Lecture 28- Glucose Metabolism, Energy Balance and Obesity Flashcards
What are four ways in which we expend energy?
- Basal Metabolic Rate
- Thermogenesis
- Locomotion
- Growth
How much energy to we consume in terms of carbs, proteins and fats? Which of these has twice the number of energy KJs per gram?
Carbohydrates: 17kJ/g
Protein: 17kJ/g
Fat: 37 kJ/g
Fat is the one with twice as much
What are the consequences of too much or too little sugar and what are the scientific terms for this?
Hypoglycemia (too little sugar)= decreased CNS function, coma, death
Hyperglycemia (too much sugar) = osmotic diuresis, dehydration, vascular collapse, death
What is more of an issue these days: hypo or hyperglycemia?
Hyperglycemia as the current western diet is sugar heavy
Why is it important that glucose is maintained at a relatively constant rate in the blood and what level is this?
- Glucose is the principal circulating sugar in the blood and the major energy source of the body therefore needs to be kept at a relatively constant rate
- Glucose metabolism maintains blood glucose levels at 4-6 mM
How do we obtain energy from glucose? Describe the different pathways depending on whether oxygen is present or not…
- The process of glycolysis breaks down glucose to pyruvate acid in the process converting 2 ADP + 2 phosphate into 2 ATP
- If oxygen is not present then anaerobic fermentation of pyruvic acid to lactic acid occurs and the 2ADP is all the energy produced
- If oxygen is present then aerobic respiration can take place. In this the kerb cycle results in 36 ATP being produced from 36ADP + 36 phosphate. Carbon dioxide and water is breathed out in this process and it occurs in the mitochondria of the cell.
What is the total energy yield from a glucose molecule as a result of aerobic respiration?
38 ATP
Does it matter what monosaccharide you inject?
No, because they are all interrelated the end result is the storage of glycogen.
The basic idea is that energy can be transformed from one chemical type to another
What is the difference between the absorptive and postabsorptive states?
Absorptive state= Anabolic (high insulin). When just ate a meal.
Glucose is converted into glycogen to stored in the liver or fat (which lasts ages)
Postabsorptive state= Catabolic (High glucagon). When you have finished eating or have been staving/ not eating for some time. Convert pyruvate, lactate, glycerol and amino acids to glucose (gluconeogenesis in order to maintain glucose levels)
What are the endocrine functions of the pancreas i.e. What do the different cells contained there secret?
β cells secrete insulin
α cells secrete glucagon
δ cells secrete somatostatin
How many pancreatic islets are there and what is the name for these?
1-3 million Islets of Langerhans
pancreatic islets
What percentage of the pancreas has endocrine function as opposed to exocrine function?
exocrine (98%) and endocrine (2%)
i.e. a greater amount is invovled in the secretion of digestive enzymes (exocrine) than in hormone release
Draw a flow chart/ hormone regulation diagram to show how insulin secretion is controlled from the pancreatic islet beta cells and the results?
Answer in slides
What are the effects of insulin on the muscle, liver and adipose tissue?
- Muscle= Increase glucose uptake from blood. increase in amino acid uptake which in turn reduces amino acid production/ release.
- Liver= inhibits glucose release/ production
- Adipose tissue= Increase glucose uptake from blood. Inhibits free fatty acid production (which went on to made into keto acids by the liver)
What is the structure of an insulin receptor like?
- 2 extracellular alpha chains
- 2 membrane spanning beta chains
Has a glycosylation site on outside and tyrosine kinase domain + phosphorylation sites on inside
