Lecture 32 - Carbohydrate Digestion & Absorption

Question 1

Enteroendocrine cells are derived from crypt cells and migrate up

Answer 1

The crypt-villus axis

Question 2

Digestion:

Answer 2

Process of breaking dietary compounds into simple molecules that can be absorbed

Question 3

Absorption:

Answer 3

Simple molecules generated from digestion are transferred into blood or lymph

Question 4

From lumen to capillary blood, nutrient molecules need to cross

Answer 4

Apical membrane: between lumen and intracellular space and extracellular fluid
Basolateral membrane: between intracellular space and extracellular fluid

Question 5

Cell membranes are composed of

Answer 5

A bilateral membrane of phospholipids: a hydrophilic head extending into the aqueous fluid on the outside and inside of the cell and hydrophobic tails between hydrophilic surfaces

Question 6

Interspersed among the phospholipids are various types of proteins:

Answer 6

Transporters, pumps, and channels are important for material to cross the lipid bilayer

Question 7

Lipid-soluble hydrophobic compounds can easily cross the

Answer 7

Lipid bilayer of cell membranes

Question 8

Water hydrophilic materials cannot easily cross the

Answer 8

Lipid bilayer on their own

Question 9

Particles will also move from one compartment of high concentration to another compartment of low concentration, if

Answer 9

The barrier between the two compartments is permeable to the substance

Question 10

The chemical driving force is proportional to

Answer 10

The concentration gradient

Question 11

If there is more than one molecule crossing a cell membrane, does each kind have its own concentration gradient or chemical gradient

Answer 11

Yes

Question 12

In electrical driving force, same charges _______ & opposite charges _______

Answer 12

Repel, attract

Question 13

In the resting cell, cations are attracted to the __________ of the cell and anions are attracted to the ___________ of the cell

Answer 13

Interior, exterior

Question 14

The magnitude of the electrical force depends upon the

Answer 14

Size of the membrane potential and the charge of the ion

Question 15

The greater the membrane potential or the charge of the ion the greater the

Answer 15

Electrical driving force

Question 16

The more lipid soluble a substance is the greater the _____

Answer 16

Permeability to that substance in phospholipid bilayers

Question 17

When going through a phospholipid bilayer, the membrane permeability is lesser if

Answer 17

The molecule is larger and more irregular in shape

Question 18

Can fatty acids and triglycerides freely cross the lipid bilayer down their concentration gradient?

Answer 18

Yes, even though they are very large and can be charged, they are very lipid soluble

Question 19

What is passive transport?

Answer 19

Molecules moving down their electro/chemical gradient to the other side of the membrane. No energy used

Question 20

All epithelial cells lining the GI tract have an

Answer 20

Apical and basolateral membrane

Question 21

Adjacent epithelial cells in the GI tract are linked to another on all sides by

Answer 21

Tight junctions

Question 22

Tight junctions form a seal between cells that is relatively impermeable to

Answer 22

bacteria, viruses, and large molecules that have been ingested

Question 23

The tight junctions also provide resistance to the passage of

Answer 23

Small ions and water, but can be overcome if electrochemical forces are great enough

Question 24

Paracellular transport is

Answer 24

Movement of solute across the tight junctions between enterocytes

Question 25

Accumulation of negatively-charged chloride anions creates an electric potential that attracts

Answer 25

Sodium, pulling it across tight junctions into the lumen. The net result is secretion of NaCl

Question 26

Secretion of NaCl creates an osmotic gradient across the tight junction and

Answer 26

Water is drawn into the lumen

Question 27

What is transcellular absorption?

Answer 27

Most of the nutrients of the body are too large to cross the tight junctions and must be moved across the absorptive enterocytes. Think endocytosis or exocytosis

Question 28

The mechanism used to transport a solute across the apical membrane is often different from that used to transport the same solute across the….

Answer 28

Basolateral membrane

Question 29

Exocytosis

Answer 29

Vesicles fusing with the plasma membrane and releasing their contents to the outside of the cell

Question 30

Endocytosis

Answer 30

Engulfing substance from outside the cell with the cell membrane, and bringing it into the cell

Question 31

LOOK AT SLIDE 33 TO GET DIAGRAM ABOUT TRANSCELLULAR / PARACELLULAR PROCESSES. Did u do it ???????

Answer 31

yes <3 i am gonna slay this midterm

Question 32

Paracellular transport is ________ driven and only functions when _______________

Answer 32

Concentration, when solute concentration in the lumen is very different than the concentration in the extracellular fluid

Question 33

The most important enzymatic reaction in digestion is

Answer 33

Hydrolysis - the breaking of a chemical bond by the addition of a water molecule

Question 34

The diet of any animal contains hundreds of if not thousands of of different molecules but the bulk of the ingested nutrients are in the form of huge macromolecules that cannot be absorbed into the blood without first being reduced to

Answer 34

Much simpler and smaller forms of the molecule

Question 35

Monosaccharides

Answer 35

Either 6 carbon sugars like glucose and galactose or 5 carbon like fructose

Question 36

_________ are the breakdown products of more complex carbohydrates and can be efficiently absorbed across the wall of the digestive tube and transported into the blood

Answer 36

Monosaccharides

Question 37

Disaccharides

Answer 37

Two monosaccharides linked together

Question 38

Most important disaccharides in nutrition and digestion are

Answer 38

Lactose and sucrose

Question 39

Oligosaccharides

Answer 39

Relatively short chains of monosaccharides

Question 40

What are intermediates in the breakdown of polysaccharides to monosaccharides

Answer 40

Oligosaccharides

Question 41

What are the most abundant dietary carbohydrates for all animals except very young ones?

