intestinal gastrin (more gastric juice for more protein digestion;
  • gut wall releases secretin and cholecytokinin
  • decreases gastric juice secretion
  • hormones continue to control secretion in duodenum (pancreatic juice)
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10
Q

What hormones are involved in intestial secretion?

A

gastrin, enterogasterone, secretin, CCK-PZ

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11
Q

How can stomach acid secretion be reduced?

A

secretin and CCK-PZ released;

proton pump inhibitor drugs can also b used which which treat symptoms of low pH;

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12
Q

How do proton pump inhibitor drugs work?

A

surpresses gastric acid production by inhibiting the activity of proton pumps;
raises pH of stomach; may also encourage growth of gut microflora (suseptible to bacterial colonization)

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13
Q

Although the stomach is strongly acidic there is a bacterium that can survive there?

A

Helicobacter pylori

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14
Q

Where does gastrin come from and what is its effect?

A

stomach wall;

- stimulates production of hydrochloric acid by partiel cells and pepsinogen by chief cells, and gastric juices

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15
Q

where does enterogasterone come from and what is its effect?

A

stomach wall;

  • slows flow of gastric juice
  • slows exit of fats from stomach
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16
Q

Where does secretin come from and what is its effect?

A

small intestine;
- stimulates the pancreas to release hydrogen carbonate ions to neutralise acidic chyme (partly digested food) from stomach

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17
Q

Where does CCK-PZ come from and what is its effect?

A

small intestine;

  • stimulates the release of bile from gall bladder
  • release of pancreatic enzymes into small intestine
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18
Q

What is the effect of having helicobacter pylori survive?

A

attaches to receptors on plasma membrane of stomach muscosa under muscus lining;
protected by mucus (of inner lining of gut);
hydrogen ions are neutralized by hydrogecarbonate ions and amonnium ions that the bacterium produced;
persistent presence on exterior of cells causes immune system to sensitize;
antibodies produced in vicinity of infection; killer cells accumulate;
defences cannot reach invading cells on exterior of membrane, they are ineffective

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19
Q

What is the relationship between ulcers and H. pylori?

A

Ulcers were supposed to be caused by H. pylori.;
H.pylori found in patients with ulcers;
antimicrobial drugs are used to kill bacteria and remove H.pylori infection; provides long term relief of symptoms and cure ulcers;
produces toxins that cause inflammation of stomach lining;
can cause stomach cancer

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20
Q

What is the epithelium layer of the small intestine called?

A

Mucosa (with goblet cells)

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21
Q

What do the goblet cells do?

A

secrete mucus (lubricating secretion); protects from mechanical damage

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22
Q

In the structure of a villi in the small intestine, what is the surface of the cells called that face the lumen?

A

apical surface

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23
Q

What is the basal surface?

A

surface of cells in small intestine that face blood vessels

24
Q

What are structural features of the small intestine that aid absorption?

A

villi & microvilli increase surface area , mitochondria, pinocytotic vesicles, basal channels, tight junctions

25
Q

What are pinocytotic vesicles?

A

they take up fluid or release tiny vesicles across plasma membrane of cell;

26
Q

What are basal channels?

A

are channels between epithelium cells and below junctions

27
Q

What are tight junctions?

A

bind together the individual epithelium cells, so that only way into tissues is through epithelium;

28
Q

What must digested material pass through to reach capillary or lacteal vessel?

A

microvilli of epithelial cells

29
Q

What does the epithelium contain to support the absorption in endothelium

A

lots of mitochondria for active transport

30
Q

What parts of the structure of the epithelium of a villi are adapted to absorption?

A

tight junctions - ensure that most materials pass into blood vessels only the epithelial cell;
microvilli - their brush order increases surface area
mitochondria - lots of mitochondria give lots of ATP for active transport
pinocytic vesicles - large number for absorption of food by endocytosis
apical surface & and basal surface - have different protein for material transport

31
Q

How are monosaccharides transported into the epithelial cells?

A

active transport (secondary pumps)

32
Q

How does fructose enter the epithelial cell?

A

facilitated diffusion

33
Q

How are disaccharides transported into epithelial cells?

A

Must be broken down by enzyme, active transport (as monosaccharide)

34
Q

How are short chain peptides transported into epithelial cell?

A
  • attach to specific protease of membrane that make their transport like amino acids; amino acid actively transported into epithelium
35
Q

What passes the epithelium through simple diffusion?

A

short chain fatty acid; vitamins

36
Q

What does the epithelium absorb through facilitated diffusion?

A

fructose (hydrophilic)

37
Q

What passes into the epithelium through active transport?

A

amino acids; mineral ions; glucose

38
Q

What does pinocytosis also draw into the epithelium?

A

small drops of liquid from the ileum

39
Q

What are chylomicrons?

A

triglycerides coated with protein forming spherical masses

40
Q

What happens to material that our body cannot absorb?

A

egested (fraction of food never leaves our body)

41
Q

What does material contain that we cannot absorb/that is egested?

A

contains INSOLUBLE/DIETRY FIBRE

42
Q

What are examples of insoluble fibres?

A

cellulose, pectin and lignin

43
Q

Why can our body not absorb cellulose?

A

do not have cellulase enzymes

44
Q

If we cannot absorb insoluble fibres, are not important?

A

add bulk;
stimulates movement of chyme through gut;
prevents constipation;
speeds up excretion;
slows absorption of glucose (no diabetes II);
reduce desire to eat
reduces risk of colon/bowel cancer;

45
Q

Do soluble or insoluble fibres absorb water?

A

soluble

46
Q

What do mammals use to digest cellulose (don’t have cellulase)?

A

fungi and bacteria that produce cellulase to break down cellulose

47
Q

what is commensalism?

A

microorganisms that do not have any effect on us like bacteria that develop in large intestine

48
Q

What products are egested as feces?

A

excretory products, unabsorbed water, undigested fibre

49
Q

How do soluble fibres help us?

A

slow down rate of digestion; helps contraction of intestinal muscles;

50
Q

How does high water content in intestine affect movement of fecal matter?

A

increase

51
Q

What kind of relationship does rate of transit of materials through large intestine and fibre content have?

A

positively correlated; rate of movement increase as fibre content increases

52
Q

What foods contain dietry fibres?

A

whole grain bread/cereal; vegetables (cabbage/salad)

53
Q

How is cholera caused?

A

infection by bacterium vibrio choleria; acquired from faece- contaminated drinking water

54
Q

What happens normally when vibrio choleria enters body?

A

gets killed by acids

55
Q

What happens if vibrio choleria reaches intestine?

A

attaches to epithelium membrane;
releases toxin to bind to receptor on intestinal cells;
cascade effect;
loss of ions from cells;
outflow of water/body loses lots of fluid (osmosis);
watery diarrhoea; water drawn from blood to replace loss;
death through dehydration

56
Q

What is the B part of a cholera enterotoxin?

A

binding protein; attaches the toxin to a glycolipid on intestine epithelial cell

57
Q

What is part A of a cholera enterotoxin?

A

enzyme; activates plasma membrane of epithelial cell; causes secretion of chloride ions into lumen; cells can’t take up sodium

Biology Option D (7 decks)

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