PHRD 5025 Lecture 15: Lipid Metabolism, Ketosis & Diabetes

What are the main biological functions of lipids?

Energy storage, structural components of cell membranes, and signaling molecules.

What is an amphipathic membrane?

A membrane that has both hydrophilic (water-attracting) and hydrophobic (water-repelling) parts.

What is the role of lipase in metabolism?

Lipase is an enzyme that catalyzes the hydrolysis of triglycerides, releasing fatty acids.

Define ketosis.

A metabolic state characterized by elevated levels of ketone bodies in the blood, often due to low carbohydrate intake.

What is the function of insulin?

Insulin signals tissues to uptake glucose and convert it to glycogen and triglycerides when blood glucose levels are high.

What triggers the mobilization of triglycerides?

Low blood glucose levels trigger mobilization through the action of epinephrine and glucagon.

What is the fate of fatty acids after triglyceride breakdown?

Fatty acids are released into the bloodstream and transported to tissues for energy production.

What are ketone bodies?

Metabolic byproducts produced during the breakdown of fatty acids, used as an alternative energy source.

What is the process of β-oxidation?

A metabolic pathway that breaks down fatty acids to generate acetyl-CoA, NADH, and FADH2.

How many ATP are produced from one molecule of FADH2?

1.5 ATP molecules.

What is the overall ATP yield from the complete oxidation of palmitoyl-CoA?

108 ATP molecules.

What is the role of glucagon in metabolism?

Glucagon signals that blood glucose is low, promoting glucose production and fat oxidation.

What occurs during the fasting state regarding metabolism?

The body mobilizes triglycerides and increases glucose production to maintain blood glucose levels.

What is the significance of the citric acid cycle in fatty acid oxidation?

Acetyl-CoA produced from β-oxidation enters the citric acid cycle for further energy extraction.

What is the role of epinephrine in metabolic regulation?

Epinephrine prepares the body for activity by promoting glucose release and fat mobilization.

How does the body store triglycerides?

Triglycerides are stored in adipose tissue and as oily droplets in eukaryotic cells.

What happens to fatty acids in the bloodstream?

They bind to albumin for transport to tissues where they are used for ATP production.

What is the role of adipocytes?

Adipocytes are specialized cells that store triglycerides and release fatty acids when needed.

What are complications associated with diabetes?

Complications can include cardiovascular disease, nerve damage, kidney damage, and vision problems.

What is the purpose of ketone body formation?

To provide an alternative energy source during periods of low carbohydrate availability.

What is the effect of insulin on blood glucose levels?

Insulin lowers blood glucose levels by promoting glucose uptake and storage.

What is the relationship between fatty acid oxidation and ATP production?

Fatty acid oxidation generates ATP through the production of acetyl-CoA, NADH, and FADH2.

What triggers the activation of triacylglycerol lipases?

Epinephrine and glucagon activate triacylglycerol lipases in response to low blood glucose.

What is the significance of water production during fatty acid oxidation?

Water is produced as a byproduct, which can be crucial for hydration in certain animals like camels.

What is the role of the liver in metabolism?

The liver processes and distributes nutrients, playing a central role in metabolic regulation.

What is the process of digestion and absorption of dietary lipids?

Occurs in the small intestine where fatty acids are released from triglycerides and delivered to tissues.

What activates triacylglycerol lipases?

The activation generates free fatty acids.

How do free fatty acids travel in the bloodstream?

They bind to the blood protein albumin.

What tissues utilize fatty acids transported by albumin?

Skeletal muscle, heart, and renal cortex.

What happens to fatty acids after they disassociate from albumin?

They are transported into cells for β-oxidation.

What occurs to the citric acid cycle during starvation or untreated diabetes?

It becomes almost inactive as its intermediates are used for gluconeogenesis.

What accumulates when the citric acid cycle slows down?

Acetyl CoA accumulates, and free CoA declines.

What is the role of ketone bodies during fasting?

They are produced and exported from the liver to provide fuel for extrahepatic tissues.

What catalyzes the formation of acetoacetyl-CoA from acetyl-CoA?

Thiolase catalyzes the condensation of two acetyl-CoA molecules.

What is ketosis?

The accumulation of ketone bodies in the blood, often due to high acetyl-CoA levels.

What can extreme acidosis lead to?

Coma and, in some cases, death.

What is the primary sterol in animal tissue?

Cholesterol.

What are the structural characteristics of sterols?

They have a steroid nucleus consisting of four rings.

What is the impact of atherosclerosis?

It leads to obstruction and reduction of blood flow due to cholesterol accumulation.

What is the most common form of diabetes?

Type 2 diabetes (non-insulin-dependent diabetes mellitus).

What causes Type 1 diabetes?

Autoimmune destruction of pancreatic β cells leading to insulin deficiency.

What are common symptoms of Type 1 diabetes?

Excessive thirst, frequent urination, and glucosuria.

What are the long-term complications of Type 2 diabetes?

Nerve damage, eye problems, skin disorders, and foot problems.

What is diabetic ketosis?

Overproduction of ketone bodies leading to increased levels in blood and urine.

What is the role of insulin in diabetes?

Insulin regulates blood glucose levels; deficiency leads to diabetes.

What is the primary treatment for Type 1 diabetes?

Insulin injections.

What are statins used for?

To lower cholesterol levels and reduce the risk of coronary heart disease.

What is the significance of the blood glucose test?

It measures glucose levels to monitor diabetes management.

What is the fate of fatty acids after β-oxidation?

They are converted into acetyl-CoA for energy production.

What is the relationship between ketone bodies and fasting?

Ketone bodies are produced from acetyl-CoA during fasting to provide energy.

What is the definition of acidosis?

A condition where blood pH decreases due to excess protons from ketone body oxidation.

What is glucosuria?

The excretion of large amounts of glucose in urine, common in diabetes.

What are the physiological defects in Type 2 diabetes?

Resistance to insulin action combined with a deficiency in insulin secretion.

What is the significance of cholesterol in the body?

It is a precursor for hormones and bile acids, and a component of cell membranes.