GI 8

Question 1

digestion

Answer 1

physical and chemical breakdown of ingested foods into absorbable molecules

Question 2

Primary Site of Digestion?

Answer 2

Small intestine

Question 3

Where do most enzymes in the small intestine come from?

Answer 3

the pancreas

Question 4

absorption

Answer 4

movement of neutrients, water, and electrolytes from the lumen of the intestine into the bloodstream

Question 5

3 Components of the Intestine that increase Surface Area

Answer 5

1. Villi
2. Microvilli
3. Glycocalyx

Question 6

glycocalyx

Answer 6

intestinal brush border on surface of microvilli, holds enzymes secreted from intestinal epithelial cells

Question 7

2 Major Forms of Starch

Answer 7

1. Amylose
2. Amylopectin

Question 8

Major Action of digestive enzymes?

Answer 8

hydrolysis

Question 9

2 Phases of Digestion

Answer 9

1. Luminal phase
2. Membrane phase

Question 10

Explain starch digestion by hydrolysis.

Answer 10

enzymes break bonds of the starches during the luminal phase into smaller molecules, but complete hydrolysis occurs during the digestive phase into singular monomers to be absorbed by the intestinal epithelium

Question 11

Luminal phase of digestion

Answer 11

incomplete hydrolysis of nutrients

Question 12

Membrane (brush border) phase of digestion

Answer 12

generates absorptive molecules or very short oligomers

Question 13

What is a possible third step in digestion?

Answer 13

cytosolic proteolysis

Question 14

Cytosolic proteolysis

Answer 14

short peptides undergo further digestion within the intestinal epithelial cell (cytosol) by intracellular hydrolases

Question 15

2 Paths for Absorption

Answer 15

1. Transcellular Path
2. Paracellular Path

Question 16

transcellular path for absorption

Answer 16

nutrient moves through intestinal cell into the interstitial fluid

Question 17

paracellular path for absorption

Answer 17

nutrients move across tight junctions between the intestinal epithelial cells

Question 18

Most common path for nutrient absorption?

Answer 18

transcellular path

Question 19

4 Transcellular Transport Mechanisms

Answer 19

1. Passive transport (facilitated diffusion)
2. Primary active transport
3. Secondary active transport
4. Tertiary active transport

Question 20

How are the active transport mechanisms named?

Answer 20

based on where the energy comes from

Question 21

Primary Active Transport

Answer 21

direct consumption of metabolic energy, move across a membrane d/t presence of electrical or chemical gradient

Question 22

2 Examples of Primary Active Transport Pumps

Answer 22

1. Sodium-Potassium-ATPase pump
2. Proton pump on parietal cells of gastric acid secretion

Question 23

On which aspect of the cell will you find your primary active transport pumps?

Answer 23

basolateral side

Question 24

Sodium Potassium ATPase Pump

Answer 24

pumps 3 Na+ in and 2 K+ out to create a gradient within the cell and generate energy for use by other transporters

Question 25

Two Types of Secondary Active Transporters

Answer 25

1. Sodium co-transporters 2. Exchangers (countertransport, antiport)

Question 26

Sodium CoTransport Protein

Answer 26

has binding sites for Na+ and other specific molecules (glucose, galactose, AAs, vitamins, bile acids)

Question 27

Secondary Active Transport

Answer 27

transport using the potential energy of a sodium gradient (rather than a direct use of metabolic energy)

Question 28

Exchangers

Answer 28

binding sites for two different ligands on opposite sides of the plasma membrane

Question 29

Tertiary Active Transport

Answer 29

driven by electrochemical gradients that were established by secondary active transport

Question 30

Of these pumps, label what type of transport each is.

Answer 30

Red = Primary Purple = Secondary (exchanger) Green = Secondary (sodium cotransporter) Yellow = Tertiary

Question 31

What is a starch?

Answer 31

glucose polymer

Question 32

Three Forms of Plant Carbohydrates

Answer 32

1. Starches 2. Sugars 3. Fibers

Question 33

How does the body digest fiber?

