Nutrient digestion and absorption Flashcards
what are the principle dietary constituents
Carbohydrate
Protein
Fat
Vitamins
Minerals
Water
monosaccaride
Monosaccharides are the simplest carbohydrates; most of them are sugars - fructose, galactose, glucose
disaccaride
sugar formed when two monosaccharides (simple sugars) are joined by glycosidic bond - sucrose, lactose, and maltose.
Oligosaccharides
Oligosaccharides are a type of carbohydrate chain made up of three to 10 simple sugars, which are also known as monosaccharides - glucose, fructose
polysaccaride
They are long chains of carbohydrate molecules, composed of several smaller monosaccharides.
10 or more monosaccarides
aldoses
An aldose is a monosaccharide (a simple sugar) with a carbon backbone chain with a carbonyl group on the endmost carbon atom, making it an aldehyde
ketoses
if a monosaccharide has a ketone group on one of the inner atoms of the carbon chain it is classified as a ketose.
glucose and galactose ketone or aldehyde
aldoses
fructose ketone or aldehyde
ketone
B-hydroxyl group
when the hydroxyl group is above the anomeric carbon
A-hydroxyl group
when the hydroxyl group is below the anomeric cabon
monosaccarides examples
what do they result from
Hexose sugars (6C) - glucose, galactose, fructose
Breakdown products of complex CHOs which are absorbed by small intestine
disaccarides examples
what are they and what do they result from
Two monosaccharides linked together by glycosidic bond
Broken down to constituent monomers by brush border enzymes in small intestine
Lactose = glucose + galactose (lactase)
Sucrose = glucose + fructose (sucrase)
Maltose = glucose + glucose (maltase)
what type of bond does starch contain
D-glucose units are connected with α-glycosidic bonds in starch
what type of bond does cellulose contain
D-glucose units are connected with β-glycosidic bonds in cellulose
what is Starch
plant storage form of glucose
what makes up starch polysaccharides
α-amylose: glucose linked in straight chains
amylopectin: glucose chains highly branched
Glucose monomers linked by α-1,4 glycosidic bonds - hydrolysed by amylases (saliva, pancreas)
what are α-1,4 glycosidic bonds hydrolysed by
amylases in saliva and pancreas
what is cellulose
constituent of plant cell walls
what makes up cellulose
Unbranched, linear chains of glucose monomers linked by β-1,4 glycosidic bonds
Dietary fibre (no enzymatic digestion in vertebrates - require bacteria (cellulase))
what is glycogen
animal storage form of glucose
Glucose monomers linked by α-1,4 glycosidic bonds
(cellulose)
B-1,4 glycosidic bonds
what happens when digested by A-amylase
results in A-1,4 glycosidic bonds
(starch, glycogen)
what happends when starch and glycogen are broken down by amylase
disaccharides - maltose, sucrose, lactose produced
what is the normal digestion of lactose
lactase breaks down lactose into glucose and galactose
if someone is lactose intolerent what happens to lactose
there is no lactase so bacteria ferments and acids and gases are produced causing irritation
maltose components
glucose and glucose
sucrose components
glucose and fructose
lactose components
galactose and glucose
what breaks down maltose
maltase into 2 glucose
what breaks down sucrose
sucrase into 1glucose and 1 fructose
basolateral membrane
membrane facing away from the lumen, faces blood vessels of small intestine
apical membrane
brush border bristles (microvilli), increasing surface area, faces lumen
tight junction complex
proteins
Polymers of amino acids linked together by peptide bonds
what is often undergone by proteins
post-translational modification (eg addition of CHO = glycoprotein; lipid = lipoprotein)
what are enzymes which hydrolyse peptide bonds and reduce proteins or peptides to amino acids called
proteases, peptidases
