Carbohydrates & glycolysis Flashcards
Describe stage 1 of carb metabolism
1) amylases in saliva break 1-4 glycosidic bond in the polysaccharides (starch and glycogen) 2) amylase in pancreas further digest 3) brush border disaccharidases in SI (isomaltase,lactase,glycoamylase)
Why cant we digest cellulose? Why do we need it then?
Because we dont have the enzymes for it breakdown the β1-4 linkages present in dietary fibre, but we need it for normal functioning of the GI tract
What is lactose intolernce? Symptoms
Deficiency in lactase enzyme responsible for breaking down lactose, undigested form of lactase travels to colon where bacteria ferment them into h2, co2, ch3,( u get gases & bloating) also short chain fatty acids r made and cannot be absorbed, this increases the osmotic pressure in the lumen which pulls water in lumen and causes diharrea.
Why does the body contain little amount of carb? Even tho we ingest so much
bc the body is using it as an energy fuel by tissues and is oxidised into Co2 & water
What happens to the excess carb in the diet?
It is converted into Glycogen for storage and if those got full, it is stored as triglycerides in adipose tissue.
Name diff types of dietry carbohydrates
-starch (carb storage in plants, its a poly…………………..).. -Glycogen ( a polymer of glucose) -sucrose>> table sugar (glucose+fructose) (my GirlFriend is sweet) -fructose>> fruit sugar -glucose -lactose (galactose+glucose) -maltose (glucose + glucose)
Describe absorbtion of carbs in SI (name the different transporters)
APICAL SIDE SGLT1>> cotransports of glucose/ galactose with Na GLUT 5>> brings in fructose BASOLATERAL SIDE GLUT 2>> all 3 sugars GLUT 1>> specialised for glucose only
Which glucose transporter is insulin dependent? Which tissues r they found in?
GLUT 4, in skeletal and adipose
What is the minimum amount of glucose required by a healthy adult?
180g/ day
Where in the body can u find GLUT2?
Liver, kidney, beta cells,SI
Some cells need an ABSOLUTE requirment of glucose to function. Name them
RBC>> have no mitochondira to generate energy so they rely on glucose
Neutrophils
Lens of eye >> no bv there
Kidney medulla>> by the time the blood gets to the medulla theres not much oxygen left, so they go through anerobic
What is glycolysis
Intracellular cytosolic pathway in catabolism of all sugars Generates ATP for cell functioning Genrated NADH and 2 PYRUVATE
End product of glycolysis?
2 pyruvate
How much atp was used during glycolysis? How much did we come out with? What is the NET gain of atp
2 were used to make 4! Net gain>> 2ATP
In glycolysis, NAD>>NADH+, what happens to this NADH+?
In those cells with mitchondria & O2, it goes to ETC and is needed to form ATP there In those cells with no mitchondria or not enough o2 (vigorously excerizse)(ex RBC) NADH to converted back into NAD.
Chemical formula of glucose
C6 H12 O6.
In low oxygen conditions, what happens to the 2 pyruvate that were made?
Its converted to lactate
Is glycolysis an excergonic or endergonic reaction?
Exergonic bc it is making more enegy than it took
What happens if your lactate levels exceed 5mM?
U get lactic acidosis, bc even renal threshold is increased here and csnt help out
In what situation can u get increased lactate?
During strenous excersize, hearty eating, shock, congestive heart disease
What 2 substrates make lactose
Glucose & galactose
What can galactose be useful for in the body? Where is it mainly metabolised?
Galactose is required for the synthesis of glycolipids and glycoproteins such as blood group antigens. In the liver
What is Galactoesemia?
Body unable to break down the galactose in the body, therefore the accumalation of galactose in the tissue will be reduced into galcitol and this reaction uses up the cell’s NADPH (The signs and symptoms of galactosemia result from an inability to use galactose to produce energy.)
Why does galactosemia cause cataracts?
Normally NADPH (nadiya and Pharida) is used to maintain crosslinks btw free -SH groups on cystine residues in certain proteins, this is disrupted in the eye.
Accumalation of galactose and galcitol im the eye may lead to increased intraocular pressure (glaucoma)
What is the pentose phosphate pathway? Why is it important? Is ATP used up here?
Instead of going through glycolysis, the glucose 6-phosphate goes through this pathways.
The main purpose of the pentose phosphate pathway is to
1) Important source of NADPH
2) It is also produces ribose sugar needed for dna and rna synthesis.
No ATP IS USED
How is pyruvate metabolised?is the pathway reversible?
Pyruvate is converted to acetyl CoA via PDH, No it is not
Why do we need NADPH?
-biosynthesis of fatty acids -sterioid biosynthesis -maintainc eof GSH levels -biosynthesis of cholestrol -detoxification reactions
_________________is the first molecule used in the pentose phosphate pathway.
Glucose -6-phosphate (G6P)
What is the rate limiting enzyme in the pentose pathway?
Glucose -6-phosphate dehydrogenease G6PDH
Over 90% of the fuel reserves are found in_______
Lipids, mainly triglycerol in adipose tissue, liver, muscle
Why r lipids favoured for long term atp synthesis
Bc they can be stored without water, and represent the lightest , most concentrated form of energy synthesis.
Why r proteins not normally used to make ATP? But in some cases they Can be used to make atp, can u name a situation?
Bc we need them for important things like making enzymes, ion pumps,contractile proteins for muscles. Starvation>> body breaks down proteins to obtain energy, amd this causes loss of lean body mass
What is anerobic glycolysis?
When no oxygen is available to complete the pathway so pyruvate is converted into LACTIC ACID.
How many amino acids do we have in our body? How much of those should we obtain from our diet?
20, 9
What r the fat soluble vitamens in our gut?
