Podcast
Questions and Answers
What is a primary function of cytokines in the body?
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?
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?
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?
Which of the following is NOT a type of cytokine based on its source?
What are batokines associated with?
What are batokines associated with?
What does synergism between two cytokines result in?
What does synergism between two cytokines result in?
How do antagonistic cytokines affect each other?
How do antagonistic cytokines affect each other?
What is the primary role of hormones in the body?
What is the primary role of hormones in the body?
In comparison to hormones, cytokines are typically found in what concentration in circulation?
In comparison to hormones, cytokines are typically found in what concentration in circulation?
Which of the following best describes cytokines?
Which of the following best describes cytokines?
What is the primary action of the insulin receptor upon binding insulin?
What is the primary action of the insulin receptor upon binding insulin?
What effect does insulin's ability to activate multiple signaling pathways have?
What effect does insulin's ability to activate multiple signaling pathways have?
Which class do glucagons belong to within the GPCR classification?
Which class do glucagons belong to within the GPCR classification?
What is true about G-protein coupled receptors (GPCRs)?
What is true about G-protein coupled receptors (GPCRs)?
What are 7-Helix receptors primarily involved in?
What are 7-Helix receptors primarily involved in?
What is the primary role of the hypothalamus in the endocrine system?
What is the primary role of the hypothalamus in the endocrine system?
Which part of the pituitary gland contains neural connections from the hypothalamus?
Which part of the pituitary gland contains neural connections from the hypothalamus?
What type of signals does the central nervous system integrate to regulate hormone release?
What type of signals does the central nervous system integrate to regulate hormone release?
How does the hypothalamus communicate with the pituitary gland?
How does the hypothalamus communicate with the pituitary gland?
What distinguishes the two parts of the pituitary gland functionally?
What distinguishes the two parts of the pituitary gland functionally?
What is the main difference between neuronal signaling and the endocrine system in terms of distance traveled?
What is the main difference between neuronal signaling and the endocrine system in terms of distance traveled?
How do neurotransmitters interact with target cells?
How do neurotransmitters interact with target cells?
What is the role of hormones in the endocrine system?
What is the role of hormones in the endocrine system?
Where do nerve cells (neurons) typically contact target cells?
Where do nerve cells (neurons) typically contact target cells?
What initiates electrical signals in neuronal signaling?
What initiates electrical signals in neuronal signaling?
Which of the following statements is true regarding the speed of signaling in the two systems?
Which of the following statements is true regarding the speed of signaling in the two systems?
Which component is primarily responsible for long-distance communication in the endocrine system?
Which component is primarily responsible for long-distance communication in the endocrine system?
What separates neurotransmitters from hormones in terms of their target range?
What separates neurotransmitters from hormones in terms of their target range?
What is the primary role of adenylate cyclases in relation to cAMP?
What is the primary role of adenylate cyclases in relation to cAMP?
What substance inhibits phosphodiesterases?
What substance inhibits phosphodiesterases?
Which proteins are involved in regulating adenylate cyclase activity?
Which proteins are involved in regulating adenylate cyclase activity?
What happens to the cytoplasmic concentration of Ca2+ ions in response to specific signals?
What happens to the cytoplasmic concentration of Ca2+ ions in response to specific signals?
At what normal concentration range are Ca2+ ions typically found in the cytoplasm?
At what normal concentration range are Ca2+ ions typically found in the cytoplasm?
How does the cytoplasmic Ca2+ level increase?
How does the cytoplasmic Ca2+ level increase?
Where is Ca2+ stored in the cell before being released into the cytoplasm?
Where is Ca2+ stored in the cell before being released into the cytoplasm?
What is the result of the action of phosphodiesterases on cAMP?
What is the result of the action of phosphodiesterases on cAMP?
What is the effect of caffeine on phosphodiesterases?
What is the effect of caffeine on phosphodiesterases?
Which of the following statements about cAMP is true?
Which of the following statements about cAMP is true?
What physiological effect is influenced by adenosine's interaction with neuronal receptors?
What physiological effect is influenced by adenosine's interaction with neuronal receptors?
How does adenosine affect wakefulness?
How does adenosine affect wakefulness?
Which statement is true about adenosine in relation to its receptors?
Which statement is true about adenosine in relation to its receptors?
Which of the following is NOT a result of increased extracellular adenosine?
Which of the following is NOT a result of increased extracellular adenosine?
What does the structure of adenosine resemble?
What does the structure of adenosine resemble?
