MEH: Carbohydrates, Glycolysis, Pentose Phosphate Pathway Flashcards
What is the general formula of carbohydrates?
(CH2O)n
What can carbohydrates contain?
Aldehyde groups, keto groups, multiple hydroxyl groups
What are dextrins?
Oligosaccharides
What is starch?
Storage molecule in plants which is a polymer of glucose
What is glycogen?
Storage molecule in animals which is a polymer of glucose
What 2 monosaccharides is sucrose composed of?
Glucose and fructose
What 2 monosaccharides is lactose composed of?
Glucose and galactose
What 2 monosaccharides is maltose composed of?
Glucose and glucose
What enzyme is present in saliva that breaks down carbohydrates?
Amylase
What does amylase in saliva break carbohydrates down into?
Dextrins
What does amylase released from the pancreas break carbohydrates down into?
Monosaccharides
Where are disaccharidases found?
Attached the brush boarder membrane of epithelial.
What is primary lactase deficiency?
- Absence of lactase persistence allele
- Only occurs in adults
What is secondary lactase deficiency?
- Caused by injury to the small intestine
- Occurs in children and adults
- Generally reversible
What is congenital lactase deficiency?
Autosomal recessive defect in lactase gene
Name some symptoms of lactose intolerance.
- Boating
- Cramps
- Flatulence
- Diarrhoea
- Vomiting
- Rumbling Stomach
How are monosaccharides absorbed at the apical membrane?
Active transport by sodium dependant glucose transporter 1 (SGLT1)
How are monosaccharides absorbed at the basal membrane?
Facilitated diffusion using transport proteins GLUT1- GLUT5
Where are GLUT2 basal membrane receptors found?
- kidney
- liver
- pancreatic beta cells
- small intestine
Where are GLUT4 basal membrane receptors found?
- adipose tissue
- striated muscle
- insulin regulated
What is the normal concentration of glucose in blood plasma?
~5mM
What is absolute requirement?
When cells can only metabolise energy from glucose, no other source.
Name 4 places that have an absolute requirement.
- Red blood cells
- Neutrophils
- Kidney medulla
- Lens of eye
What is different about the brain in regards to its metabolism preferences?
It prefers glucose as a fuel but can use ketone bodies for some energy requirements in times of starvation but needs time to adapt.
Name the 2 phases of glycolysis.
- Investment
2. Payback
What is the net gain of ATP from one glucose during glycolysis?
2 molecules
What enzyme is required to convert glucose into glucose-6-phosphate?
Hexokinase (glucokinase in liver)
What enzyme is required to convert fructose-6-phosphate to fructose 1,6-bisphosphate?
Phosphfructokinase-1
What enzyme is required to convert phosphoenolpyruvate into pyruvate?
Pyruvate kinase
What is the key control enzyme in glycolysis?
Phosphofructokinase-1
In the first stage of glycolysis, glucose is phosphorylated. Why is this necessary?
- Makes glucose negatively charged preventing passage back across the plasma membrane
- Increases reactivity
Reactions 1 and 3 of glycolysis have a large -deltaG. What does this tell you about the reaction?
It’s irreversible
True or false: rate of glycolysis is up to 200x greater in cancer?
True, the uptake of a radioactive modified hexokinase substrate can be measured and imaged using positron emission tomography
Name the 2 different ways phosphfructokinase can be regulated.
- Allosteric (muscle) Inhibited by High ATP, Stimulated by high AMP
- Hormonal (liver) Inhibited by glucagon, Stimulated by insulin
Name 2 important intermediates of glycolysis and state their importance.
- Glycerol phosphate (fat synthesis)
2. 2,3-bisphosphoglycerate (modulates affinity of haemoglobin for oxygen)
Is a tissue has no stage 3 or 4 metabolism (I.e. No ECT), what enzyme is required to regenerate NADH?
Lactate Dehydrogenase (LDH)
Above what concentration is a patient diagnosed as having lactic acidosis?
About 5mM
What is the purpose of the penthouse phosphate pathway?
Used to produce NADPH and ribose sugars
Name the rate limiting enzyme in the pentode phosphate pathway.
G6PDH
Is any energy required during the pentose phosphate pathway?
Nope:)
