W4 - CHO Metabolism & Diet Analysis Flashcards
What are glycated proteins?
Modified proteins formed by the addition of glucose mol to aa chains.
What are glycosaminoglycans (GAGs)?
Linear polysaccharides
Consist of repeating disaccharide units containing a uronic sugar + an amino sugar.
Examples of glycosaminoglycans (GAGs)
Hyaluronic acid
Keratan sulfate
Heparan sulfate
Proteoglycans
What is keratan sulfate important for?
Cornea
Joints
Where are monosaccharides transported to once absorbed into the blood from the small intestine?
Liver via hepatic portal vein
Where does fructose metabolism mainly occur?
Liver
What is fructose mainly used for in the liver?
To make liver glycogen
But some to glucose + lactate
Overview of fructose metabolism in liver
Fructose – (Fructokinase) + ATP–> Fructose-1-P + ADP
Fructose-1-P –(aldolase B)–> Dihydroxyacetone-P (DHAP) + Glyceraldehyde
Other than the liver, where else can fructose be metabolised?
Intestine
Kidney
Skeletal muscle
Fat tissues
Brain
Is fructose transported into cells via insulin-density pathways (insulin reg transporters GLUT1 + GLUT4)?
NO, instead…
Fructose taken in by GLUT5
What is fructose phosphorylated by in muscles + adipose tissue?
Hexokinase
Is fructose uptake insulin dependent?
NO
FRUCTOSE METABOLISM IN LIVER
After aldolase B has caused:
Fructose-1-P -> Dihydroxyacetone-P (DHAP) + Glyceraldehyde
What happens to the glyceraldehyde?
Glyeraldehyde – (triose kinase) –> Glyceraldehyde-3-P
OR…
Glyceraldehyde + NADH —> NAD+ + Glycerol
FRUCTOSE METABOLISM IN LIVER
After aldolase B has caused:
Fructose-1-P -> Dihydroxyacetone-P (DHAP) + Glyceraldehyde
And then glyceraldehyde follows this route:
Glyceraldehyde + NADH —> NAD+ + Glycerol
What are the options for glycerol?
To undergo lipid metabolism
OR
Glycerol – (glycerol kinase) – > Glycerol 3-phosphate – ( Glycerol-3-P dehydrogenase) –> Dihydroxyacetone -P (DHAP)
FRUCTOSE METABOLISM IN LIVER
After aldolase B has caused:
Fructose-1-P -> Dihydroxyacetone-P (DHAP) + Glyceraldehyde
What happens to the Dihydroxyacetone-P (DHAP)?
Can undergo a reversible reaction by aldolase A, B to fructose-1,6-biphosphate (in glucose metabolism pathway)
What type of hormone is insulin?
Anabolic Peptide hormone
Where is insulin produced from?
beta-cells of the pancreatic islets
What does insulin do to glycogen storage?
Promotes it
What does insulin help prevent
Hyperglycemia
What is the glucose transporter cell on the liver cell walls?
GLUT2
Glucose diffuses DOWN conc gradient from blood to liver.
Glucose diffuses DOWN conc gradient from blood to liver, how is glucose prevented from diffusing back into the blood across the GLUT2 transporter?
Insulin binds to insulin receptor on liver cell wall
= ⬆️ conc + activity of glucokinase
= maintains glucose conc between blood + liver cell
= More glucose diffuses from blood to liver
What does glucokinase do?
Causes:
Glucose + ATP –> ADP + G-6-P –> Glycogen
What is the brains predominant fuel?
Glucose
But can also use ketones. (only if needed)
Why is glucose needed in the brain?
Continual turnover of cells
Neurotransmitter synthesis
What % of your body weight is the brain?
2%
How much of the glucose we ingest does the brain use?
~20%
Is the process of getting glucose into the brain insulin mediated?
NO
What transporter does glucose use to cross the blood brain barrier?
GLUT1
What are the 2 main types of cells in the brain?
Neuron - Main brain functional cell
Astrocyte - support cell
Neuron cells in the brain
What are they?
Information messengers
How does glucose enter the neuron from the ECF in the brain?
Through GLUT3
P group is attached
= G-6-P
Then oxidised to Pyruvate to enter TCA cycle
How does glucose enter the astrocyte from the ECF in the brain?
Through GLUT1
P group is attached = G-6-P
Then oxidised to pyruvate to enter TCA cycle
When is there communication between the neuron + astrocyte cells in the brain?
