10-12

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Questions and Answers

What is a primary function of cytokines in the body?

To regulate immune responses

To influence metabolic pathways (correct)

To facilitate nutrient absorption in the gut

To act as long-term energy storage

Which type of signaling molecules is referred to as hepatokines?

Signaling molecules from white adipose tissue

Signaling molecules from muscle tissues

Signaling molecules from the liver (correct)

Signaling molecules from the brain

What determines the variation in secretion of cytokines?

Environmental factors alone

The body's nutritional intake

The presence of pathogens only

The metabolic status of the body (correct)

Which of the following is NOT a type of cytokine based on its source?

Neurokines Signup and view all the answers

What are batokines associated with?

Brown adipose tissues Signup and view all the answers

What does synergism between two cytokines result in?

An effect greater than the additive effects of individual cytokines Signup and view all the answers

How do antagonistic cytokines affect each other?

One inhibits or offsets the effects of another Signup and view all the answers

What is the primary role of hormones in the body?

To facilitate communication between organs Signup and view all the answers

In comparison to hormones, cytokines are typically found in what concentration in circulation?

Lower concentration Signup and view all the answers

Which of the following best describes cytokines?

They are small proteins produced by a variety of cells Signup and view all the answers

What is the primary action of the insulin receptor upon binding insulin?

It undergoes autophosphorylation. Signup and view all the answers

What effect does insulin's ability to activate multiple signaling pathways have?

It allows for a diverse array of physiological effects. Signup and view all the answers

Which class do glucagons belong to within the GPCR classification?

Class B Signup and view all the answers

What is true about G-protein coupled receptors (GPCRs)?

They can be grouped into six classes based on homology. Signup and view all the answers

What are 7-Helix receptors primarily involved in?

Transmitting signals across cell membranes. Signup and view all the answers

What is the primary role of the hypothalamus in the endocrine system?

To coordinate hormonal signals by integrating messages Signup and view all the answers

Which part of the pituitary gland contains neural connections from the hypothalamus?

Posterior pituitary, containing axonal endings Signup and view all the answers

What type of signals does the central nervous system integrate to regulate hormone release?

Both internal and external signals Signup and view all the answers

How does the hypothalamus communicate with the pituitary gland?

By producing releasing factors and passing them to the pituitary gland Signup and view all the answers

What distinguishes the two parts of the pituitary gland functionally?

The anterior pituitary synthesizes hormones, while the posterior contains neural endings Signup and view all the answers

What is the main difference between neuronal signaling and the endocrine system in terms of distance traveled?

Neuronal signaling travels short distances, while the endocrine system travels long distances. Signup and view all the answers

How do neurotransmitters interact with target cells?

By binding to specific receptors on or in target cells. Signup and view all the answers

What is the role of hormones in the endocrine system?

To circulate through the bloodstream to distant target tissues. Signup and view all the answers

Where do nerve cells (neurons) typically contact target cells?

At synapses. Signup and view all the answers

What initiates electrical signals in neuronal signaling?

Stimuli received by the neuron. Signup and view all the answers

Which of the following statements is true regarding the speed of signaling in the two systems?

Neuronal signaling is faster than hormone signaling. Signup and view all the answers

Which component is primarily responsible for long-distance communication in the endocrine system?

Hormones. Signup and view all the answers

What separates neurotransmitters from hormones in terms of their target range?

Neurotransmitters act on nearby cells, while hormones reach distant cells. Signup and view all the answers

What is the primary role of adenylate cyclases in relation to cAMP?

To synthesize cAMP Signup and view all the answers

What substance inhibits phosphodiesterases?

Methylxanthines Signup and view all the answers

Which proteins are involved in regulating adenylate cyclase activity?

G proteins Signup and view all the answers

What happens to the cytoplasmic concentration of Ca2+ ions in response to specific signals?

It increases dramatically Signup and view all the answers

At what normal concentration range are Ca2+ ions typically found in the cytoplasm?

10-100 nM Signup and view all the answers

How does the cytoplasmic Ca2+ level increase?

By opening Ca2+ channels Signup and view all the answers

Where is Ca2+ stored in the cell before being released into the cytoplasm?

