Chapter 13 Flashcards
What are the 6 enzyme classifications?
“Over The HILL”
Oxidoreductase
Transferase
Hydrolase
Isomerase
Lyases
Ligase
What is the function of an oxidoreductase?
electron transfer (redox reactions)
What is the function of transferase?
transfer of functional groups
What is the function of hydrolase?
bond breakage with water
What is the function of lyases?
double bond formation from group elimination
What is the function of isomerases?
change isomer
What is the function of ligase?
bond formation from ATP hydrolysis
Where does glycolysis occur?
Cytosol
What reactions are rate-limiting in glycolysis?
Reactions 1, 3, and 10
What are the three rate-limiting enzymes of glycolysis?
Hexokinase
PFK
PK
Which reactions of glycolysis produce ATP?
PGK (reaction 7) and PK (reaction 10)
What are endocrine hormones?
Hormones released from endocrine glands into the bloodstream
What is the function of endocrine hormones?
Regulate physiological processes:
Maintain homeostasis
Respond to external stimuli
Developmental programs
What determines the specificity of signaling?
Presence of receptor
What is an agonist?
Substances that initiate a physiological response
What is an antagonist?
Substance that interferes with or inhibits the physiological action of another
What is exocrine secretion?
Release of substances onto the body surface (outside body)
Where do pancreatic secretions go?
Mostly digestive system (exocrine), but 1-2% are endocrine hormones
What type of hormones does the pancreas create?
Polypeptide (protein) prohormones
What organ of the endocrine system has alpha, beta, and gamma cells?
Pancreas
What do alpha-pancreatic cells secrete?
Glucagon
What is the purpose of glucagon?
Responds to low blood glucose
What do beta-pancreatic cells secrete?
Insulin
What is the purpose of insulin?
Responds to high blood glucose
What do gamma-pancreatic cells secrete?
Somatostatin
What is the purpose of somatostatin?
Inhibits secretion of insulin and glucagon
What is/are the primary targets of pancreatic hormones?
Liver, muscle, and adipose cells
Where are the adrenal glands located?
Above the kidneys
What are catecholamines?
Hormones made in the adrenal glands
What are the main hormones secreted by the adrenal medulla?
Norepinephrine and epinephrine
What are the two parts of the adrenal glands?
Cortex and medulla
What is the target of catecholamines?
alpha and beta-adrenergic receptors
What is the function of a beta-adrenergic agonist?
mimic the effect of adrenalin on beta-adrenergic receptors
What is the function of beta-adrenergic antagonists?
Minimize the effect of adrenaline release
What is the real name of beta blockers?
Beta-adrenergic antagonist
What drug is an example of a beta-adrenergic agonist?
Isoproterenol
What drug is an example of a beta-antagonist?
Propranolol
What drug is an example of an alpha-adrenergic antagonist?
Phentolamine
What is the function of glucocorticoids?
Regulate fuel metabolism, inflammatory reactions, and stress
What is an example of a glucocorticoid?
Cortisol
What is the function of mineralocorticoids?
Regulate salt and water balance
What is an example of a mineralocorticoid?
Aldosterone
What is the function of androgens?
Sexual development and function
What is an example of an androgen?
Testosterone
Where are steroid hormones produced?
Adrenal cortex, testes, and ovaries
What is unique about steroid hormones?
Lipid soluble; allows them to pass through the lipid bilayer and bind to cytosolic receptors
What do steroid hormones do upon binding to their receptor?
Move into the nucleus and act as a transcription factor
What is referred to as the “master gland”?
Pituitary gland
What is the function of hormones produced by the pituitary gland?
Regulate other endocrine glands
What amino acid is epinephrine and norepinephrine synthesized from?
Tyrosine
What is the function of adrenocorticotrophic hormone?
Signals kidney to regulate cortisol
What is the function of gonadotropins?
Regulate ovarian and testicular function
What is the function of prolactin?
Regulate mammary gland development and milk production
What is the function of thyroid stimulating hormone?
Regulate the amount of thyroid hormone that is being produced/released
What type of hormone is growth hormone?
Peptide Hormone
Where are the target receptors of growth hormone?
Muscle, bone, and cartilage
What is the difference between gigantism and acromegaly?
Gigantism is before skeletal system maturity (excess growth, but normal proportions) and acromegaly is after (excess growth of soft tissues)
What hormone is produced by adipose tissue?
Leptin
What is leptin?
Protein hormone that regulates appetite and metabolism
What cells does leptin act on? What does binding cause?
Hypothalamus; prevents hunger
What are the 3 ways the body controls enzyme activity?
Product/Substrate Availability
Allosteric Regulation
Covalent Modification
What are the 3 main types of covalent modification?