If 1 of them has too much glucose in which case:
Pyruvate is converted to lactate.
Lactate then leaves one of the cells, across ECF then to the other cell.
What can the astrocyte cell in the brain do that the neuron cell can’t?
Can put G-6-P through glycogen synthesis to store glycogen.
But ONLY when receiving lactate from the neuron cell.
What is Positron Emission Tomography
Imaging technique
Uses radioactive substances to visualise + measure changes in metabolic processes, bf, regional chemical composition + absorption.
When used for radio labelled glucose post meal: shows that brain, heart + bladder uses the most glucose.
Where is the radio activity in Positron Emission Tomography
In the darker areas
Where does GLUT4 work?
Facilitated transport of glucose into skeletal muscle
Glucose absorption into skeletal muscle
Facilitated transport across GLUT4
Insulin binds to insulin receptor on muscle cell wall = stimulates activity of hexokinase
Hexokinase: Glucose + ATP –> ADP + G-6-P
== Maintaining conc. grad. so that glucose can continue to diffuse into muscle cell
G-6-P to Glycogen OR glycolysis
Once a P group has been attached to glucose in the liver it can be removed. Is this the case for skeletal muscle?
NO, the P group can’t be removed in skeletal muscle.
Where can more glycogen be stored? Muscle or liver?
Muscle
What can insulin do in regards to GLUT4 in the skeletal muscle cell?
⬆️ its amount on the membrane
How does insulin ⬆️ amount of GLUT4 on the skeletal muscle cell membranes?
Insulin binds to insulin receptor
= IRS-1 + PI-3-Kinase are activated
== Activates translocation of GLUT4 transporters to cell wall = ⬆️ absorption of glucose.
Other than insulin, what is another way to ⬆️ amount of GLUT4 transporters in the skeletal muscle cell membrane?
Through contraction during exercise:
SR releases Ca2+
Ca2+ sends signal + causes translocation of multiple GLUT4 to membrane.
PROCESS INDEPENDENT OF INSULIN
Enzyme to get glucose to G-6-P in liver
Glucokinase
Enzyme to get glucose to G-6-P in skeletal muscle
Hexokinase
Enzyme to get glucose to G-6-P in brain
Hexokinase
Enzyme used to convert G-6-P to G-1-P
Mutase
Equation for G-1-P to UDP-Glucose
G-1-P + UTP – (UDP-glucose pyrophosphorylase) –> PPi + UDP-Glucose
What is the core of a glycogen molecule?
Glycogenin protein
where UDP glucose initially attaches to
What do you have once 8-10 glucose units have attached to glycogenin?
A pro glycogen
Glycogen synthase takes over to prod a macro glycogen.
What is glycogen synthase regulated by?
Insulin
What are the 2 forms in which glycogen synthase is present?
Active
Inactive - has a P group attached
What does the active form of glycogen synthase do?
G-1-P –> glycogen
What enzyme is used to convert the inactive form of glycogen synthase to its active form?
What is it stimulated by?
Protein phosphatase
- Stimulated by insulin
What does protein phosphatase do to the inactive form of glycogen synthase?
Removes its P group + donates it to glycogen
What enzyme converts the active form of glycogen synthase back into its inactive form?
What is it stimulated by?
Protein Kinase A
- Stimulated by Ca2+ + adrenaline
What enzyme breaks down glycogen into G-1-P?
Glycogen phosphorylase
There are 2 forms of glycogen phosphorylase: active + inactive form.
Which has the P group attached?
Active form
How is the inactive form of glycogen phosphorylase converted into the active form? By which enzyme?
Glycogen phosphorylase kinase
What is the Glycogen phosphorylase kinase enzyme stimulated by?
Glucagon
Ca2+
Adrenaline
AMP
By what enzyme is the active form of glycogen phosphorylase converted into its inactive form?
By what is it stimulated by?
Glycogen phosphorylase phosphatase
Stimulated by insulin
What does the glycogen phosphorylase phosphatase do?
Removes P group from active glycogen phosphorylase to make it inactive
What is glycogen phosphorylase phosphatase inhibited by?
High levels of:
ATP + G-6-P
What does adrenaline do overall in regards to glycogen?
Stimulates its breakdown
What does insulin do overall in regards to glycogen?
Reduces breakdown
Stimulates storage
What does glucagon do overall in regards to glycogen?