Which of the following best describes the action of adenosine on wakefulness?
Which of the following best describes the action of adenosine on wakefulness?
What role does adenosine NOT play in physiological activity?
What role does adenosine NOT play in physiological activity?
What is the potential consequence of blocking adenosine receptors?
What is the potential consequence of blocking adenosine receptors?
What is the primary function of oxidative phosphorylation?
What is the primary function of oxidative phosphorylation?
What reaction is catalyzed by nucleoside diphosphate kinase?
What reaction is catalyzed by nucleoside diphosphate kinase?
Which enzyme catalyzes the salvage pathway reaction between free adenine and PRPP?
Which enzyme catalyzes the salvage pathway reaction between free adenine and PRPP?
What is the role of PRPP synthetase in purine synthesis regulation?
What is the role of PRPP synthetase in purine synthesis regulation?
Which correct pair of purines and their corresponding salvage enzyme is stated?
Which correct pair of purines and their corresponding salvage enzyme is stated?
Which of the following is NOT a restriction point for regulation in purine synthesis?
Which of the following is NOT a restriction point for regulation in purine synthesis?
What type of pathway does the degradation of nucleic acids relate to?
What type of pathway does the degradation of nucleic acids relate to?
The primary substrate for the salvage pathway reaction involving adenine is?
The primary substrate for the salvage pathway reaction involving adenine is?
Which enzymes are responsible for regulating the synthesis of IMP?
Which enzymes are responsible for regulating the synthesis of IMP?
What is the function of purine nucleoside phosphorylase (PNP) in nucleotide metabolism?
What is the function of purine nucleoside phosphorylase (PNP) in nucleotide metabolism?
Which product is formed directly from the action of xanthine oxidase?
Which product is formed directly from the action of xanthine oxidase?
What distinguishes the pathway of nucleotide degradation from nucleotide synthesis?
What distinguishes the pathway of nucleotide degradation from nucleotide synthesis?
What role does guanine deaminase play in purine metabolism?
What role does guanine deaminase play in purine metabolism?
Which statement is true regarding the regulation of adenylosuccinate synthetase?
Which statement is true regarding the regulation of adenylosuccinate synthetase?
What is the significance of xanthine oxidase being found in the liver and intestinal mucosa?
What is the significance of xanthine oxidase being found in the liver and intestinal mucosa?
How do most mammals deal with the accumulation of uric acid?
How do most mammals deal with the accumulation of uric acid?
What is the role of UTP in carbohydrate metabolism?
What is the role of UTP in carbohydrate metabolism?
What distinguishes cyclic AMP from cyclic GMP regarding their functions?
What distinguishes cyclic AMP from cyclic GMP regarding their functions?
How does the removal of the adenosine part from an enzyme cofactor affect its activity?
How does the removal of the adenosine part from an enzyme cofactor affect its activity?
What is one primary function of GTP in cellular processes?
What is one primary function of GTP in cellular processes?
Which statement accurately describes a function of cyclic AMP?
Which statement accurately describes a function of cyclic AMP?
What role do adenine nucleotides play beyond energy transfer?
What role do adenine nucleotides play beyond energy transfer?
Which of the following statements about the role of G proteins is true?
Which of the following statements about the role of G proteins is true?
What is a consequence of the action of phosphodiesterases on cyclic AMP?
What is a consequence of the action of phosphodiesterases on cyclic AMP?
What is the ultimate source of electrons for ribonucleotide reductase (RNR)?
What is the ultimate source of electrons for ribonucleotide reductase (RNR)?
Which molecules are responsible for shuttling electrons to RNR?
Which molecules are responsible for shuttling electrons to RNR?
What is the role of ATP in the regulation of RNR?
What is the role of ATP in the regulation of RNR?
How many classes of control sites does RNR have?
How many classes of control sites does RNR have?
How do specificity sites influence RNR?
How do specificity sites influence RNR?
What happens to RNR when ATP is bound to its active sites?
What happens to RNR when ATP is bound to its active sites?
What aspect of RNR activity and specificity is strictly regulated?
What aspect of RNR activity and specificity is strictly regulated?
What is indicated by a 'shut down' state of RNR?
What is indicated by a 'shut down' state of RNR?
What is the primary metabolic role of ribonucleotides compared to deoxyribonucleotides?
What is the primary metabolic role of ribonucleotides compared to deoxyribonucleotides?
Which two processes are essential for dNTP biosynthesis?
