W4 - CHO Metabolism & Diet Analysis Flashcards by Holly Tomlinson

What are glycated proteins?

Modified proteins formed by the addition of glucose mol to aa chains.

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What are glycosaminoglycans (GAGs)?

Linear polysaccharides

Consist of repeating disaccharide units containing a uronic sugar + an amino sugar.

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Examples of glycosaminoglycans (GAGs)

Hyaluronic acid

Keratan sulfate

Heparan sulfate

Proteoglycans

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What is keratan sulfate important for?

Cornea

Joints

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Where are monosaccharides transported to once absorbed into the blood from the small intestine?

Liver via hepatic portal vein

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Where does fructose metabolism mainly occur?

Liver

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What is fructose mainly used for in the liver?

To make liver glycogen

But some to glucose + lactate

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Overview of fructose metabolism in liver

Fructose – (Fructokinase) + ATP–> Fructose-1-P + ADP

Fructose-1-P –(aldolase B)–> Dihydroxyacetone-P (DHAP) + Glyceraldehyde

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Other than the liver, where else can fructose be metabolised?

Intestine

Kidney

Skeletal muscle

Fat tissues

Brain

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Is fructose transported into cells via insulin-density pathways (insulin reg transporters GLUT1 + GLUT4)?

NO, instead…

Fructose taken in by GLUT5

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What is fructose phosphorylated by in muscles + adipose tissue?

Hexokinase

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Is fructose uptake insulin dependent?

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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

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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

Glycerol – (glycerol kinase) – > Glycerol 3-phosphate – ( Glycerol-3-P dehydrogenase) –> Dihydroxyacetone -P (DHAP)

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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)

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What type of hormone is insulin?

Anabolic Peptide hormone

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Where is insulin produced from?

beta-cells of the pancreatic islets

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What does insulin do to glycogen storage?

Promotes it

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What does insulin help prevent

Hyperglycemia

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What is the glucose transporter cell on the liver cell walls?

GLUT2

Glucose diffuses DOWN conc gradient from blood to liver.

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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

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What does glucokinase do?

Causes:

Glucose + ATP –> ADP + G-6-P –> Glycogen

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What is the brains predominant fuel?

Glucose

But can also use ketones. (only if needed)

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Why is glucose needed in the brain?

Continual turnover of cells

Neurotransmitter synthesis

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What % of your body weight is the brain?

How much of the glucose we ingest does the brain use?

~20%

Is the process of getting glucose into the brain insulin mediated?

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?

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?

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

W4 - CHO Metabolism & Diet Analysis Flashcards

(105 cards)