6.1 Digestion and Absorption

Question 1

mouth

Answer 1

Voluntary control of eating and swallowing

Mechanical digestion by chewing

Chemical digestion by saliva

Saliva moistens food to make a bolus

Question 2

Salivary glands

Answer 2

Produces saliva

Saliva digests starches (contains amylase)

Question 3

Esophagus

Answer 3

Movement of food by peristalsis (waves of muscle contractions) from the mouth to the stomach

Question 4

Stomach

Answer 4

Muscle contractions churn contents (mechanical digestion)

Stomach acid kills foreign bacteria and other pathogens in food

Initial stages of protein digestion by the enzyme pepsin

Question 5

Small intestine - duodenum (start of SI)

Answer 5

Bile from liver and gallbladder neutralize stomach acid and emulsifies fats.

Pancreatic amylase and lipase digests carbohydrates and fats

Trypsin digests polypeptides

Question 6

Small intestine - ileum (lower half of SI)

Answer 6

Absorbs nutrients into the blood via the villi and microvilli

Question 7

Pancreas

Answer 7

Secretion of lipase, amylase and protease into the SI
Neutralizes acidic chyme using sodium bicarbonate

Question 8

Liver

Answer 8

Secretion of bile used to break up lipid droplets

Question 9

Gallbladder

Answer 9

Storage of bile from liver and regulated release of bile into SI

Question 10

Large intestine

Answer 10

Reabsorption of water into the blood
Formation of feces

Question 11

Rectum

Answer 11

Storage of feces

Question 12

Anus

Answer 12

Release of feces

Question 13

Peristalsis

Answer 13

a series of muscle contractions that moves food through the alimentary canal

Question 14

Peristalsis steps

Answer 14

1. Contraction of longitudinal muscle expand the lumen in front of the food giving it space to move into.
2. Contraction of circular muscles behind the food propels it forwards.

Question 15

In the small intestine peristalsis also…

Answer 15

mixes food with enzymes and forces the products of digestion into contact with the wall of the intestine

Question 16

The pancreas synthesises the three main types of digestive enzyme:

Answer 16

amylase to digest starch

lipases to digest lipids

proteases to digest proteins and polypeptides

Question 17

Release of enzymes mediated by…

Answer 17

hormones created and secreted by the stomach

Question 18

Digestive enzymes are created in…

Answer 18

pancreatic gland cells on ribosomes on the rough ER and processed by Golgi and secreted by exocytosis

Question 19

Ducts within the pancreas merge into…

Answer 19

larger ducts and pancreatic duct which release pancreatic juice into the small intestine

Question 20

large food molecules need to be…

Answer 20

digested before the nutrients can be absorbed

Question 21

type of reaction to digest?

Answer 21

catabolic

Question 22

products of digestion are

Answer 22

soluble, small enough for absorption to blood and tissues

Question 23

pancreas enzymes

Answer 23

Amylase
starch —> Maltose

Lipase
triglycerides —> Fatty acids, glycerol

Phospholipase
phospholipids —-> fatty acids, glycerol, phosphate

Protease
proteins, polypeptide —-> Shorter peptides

Question 24

Small intestine enzymes

Answer 24

Nuclease
DNA, RNA —> Nucleotides

Maltase
Maltose —> Glucose

Lactase
Lactose —> Glucose, galactose

Sucrase
Sucrose —> Glucose, fructose

Exopeptidase
Peptides —> dipeptides

Dipeptidase
Dipeptides —> Amino acids

Question 25

Mucosa

Answer 25

inner lining, includes villi

Question 26

Submucosa

Answer 26

connective tissue (between the mucosa and muscle)

Question 27

Muscular layer

Answer 27

inner circular and outer longitudinal muscle perform peristalsis

Question 28

Serosa

Answer 28

protective outer layer

Question 29

Epithelial cells

Answer 29

single outer layer of cells on each villus

Question 30

Many villi protrude into the lumen, greatly increasing the…

Answer 30

surface area for absorption.

Question 31

Absorption:

Answer 31

the uptake of molecules into the blood from the lumen of the ileum.

Question 32

Microvilli

Answer 32

on the surface of each cell to increase surface area even further.

Question 33

Lacteals (lymph vessels)

Answer 33

Allow for rapid absorption and transport of lipids.

Question 34

Capillaries close to epithelium

Answer 34

Short path for diffusion, rich supply of blood

Question 35

Rich blood supply

Answer 35

Maintains concentration gradients between lumen and blood.

Question 36

Single-cell layer of epithelial cells

Answer 36

Short path for diffusion

Question 37

villi absorbs both…

Answer 37

vitamins and minerals

Question 38

Fatty acids Monoglycerides

Answer 38

transport: Simple diffusion

Once inside epithelium cells, fatty acids combine with monoglycerides to which cannot diffuse back into lumen on SI

Question 39

Fatty acids

Answer 39

transport: Facilitated diffusion via transmembrane proteins

Once inside epithelium cells, fatty acids combine with monoglycerides to which cannot diffuse back into lumen on SI

Question 40

Glucose

Answer 40

transport: Facilitated diffusion via glucose channels

Polar molecules, large so simple diffusion cannot occur

Question 41

Sodium

Answer 41

transport: Active transport

Na+ pumped into epithelial cells

Question 42

Sodium and glucose

Answer 42

transport: Sodium-glucose cotransporter
Facilitated diffusion

Transfer Na+ and glucose together

Question 43

The digested glucose is absorbed and then transported to various body tissues (process)

Answer 43

Glucose is co-transported* with sodium ions into the epithelial cells (of the villus).

Glucose moves by facilitated diffusion into the lumen of the villus.

Glucose then diffuses a short distance into the adjacent capillaries where it dissolves into the blood plasma.

Blood in the capillaries moves to to venules then to the hepatic portal vein which transports the glucose to the liver.

The liver absorbs excess glucose which it converts to glycogen for storage.