M104 T1 L8 * T7 is in folder T2 Flashcards
What types of persitalsis are there?
segmentation - at the brush border
haustra churning - in the LI
What proportion of the NHS Eat Well Plate consists of carbohydrates?
a third of total dietary intake
What are the three monosaccharides?
glucose
fructose
galactose
What are the three disaccharides? MSL
sucrose
lactose
maltose
What are the three brush border enzymes that digest disaccharides?
sucrase
lactase
maltase
What are the two oligosaccharides?
raffinose
stachyose
What is a special feature of oligosaccharides regarding their digestibility?
they are resistant to digestion and often pass unchanged into the colon
AAR they contribute to the faecal matter and also help support the microbiome
What are Lactulose-derived oligosaccharides used for?
to treat constipation
What happens to Lactulose once it enters the digestive system?
is not digested by the SI - it travels unchanged into the colon
through osmosis, more water enters the colon, softening the stools to facilitate defaecation
What are the three polysaccharides?
starch
glycogen
cellulose
What are the four groups of carbohydrates?
monosaccharides
disaccharides
oligosaccharides
polysaccharides - the main polysaccharide in diet
What is each starch mlc made up of?
two glucose mlcs
What are the two types of non storage polysaccharides?
cellulose - insoluble
pectin - soluble
What two processes convert carbs into E in the body?
glycolysis
the Citric Acid Cycle
What are normal serum blood glucose levels?
4 - 7 M/L
What is a special feature of oligosaccharides regarding their digestibility?
they aren’t digested in the GI tract
they are important to provide faecal bulk which allows the excretion of dead cells and the increase of transit time
What are the polyunsaturated FAs otherwise known as?
the essential FAs
What does 95% of dietary fat intake consist of?
Triacylglycerol
What happens to essential FAs once consumed?
they are elongated, desaturated and used in synthesis
What product is formed from linoleic acid?
arachidonic acid
What products are formed from a-linoleic acid?
eicosapentaenoic acid
docosahexaenoic acid
What are two dietary sources of linoleic acid?
vegetable and safflower oils
What are four dietary sources of a-linoleic acid?
green leafy vegetables
canola
wheat and soybean oils
What are the omega-3 FAs?
ALA, EPA and DHA
What are three dietary sources of arachidonic acid?
meat, poultry and eggs
What are the dietary sources of EPA and DHA?
oily fish
What is the role of lipoprotein lipase?
mediates the storage of adipose tissues in the outermost tissue
How is the action of lipoprotein lipase affected by the presence of insulin?
insulin - upregulated
FA release during fasting - downregulation
What is the effect of fat on food?
it enhances flavour and increases palatability
Which vitamins are contained in fats?
the essential fat soluble vitamins A D E K
What is vitamin A important for?
black and white vision
What is vitamin D important for?
the absorption of calcium - maintains good bone health
has the potential to protect against the negative impacts of COVID
What term is associated with vitamin E?
antioxidant
What is vitamin K important for?
its role in the clotting cascade
What is white brain matter predominately composed of?
fat
What are fats the precursors of?
steroids, hormones and some vitamins
What are the three macronutrients?
fat
protein
carbohydrates
What is added to low fat yoghurt to make it less runny than it is?
carbohydrates and gums
gives it a similar consistency to high fat yoghurts
Are there any stores of protein or fat in the body?
protein - none at all
fat - glycogen
What is a waste product of deanimation?
alpha ketoacid residues
What are alpha ketoacid residues from deanimation used for?
as E for metabolic pathways of glucose or FAs
What happens to excess alpha ketoacid residues?
they are excreted as urea and ammonium via urine
What can be made from the amac pool inside the body?
amac derivatives (e.g. NTs)
What are the protein requirements for normal and older adults in g/kg/day?
normal - 0.8g/kg/day
elderly - 1.2g/kg/day
How are the protein requirements for patients with acute illness affected / deviated from normal level?
will exceed normal levels bc the immune response requires more to allow full recovery and repair so tissue proteins are broken down and amacs are used for other functions instead
in an acute illness, there is often a negative nitrogen balance due to inflammation induced catabolism (COVID19)
How many amacs are needed in the body?
