Week 3 Glucose metabolism Flashcards
What is Glucose 6-phosphatase definciency (Von Gierke)? Biochemically what does it cause?
A deficiency in Glucose 6-phosphatase prevents the conversion of G6P to glucose, causing hypoglycemia. Biochemically is causes an increase in: 1. glycolysis 2. PPP 3. glycogenesis
What are the biochemical consequences as a result of a glucose 6-phosphate dehydrogenase (G6PD) deficiency with respect to oxidative stress on RBCs? How does this pertain to malaria?
Normally within the PPP G6PD allows reduction of NADP+ —>NADPH. NADPH then reacts with glutathione reductase to reduce GSSG —> GSH. GSH then donates an electron to the free radical H2O2 converting it to H2O.
This is very important in RBCs bc a deficiency in G6PD causes the cell to be attacked by free radicals leading to hemolysis.
Because mature RBCs are the ones being lysed, the malarial parasite can’t thrive bc only immature RBCs are available so it dies off.
Why is Hb used to test glucose levels in hyperglycemics?
HbA1C is used to evaluate a person’s blood glucose. Hb is used bc it lasts as long as an RBC (roughly 120 days) and is greatly affected by blood glucose bc RBCs only use glucose as a fuel and is unable to store it.
What are the physiological (oxidative damage) consequences of diabetes mellitus?
Hyperglycemia is associated with oxidative damage including:
- Increase heart vessel wall thickening
- deficiency in GSH
- vascular occlusion (eye damage)
What are the general metabolic changes that occur during acute fasting and exercise?
decreased insulin, INCREASED glucagon
(AKA glycogenolysis)
In Liver: Glycogen –> G1P –> G6P –> Glucose –> blood stream
Small production of ketone bodies (3-hydroxibuterate) can form
What are the general metabolic changes that occur during prolong fasting?
With long-term fasting amino acids become a source of ketone bodies. Amino acids (from skeletal muscles) are shuttled to the liver then turned into pyruvate --> acetyl-CoA --> ketone bodies.
What are the general metabolic changes that occur in the liver after a meal?
Increase in insulin, decrease in glucagon
Glucose –> G6P has choice of three different pathways:
1. Make glycogen
2. PPP
3. Triglyceride formation
What are the general metabolic changes that occur in the skeletal muscle after a meal?
Glucose –> G6P has choice of two different pathways:
- Make glycogen
- TCA
What are the general metabolic changes that occur in the adipocytes after a meal?
Glucose –> G6P has choice of three different pathways:
- Make fatty acids
- TCA
- PPP
What are the general metabolic changes that occur in the brain after a meal?
Glucose –> pyruvate –> acetyl CoA –> TCA
What is the purpose of carbohydrate, fats and protein catabolism?
The purpose is to break them down to create metabolic intermediates so we can anabolize building blocks to make proteins, DNA, RNA, lipids, and glucose.
Name the end products of the following: carbohydrates, lipids, and protein.
Carbohydrate end product: glucose
Lipid end product: triglycerides
Protein end product: amino acids
What are the metabolic intermediates from catabolism and anabolism?
Catabolism: ATP, NADH, NAD+
Anabolism: NADPH and NADP+
What is the function of ATP, NADH, and NADPH in metabolism?
ATP: used as energy because of high energy bonds between phosphate groups
NADH: used by cells to help generate ATP
NADPH: Used to reduce other molecules
Name some common dietary carbohydrates and describe the process of uptake into the cells.
Carbs include: Starch, lactose, sucrose, cellulose (cellulose will never be broken down by humans)
Pathway: They get broken down by salivary and pancreatic amylase to produce monosaccharides glucose, fructose and galactose. The monosaccharides are taken up by the lymph system and delivered to the liver to be absorbed by cells. Glucose is cotransported into the cell by Na+. The Na+ ion gradient is maintained by Na+/K+ ATPase which also allows glucose to leave the cell to go into the capillary.
