nutrient digestion and absorption 1 Flashcards
how can you hydrate?
drinking water, and also through our skin (!) so if sick and dehydrated, we can lie in a cool bath and eventually we’ll need to wee!!
What are the 3 monosaccerides?
glucose, galactose and fructose
(Go GirlFriend)
Where are monosaccharieds absorbed?
Small intestine
What form of carbs can be absorbed in the small intestine (only form of carbs that can be absorbed)
Monosaccharides
WHat is a glycosidic bonds?
The bonds between monosaccarides (form disaccarides and polysaccharides)
Where are disaccharide glycosidic bonds broken down?
small intestine - brush border enzymes
What are the 3 dissacharides and what are they composed of and enzzyme and where found?
Lactose - glucose and galactose - lactase - brush boarder(Small intestine)
Maltose - Glucose +glucose - maltase - brush boarder(SI)
Sucrose - Glucose and fructose - sucrase - brush boarder (SI)
Lots More Sugar!
how do plants store carbs?
Startch!!
alpha amylose vs amylopectin
alpha amylose - glucose in straight chains
amylopectin - highly branched glucose
How are glucose monomers linked in starch and how is it hydrolysed ? Where?
Alpha - 1, 4 glycosidic bonds, hydrolysed by amylases (saliva, pancreas)
How is cellulose (plant cell wall) joined together? Can we digest? Who can digest?
Beta 1,4 glycosidic bonds. No vertebrate can digest… BUT bacteria can, so they do it for us in the large intestine
how is glygogen bonded
Alpha 1,4 glycosidic bonds
Lactose intollerencec meaning and consequenses
don’t have/reduced lactase enzyme. Cand break dopwn lactose. Osmosis, influx of water, diiahhorea
Where is the brush boarder? what is the brush boarder comprised of? What joins the apical membranes? How can we remember what it is?
Apical surface of epithelial cells in the small intestine. Has loads of microvilli to increase absorption. Apical membranes joined by tight junctions. Like Bart simpsons heads (the cells)
How can food etc travel across epithelial cells?
Transcellular (often using vector enzyme) or paracellular (between the cells - think tight junctions as the plastic bit that use to hold beer cans together)
How are proteins formed from within cells?
Transcription by DNA, translation by RNA, rough endoplasmic reticulum (has ribosomes - puts amino acid in order) creates protein and is quality checked by the golgi apperatus.
How is glocose (D) transported across the epithelial cells, can there be a problem with this?
Trans cellular - via a vector (think transporter across cell, as only fat soluble things can pass through the cell membrane.
Yes, sometimes people may not have this vector and means that glucose can’t be absorbed! Big issue.
What decides if the protein goes to the baso or apical membranes?
The golgi apperatus
Where is the ncleus usually on these cells?
Which 2 membranes are there in these epithelial cells?
Basolateral and apical (apical has barts hair)
How many transport proteins are required for vectorial transport across the epithelial cells?
At least 2!
What is glucose glactose malabsorptionn syndrome?
When the vector for transporting one of the isomers of glucose is missing.
Where is the na k atpase pump found? in epithelial cells
Basolateral membrane
Na K conc in cells
Na is pumped out, so low conc in the cell, K is pumped in so higher in the cell (because 3 Na out for 2 K in)
charge inside vs charge outside cell
relatively negative charge inside the cell
SGLT1 is expressed where and does what?
SGLT1 (Sodium Glucose L Transporter 1)
On the apical membrane of cells in the small intestine.
Requires 2 Na and 1 glucose to attach to undergo a conformational change and move them into cell.
Na K ATPase pump keeps Na electrochemical gradient pulling in the v strong, so even when against glucose gradient, it is pulled into cells.
How does glucose go against its concentration gradient into the epithelial cells?
Because of the Na Electochemical gradient, so Na is drawn in and so is glucose
What does GLUT-2 do?
It facilitates the diffusion of glucose out of the cell and into the blood stream
What mode of transport is SGLT 1?
secondary active transport (can only occur secondary to the active Na K ATPase pump)
SGLT 1 works for which sugars?
Glucose and galactose
How is fructose transported?
Through glut 5 (no maintenance of blood fructose level) so it is facilitatidly diffused accross the membrane
What escapes via glut 2?
Glucose, galactose and fructose
Does fructose lead to an osmotic effect of bringing water into the cell through its absorption?
Nope, becuase it doesn;t bring in any Na ions
What is the primary route for getting water into the blood stream and body?
Because of the osmotic gradient caused by the sodium being transported across the epithelial cells
What makes up a protein?
amino acids (amino NH2 and acid COOH) joined by peptide bonds (CONH)
How many amino acids for peptides?
2-10 then becomes a protein
how are peptide bonds broken down?
Through proteases/peptidases hydrolysis (breaking down with water)
Endopeptidase (breaks splits up amino acids into smaller amino acids)
Exoprotease - splits off ends of amino acids (aminopeptidase and carboxypeptidase)
where does an endopeptidase work?
In the middle of an amino acid
What are the 2 types of exopeptidase?
Carboxypeptidase and aminopeptidase
How are the majority of individual amino acids taken into the cell?
Through a similar way to glucose (but many different specific transports, eg SAAT1) but essentially though secondary active transport using Na as a driver into the cell.
How do the amino acids leave cell?
Through a specific sodium independent amino acid carrier (facilitated diffusion)
Does amino acids transport bring water into the cells?
Yes, because Na is brought across, so therefore the osmotic gradient means that water is brought across too.
Is the brush boarder acidic?
Yes, because the main way that peptides are transported across the cell is through using a proton motive force
How are most peptides transported across the cell? (and therefore most forms of protein ~70%)
Through PepT1 (Peptide transporter1), H+ and Dipeptide/tripeptide transported across, (down H gradient), then H pumped back out with Na coming in (NHE3 - Sodium Hydrogen Exchange 3). All in apical membrane.
Na pumped out basal membrane (NaKATPase pump)