Endoplasmic reticulum Signup and view all the answers

What is the result of the action of phosphodiesterases on cAMP?

Conversion of cAMP to AMP Signup and view all the answers

What is the effect of caffeine on phosphodiesterases?

It inhibits their activity Signup and view all the answers

Which of the following statements about cAMP is true?

cAMP functions as a secondary messenger in signaling pathways Signup and view all the answers

What physiological effect is influenced by adenosine's interaction with neuronal receptors?

Blood vessel dilation Signup and view all the answers

How does adenosine affect wakefulness?

By blocking the interaction with neuronal receptors Signup and view all the answers

Which statement is true about adenosine in relation to its receptors?

Adenosine functions as a substrate for specific receptors Signup and view all the answers

Which of the following is NOT a result of increased extracellular adenosine?

Increased physical activity Signup and view all the answers

What does the structure of adenosine resemble?

Adenine Signup and view all the answers

Which of the following best describes the action of adenosine on wakefulness?

It prolongs wakefulness by blocking adenosine receptors Signup and view all the answers

What role does adenosine NOT play in physiological activity?

Stimulator of muscle contraction Signup and view all the answers

What is the potential consequence of blocking adenosine receptors?

Prolonged wakefulness Signup and view all the answers

What is the primary function of oxidative phosphorylation?

Conversion of ADP into ATP Signup and view all the answers

What reaction is catalyzed by nucleoside diphosphate kinase?

GDP + ATP ↔ GTP + ADP Signup and view all the answers

Which enzyme catalyzes the salvage pathway reaction between free adenine and PRPP?

Adenosine phosphoribosyltransferase Signup and view all the answers

What is the role of PRPP synthetase in purine synthesis regulation?

Produces PRPP from ribose-5-phosphate and ATP Signup and view all the answers

Which correct pair of purines and their corresponding salvage enzyme is stated?

Hypoxanthine - Hypoxanthine-guanine phosphoribosyltransferase Signup and view all the answers

Which of the following is NOT a restriction point for regulation in purine synthesis?

Dipeptidase Signup and view all the answers

What type of pathway does the degradation of nucleic acids relate to?

Catabolism Signup and view all the answers

The primary substrate for the salvage pathway reaction involving adenine is?

PRPP Signup and view all the answers

Which enzymes are responsible for regulating the synthesis of IMP?

IMP dehydrogenase and adenylosuccinate synthetase Signup and view all the answers

What is the function of purine nucleoside phosphorylase (PNP) in nucleotide metabolism?

It hydrolyzes nucleotides to release purine bases Signup and view all the answers

Which product is formed directly from the action of xanthine oxidase?

Uric acid Signup and view all the answers

What distinguishes the pathway of nucleotide degradation from nucleotide synthesis?

Degradation involves nucleoside phosphorylase Signup and view all the answers

What role does guanine deaminase play in purine metabolism?

It deaminates guanine to form xanthine Signup and view all the answers

Which statement is true regarding the regulation of adenylosuccinate synthetase?

It is regulated by feedback inhibition Signup and view all the answers

What is the significance of xanthine oxidase being found in the liver and intestinal mucosa?

It impacts the metabolism of uric acid in those organs Signup and view all the answers

How do most mammals deal with the accumulation of uric acid?

They convert it to allantoin using urate oxidase Signup and view all the answers

What is the role of UTP in carbohydrate metabolism?

Involved in the synthesis of storage polysaccharides. Signup and view all the answers

What distinguishes cyclic AMP from cyclic GMP regarding their functions?

Cyclic AMP acts primarily in metabolic control, whereas cyclic GMP is a neurotransmitter. Signup and view all the answers

How does the removal of the adenosine part from an enzyme cofactor affect its activity?

It drastically reduces the cofactor's activities. Signup and view all the answers

What is one primary function of GTP in cellular processes?

To activate GDP-activated sugars for carbohydrate synthesis. Signup and view all the answers

Which statement accurately describes a function of cyclic AMP?

Cyclic AMP often acts as a second messenger in signal transduction. Signup and view all the answers

What role do adenine nucleotides play beyond energy transfer?

