Carbohydrates Flashcards
Which tissues rely solely on glucose for energy?
Nervoius, RBC, testes and embryonic
How much glucose vs glycogen does the body store?
Glucose= 20g Glycogen= 190g
What is an anomeric carbon?
Carbon molecule that arises from a carbonyl group
Which of sucrose, maltose or lactose has no anomeric carbon available for oxidation
Sucrose
Which of amylose or amylopectin is branched?
Amylose is straight chained (alpha 1,4)
Amylopectin is highly branched (alpha 1,4 and 1,6)
Where is the majority of glucose in the body found?
90% in the liver and skeletal muscle
Does glucose have non-reducing ends and what does this mean for the molecule?
Yes it does and it means that the glucose can be readily formed or degraded
How osmotically active is glucose?
not at all, it forms a hydrated gel
What can CHO attached to proteins do for the protein?
Increase solubility, alter folding and protect from degradation
Where can Glycosaminoglycans (GAG) be found?
Synovial fluid and mucous.
What differentiates proteoglycans from glycosaminoglycans?
Proteoglycans are GAGs that have been bound to protein molecules- they usually from as a part of the connective tissue.
What characterises mucopolysaccharidose disorders?
Genetic disorders that affect the ability to breakdown GAGs
What can mucopolysacchaaridoses cause?
Build up of GAGs can result in damage to connective tissue. Inflammation in those areas occurs, potential heart problems and dementia.
Name a mucopolysaccharidose and a key feature of the disease.
Hurlers syndrome where development stops at around 4 years old.
Does digestion of CHO occur in the mouth, and if so, what exact digestion occurs?
Yes. Salivary amyloses hydrolyse alpha 1,4 glycosidic bonds.
Does digestion of CHO occur in the stomach, and if so, what exactly occurs.
No.
Does digestion occur of CHO occur in the duodenum, and if so, what exactly occurs?
Yes. Amyloses hydrolyse alpha 1,4 glycosidic bonds
Does CHO digestion occur in the jejunum, and if so, what exactly occurs?
Yes. Sucroses, lactases, isomaltase and glucoamylases function here.
What breaks down cellulose and hemicellulose, and what does this produce?
Colonic bacteria break them down forming methane and hydrogen gas.
By what method of transport is glucose transported into the epithelial cells?
Co-transport with 2Na+
How do epithelial cells allow glucose transportation?
Sodium is pumped out of the cell into the lumen to keep a low intracellular sodium in order for glucose to be transported into the cell.
Is galactose or fructose transported by the same method as glucose, and what is the other method?
Galactose is transported by the same method.
Fructose binds to GLUT5 and diffuses in.
Briefly explain how lactose intolerance causes its symtpoms.
Bacteria in the colon breakdown lactose into lactic acid. Lactic acid is osmotically active and therefore draws more water into the colon. This results in diarrhoea and dehydration.
What does the body do to freshly acquired glucose?
Phosphorylates it to Glc-6-Pi
Which enzymes does the body use to alter glucose for storage?
Liver= Glucokinase
Rest of the body= Hexokinase.
Which enzyme is most effective at dealing with glucose for storage, and what does this mean for the tissue?
Glucokinase has a much higher Vmax and can ‘grab’ much more glucose for the liver than the rest of the body can.
Is Glc-6-Pi osmotically active?
NO.
Which enzyme initiates glycogen synthesis and how does it do?
Glucogenin bonds glucose from UDP to form disaccharides.
Which enzyme extends glucose disaccharides?
Glycogen synthase.
Which enzyme forms alpha 1,6 bonds to branch glycogen?
Glycogen branching enzyme forms alpha 1,6 bonds
What does glycogen phosphorylase do, in terms of glycogen mobilisation?
Cleaves non- reducing glucose off the end of glycogen chains and phosphorylates them to glc-1-pi
What does the transferase enzyme do in terms of mobilisation?
Transfers the shortened branch to the non-reducing end of the main chain.
Which enzyme cleaves the alpha 1,6 bond?
Glucosidase
What is Von Gierkes disease?
Inability to breakdown glycogen in the cells and subsequent over-storage.
What is McArdles disease?
Inability to break down glycogen in the skeletal muscles.
What is the initial step in glycolysis and is it reversible?
Hexokinase phosphorylation of glucose. it is not reversible.
The second step of glycolysis, what is Glc-6-Pi conversion
Phosphexose isomerase (with Mg co-factor) changes the glc-6-pi to fructose-6-Pi
In the third glycolysis step, what does phosphofructokinase 1 (PFK1) do?
Phosphorylates F-6-Pi to F-1,6-BisPi.
This is the first commited step.
In the fourth step of glycolysis, what is F-1,6-Bispi cleavage?
Aldose Splits the molecule into two 3c carbons
G-3-P and DAP
In the fifth glycolysis step, what is triose interconversion?
Conversion of DAP to G-3-P by triose phosphate isomerase.
In the sixth step of glycolysis, what is G-3-P oxidation?
G-3-Pase oxidises G-3-P into 1,3-BisPG
In the seventh step of glycolysis, what does phosphoglycerate kinase do?
transfers the Pi to phosphorylate ADP to form ATP and 3-phosphoglycerate.
In the eighth step, what does phosphoglycerate mutase do?
Moves the Pi on the molecule to form 2-PG from 3-PG
In the ninth step of glycolysis, what forms phosphoenolpyruvate?
Enolase froms PEP from 2-PG
In the tenth step of glycolysis, how does ATP get generated?
Pyruvate kinase transfers the Pi to ADP.
Which vitamin is NAD+ formed from?
B3 Niacin
Anaerobic respiration in muscle and RB cells forms what?
Lactate.
When converting pyruvate to ethanol, what does pyruvate decarboxylase do?
Removes CO2 to from acetaldehyde.
When converting from pyruvate to ethanol, what does alcohol dehydrogenase do?
Converts acetaldehyde to ethanol and forms NADH from NAD
Which enzyme is involved in pyruvate-lactate fermentation?
Lactate dehydrogenase.
When and where does the cori-cycle occur?
During anaerobic respiration and between the liver and skeletal muscle.
What occurs in the cori-cycle?
Muscle forms lactate from glucose and pyruvate.
The liver reforms glucose through lactate then pyruvate.
What does pyruvate dehydrogenase do to pyruvate?
Turns it into Acetyl Co-A and forms NADH
