medchem lecture 1 final

What is metabolism?

The sum of all chemical transformations in a cell or organism that occur through enzyme catalyzed reactions and make up metabolic pathways

What is catabolism?

The degradation phase of metabolism where nutrient rich molecules like carbohydrates fats and proteins are broken into smaller products to release energy

What is anabolism?

The biosynthetic phase of metabolism where small precursor molecules are built into larger more complex molecules

What are the major energy fuels in metabolism?

Carbohydrates fats and amino acids

What is the primary site of energy storage in the body?

The liver

What are the two major metabolic roles of the liver?

Central regulation of glucose metabolism and lipid metabolism

How is excess energy stored in the liver?

As glycogen

What happens when liver glycogen stores are full?

Excess energy is stored as lipid in adipose tissue

What major glucose metabolism pathways occur in the liver?

Glycolysis and gluconeogenesis

What substances can the liver use to make glucose?

Amino acids glycerol and lactic acid

What happens in the liver during low glucose conditions?

The liver produces keto acids to supply the brain with fuel

Which organ provides hormonal signals that regulate liver metabolism?

The pancreas

What is glycolysis?

A metabolic pathway where glucose is converted to pyruvate and ATP is produced

What happens to pyruvate in muscle during anaerobic glycolysis?

Pyruvate is converted to lactate

What are the products of the citric acid cycle?

ATP and carbon dioxide

What is the role of the pentose phosphate pathway?

Production of nucleotides and NADPH

What is Acetyl CoA used for?

It can be used to make cholesterol fatty acids or enter the citric acid cycle

What fuels are primarily oxidized by muscle?

Carbohydrates fatty acids and ketone bodies

What is the major storage form of glucose in muscle?

Glycogen

Why does glucose become trapped in muscle tissue?

High levels of glucose 6 phosphate encourage trapping of glucose in the tissue

What is fluorodeoxyglucose used for?

PET imaging

What radioactive isotope is substituted into fluorodeoxyglucose?

Fluorine 18

What do PET scanners detect using fluorodeoxyglucose?

Areas where glucose is rapidly absorbed and trapped

Why is FDG PET useful in cancer diagnosis?

Rapidly dividing tumors absorb high amounts of glucose

What is the Cori cycle?

A cycle where lactate produced by muscles travels to the liver is converted to glucose and returns to muscles

Where is lactate produced in the Cori cycle?

In muscle during anaerobic glycolysis

What happens to lactate after it leaves muscle?

It travels to the liver and is converted into glucose

What happens to glucose made in the liver during the Cori cycle?

It returns to the muscles and can be converted back into lactate

What is one purpose of the Cori cycle?

Prevention of lactic acidosis during anaerobic conditions

What causes muscle pain and cramps during anaerobic conditions?

Accumulation of lactic acid

Which enzyme converts pyruvate to lactate?

Lactate dehydrogenase or LDH

What is the primary fuel source for the brain under normal conditions?

Glucose

What fuel does the brain use during starvation?

Ketone bodies

Why can fatty acids not be used directly by the brain?

They are bound to albumin and cannot cross the blood brain barrier

Which organs help regulate the brain’s metabolic state?

Adipose tissue pancreas and liver

What is the major fuel reservoir in adipose tissue?

Triacylglycerols

How are fatty acids transported to adipose tissue?

Fatty acids are esterified in the liver and transported by lipoproteins

What does adipose tissue release during fat breakdown?

Glycerol

What stimulates lipases in adipose tissue?

Insulin

What happens when triacylglycerols are hydrolyzed in adipose tissue?

Glycerol and fatty acids are produced

What happens to CoA derivatives released during adipose metabolism?

They are transferred to glycerol

What is glucose needed for in adipose tissue?

Triacylglycerol synthesis

What determines whether fatty acids are released into the blood from adipose tissue?

Blood glucose levels

What happens to fatty acid release when glucose is scarce?

Fatty acid release into the blood increases and fatty acids return to the liver

What is the primary function of the kidney?

Excretion of waste as urine

Why do kidneys reabsorb water soluble materials?

To conserve energy because filtration requires energy

How do kidneys contribute to metabolism during starvation?

They perform gluconeogenesis

What is the brain’s primary fuel under normal conditions according to the fuel table?

Glucose

What is the brain’s backup fuel when glucose is unavailable?

Ketoacids

Does the brain use fatty acids for fuel?

No fatty acids are not used by the brain