20 amacs
What are the three types of amacs needed in the body?
essential (9)
non-essential (4)
conditionally non-essential (7)
What essential precursor does tyrosine amac require?
phenylalanine
In what conditions will glutamine be depleted?
burns, COVID or sepsis
How are conditionally non-essential amacs sourced?
mostly from the normal everyday breakdown of cells within the body - non essential
but in hypercatabolic states, will be required from diet to meet the shortfall fall inside the body
What happens to conditionally non-essential amacs in hypercatabolic states?
there is a condition that is using them all up
so their use is exceeded, causing a deficiency
What is dumping syndrome usually caused by?
gastric surgery or damage to the pyloric sphincter
What are the effects of dumping syndrome?
hypotension
tachycardia
a feeling of faintness
What is the role of the internal, external and anal sphincters?
allows the body to feel the presence of faecal matter and to control defaecation
What is the role of the cognitive and emotional brain?
it acknowledges environmental and habitual cues from the environment to enact hunger / thirst mechanisms)
How does the barker hypothesis come to play in terms of if a pregant mother is in a state of starvation?
when the infant is born, as they grow up, they have a greater risk of obesity and high bp
What is the role of the metabolic brain?
it monitors whether the metabolic demands of the body are being met
What is the role of lingual lipase?
to lipolyse dietary fats during oral processing
What is different about fundic mucosal gastric lipase compared to SI gastric lipases?
it’s an acid enzyme
Where is gastric lipase secreted from?
gastric cells in the fundic mucosa
What is special about gastric acid enzymes?
they don’t require any stabilisation
doesn’t require bile acid from the liver or colipase from the pancreas for optimal functioning
What percentage of lipid hydrolysis in neonates and in adults is conducted by gastric lipase in the fundic mucosa?
neonates - up to 50% of lipid hydrolysis
adults - up to 30% of lipid hydrolysis
What is the role of chief cells?
they produce pepsinogen, which is converted to pepsin in presence of HCL
Why is lipid hydrolysis essential in neonates?
bc breast milk contains a moderate amount of fat so it’s important that lipid hydrolysis is occuring
What are the two bile acids?
cholic and chenodeoxycholic acid
What is a special feature of bile acids?
each molecule is amphipathic
What are the effects of bile acids being amphipathic?
allows it to act as a detergent (polarity-wise) to solubilize lipids to form mixed micelles
What is pancreatic lipase secreted along-side?
pro-colipase
Where is pro-colipase activated, and by what substance?
in the intestinal lumen by trypsin
What is the role of colipase?
to stabilise pancreatic lipase - stops it breaking down, which increases its efficiency
What is the effect of pancreatic lipase?
it hydrolyses tryglycerols to form monocyglycerol, FAs and glycerol
What are the two important primary pancreatic proteases?
trypsin and chymotrypsin
What are the two inactive proenzyme forms of the primary pancreatic proteases?
trypsinogen and chymotrypsinogen
What happens to trypsinogen and chymotrypsinogen?
they are synthesized and packaged within secretory vesicles
they are then activated by an enteropeptidase - enterokinase secreted by the mucosal membrane of duodenum
What substances are contained in the secretory vesicles containing the two inactive proenzyme forms of the primary pancreatic proteases?
trypsinogen and chymotrypsinogen
a trypsin inhibitor
What is the purpose of the trypsin inhibitor in the secretory vesicles?
it serves as a safeguard against trypsinogen converting to trypsin within the pancreas or pancreatic ducts
How does chenodeoxycholic acid work as a bile acid?
it dissolves the cholesterol that makes gallstones
it inhibits cholesterol synthesis in the liver and its absorption in the intestines, which helps to decrease the formation of gallstones
What enzymes are exocrine pancreas secretions that empty into the SI?
trypsin, chymotrypsin
elastase, carboxypeptidase
What are the precursosrs of elastase and carboxypeptidases?
PROelastase
PROcarboxypeptidase
Which amacs does trypsin break down the bonds between?
arginine and lysine
Which amacs does chymotrypsin break down the bonds between?
tryptophane
phenylalanine
tryosine
leucine
Which amacs does elastase break down the bonds between?
alanine
glycine
serine
Which amacs does carboxypeptidase break down the bonds between?
hydrophobic amacs basic amacs (arginine, lysine...)
What reactions does trypsin catalyse?
the conversion of chymotrypsinogen, proelastase and procarboxypeptidase into their activated enzyme forms
What are the components of starch and their proportions?
amylopectin - 70%
amylose - 30%
Why doesn’t salivary amylase have much of a digestory impact?
bc food doesn’t stay long enough in the mouth for the starch to be fully digested
Where is amylase released from?
the salivary glands
the pancreas
What proportion of fluid entering the GI tract will be absorbed at the SI?