They are components of many enzyme cofactors. Signup and view all the answers

Which of the following statements about the role of G proteins is true?

G proteins assist in the transmission of information across cell membranes. Signup and view all the answers

What is a consequence of the action of phosphodiesterases on cyclic AMP?

It degrades cyclic AMP, leading to decreased signaling activity. Signup and view all the answers

What is the ultimate source of electrons for ribonucleotide reductase (RNR)?

NADPH Signup and view all the answers

Which molecules are responsible for shuttling electrons to RNR?

Thioredoxin and Glutaredoxin Signup and view all the answers

What is the role of ATP in the regulation of RNR?

It binds to active sites to activate the enzyme. Signup and view all the answers

How many classes of control sites does RNR have?

Two Signup and view all the answers

How do specificity sites influence RNR?

They determine the activity of the enzyme indirectly. Signup and view all the answers

What happens to RNR when ATP is bound to its active sites?

The enzyme is activated. Signup and view all the answers

What aspect of RNR activity and specificity is strictly regulated?

The concentration of nucleotides. Signup and view all the answers

What is indicated by a 'shut down' state of RNR?

Binding of inhibitory nucleotides. Signup and view all the answers

What is the primary metabolic role of ribonucleotides compared to deoxyribonucleotides?

Serve multiple metabolic roles Signup and view all the answers

Which two processes are essential for dNTP biosynthesis?

Origin of deoxyribose and origin of the thymine methyl group Signup and view all the answers

What factor determines the relative quantities of RNA and DNA in most cells?

RNA is typically more abundant, with 5 to 10 times greater quantity than DNA Signup and view all the answers

What does the dephosphorylation step contribute to the synthesis of deoxyribonucleoside triphosphates?

It creates a deoxyribonucleoside triphosphate from a diphosphate Signup and view all the answers

What is a significant difference between ribonucleotides and deoxyribonucleotides?

Ribonucleotides contain ribose sugar, while deoxyribonucleotides do not Signup and view all the answers

What is the end product of the conversion process involving UMP and TMP?

Thymidylate Signup and view all the answers

Which of the following best describes the significance of the thymine methyl group in dNTP synthesis?

It plays a critical role in the biosynthesis of deoxyribonucleotides Signup and view all the answers

What is the main difference between how ribonucleotides and deoxyribonucleotides function in cellular metabolism?

Ribonucleotides primarily support metabolic processes, whereas deoxyribonucleotides are solely for DNA Signup and view all the answers

What is the primary function of amino acids?

To act as monomer units in protein synthesis Signup and view all the answers

Which compound is synthesized from the amino acid tryptophan?

Serotonin Signup and view all the answers

What type of compounds can amino acids be used as substrates for in biosynthesis?

Hormones and signaling molecules Signup and view all the answers

Which amino acids are involved in the synthesis of purine and pyrimidine bases for nucleic acids?

Aspartate and Glutamate Signup and view all the answers

What is NOT a function of amino acids in metabolism?

Generating ATP through glycolysis Signup and view all the answers

What is the result of non-oxidative deamination in amino acid catabolism?

Formation of corresponding α-keto acids Signup and view all the answers

Which enzyme is primarily responsible for oxidative deamination of glutamate?

Glutamate dehydrogenase Signup and view all the answers

What is the role of NAD+ and NADP+ in the deamination process?

They are coenzymes used in oxidative deamination. Signup and view all the answers

What occurs during the action of transaminases in amino acid catabolism?

They facilitate the transfer of amino groups to α-ketoglutarate. Signup and view all the answers

Which amino acids primarily undergo non-oxidative deamination?

Serine and threonine Signup and view all the answers

What is the function of carbamoyl phosphate synthetase (CPS-I) in the Krebs–Henseleit urea cycle?

It converts ammonia from glutamate into carbamoyl phosphate. Signup and view all the answers

What drives the reaction catalyzed by ornithine transcarbamoylase in the urea cycle?

The conversion of ATP to AMP and pyrophosphate. Signup and view all the answers

Which enzyme is responsible for the synthesis of argininosuccinate from citrulline and aspartate?