Which two processes are essential for dNTP biosynthesis?
What factor determines the relative quantities of RNA and DNA in most cells?
What factor determines the relative quantities of RNA and DNA in most cells?
What does the dephosphorylation step contribute to the synthesis of deoxyribonucleoside triphosphates?
What does the dephosphorylation step contribute to the synthesis of deoxyribonucleoside triphosphates?
What is a significant difference between ribonucleotides and deoxyribonucleotides?
What is a significant difference between ribonucleotides and deoxyribonucleotides?
What is the end product of the conversion process involving UMP and TMP?
What is the end product of the conversion process involving UMP and TMP?
Which of the following best describes the significance of the thymine methyl group in dNTP synthesis?
Which of the following best describes the significance of the thymine methyl group in dNTP synthesis?
What is the main difference between how ribonucleotides and deoxyribonucleotides function in cellular metabolism?
What is the main difference between how ribonucleotides and deoxyribonucleotides function in cellular metabolism?
What is the primary function of amino acids?
What is the primary function of amino acids?
Which compound is synthesized from the amino acid tryptophan?
Which compound is synthesized from the amino acid tryptophan?
What type of compounds can amino acids be used as substrates for in biosynthesis?
What type of compounds can amino acids be used as substrates for in biosynthesis?
Which amino acids are involved in the synthesis of purine and pyrimidine bases for nucleic acids?
Which amino acids are involved in the synthesis of purine and pyrimidine bases for nucleic acids?
What is NOT a function of amino acids in metabolism?
What is NOT a function of amino acids in metabolism?
What is the result of non-oxidative deamination in amino acid catabolism?
What is the result of non-oxidative deamination in amino acid catabolism?
Which enzyme is primarily responsible for oxidative deamination of glutamate?
Which enzyme is primarily responsible for oxidative deamination of glutamate?
What is the role of NAD+ and NADP+ in the deamination process?
What is the role of NAD+ and NADP+ in the deamination process?
What occurs during the action of transaminases in amino acid catabolism?
What occurs during the action of transaminases in amino acid catabolism?
Which amino acids primarily undergo non-oxidative deamination?
Which amino acids primarily undergo non-oxidative deamination?
What is the function of carbamoyl phosphate synthetase (CPS-I) in the Krebs–Henseleit urea cycle?
What is the function of carbamoyl phosphate synthetase (CPS-I) in the Krebs–Henseleit urea cycle?
What drives the reaction catalyzed by ornithine transcarbamoylase in the urea cycle?
What drives the reaction catalyzed by ornithine transcarbamoylase in the urea cycle?
Which enzyme is responsible for the synthesis of argininosuccinate from citrulline and aspartate?
Which enzyme is responsible for the synthesis of argininosuccinate from citrulline and aspartate?
Where is the end product of the Krebs–Henseleit urea cycle primarily transported for excretion?
Where is the end product of the Krebs–Henseleit urea cycle primarily transported for excretion?
What role does the hydrolysis of pyrophosphate play in the urea cycle?
What role does the hydrolysis of pyrophosphate play in the urea cycle?
What role does N-acetylglutamate play in the urea cycle?
What role does N-acetylglutamate play in the urea cycle?
Which metabolic cycle does fumarate directly link?
Which metabolic cycle does fumarate directly link?
What can oxaloacetate be converted to via a transamination reaction?
What can oxaloacetate be converted to via a transamination reaction?
Which amino acid's high concentration contributes to the allosteric activation of CPS?
Which amino acid's high concentration contributes to the allosteric activation of CPS?
Who discovered both the urea cycle and the citric acid cycle?
Who discovered both the urea cycle and the citric acid cycle?
What is the potential consequence of phenylalanine hydroxylase deficiency?
What is the potential consequence of phenylalanine hydroxylase deficiency?
Which of the following is a major consequence of untreated phenylketonuria (PKU)?
Which of the following is a major consequence of untreated phenylketonuria (PKU)?
What role does transamination play in amino acid metabolism?
What role does transamination play in amino acid metabolism?
Which statement about phenylalanine is true in the context of metabolic disorders?
Which statement about phenylalanine is true in the context of metabolic disorders?
How do genetic disorders of amino acid metabolism typically affect health?
How do genetic disorders of amino acid metabolism typically affect health?
What compound is formed when 3-phosphohydroxypyruvate undergoes transamination with glutamate?
What compound is formed when 3-phosphohydroxypyruvate undergoes transamination with glutamate?
