Question

please help with these questions

1. Discuss how the basic units of carbohydrate, protein, and lipid are utilized in energy pathways to produce energy. You will need to list and describe the specific energy pathways that are used by each nutrient. What are the differences and similarities?
2. In a state of starvation, several changes happen within our bodies. Discuss these metabolic changes.
3. Using information regarding the energy pathways, discuss why dietary plans that only stress one or a couple of food groups are unhealthy physiologically.
4. Describe how the body synthesizes new molecules from glucose, fatty acids, and amino acids.

Answer 1

Carbohydrate, protein and lipids are biopolymers made up of monomers units. The degradation and formation of these biopolymers with the utilization and release of cellular energy (ATP) is called as metabolism. The formation of polymers from monomers using energy is called as anabolism while the degradation of polymers into monomers with energy release is called as catabolism. The integrated form of anabolism and catabolism is metabolism.

The metabolic pathways of the bio-molecules are integrated i.e. the substances generated in one pathway enters another pathway, the intermediate compounds comes from different pathways and goes into another pathways. Thus, the integrated system is thought to be as ‘porous’.

As, the carbohydrates + amino acids, the lipid catabolic pathways are also connected to the glucose metabolism.

Glycogen, a storage carbohydrate molecule, is produced when excess glucose in present in animals. It is synthesized in the liver and muscles tissues. Is the animal blood sugar lowers down, the glycogen molecule is hydrolyzed in the glucose monomer (glucose-1-phosphate) known as glycogenolysis. This glucose is further used degraded via glycolysis, pyruvate oxidation, krebs cycle (citric acid cycle) and oxidative phosphorylation to produce energy.

Glycogen Pathway: Glycogen from the liver and muscles, hydrolyzed into glucose-1-phosphate, together with fats and proteins, can feed into the catabolic pathways for carbohydrates Amino Acids Carbohydrates, Amino Acids and Glycerol Fatty Acids and Amino Acids Glycolysis ----------→ Phosphorylation Pyruvate Oxidation-→ Krebs Cycle---→ Oxidative

When the body glucose is depleted, the stored glycogen molecules are utilized by the body as shown above. But when this glycogen starts to be depleted, the condition of starvation starts results into generating the keto-acidosis. During the initial fasting (first 14 hours), glucose levels are maintained primarily by glycogenolysis but afterwards the glycogen level too starts to reduce resulting into the glucose formation from non carbohydrate precursors, known as gluconeogenesis. The major substrates for gluconeogenesis are amino acids derived from skeletal muscle protein breakdown. The other metabolic changes during starving conditions are- increase in circulating ketone body concentrations, utilization of fatty acids or ketones to form glucose molecule for brain functions, significant excretion of ketones and urinary ketones are excreted as ammonium salts derived from the renal metabolism of glutamine with the carbon skeleton being recovered through renal gluconeogenesis.

Since, the degradation and synthesis of all bio-molecules are interconnected and the whole body metabolism is based on every bio-molecule, it is essential that body must get all types of food through the habit of healthy diet. Single food intake promotes specific metabolic pathways and lowers down or eliminates the other metabolic pathways. This favour the stress on body overall mechanism which can result into negative impacts. This type of mono food diets is also unsustainable and doesn’t promote the healthy food habit.

The part of metabolism which generates new molecules from the monomers (glucose, amino acids and fatty acids) is called as anabolism. The creation of new molecules requires energy to synthesize complex molecules. Example- the synthesis of large proteins from amino acid building blocks and the synthesis of new DNA strands from nucleic acid building blocks.