Argininosuccinate synthetase Signup and view all the answers

Where is the end product of the Krebs–Henseleit urea cycle primarily transported for excretion?

Kidneys Signup and view all the answers

What role does the hydrolysis of pyrophosphate play in the urea cycle?

It drives the reaction forward by releasing energy. Signup and view all the answers

What role does N-acetylglutamate play in the urea cycle?

Acts as an allosteric activator of CPS Signup and view all the answers

Which metabolic cycle does fumarate directly link?

Urea cycle and citric acid cycle Signup and view all the answers

What can oxaloacetate be converted to via a transamination reaction?

Aspartate Signup and view all the answers

Which amino acid's high concentration contributes to the allosteric activation of CPS?

Arginine Signup and view all the answers

Who discovered both the urea cycle and the citric acid cycle?

Hans Krebs Signup and view all the answers

What is the potential consequence of phenylalanine hydroxylase deficiency?

Accumulation of phenylalanine leading to brain damage Signup and view all the answers

Which of the following is a major consequence of untreated phenylketonuria (PKU)?

Severe mental retardation Signup and view all the answers

What role does transamination play in amino acid metabolism?

It allows for the transfer of amino groups between amino acids Signup and view all the answers

Which statement about phenylalanine is true in the context of metabolic disorders?

It can cause brain damage if accumulated excessively Signup and view all the answers

How do genetic disorders of amino acid metabolism typically affect health?

They can lead to toxic accumulation of amino acids Signup and view all the answers

What compound is formed when 3-phosphohydroxypyruvate undergoes transamination with glutamate?

3-phosposerine Signup and view all the answers

Which cofactor is NOT required for the reactions catalyzed by serine hydroxymethyltransferase?

Vitamin B12 Signup and view all the answers

From which essential amino acid is tyrosine synthesized?

Phenylalanine Signup and view all the answers

Which component of folate is responsible for its specific biochemical properties?

Pterin Signup and view all the answers

Which amino acid does serine serve as a major source for through its conversion?

Glycine Signup and view all the answers

What is the primary product of the hydrolysis of 3-phosposerine?

Serine Signup and view all the answers

What substrate do plants use for synthesizing cysteine with H2S?

O-acetylserine Signup and view all the answers

Which of the following is an incorrect statement about PLP dependent transamination?

It can occur without cofactors. Signup and view all the answers

Study Notes

Inter-organ Communication

Multiple organs work together to regulate the body's metabolic processes.
Fuel metabolites and stores are shown along with major pathways related to energy.
Major fuel metabolites imported/exported by each organ are illustrated.
Lipid-derived metabolites are highlighted in yellow, and carbohydrate-derived metabolites in blue.
Fuel reserves and energy pathways are specific to each organ.
Brain uses glucose (or ketone bodies during starvation) as primary fuel source.
Skeletal muscle primarily uses glycogen and protein as fuel reserves, and fatty acids as preferred fuel.
Skeletal muscle during exertion uses glucose as a primary fuel source.
Heart primarily uses fatty acids for energy.
Adipose tissue uses triacylglycerols as primary fuel reserve.
Liver uses glycogen, fatty acids, and amino acids as fuel sources.
It carries out processes such as glycolysis, gluconeogenesis, β-oxidation, and fatty acid synthesis.
Intestine does not have fuel reserves.

Coordination of Fuel Metabolism

Coordination is maintained through the nervous system and the endocrine system.
Neuronal signals trigger rapid responses over short distances, often by releasing neurotransmitters in synapses.
Endocrine system involves hormones secreted into the bloodstream to travel and affect target tissues over longer distances.
Neurotransmitters and hormones interact with receptors on target cells to elicit responses.