Glycosylation (adding carb)
Methylation (adding -CH3)
Phosphorylation (adding phosphate)
What amino acids are targeted by phosphorylation?
Hydroxylated amino acids
Serine, Ser, S
Threonine, Thr, T
Tyrosine, Tyr, Y
What type of enzyme adds a phosphate group? Removes?
Kinase: adds
Phosphatase: remove
What is dimerization?
Process of joining two molecular entities
What binds to the autophosphorylated tyrosine kinases of an RTK?
SH2 Domain
What does a SH3 domain bind to?
Proline-rich sequences
What are the steps of an RTK?
- Ligand binding
- Dimerization
- Autophosphorylation
- SH2 domain binding
- Adaptor protein linkage to G-protein
What is a G-protein?
GTP Hydrolyzing protein
What is a GAP?
GTPase Activating Protein
What is a GEF?
Guanine Nucleotide Exchange Factor
What is an example of a GEF?
Sos
What are the steps of small G-protein activation?
- Sos binding to SH3 domain of RTK
- Sos removes GDP for Ras
- New GTP binds to Ras
- GTP-bound Ras is active
- Ras activated Raf
- Activated Raf causes MEK to be phosphorylated
- pMEK phosphorylates MAPK
- pMAPK moves into nucleus
- pMAPK phosphorylates transcription factors
What transcription factors get activated during the MAP kinase pathway?
Fos, Jun, and Myc
What do Non-Receptor Tyrosine Kinases include?
Growth Hormone Receptor
Cytokine Receptor
Interferon Receptor
T Cell Receptor
Src
What type of protein is Src?
Myristoylated Protein
- Myristoyl is a fatty acid
- Associated with lipid bilayer
What are the domains of Src?
SH2
SH3
PTK (N and C lobe)
What is autoinhibitory of Src?
pY527
What is the result of pY527 in Src?
SH2 domain will bind to its own phosphotyrosine
What phosphorylation is required for the activity of Src?
pY416
What is the result of pY416 in Src?
416 phosphotyrosine will move out of binding pocket, allowing other molecules to be phosphorylated by Src’s ATP
Where does the phosphate needed for Src activity come from?
The ATP in its own binding pocket
What is the function of the enzyme PTP?
Dephosphorylate tyrosine residue
How does PTP function?
Transfers phosphoryl group to Cys residue on enzyme and then hydrolyzes it off
What domain is autoinhibitory of PTP?
SH2 Domain
How many transmembrane domains are present in GPCR?
7
What is a GPCR?
G-Protein Coupled Receptor; has 3 G-Proteins in a complex (alpha, beta, and gamma)
What is the activity of the trimeric complex of a GPCR?
Trimeric complex is inactive
What is the pathway of a GPCR?
- Ligase binding
- Alpha subunit released
- Exchange of GDP for GTP
- Protein signaling (ex. adenylate cyclase)
What is the structure of cAMP?
3’,5’-Cyclic AMP
Adenosine + Sugar w/ oxygen (from one phosphate) on carbon 3 and carbon 5
What is the effect of G-alpha-s?
Increase cAMP by stimulating adenylate cyclase
What inhibits G-alpha-s?
Cholera toxin
What is the effect of G-alpha-i?
Stops cellular cAMP production by inhibiting Adenylate Cyclase
What inhibits G-alpha-i?
Pertussis toxin
What is the function of cAMP phosphodiesterase?
Hydrolyzes cAMP to AMP, preventing activation of PKA
What drug inhibits cAMP PDE?
Sildenafil (Viagra)
What is Protein Kinase A?
Serine/Threonine Kinase
What is the function of Protein Kinase A?
Activated by 4 molecules of cAMP -> Phosphorylates Protein -> Cellular response
What enzyme removes phosphates from proteins?
Phosphoprotein phosphatase
What form is the G-alpha subunit in during the phosphoinositide pathway?
G-alpha-q
What occurs in the phosphoinositide pathway?
GTP-bound Gaq binds to phospholipase C and hydrolyzes PIP to DAG and IP3
What occurs after IP3 is produced by PLC?
- Binds to ER calcium channel
- Releases Ca2+
- Ca2+ binds to calmodulin
- Ca2+-CaM binds to CaM kinase
- CaM kinase phosphorylates protein
- Cellular response
What occurs after DAG is produced by PLC?
- Binds to Protein Kinase C
- PKC binds to Ca2+ through phosphatidylserine
- PKC (bound to DAG and PS) phosphorylates a protein
- Cellular response
What enzyme is used to hydrolyze IP3 to IP2?
Inositol Polyphosphate 5-phosphatase