8 / 9 L
What area of the SI is particularly provided for by the SI’s large vascular supply?
the messentry
What are the differences between all the nervous systems?
somatic - conscious autonomic - unconscious sympathetic - excitation parasympathetic - (longer word) relaxes and digests enteric - digestive tract relax
What is an effect of hyperkalemia?
blood flow to the SI is compromised
so patients are less able to absorb nutrients form the SI due ot reduced blood flow
Why is peristalsis changed to a form of segmentation in the SI?
so that food is pushed against the wall of the brush border so that the enzymes can come in contact with the food
What is the role of the brush-border enzyme maltase-glucoamylase?
to break down maltose / maltotriose / oligosaccharides into glucose
What are the intraluminal-saccharides in the SI?
sucrose, lactose
maltose, maltotriose, oligosaccharides
a-limit dextrins
What is the role of the brush-border enzyme sucrase-isomaltase?
to break down a-limit dextrins into glucose
to break down SUCROSE into glucose and fructose
Which carbohydrates are absorbed into the body?
the monosaccharides only - glucose, galactose and fructose
What is the role of GLUT-5?
to absorb fructose
What are the importers of monosaccharides in the SI?
Na+/glucose symporters
GLUT-5
What is the role of GLUT-2?
to transport absorbed monosaccharides from intestinal cells into the bloodstream
What happens when emulsified fat droplets are mixed with bile?
forms mixed micelles that float in the still water of the SI
How are chylomicrons generated?
the ER puts together fats in clusters and encases them with proteins covers
How are FAs contained in micelles transported to the left thoracic duct?
when in the still water, they come into contact with lipases in the brush border, where they are absorbed into the intestinal cells
the ER builds chylomicrons which enter the lacteal
the lacteal transports the fats to the left thoracic duct
Do intestinal cells absorb free FAs?
yes, but it’s limited
How are proteins absorbed in the SI?
via a range of transporters that use Na+ for amac absorption
via the HPT1 transporter for the absorption of di & tripeptides
What are the two processes by which proteins are absorbed in the SI?
Na+ transporters
HPT1 transporter
What do HPT1 transporters require to work?
hydrogen ions
What happens to proteins once inside intestinal cells?
there’s further break down of the di & tripeptides to form amacs
then they move into the bloodstream via facilitated diffusion
What are the Na+ exchangers in intestinal cells?
NHE3 (between the SI lumen and the cell) NaK ATPase (between the cell and the bloodstream)
How does the NHE3 exchanger work?
it exchanges H+ for Na+
H+ leaves the cell
Na+ enters from the lumen
How does NaK ATPase work?
it exchanges K+ for Na+
3 Na+s leave the cell
2 K+s enter from the bloodstream
What happens to NSPs after ingestion?
they usually aren’t digested in the SI
they pass onto the colon unchanged
What are examples of NSPs?
most oligosaccharides
resistant starch
How are soluble fibres digested?
they are fermented by bacteria in the colon
What are examples of soluble fibres?
lentils, baked beans
What happens to insoluble fibres after ingestion?
they make up the cellulose ‘roughage’ in the diet
What substances are contained in soluble fibres?
pectin / gum
What happens to NSPs in the LI?
they are fermented by microbes in the colon
What are the products of NSP fermentation?
gas and short chain FAs acids
What is the structural formula of the gas byproduct of NSP fermentation?
CO2-H2-CH4
What are the short chain FAs acids produced from NSP fermentation?
acetate
propionate
butyrate
How does the GI tract chance over time?
at birth - sterile
during the birth process and feeding - gradually becomes colonised with microbes
7 / 8 years old - the adult population of microbes is achieved
older adults - microbe population is compromised, more vomiting / diarrhoea
What happens to propionate once it has been produced from NSP fermentation?
it is taken up by the liver
What happens to butyrate once it has been produced from NSP fermentation?
it is used by colonic cells
On average, how many different species are present in the microbiome?
over 500 different species
What are features of the classic Western diet?
high in animal protein
high in fat and refined sugar
low in fibre
On average, how many microbes are present per m3 of fluid in the colon?
a maximum of 10^12 microbes / m3 of fluid in the colon
How does the classic Western diet affect the microbiome?
reduction in bacterial diversity, so lower levels of good bacteria and FAs
What are features of the agrarian diet?
has lots of fibre, nuts, legumes and vegetables
is low in animal fat and in animal protein
How does the agrarian diet affect the microbiome?
has a better bacterial diversity
lots of short chain FA synthesis