Which cofactor is NOT required for the reactions catalyzed by serine hydroxymethyltransferase?
Which cofactor is NOT required for the reactions catalyzed by serine hydroxymethyltransferase?
From which essential amino acid is tyrosine synthesized?
From which essential amino acid is tyrosine synthesized?
Which component of folate is responsible for its specific biochemical properties?
Which component of folate is responsible for its specific biochemical properties?
Which amino acid does serine serve as a major source for through its conversion?
Which amino acid does serine serve as a major source for through its conversion?
What is the primary product of the hydrolysis of 3-phosposerine?
What is the primary product of the hydrolysis of 3-phosposerine?
What substrate do plants use for synthesizing cysteine with H2S?
What substrate do plants use for synthesizing cysteine with H2S?
Which of the following is an incorrect statement about PLP dependent transamination?
Which of the following is an incorrect statement about PLP dependent transamination?
Flashcards
Hormonal Regulation
Hormonal Regulation
Hormones influence metabolic pathways, impacting how the body uses energy.
Cytokines
Cytokines
Signaling molecules (proteins, peptides, or glycoproteins) secreted by immune cells; some from metabolic organs.
Hepatokines
Hepatokines
Signaling molecules produced by the liver affecting metabolism.
Myokines
Myokines
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Adipokines/Batokines
Adipokines/Batokines
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Nervous system
Nervous system
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Endocrine system
Endocrine system
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Neurotransmitters
Neurotransmitters
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Synapse
Synapse
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Hormones
Hormones
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Target cell
Target cell
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How do neurotransmitters differ from hormones?
How do neurotransmitters differ from hormones?
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What are the two main systems coordinating communication in the body?
What are the two main systems coordinating communication in the body?
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cAMP synthesis
cAMP synthesis
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cAMP degradation
cAMP degradation
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Methylxanthines & Phosphodiesterase
Methylxanthines & Phosphodiesterase
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cAMP & G proteins
cAMP & G proteins
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Ca2+ signaling substance
Ca2+ signaling substance
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Cytoplasmic Ca2+ concentration
Cytoplasmic Ca2+ concentration
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Sudden Ca2+ increase
Sudden Ca2+ increase
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Ca2+ channels
Ca2+ channels
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Calcium pumps
Calcium pumps
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Calcium-binding proteins
Calcium-binding proteins
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Synergism
Synergism
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Antagonism
Antagonism
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Cytokine Concentration
Cytokine Concentration
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Insulin receptor autophosphorylation
Insulin receptor autophosphorylation
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Insulin receptor's downstream effects
Insulin receptor's downstream effects
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G-protein coupled receptors (GPCRs)
G-protein coupled receptors (GPCRs)
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GPCR classes
GPCR classes
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Why multiple signaling pathways?
Why multiple signaling pathways?
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Hypothalamus
Hypothalamus
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Releasing Factors
Releasing Factors
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Pituitary Gland
Pituitary Gland
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Posterior Pituitary
Posterior Pituitary
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Anterior Pituitary
Anterior Pituitary
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Adenosine's Role in Wakefulness
Adenosine's Role in Wakefulness
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Caffeine's Mechanism
Caffeine's Mechanism
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Why Caffeine Keeps You Awake
Why Caffeine Keeps You Awake
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How Does Caffeine Affect Blood Vessels?
How Does Caffeine Affect Blood Vessels?
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What is Adenosine's Role in the Body?
What is Adenosine's Role in the Body?
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What is the Key Difference Between Adenosine and Caffeine?
What is the Key Difference Between Adenosine and Caffeine?
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What Happens When Adenosine Binds to its Receptors?
What Happens When Adenosine Binds to its Receptors?
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What Happens to Adenosine When Caffeine is Present?
What Happens to Adenosine When Caffeine is Present?
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Purine Biosynthesis Regulation
Purine Biosynthesis Regulation
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Feedback Inhibition
Feedback Inhibition
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Purine Degradation
Purine Degradation
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Purine Nucleoside Phosphorylase (PNP)
Purine Nucleoside Phosphorylase (PNP)
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Xanthine Oxidase
Xanthine Oxidase
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Uric Acid
Uric Acid
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Allantoin
Allantoin
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Why is purine degradation important?
Why is purine degradation important?