Stimulates breakdown
Inhibits storage
During exercise, what is the main stimulation for glycolysis?
Ca2+
Adrenaline
Net result of glycolysis?
2 mol of ATP
2 mol of NADH
Pyruvate dehydrogenase has an active + inactive form.
Which has a P group attached?
Inactive form
What enzyme converts the inactive form of pyruvate dehydrogenase to its active form?
What is it stimulated by?
Pyruvate dehydrogenase phosphatase
Stimulated by:
Ca2+
Mg2+
What enzyme converts the active form of pyruvate dehydrogenase to its inactive form?
What is it stimulated by?
Pyruvate dehydrogenase kinases (1,2,3,4)
+ ATP
Stimulated by - NADH, ATP + ACoA
What does the pyruvate dehydrogenase phosphatase do to the inactive form of pyruvate dehydrogenase?
Removes its P group
What is the role of the active pyruvate dehydrogenase?
Converts pyruvate + CoA + NAD+ to:
ACoA
NADH
H+
CO2
What are Pyruvate dehydrogenase kinases (1,2,3,4) inhibited by?
Pyruvate
NAD+
ADP
CoA
Ca2+
What are the stimulators for PFK?
ADP
Pi
Low pH
NH4+
What are the main functions of the TCA?
Decarboxylation of ACoA
ATP prod
FADH2 prod
NADH prod
TCA CYCLE
Enzyme for ACoA –> Citrate
Citrate synthase
TCA CYCLE
Enzyme for isocitrate –> alpha-ketoglutarate
Isocitrate dehydrogenase
TCA CYCLE
Enzyme for alpha-ketoglutarate to succinylcholine-CoA
Alpha KGDH
TCA CYCLE
Stimulators for the citrate synthase enzyme
High oxaloacetate
Ca2+
ADP
TCA CYCLE
Stimulators for isocitrate dehydrogenase
ADP
Ca2+
TCA CYCLE
Stimulators for alpha-ketoglutarate dehydrogenase
ADP
Ca2+
TCA CYCLE
Inhibitors for citrate synthase
High levels of citrate
TCA CYCLE
Inhibitors for isocitrate dehydrogenase
ATP
TCA CYCLE
Inhibitors for alpha-ketoglutarate dehydrogenase
Lots of succinyl-CoA
ATP
NADH
How many large protein complexed are there in the ETC?
4
What is the 1st + foremost reserve for glucose in its postabsroptive state?
Liver
How many g of glucose does the brain need a day?
~100g
Where does gluconeogenesis predominantly occur?
In liver
But small amount in kidneys
Are Pyruvate dehydrogenase and pyruvate kinase reactions reversible?
NO, they’re irreversible
Can the ACoA from FAs be used to make glucose?
NO
ACoA can come from pyruvate through oxidation.
Where else can it come from?
Beta oxidation
What happens when oxaloacetate is converted into malate?
Malate is transported OUT of mit through malate-aspartate shuttle.
Then converted back to oxaloacetate to then be converted into phosphoenolpyruvate which can (over a series of steps) be converted back to glucose.
What aa broken down from the muscle is a precursor for pyruvate?
Alanine
So will enter liver, be converted to pyruvate + follow process to become glucose.
What do phosphatases do?
Removes a phosphate group from a protein
Glycosaminoglycans are made from which macronutrients?
CHO & proteins
If I wanted to make a milkshake that would give me the impression of having the most flavour which type of milk should I use and why?
Full fat milk as it has the highest dietary fat content
Other than fat what other functional group is present in sphingolipids?
Amino group
What does the RNI represent?
Reference nutrient intake which tells us that that specific amount is recommended for 97.5% of the population.
What dietary assessment method would you use to understand how much processed food all SHS students ate over a year?
FFQ
Digestive enzymes digest CHO, fat + protein but the wall of the tract is made of these nutrients. How does the wall of the tract not get digested as well?
Bicarbonate protects, mucus protection from enzymes.
Proteases are released in inactive form when they can pot touch the wall lining.
Also, lining has a high turnover so protects against destruction.
What processes allow smooth movement of food through the digestive tract?
Peristalsis + segmentation
Which macronutrient is going to lead to the largest increase in CCK release?
FAT
Does CCK make you feel hungry or full?
Full
How is gastric emptying effected by exercise above 80% VO2 max?
Slowed down