Answer 33

it is dependent on bacteria

Question 34

End product of carbohydrate digestion? (3)

Answer 34

Monosaccharides! 1. Glucose 2. Fructose 3. Galactose

Question 35

Fructose absoprtion is by what transport mechanism?

Answer 35

facilitated diffusion

Question 36

Glucose and galactose are absorbed through the apical surface by what transport mechanism?

Answer 36

Secondary active transport by cotransporters (specifically SGLT-1, sodium ______ linked tranporters)

Question 37

How are monosaccharides absorbed on the basolateral side?

Answer 37

facilitated diffusion (all three)

Question 38

oligomer

Answer 38

short peptide

Question 39

monomer of protein

Answer 39

amino acid

Question 40

Can carbs be digested with cytosolic proteolysis?

Answer 40

no

Question 41

5 Pancreatic Proteases

Answer 41

1. Trypsinogen 2. Chymotrypsinogen 3. Proelastase 4. Procarboxypeptidase A 5. Procarboxypeptidase B

Question 42

Are any of the proteases secreted in active form?

Answer 42

no, all as zymogens from the pancreas

Question 43

Which protease is secreted the most?

Answer 43

trypsinogen (40% of all proteases)

Question 44

Where do you find pepsinogen and when is it activated?

Answer 44

in the stomach; activated as long as pH in the small intestine remains below 4.5

Question 45

What enzyme in the small intestine converts trypsinogen to its active form? Where is this found?

Answer 45

enterokinase, in the brush border (glycocalyx)

Question 46

What activates the remaining proteases in the small intestine?

Answer 46

trypsin

Question 47

Can trypsin act on trypsinogen?

Answer 47

yes

Question 48

Is protein digestion by pepsin in the stomach essential?

Answer 48

no, it is non-essential

Question 49

Peptidases

Answer 49

additonal enzymes present in the membrane phase of digestion to continue to break down proteins into monomers and oligomers

Question 50

Mechanism of amino acid transport across the apical membrane?

Answer 50

Secondary active (sodium cotransporter)

Question 51

Mechanism of dipeptide and tripeptide absorption across the apical membrane?

Answer 51

PEPT-1 (peptide transporter 1), cotransporter with H+ ion

Question 52

Mechanism by which amino acids cross the basolateral membrane?

Answer 52

facilitated diffusion

Question 53

Are lipids water soluble?

Answer 53

no

Question 54

3 Dietary Lipids

Answer 54

1. Triglycerides 2. Cholesterol 3. Phospholipids

Question 55

amphipathic

Answer 55

hydrophilic and hydrophobic components

Question 56

Emulsification

Answer 56

bile salts surround lipids (preventing them from joining as one large glob, increasing surface area) and form micelles

Question 57

Micelle

Answer 57

lipid droplet surrounded by bile salts carried to the intestinal epithelial cells before the hydrophillic side dissolves inthe aqueous part

Question 58

Are all enzymes for lipid digestion secreted as zymogens?

Answer 58

No, some are secreted in active form (such as those for cholesterol esters or triglycerides (lipases))

Question 59

5 Steps of Lipid Absorption

Answer 59

1. Form micelles in the lumen 2. Diffuse across apical membrane 3. Re-esterification 4. Packaged into chylomicrons (vesicles) 5. Excytosed across basolateral membrane into lymph (thoracic duct), and eventually to blood

Question 60

Where are bile salts absorbed?

Answer 60

ileum

Question 61

What % of lipid digestion products are re-esterified inside the cell?

Answer 61

70

Question 62

Are fat soluble vitamins absorbed the same way as lipids?

Answer 62

yes

Question 63

Mechanism of water soluble vitamin transport?

Answer 63

Soium-dependent cotransporters (secondary active transport) (just like glucose, galactose, and AAs)

Question 64

Vitamin B12 absorption?

Answer 64

dependent on the intrinsic factor released by parietal cells, happens in the ileum