8 Absorption Of Cho, Protein And Fat

Front 1

Summarise how CHO are absorbed.

Back 1

CHO are hydrolysed by soluable brush border enzymes to monosaccharides.
Absorbed by:
Glu/Gala - SGLT1 (requires Na+)
Fru - GLUT 5
All passed through basal side by GLUT2.

Front 2

Summarise how proteins are absorbed.

Back 2

Proteins are hydrolysed by soluble brush border enzymes to AA or di-/tri-peptides.
Absorved by specific transporters by PepT1 (requires H+) or active diffusion (requires Na+).

Front 3

Summarise how fats are absorbed.

Back 3

Fats are transported in bile micelles, hydrolysed by lipases to glycerol and FFA and absorbed by diffusion.
Reformed and transported out of basal side when exocytosed by chylomicrons into lacteal lymph system.

Front 4

What structural elements do cells have to assist absorption (apical)?

Back 4

1) Microvilli - increase surface area for absorption and transporters.

2) Glycocalyx - Facilitate diffusion type.

Front 5

What is associate with "stirred" and "unstirred" layers?

Back 5

Stirred - Peristaltic contractions, secreted enymes.
Unstirred - Glycocalyx, tethered enzymes

Front 6

What does sucro-isomaltase do?

Back 6

Breaks down CHO, specifically a-limit dexterin (from amylopectin; starch; 90%) where sucrose breaks off the 3 link and isomaltase breaks off the 2 link.

Front 7

True or False: Monosaccharides are the only carboyhydrates able to be absorbed.

Back 7

False, starches can also be absorbed.

Front 8

What starches are absorbed and introduced into the digestive tract?

Back 8

Amylopectin (90%) and amylose (10%; easily digestable).

Front 9

Where is α-amylase secreted?

Back 9

Saliva of the mouth, pancreas.

Front 10

What are the components of sucrose?

Back 10

Glucose + Fructose

Front 11

What are the components of maltose?

Back 11

Glucose + Glucose.

Front 12

What are the components of lactose?

Back 12

Glucose + Galactose.

Front 13

How is Lactose absorbed?

Back 13

Lactose is broken down by lactase into Glucose and Galactose which passes through SGLT1 (with assistance of Na+).

Front 14

Why is Na+ important for glucose transport?

Back 14

Because glucose is dependent on it for transport across the membrane.

Front 15

How is the Na+ gradient maintined on the apical side?

Back 15

Na+ is pumped out of intestinal cells by Na/K pump so that it can continue to enter the cell (high to low) and drag glucose with it.

Front 16

True or False: Fructose passes through the SGLT1 transporter.

Back 16

Flase, fructose, if absorbed, will pass through GLUT5 and exit through GLUT 2.

Front 17

What is the maximum rate of diffusion for glucose?

Back 17

120g per hour, any more will be passed through the digestive system.

Front 18

What is lactase deficiency and what does it result in?

Back 18

Lactase deficiency is the deficiency of the lactase enzyme. Deficiency in lactase means that lactose can not be broken down. Bacteria and gut flora ferment lactose to produce lactic acid, CO2 and H2 which can cause bloating. Lactose can cause diffusion of water into lumen, resulting in osmotic diarrhea.

Front 19

Summarise how amylose is digested and absorbed.

Back 19

α-amylase (saliva, pancreas) break down straight chain amylose into matotriose, which is further broken down into maltose. Moltose is broken down into glucose (x2) and absorbed by SGLT1 transporter.

Front 20

Summarise how amylopectin is digested and absorbed.

Back 20

α-amylase (saliva, pancreas) breaks down kinked chain amylopectin which is converted into α-limit dextrin. Sucrose-isomaltase then breaks down the three and two links and glucose is uptaken by SGLT1.

Front 21

True or False: The digestive tract can only absorb single amino acids.

Back 21

False, di-/tri-peptides can also be absorbed by endocytosis.

Front 22

Summarise protein digestion and absorption.

Back 22

Polypeptides begin digestion in the stomach via pepsin, passed into duodenum where trypsin digests peptides to free amino acids. Amino acids diffuse across the membrane and di-/tri-peptides are transported across PepT1 (with H+ assistance).

Front 23

How is the H+ gradient produced for PepT1 to function?

Back 23

H+ is pumped out of cel by NaH pump. This increases apical acidity levels and excites PepT1 action.

Front 24

True or False: Both the apical and basal side of the cell membrane is dependent on Na+ for diffusion if amino acids.

Back 24

False, only the apical side depends on Na+.

Front 25

What is triglyceride composed of and what are it's functional features?

Back 25

Structure: 3 FA + 1 Glycerol (de-esterification to break down).
Function: Energy storage and transport, insulation and protection,

Front 26

What is phospholipids composed of and what are it's functional features?

Back 26

Structure: 2 FA + 1 Glycerol + Phosphorous group
Function: Cell membrane function (phospholipids; polar and non-polar sides).
Types: Lecithin, Cephalin

Front 27

What synthesises cholesterol and what is it's function?

Back 27

ACoA synthesises Cholesterol.
Function: Cell structure support
Precursor: Bile salts, Vit D, steroid hormones

Front 28

How does emulsification of fats occur?

Back 28

Bile salts contain phospholipid lecithin which has a non-polar tale and polar head. This dissolves the fat into smaller and smaller globules before diffusing into the unstirred layer (glycocalyx).

Front 29

What is the "Critical Micelle Concentration"?

Back 29

A concentration at which fat:detergent proportion looks milky and can be absorbed into unstirred layer.

Front 30

Summarise how triglycerides are digested.

Back 30

Lingual, gastric and pancreatic lipase break down outer 2 fatty acids which allows for the trigylceride to be emulsified (?).

Front 31

What are the stages of fat absorption and what happens during them?

Back 31

Diffusion: mixed micelle diffuses straight across the membrane.

Enterocyte phase: repackage fats for transport by coating it in chlyomicron.|

Exocytosis: Chylomicron is exocytosed into lacteal lymph system and into blood.

Front 32

What are chloymicrons?

Back 32

Lipoproteins that carry lipids into circulation to distribute fat. They are 85% triglyceride and have apolipoproteins and cholesterol elements.

Front 33

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Back 33

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