hormones and metabolism SDL Flashcards
why do animals need to keep their blood sugar levels at a minimum level, even between meals?
A major driving force is to
keep blood glucose levels within normal ranges so that the brain,
nervous tissues, and erythrocytes, which rely on glucose for
nearly all their energy needs, are able to function properly.
what is glycolysis and what role does it play in the supply of energy
glycolysis is the break down of glucose
Glycolysis plays a crucial role in the supply of energy to cells by breaking down glucose to generate ATP, the primary energy currency of cells. While glycolysis itself doesn’t yield a large amount of ATP compared to aerobic respiration, it is essential for providing energy in situations where oxygen availability is limited, such as during intense exercise or in anaerobic environments. Additionally, the intermediates produced during glycolysis can be used in other metabolic pathways for the synthesis of various molecules needed by the cell.
what influence does insulin have in the absorptive phase of macronutrients in liver, fat and muscle
Liver:
- Glucose Uptake: Insulin stimulates the uptake of glucose by liver cells
- Glycogen Synthesis: Insulin promotes glycogen synthesis in the liver. This leads to the conversion of glucose into glycogen, which is stored for future energy needs.
- Fat Synthesis: Insulin enhances lipogenesis (the synthesis of fatty acids) in the liver
Adipose Tissue (Fat):
- Glucose Uptake: Insulin promotes the uptake of glucose by adipocytes
- Lipogenesis: Insulin stimulates lipogenesis in adipose tissue by promoting the uptake of fatty acids and glucose, which are then converted into triglycerides for storage.
- Inhibition of Lipolysis: Insulin inhibits lipolysis, the breakdown of triglycerides into fatty acids and glycerol. This reduces the release of fatty acids into the bloodstream.
Muscle:
- Glucose Uptake: Insulin enhances glucose uptake by muscle cells (myocytes)
- Glycogen Synthesis: Insulin promotes glycogen synthesis in muscle cells. This helps replenish glycogen stores in muscle tissue.
- Protein Synthesis: Insulin stimulates protein synthesis in muscle cells by increasing the uptake of amino acids
Overall, insulin promotes the uptake, storage, and utilization of glucose, fatty acids, and amino acids in liver, adipose tissue, and muscle during the absorptive phase, thereby facilitating energy storage and anabolic processes.
what influence does insulin have in the inter-prandial (post absorptive) phase on macronutrients in liver, fat and muscle
During the post-absorptive phase, also known as the inter-prandial phase (occurring between meals), insulin levels decrease, and other hormones, such as glucagon, become more prominent.
Liver:
- Glycogenolysis: In the absence of insulin, glycogenolysis—the breakdown of glycogen into glucose—is stimulated in the liver. Glucagon and epinephrine are the primary hormones responsible for this process. Glycogen phosphorylase is activated, and glycogen breakdown occurs to release glucose into the bloodstream, maintaining blood glucose levels during fasting.
- Gluconeogenesis: Glucagon also stimulates gluconeogenesis, the synthesis of glucose from non-carbohydrate sources such as amino acids and glycerol. This process occurs mainly in the liver and helps maintain blood glucose levels during fasting.
Adipose Tissue (Fat):
- Lipolysis: In the absence of insulin, lipolysis—the breakdown of triglycerides into fatty acids and glycerol—is promoted in adipose tissue. Hormones like glucagon and catecholamines (e.g., epinephrine) stimulate the activity of hormone-sensitive lipase, leading to the release of fatty acids into the bloodstream for energy production in other tissues.
- Fatty Acid Oxidation: The fatty acids released from adipose tissue can be taken up by other tissues, such as muscle and liver, where they undergo β-oxidation to generate ATP through the citric acid cycle and oxidative phosphorylation.
Muscle:
- Glucose Conservation: In the absence of insulin, muscle cells become less dependent on glucose for energy and shift towards using fatty acids and ketones as alternative fuel sources. This conserves glucose for tissues that are more reliant on glucose, such as the brain.
- Protein Breakdown: During prolonged fasting or starvation, muscle protein breakdown may occur to provide amino acids for gluconeogenesis in the liver and to maintain blood glucose levels.
In summary, during the post-absorptive phase, when insulin levels are low, the body shifts its metabolic priorities to mobilize stored energy sources (glycogen and fat) and conserve glucose for essential tissues like the brain. Insulin’s influence on macronutrient metabolism is minimal during this phase, as its primary role is to lower blood glucose levels, which is not necessary when glucose levels are already low.
what is the difference between glycogenolysis and gluconeogenesis as methods of creating glucose from stored resources; what stored resources are used in these 2 processes
while both glycogenolysis and gluconeogenesis contribute to the maintenance of blood glucose levels, they operate under different conditions and utilize different substrates. Glycogenolysis primarily mobilizes glucose from stored glycogen in response to immediate energy needs, while gluconeogenesis synthesizes glucose from non-carbohydrate precursors to sustain blood glucose levels during fasting or low carbohydrate availability
