47 Questions
What is the main focus of metabolism?
Interconversion of chemical compounds in the body
Which type of pathway involves the synthesis of larger compounds from smaller precursors?
Anabolic pathways
What characterizes catabolic pathways?
They are exothermic
Which pathway acts as a link between anabolic and catabolic pathways?
Amphibolic pathways
What type of reaction do catabolic pathways commonly involve?
Oxidative reactions
Which category of pathways is mainly responsible for producing ATP?
Catabolic pathways
What is the primary metabolic fuel for most tissues in the fed state?
Glucose
Which tissues rely wholly on glucose as a metabolic fuel in the fasting state?
Red blood cells
What do muscle and liver primarily oxidize when glucose availability decreases?
Fatty acids
What is the process by which the liver synthesizes ketone bodies from fatty acids?
Ketogenesis
What is the main consequence of impaired sensitivity of tissues to insulin action in type II diabetes?
Impaired glucose uptake by tissues
In what condition does impaired synthesis and secretion of insulin occur, leading to severe metabolic derangement?
Type I diabetes
Which tissue stores glycogen as a fuel for muscle contraction during prolonged fasting or starvation?
Skeletal Muscle
What is the main fuel reserve of the body stored in Adipose Tissue?
Triacylglycerol
Which organ synthesizes urea and exports ketone bodies to provide fuel during fasting and starvation?
Liver
Where are excess amino acids deaminated to synthesize urea for excretion?
Liver
Which tissue accounts for approximately 50% of body mass and serves as a significant store of protein for amino acid supply during starvation?
Skeletal Muscle
In which tissue is triacylglycerol first metabolized by lipoprotein lipase before being incorporated into tissue lipids or oxidized as fuel?
Skeletal Muscle
Which type of reactions are normally present in a metabolic pathway?
Nonequilibrium reactions
Why are enzymes catalyzing nonequilibrium reactions usually present in low concentration?
To prevent excessive product formation
What is a flux-generating reaction in a metabolic pathway?
A nonequilibrium reaction with low Km
Why is the first reaction in glycolysis, catalyzed by hexokinase, considered a flux-generating step?
Because its Km for glucose is considerably lower than normal blood glucose concentration
How does the availability of the initial substrate regulate the flux of metabolites through metabolic pathways?
By affecting the supply of substrates from the blood
In response to which hormone do muscle and adipose tissue take up glucose from the bloodstream?
Insulin
What happens in prolonged starvation regarding protein catabolism?
Protein catabolism increases significantly to provide amino acids for gluconeogenesis.
What happens in patients with cachexia as a result of tumors and disease?
Increase in tissue protein catabolism and metabolic rate.
What can lead to ketosis in pregnancy and lactation?
High demand for glucose by the fetus and lactose synthesis in lactation.
How does poorly controlled type 1 diabetes mellitus affect glucose levels?
It results in hyperglycemia due to lack of insulin and increased gluconeogenesis.
What happens in adipose tissue due to lack of insulin action in poorly controlled type 1 diabetes mellitus?
Increased lipolysis leading to ketogenesis.
What is the consequence of essential tissue proteins being catabolized and not replaced?
Death.
What can lead to ketosis in pregnancy and lactation?
High demand for glucose
In poorly controlled type 1 diabetes mellitus, why do patients become hyperglycemic?
Lack of insulin to stimulate glucose utilization
Why does death result in patients with cachexia?
Increased tissue protein catabolism without replacement
What is the consequence of a very considerable increase in protein catabolism in prolonged starvation?
Death
What happens to adipose tissue reserves in prolonged starvation?
They provide amino acids for gluconeogenesis
Why do patients with cachexia experience an increased metabolic rate?
Release of cytokines as a response to tumors and disease
What is the main metabolic abnormality observed in cachexia as a result of tumors and disease?
Increased rate of tissue protein catabolism without replacement
What is the characteristic of the Km of enzymes catalyzing flux-generating reactions in metabolic pathways?
Km for the enzyme is considerably lower than the normal substrate concentration
Why are enzymes catalyzing nonequilibrium reactions usually present in low concentrations in metabolic pathways?
To allow for regulation and control of the pathway
Which factor primarily determines the availability of the initial substrate in regulating the flux of metabolites through metabolic pathways?
Food intake and tissue reserves
In poorly controlled type 1 diabetes mellitus, what response do muscle and adipose tissue have to glucose in the bloodstream?
They uptake glucose even without insulin
What effect does a considerable increase in protein catabolism during prolonged starvation have on the body?
Severe metabolic derangement
Which characteristic of the first reaction in glycolysis makes it a flux-generating step?
Low Km value compared to glucose concentration
What determines whether muscle and adipose tissue take up glucose from the bloodstream?
Insulin resistance
'Most reactions in metabolic pathways cannot be classified as equilibrium or nonequilibrium' implies what about these reactions?
'Nonequilibrium' and 'equilibrium' are relative terms for them
'The flux through this pathway can be regulated by the availability of the initial substrate' highlights what regulatory aspect of metabolic pathways?
'Substrate-level regulation'
Why is the Km of hexokinase for glucose in glycolysis compared to normal blood glucose concentration essential for its role as a flux-generating step?
It facilitates rapid uptake and phosphorylation of glucose by cells
Explore the functions of the liver in metabolic pathways, including the export of ketone bodies, synthesis of plasma proteins, and urea production. Learn about the levels of organization of metabolic pathways at the tissue and organ level.
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