3. Digestion & Absorption

Question 1

Ingestion

Answer 1

Taking in food

Question 2

Digestion

Answer 2

The breakdown of large insoluble molecules into small soluble molecules

Question 3

Absorption

Answer 3

Movement of nutrients into cells

Question 4

Assimilation

Answer 4

Using products of digestion to build new parts of the cell

Question 5

Elimination/Egestion

Answer 5

Removing undigested food/material

Question 6

Physical breakdown

Answer 6

Broken into smaller pieces by the teeth and tongue

Question 7

Why is physical breakdown useful?

Answer 7

Increases surface area for action of enzymes

Question 8

Where/how does physical breakdown continue after the mouth?

Answer 8

Continues by churning in the stomach

Question 9

Chemical breakdown

Answer 9

Hydrolysis of large insoluble molecules into smaller soluble ones by enzymes, often in stages.

Question 10

What 3 things does saliva contain?

Answer 10

1. Water - dissolves soluble substances
2. Mucus - lubrication
3. Amylase - hydrolyses starch (which consists of amylose and amylopectin)

Question 11

Does digestion take place in the oesophagus?

Answer 11

NONONO

Question 12

What process moves food through the alimentary canal?

Answer 12

Peristalsis

Question 13

What type of muscles are in the oesophagus?

Answer 13

Circular and longitudinal - they are an antagonistic pair (one relaxes while the other contracts)

Question 14

What do the glands of the stomach secrete?

Answer 14

Gastric juice

Question 15

What does gastric juice contain?

Answer 15

Hydrochloric acid (pH 2) to kill bacteria
Some protease enzymes

Question 16

What does the bolus become in the stomach?

Answer 16

Chyme

Question 17

What is emptied into the duodenum?

Answer 17

Bile from the gall bladder and liver

Pancreatic enzymes

Question 18

What does bile do?

Answer 18

Neutralise acidic contents from stomach

Emulsifies lipids

Question 19

What happens in the large intestine?

Answer 19

Absorption of water

Question 20

What does bacteria in the large intestine do?

Answer 20

Aid digestions & helps to synthesise vitamin K

Question 21

Where is faeces stored?

Answer 21

Rectum

Question 22

The process of removing faeces via the anus is called…

Answer 22

Egestion

Question 23

Pancreatic juice containing pancreatic enzymes is released via…

Answer 23

the pancreatic duct

Question 24

The pancreas synthesises three main types of digestive enzyme:

Answer 24

1. Amylase
2. Lipases
3. Proteases

Question 25

Polysaccharides and disaccharides are digested into monosaccharides by...

Answer 25

hydrolysis of the glycosidic bonds

Question 26

Where are membrane-bound disaccharidases found, and what do they do?

Answer 26

The epithelial lining of the ileum | They hydrolyse the single glycosidic bond

Question 27

How is maltose hydrolysed?

Answer 27

Using maltase: glucose + glucose

Question 28

How is sucrose hydrolysed?

Answer 28

Using sucrase: | glucose + fructose

Question 29

How is lactose hydrolysed?

Answer 29

Using lactase: | glucose + galactose

Question 30

Why is it beneficial for enzymes to be attached to the membranes of the epithelium?

Answer 30

1. Always be in contact: more efficient 2. Don't want to egest enzymes! 3. Could be auto-digested if they come into contact with proteases 4. Enzymes can be reused over and over again

Question 31

What does bile contain?

Answer 31

Bile salts and pigments (bilirubin)

Question 32

Bile salt molecules have...

Answer 32

A hydrophobic surface and a hydrophilic surface. | They are amphipathic!

Question 33

The hydrophobic end of the bile salt molecule...

Answer 33

interacts with the lipid

Question 34

The hydrophilic end of the bile salt molecule...

Answer 34

faces out and prevents lipids from coalescing

Question 35

What do bile salts do?

Answer 35

Divide the fat globule into smaller droplets (emulsification)

Question 36

Why is emulsification useful?

Answer 36

Increases the total surface area available for lipase activity

Question 37

Bile salts enter the ileum via the...

Answer 37

bile duct

Question 38

Bile salts emulsify lipids into...

Answer 38

micelles

Question 39

How do lipases digest lipids?

Answer 39

Hydrolyse the ester bond to form fatty acids and monoglycerides

Question 40

Endopeptidases

Answer 40

Hydrolyse the peptide bond between amino acids in the central region of the protein, forming peptide molecules

Question 41

Exopeptidases

Answer 41

Hydrolyse peptide bonds on the terminal amino acid of the peptides formed by endopeptidases

Question 42

Dipeptidases

Answer 42

Hydrolyse bond between two amino acids of dipeptide

Question 43

What is special about dipeptidases?

Answer 43

They are membrane-bound in the ileum

Question 44

What type of protease is found in the gastric juice in the stomach?

Answer 44

Endopeptidase

Question 45

What type of protease is found in the pancreas?

Answer 45

Endopeptidase AND exopeptidase

Question 46

What type of protease is found in the epithelium of the small intestine?

Answer 46

Dipeptidase

Question 47

Serosa

Answer 47

Outermost layer of the ileum. It is strong and protective.

Question 48

Muscularis

Answer 48

Right after the serosa: consists of inner (circular) and outer (longitudinal) muscles which perform peristalsis

Question 49

Sub-mucosa

Answer 49

Right after the muscularis: connective tissue between the mucosa and muscle

Question 50

Mucosa

Answer 50

Right after the sub-mucosa | Inner lining which includes villi

Question 51

Location of villi and microvilli

Answer 51

Circular folds in the mucosa contain villi. | Epithelial cells on each villus contain microvilli.

Question 52

Co-transport

Answer 52

Glucose & amino acids

Question 53

Facilitated diffusion

Answer 53

Monosaccharides

Question 54

Simple diffusion

Answer 54

Triglycerides

Question 55

Initially, absorption of monosaccharides and amino acids will be by...

Answer 55

facilitated diffusion

Question 56

What is the problem with only facilitated diffusion in absorption of monosaccharides and amino acids? What is the solution?

Answer 56

Diffusion can only result in equal concentrations either side of the intestinal epithelium. Therefore active transport is involved in the uptake of these monomers.

Question 57

How is active transport of monosaccharides and amino acids carried out?

Answer 57

Via co-transport using sodium ions (review from previous topic)

Question 58

What happens following emulsification?

Answer 58

The bile salts remain associated with monoglycerides and fatty acids, forming micelles

Question 59

What happens when micelles come into contact with the epithelium of the ileum? What happens after that?

Answer 59

They break down, releasing monoglycerides and fatty acids. | Because they are non-polar molecules, they easily diffuse across the cell surface membrane into the epithelial cells.

Question 60

What happens to the monoglycerides and fatty acids once inside the epithelial cells?

Answer 60

They are transported to the smooth endoplasmic reticulum and reformed into triglycerides.

Question 61

What happens after triglycerides are reformed in the epithelium?

Answer 61

They associate with cholesterol and lipoproteins in the ER and Golgi to form chylomicrons

Question 62

What are chylomicrons?

Answer 62

Lipoprotein particles that consist of triglycerides, phospholipids, cholesterol and proteins that transport dietary lipids from the intestines to other locations in the body

Question 63

What happens right after chylomicron formation?

Answer 63

They enter the lacteal via exocytosis, and enter the blood circulation via the lymphatic system. Enzymes in the endothelium of the blood vessels hydrolyse the triglycerides and they diffuse into cells.