Answer 41

Polysaccharides

Question 42

Name 3 large polymers of glucose

Answer 42

Starch, cellulose, glycogen

Question 43

Starch

Answer 43

A major plant storage form of glucose. Glucose molecules are linked by alpha (1-4) glycosidic bonds

Question 44

Cellulose

Answer 44

The other major plant carbohydrate. It’s the major constituent of plant cell walls

Question 45

Cellulose - glucose molecules are linked by

Answer 45

Beta (1-4) glycosidic bonds.

Question 46

Can vertebrates enzymatically digest beta (1-4) glycosidic bonds

Answer 46

No

Question 47

Glycogen

Answer 47

Major animal storage form of carbohydrate. It is multi-branched

Question 48

Glycogen - what links glucose molecules

Answer 48

Alpha (1,4) glycosidic bonds.

Question 49

Where does fructose come from

Answer 49

Fructose is a naturally occurring sugar found primarily in fruits (such as apples, dates, figs, pears, and prunes) Vegetables (such as sugar beets, sugar cane, artichokes, asparagus, mushrooms, onions, and red peppers Honey

Question 50

What begins the digestion of starch and glycogen and reduces them to disaccharides or oligosaccharides

Answer 50

Salivary and pancreatic amylase

Question 51

Do stomach acids and proteolytic enzymes have any effects on starches

Answer 51

Nope

Question 52

If u have 1M of glucose monomers and 1M of maltose (a disaccharide), do they have the same osmolarity?

Answer 52

Yes, as it depends on osmolarity

Question 53

What is the brush border

Answer 53

The microvillus border of intestinal epithelial cells

Question 54

What are brush border enzymes

Answer 54

Enzymes present on the apical membrane of absorptive cells lining the small intestines, complete digestion to monosaccharides

Question 55

Transporter proteins located near brush border enzymes facilitate

Answer 55

Absorption of monomers

Question 56

Example of development changes according to food intake

Answer 56

Lactase, which digests milk lactose, is found on the enterocyte brush border of all mammalian neonates. It often disappears after the animal is weaned. OR Sucrase, which digests sucrose, is often lacking in neonates and is expressed only after the animal is several weeks old

Question 57

Carbohydrate intolerance is the

Answer 57

Inability to digest certain carbohydrates due to a lack of one or more intestinal enzymes

Question 58

CHO intolerance - undigested disaccharides cause an osmotic load that attracts water and electrolytes into the bowel, causing

Answer 58

Water diarrhea. Bacterial fermentation of CHO in the colon produces gases (hydrogen, CO2, and methane), resulting in excessive flatulence, bloating and distension, and abdominal pain

Question 59

Treatment of CHO intolerance

Answer 59

Removal of the causative disaccharides from the diet

Question 60

Lactose intolerance (shoutout steph) is a digestive disorder caused by the

Answer 60

The inability to digest lactose, the main CHO in dairy products

Question 61

Lactose intolerance can cause

Answer 61

Various symptoms, including bloating, diarrhea, and stomach cramps

Question 62

People with lactose intolerance (steph its ur moment to shine) dont make enough of

Answer 62

The enzyme lactase

Question 63

Does lactose intolerance happen in dogs

Answer 63

Yes & it can cause diarrhea, vomiting, lack of appetite, bloating, flatulence

Question 64

Absorption of monosaccharides entails transport from

Answer 64

The intestinal lumen, across the epithelium and into the blood

Question 65

Monosaccharides liberated by the brush border enzymes are too large to cross the

Answer 65

Apical membrane easily

Question 66

Monosaccharides concentration over the apical membrane rises following a meal so there is a concentration gradient that can help them cross into

Answer 66

The cytoplasm, which the help of transporters (both active and passive)

Question 67

Once inside cytosol, the sugars exit the cells across the basolateral membrane by

Answer 67

Facilitated diffusion

Question 68

Why doesn’t the intestine digest all dietary starch and disaccharides to monosaccharides in the lumen?

Answer 68

The reason digestion is completed at the brush border is to prevent the osmolarity of the lumen contents from rising too high and drawing excessive amounts of water into the lumen. By liberating monomers in the brush border they can be absorbed almost as soon as they are liberated, preventing a rise in the osmolarity of the lumen contents

Question 69

Excess glucose gets stored in the

Answer 69

Liver and skeletal muscles as glycogen or, with the help of insulin, converted into fatty acids, circulated to other parts of the body and stored as fat in adipose tissue.

Question 70

Glucose can be converted to fatty acids and cholesterol through

Answer 70

De novo lipid biosynthesis pathways

Question 71

Diabetes is more common in __________ but can also occur in younger or pregnant pets

Answer 71

Older pets

Question 72

Diabetes is more manageable if

Answer 72

It’s detected early and managed with the help of a veterinarian

Question 73

Can diabetic pets have long and happy lives

Answer 73

Yes! With proper monitoring, treatment, diet, and exercise