Neurotransmitters and Neurohormones

Neuronal signaling occurs at synapses, where neurotransmitters are released and diffuse, binding to target cell receptors.
Neurohormones are signaling molecules originating from neurons.
Neurotransmitters play roles in sensation, memory, cognition and movement.
Neurohormones often are secreted into the bloodstream, eg. oxytocin & vasopressin

Hormonal Regulation

Hormones regulate growth, differentiation of cells, tissues, and organs.
Include processes like cell proliferation, embryonic development, and sexual differentiation (steroid hormones often important here).
Hormones influence metabolic pathways, and mechanisms are often fast-acting.
Hormones regulate the interconversion of enzymes within metabolic pathways.
Hormones regulate digestion, usually by local acting peptides (paracrine mediators), and biogenic amines.
Hormones regulate ion concentration (homeostasis).
Hormones act via separate mechanisms (e.g., hydrophilic versus lipophilic).
Hormones are transported in the circulatory system for communication between different organs.
Production of hormone precursors and metabolites occurs at various levels.
Different types of hormones are classified based on chemical structure, synthetic pathways, and mode of action.

Hormonal Regulation of Fuel Metabolism

Hormones play a critical part in regulating fuel metabolism.
Hormones like insulin, glucagon, and epinephrine influence glucose and lipid metabolism in different tissues (like liver, muscle, and adipose tissue).
Different hormones trigger distinct responses.
Hormones can stimulate or inhibit various metabolic enzymes, impacting glycogenolysis, gluconeogenesis, glycogen synthesis, and more.

Cytokines Regulation of Fuel Metabolism

Cytokines are signaling molecules released mainly by immune system cells.
Myokines, hepatokines, and adipokines are produced by organs for metabolic regulation.
The secretion of these signaling molecules varies across metabolic status.
These cytokines influence diverse responses pertaining to metabolic regulation (eating/fasting/stress).
The signaling molecules respond to different factors, such as fasting/feeding cycles, circadian rhythm, cold exposure, and exercise.

Hormones- class of proteins

Hormones act as signaling proteins secreted by tissues for inter-organ communication.
Hormones trigger integrative responses to specific stimuli.

Cytokines - class of small proteins

Cytokines act as signaling molecules, produced by cells, to communicate.
They are generally found in lower concentrations than hormones.

Hormonal/Cytokine Regulation of Fuel Metabolism

Classification based on method of reaching target tissue
Endocrine - long-distance signals via bloodstream.
Paracrine - neighboring cells by diffusion.
Autocrine - cells releasing signals and affecting themselves.

Signal transduction pathways

Receptor activation begins the signal transduction cascade.
Various changes occur in plasma membrane permeability, transport properties, electrical state, metabolism, secretory activity, cell proliferation, differentiation, and contractile activity.
Signal transduction pathways/responses differ for soluble and insoluble messengers.
Receptors for soluble messengers are inside cells.

Mechanism of action of lipophilic hormones

Lipophilic hormones diffuse across membranes and require intracellular receptors.
They bind to a receptor protein, form a complex, and enter the nucleus to bind to DNA-activating gene transcription, leading to protein synthesis.
Specific types of receptors bind to particular types of ligands.

Mechanism of action of hydrophilic hormones

Hydrophilic hormones signal through membrane receptors.
They initiate a cascade of intracellular events through second messengers.
Common hydrophilic signaling substances include epinephrine, insulin, glucagon, and growth factors.

Mechanism of Action for cAMP

Nucleotide cAMP is synthesized via membrane-bound adenylate cyclases
Degradation via cAMP phosphodiesterases.
Methylxanthines can inhibit these phosphodiesterases, impacting CAMP levels.

Mechanism of Action for Ca2+ ions

Calcium levels are low in cytoplasm, but signals can cause a rapid increase by triggering channels in the plasma membrane or membranes of endoplasmic/sarcoplasmic reticulum.
Biochemical effects of Ca^2+ are mediated by calcium sensors (special proteins), influencing various processes.

Mechanism of Action for InsP3 and DAG

Type Gq protein activates phospholipase C.
Inositol 1,4,5-trisphosphate (InsP3) and diacylglycerol (DAG) are second messengers.
InsP3 causes calcium release, while DAG activates protein kinase C.

Questions that require the regulation of hormones

What affects the level of each hormone?
How are hormone release rates regulated?

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Description

Explore how different organs in the body work together to regulate metabolic processes. This quiz covers fuel metabolites, pathways, and the energy usage of organs like the brain, skeletal muscle, heart, liver, and adipose tissue. Understanding these interactions is crucial for grasping the body's energy dynamics.