digestive system

Question 1

what is heterotrophy?

Answer 1

that all animals obtain energy and nourishment from molecules made by other organisms

Question 2

what is digestion?

Answer 2

the hydrolysis of macromolecules into their subunits catalysed by enzymes

Question 3

what are the 4 macromolecules and their monomers

Answer 3

-carbohydrates go to monosaccharides
-proteins go to amino acids
-nucleic acids go to nucleotides
-triglycerides go to monoglycerides and fatty acids

Question 4

what are the 5 main processes that take place in the digestive system

Answer 4

1.ingestion
2.digestion
3.absorption
4.motility
5.excretion

Question 5

what is the order of structures in the GI tract?

Answer 5

1.mouth
2.pharynx
3.oesophagus
4.stomach
5.small intestine
6.large intestine
7.rectum
8.anus

Question 6

what does the mouth do in digestion and what salivary glands does the mouth contain?

Answer 6

mechanical and chemical digestion:
-parotid
-submandibular
-sublingual
-minor glands in inner cheeks

Question 7

what does saliva do and name the three types of salivary enzymes and their examples

Answer 7

it lubricates food and forms a bolus for swallowing:
-amylase
-proteolytic enzymes, lipases, phosphates
-lysozyme and IgA antibodies

Question 8

what is the pharynx

Answer 8

a tube composed of skeletal muscle lined with mucous membrane and muscular contractions propel food into oesophagus

Question 9

what is the oesophagus

Answer 9

muscular tube that secretes mucus, it’s peristaltic movements moves food into the stomach

Question 10

How does the stomach do chemical digestion

Answer 10

by secreting gastric juice:
-parietal cells in gastric glands secrete HCL which lowers the pH to 1.5-2 and so kills many bacteria
-chief cells secrete pepsinogen to form pepsin that hydrolyses protein

Question 11

how are proteins broken down in the stomach?

Answer 11

pepsinogen gets hydrolysed via HCL into pepsin and the proteins get hydrolysed via pepsin into peptides

Question 12

how does pepsin digest proteins?

Answer 12

pepsin digests proteins and peptides by cleaving preferentially after the N terminal of aromatic amino acids such as phenylalanine

Question 13

give three things gastrin does

Answer 13

-simulates secretion of gastric juice
-increases motility of the GI tract
-relaxes the pyloric sphincter

Question 14

what does pancreatic juice contain?

Answer 14

-water, salts, sodium bicarbonate
-digestive enzymes

Question 15

what digestive enzymes are in pancreatic juice?

Answer 15

-pancreatic amylase
-trypsin
-chymotrypsin
-elastase
-carboxypeptidase
-pancreatic lipase
-ribonuclease
-deoxyribonuclease

Question 16

what does the liver do?

Answer 16

-solubilises fat for attack by lipases via release of bile from the gall bladder
-removes toxins
-phagocytoses worn out blood cells and bacteria
-stores and metabolises nutrients and vitamins

Question 17

what enzymes does the small intestine release?

Answer 17

-maltase, sucrase and lactase
-peptidases
-ribonuclease
-deoxyribonuclease

Question 18

what are the three secretions of the small intestine and what do they do?

Answer 18

-secretin: regulates the secretions of the stomach, pancreas and osmoregulation throughout the body
-cholecystokinin: simulates release of digestive enzymes from pancreases and bile from gall bladder acting as a hunger suppressant
-gastric inhibitory polypeptide (GIP) simulates insulin secretion

Question 19

What are the parts of the small intestine?

Answer 19

jejunum, ileum, villi

Question 20

what are the secretory organs in the digestive system?

Answer 20

-salivary glands
-stomach
-liver
-pancreas
-small intestine

Question 21

how are monosaccharides absorbed into the epithelial cells of the villus?

Answer 21

-glucose and galactose diffuse by active transport
-fructose by facilitated diffusion

Question 22

how are amino acids, dipeptides and tripeptides absorbed into the eputhelial cells of the villus?

Answer 22

active transport

Question 23

how are short chain fatty acids absorbed into the epithelial cells of the villus?

Answer 23

via diffusion

Question 24

How are lipids absorbed into the epithelial cells of the villus?

Answer 24

the micelles simply diffuse

Question 25

how is vitamin A and carotenoids absorbed through the villus and into the blood?

Answer 25

1. receptor mediated passive diffusion
2. either incorporated into HDLs and secreted into blood plasma or into chylomicrons and secreted into the lymph

Question 26

what vitamins does the liver store?

Answer 26

lipophilic vitamins such as A, D, E and K

Question 27

what sections does the large intestine consist of?

Answer 27

-caecum (appendix)
-colon
-rectum
-anal canal
-anus

Question 28

what does the large intestine epithelium contain?

Answer 28

-no villi
-numerous microvilli in absorptive cells
-many goblet cells secreting lubricative mucus

Question 29

Give an example of symbiotic bacteria in the GI tract

Answer 29

lactobacillus acidophilus and this produces vitamin B

Question 30

what is helicobacter pylori?

Answer 30

bacteria in the GI tract that causes gastritis and gastric and duodenal ulcers

Question 31

what proteins does pepsin not digest?

Answer 31

proteins that have bonds containing valine, alanine or glycine

Question 32

which layer of the GI tract is closest to ingested food?

Answer 32

serosa

Question 33

what kind of epithelium is that of the stomach?

Answer 33

simple columnar epithelium