A K E D
Low fiber intake can be associated with……
Bowel cancer and constipation
How does fiber lower cholestrol?
U know
Atp functions
ATP acts as a carrier of FREE energy! Not a source!
*****GLYCOLYSIS IS THE ONLY PAYHWAY TO GENERTAE ATP UNDER ANEROBIC CONDITIONS!
Just saying :p
pyruvate is converted to acetyl coA via what enzyme
Pyruvate dehydrogenease PDH
What is the function of pyruvate dehydrogenease
It covnverts pyruvate to acetyl Coa
List the major carbohydrates found in a typical Western diet and describe how they are digested.
Starch Glycogen Cellulose Lactose Sucrose
Under anaerobic conditions, the pyruvate produced by glycolysis in skeletal muscle may be reduced to lactate. What advantage is this to the muscle cells?
There is a fixed amount of NAD+ & NADH in the cell. The reactions of glycolysis require the presence of NAD+ in the presence of oxygen, NADH is converted back to NAD+ by the electron transport chain in the mitochondria. However, in the absence of oxygen (anaerobic conditions) or mitochondria (red blood cell) electron transport cannot occur. Under these condition pyruvate is converted to lactate via the enzyme lactic dehydrogenase (LDH) using NADH which is oxidised to NAD+ This enables glycolysis to continue so that it can provide the cell with ATP via substrate level phosphorylation.
Compare and contrast the functions of GLYCOLYSIS in adipose tissue, skeletal muscle and red blood cells.
RBC it is the only mechanism for making ATP SKELETAL allows ATP production to occur at anarobic states ADIPOSE minor route for tap production ;( LOSer
List the end-products of glycolysis under aerobic and anaerobic conditions in rbc & skeletal muscle.
Rbc> produces lactate in both conditions Skeletal muscle> produces pyruvate in aer and lactate in aneor
how can u treat overdose of paracetamol? why should u act FAST?
Because effects r IRREVERSIBLE give antidote ACETYLCYSTINE w/ in 8HRS! -works by restoring glutathione levels SOOO.. Acetylcysteine serves as a prodrug to ‘L-cysteine.’ it’ll act as a PRECURSOR for more glutsthione to be made. (remember glutathione is a tripeptide! Glycine-Cys-Glutamate)
Pyruvate kinase deficiency is diagnosed in a 4 year old girl. She develops haemolytic anaemia due to complete absence of this enzyme in her red blood cells. What would be the net gain of ATP from each molecule of glucose passing through glycolysis in the red blood cells of this patient?
0
Which glucose transporter is is the main transporter facilitating uptake of glucose in the brain?
GLUT 3
What is the net production of ATP from 1 molecule of glucose in glycolysis?
2 ATP molecules. 4 molecules of ATP are produced per molecule of glucose in glycolysis but 2 ATP are required in the “investment phase” (one to produce glucose-6-phosphate and one in the conversion of fructose 6-phosphate to fructose 1,6-bisphosphate). The net production of ATP is therefore 2 (4-2=2).
explain where u would find GLUT 1-5 ?
All tissues can metabolise glucose but some cells need an absolute requirement.
-Name 4
• Red blood cells
- Neutrophils
- Innermost cells of kidney medulla
• Lens of the eye
what r the 3 key enzymes in Glycolysis?
which of the 3 is the KEY CONTROL ENZYME
PFK
Above what level of lactate will u get Lactic Acidosis? What values indicate hyperlactemia?
Above 5mM Hyperlactemia>>2-5mM
_____________ is the key regulator of glycolysis
PFK
PHOSPHOFRUCTO KINASE
What is the composition of the disaccharide sucrose?
table sugar= Glucose-fructose
my Girl Friend is sweet
what is galactosemia?
symptoms?
Treatment?
Addition: the absence of which enzyme is most common? why is that more serious
NADPH (nadiah and pharida) is consumed! to convert galastose into Galcitol! via aldose reducatse
***The absence kinase > rare > only galactose accumalte in tissues.
****The absence of the Uridyl Transferase >common> BOTH galactose & galactose 1- phosphate accumulate in tissues…..shit
so “GUT> Galactosemia> UT
Describe the general structures and functions of carbohydrates and how they are digested and absorbed.
notes.
major store for glucose in the body, and where is it made?
Describe the glucose-dependency of some tissues.
how many grams of glucose should we ingest per day
180g
~40 g are required by tissues which can only use glucose such as red blood cells, neutrophils, kidney medulla, lens of the eye.
~140 g are required by the brain & CNS
Glycogen>> liver and muscle cells
Explain why lactic acid (lactate) production is important in anaerobic glycolysis and explain how the blood concentration of lactate is controlled.
Lactate is released from muscle cells
carried in the blood to the liver and heart muscle.
In both tissues it is converted back to pyruvate by LDH.
In heart muscle the pyruvate is converted to acetyl~CoA > TCA cycle>provide energy.
Define lactic acidosis and explain why it may occur
Lactic acidosis is an elevation of plasma lactate (above 5Mm) that affects the buffering capacity of the plasma
Due to strenuous exercise, hearty eating, shock and congestive heart disease.
Due to decreased utilisation occur in liver disease, thiamine deficiency and during alcohol metabolism.
Explain the key role of pyruvate dehydrogenase in glucose
metabolism. when is it activated?
Pyruvate is converted to acetyl~CoA
***PDH is activated when there is plenty of glucose to be catabolised (insulin activates PDH by promoting its dephosphorylation).
The PDH reaction cannot be reversed in the cell!!!! bc theres a loss of Co2.
Name TWO molecules that can cause metabolic acidosis and explain why?
Ketone bodies, pyruvate, lactate, fatty acids, amino acids.
bc All contain acidic groups.