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Oxidative Phosphorylation's Role
Oxidative Phosphorylation's Role
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Nucleoside Diphosphate Kinase
Nucleoside Diphosphate Kinase
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Salvage Pathways
Salvage Pathways
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Adenosine Phosphoribosyltransferase
Adenosine Phosphoribosyltransferase
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Hypoxanthine-Guanine Phosphoribosyltransferase
Hypoxanthine-Guanine Phosphoribosyltransferase
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Regulation of Purine Synthesis
Regulation of Purine Synthesis
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UTP's Role in Carbohydrate Synthesis
UTP's Role in Carbohydrate Synthesis
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GTP's Role in Biosynthesis
GTP's Role in Biosynthesis
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Adenine Nucleotides: Enzyme Cofactors
Adenine Nucleotides: Enzyme Cofactors
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Cofactor Importance
Cofactor Importance
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What is cAMP's Role?
What is cAMP's Role?
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cGMP's Role
cGMP's Role
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Why are nucleotides regulatory molecules?
Why are nucleotides regulatory molecules?
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What is the purpose of signal transduction?
What is the purpose of signal transduction?
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Deoxyribonucleoside Triphosphate (dNTP) Synthesis
Deoxyribonucleoside Triphosphate (dNTP) Synthesis
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Origin of Deoxyribose
Origin of Deoxyribose
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Origin of Thymine Methyl Group
Origin of Thymine Methyl Group
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What are the two processes that make up dNTP biosynthesis?
What are the two processes that make up dNTP biosynthesis?
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How do cells ensure there's more RNA than DNA?
How do cells ensure there's more RNA than DNA?
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What are the roles of ribonucleotides and deoxyribonucleotides?
What are the roles of ribonucleotides and deoxyribonucleotides?
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What is the role of thymidylate synthase?
What is the role of thymidylate synthase?
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What is the significance of UMP to TMP conversion?
What is the significance of UMP to TMP conversion?
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What is RNR?
What is RNR?
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What is the primary source of electrons for RNR?
What is the primary source of electrons for RNR?
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How are electrons shuttled to RNR?
How are electrons shuttled to RNR?
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What are the two types of sites on RNR?
What are the two types of sites on RNR?
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How does ATP affect RNR activity?
How does ATP affect RNR activity?
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What is the function of RNR's activity sites?
What is the function of RNR's activity sites?
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What do RNR's specificity sites control?
What do RNR's specificity sites control?
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Why is RNR's regulation important?
Why is RNR's regulation important?
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Amino acid metabolism
Amino acid metabolism
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Primary functions of amino acids
Primary functions of amino acids
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What are the key differences of amino acid degradation and biosynthesis?
What are the key differences of amino acid degradation and biosynthesis?
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Where do amino acids come from?
Where do amino acids come from?
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What are the products of purine and pyrimidine degradation?
What are the products of purine and pyrimidine degradation?
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Transaminase Mechanism
Transaminase Mechanism
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Oxidative Deamination
Oxidative Deamination
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Non-Oxidative Deamination
Non-Oxidative Deamination
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Transdeaminase
Transdeaminase
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Fate of Nitrogen in Amino Acid Catabolism
Fate of Nitrogen in Amino Acid Catabolism
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Urea Cycle
Urea Cycle
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Ornithine Transcarbamoylase
Ornithine Transcarbamoylase
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Argininosuccinate Synthetase
Argininosuccinate Synthetase
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Arginase
Arginase
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Carbamoyl Phosphate Synthetase I
Carbamoyl Phosphate Synthetase I
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N-acetyl-glutamate
N-acetyl-glutamate
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Urea Cycle Regulation
Urea Cycle Regulation
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How does the Urea Cycle connect to the Citric Acid Cycle?
How does the Urea Cycle connect to the Citric Acid Cycle?
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CPS Activation Mechanism
CPS Activation Mechanism
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Urea Cycle Location
Urea Cycle Location
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PLP-dependent Transamination
PLP-dependent Transamination
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Serine Hydroxymethyltransferase
Serine Hydroxymethyltransferase
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What is Tetrahydrofolate?
What is Tetrahydrofolate?
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How is Cysteine Synthesized?
How is Cysteine Synthesized?
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Tyrosine Synthesis from Phenylalanine
Tyrosine Synthesis from Phenylalanine
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Feedback Inhibition in Amino Acid Synthesis
Feedback Inhibition in Amino Acid Synthesis
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PKU
PKU
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Transamination
Transamination
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What is the role of ornithine transcarbamoylase?
What is the role of ornithine transcarbamoylase?
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What happens to ammonia in amino acid catabolism?
What happens to ammonia in amino acid catabolism?
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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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