Test 3: Lecture 54 Flashcards
___ a molecule secreted by ductless glands into the circulatory system to regulate physiology and behavior of organs throughout the body
hormone
hormones are produced by ___ glands
endocrine
hormones offer a critical means of ___ between tissues and organ systems in response to internal and external stimuli
communication
Hormones do not initiate reactions but rather they affect the ___of pre-existing metabolic functions in a positive or negative fashion
rate
Some hormones have specific effects on a single cell type, others a more __ effect
general
Hormones are effective at ___ concentrations
minute (very small amount)
Hormones have a very ___ half-life in circulation
short
(ranging from minutes to hours)
endocrine glands produce and secrete hormones ___ into the circulatory system
directly
endocrine glands ___ have ducts
do not
key functions of hormones
reproduction
growth and dev
homeostasis
energy production, utilization and storage
two main classes of hormones
amion acid derived
lipid derived (steroids)
amino acid derived hormones are :
- Whole proteins
- Peptides (fragments of proteins)
- Amines (derivatives of the amino acid tryptophan)
Lipid derived hormones are derived from ___
cholesterol
how do hormone achieve an effect on target cells?
receptors
each type of hormone has a specific ___ to which it can bind
receptor
two types of hormone receptors
plasma membrane bound
intracellular
plasma membrane bound hormone receptors usually bind to ___
peptide hormones
plasma membrane bound hormone receptors work by ___
Binding to cell membrane activates intracellular signal transduction programs that lead to gene expression responses in the nucleus.
intracellular hormone receptors usually bind to what type of hormone?
steroid (lipid derived)
how do intracellular hormone receptors work?
Binding to cell membrane activates intracellular signal transduction programs that lead to gene expression responses in the nucleus.
two types of control of hormone production
external and internal stimuli
___ is the main way of regulation of hormone production
feedback loops
negative feedback loops
end product/ intermediates stop reaction
positive feedback loops
intermediate/ end products induce production
pancreas secretion of insulin and glucagon peptides is an examples of ___ hormone
amino acid derived
levels of blood sugar regulate secretion of hormones from the ___
pancreas
pancreas secretes ___ when glucose levels are high
insulin
insulin binds to insulin receptors on fat and muscle and ___ glucose uptake
promotes
three types of cells in the pancreas
islets of langerhans
alpha
beta
delta
alpha cells:
secrete glucagon
facilitate the breakdown of glycogen to glucose. This elevated the blood sugar
(islet of langerhans in pancreas)
___ secrete the hormone insulin, which is essential for the maintenance of normal blood sugar levels. Inadequate levels result in diabetes mellitus
Beta cells
beta cells secrete the hormone ___, which is essential for the maintenance of normal blood sugar levels. Inadequate levels result in ___
insulin
diabetes mellitus
___ suppress the release of glucagon and insulin in the pancreas
delta cells
delta cells suppress the release of ___ and ___.
glucagon
insulin
___ secrete glucagon in the pancreas
alpha cells
Human insulin consists of 51aa in two chains connected by 2 ___ bridges
disulfide
insulin is a single gene product cleaved into 2 chains during ___ modification.
post-translational
insulin is degraded by ___
glutathione-insulin transhydrogenase (insulinase)
insulinase does what?
degrades insulin by cleaving the disulfide links
half life of insulin 5-10 minutes
glutathione-insulin transhydrogenase (insulinase)
insulin is synthesized as ___ in the pancreatic beta cells.
preproinsulin
preproinsulin is cleaved to ___ in the ER
proinsulin
proinsulin is converted into active insulin by ___ in the ___
cellular endopeptidases in the golgi apparatus
The endopeptidases cleave ___ at 2 positions, releasing a fragment called the C-peptide, and leaving 2 peptide chains, the B- and A- chains, linked by 2 ___bonds.
proinsulin
disulfide
what is the quaternary structure of insulin
- Insulin monomers can be in R-state or T-state conformations. (monomer are two strands an alpha and a beta chain)
- Insulin monomers form dimers (T state and R state combine- 4 in total)
- Insulin dimers for hexamers around a Zn2+ (zinc) ion ( 3 dimers bind together)
Insulin dimers for hexamers around a ___ ion
zinc
the insulin dimer is stabilized by ___ bonds
hydrogen
Insulin binding to target cell insulin receptors initiates signal transduction cascades that lead to ___ localizing to plasma membrane
glucose transporters (GLUT 4)
glut 4 lives in vesicles of cell, will get triggered to move to cell membrane and will bring glucose into cell
___ facilitate influx of glucose into the cell
Glucose transporters (GLUT 4)
eat high sugar food will trigger :
beta cells in pancreas to release insulin: cells will use glucose and liver will store glucose as glycogen= normal levels of blood glucose 90 mg/100 ml
if you don’t eat, blood glucose will fall which leads to ___
alpha cells in pancreas will release glucagon.
this triggers liver to breakdown glycogen into glucose and blood glucose will increase back to normal levels
Type 1 diabetes
insulin dependent
insulin not made: can be treated by giving insulin
Type 2 diabetes
non insulin dependent
insulin not recognized by cells, can’t bring sugar into the body
what is the “master” gland that regulated all other endocrine glands and also releases ___
pituitary
growth hormone
Growth hormone is a ___hormone
protein
growth hormone is secreted by the ___
pituitary gland
Pituitary release is controlled by the ___
hypothalamus
direct effects of growth hormones
anti insulin action
increased lipolysis
increased blood and sugar and other anti-insulin effects
example of indirect effects of growth hormones
will effect liver and other tissues to make insulin- like growth factors (IGFs)
which will then cause an indirect effect of
increased cartilage formation and skeletal growth, increased protein synthesis and cell growth and proliferation
___ feedback control of growth hormone release
negative
negative feedback of GH release
growth hormone stops GHRH (growth hormone releasing hormone)
insulin like growth factor 1 (IGF-1) stops growth hormone and activates GHIH (Growth hormone inhibiting hormone)
high levels of growth factor will inhibit
growth hormone releasing hormone
high levels of insulin like growth factor 1 (IGF1) will stimulate __ and decrease __
growth hormone inhibiting hormone
secreting of growth hormone
neurohormones are ___
hypothalamus hormones
___ regulate the release of pituitary hormones
hypothalamus hormones
steroid hormones are produced in the ___
adrenal cortex, testis, ovary and some peripheral tissues (adipose tissue)
All steroid hormones share a typical (but not identical) ___ ring structure
carbon-based
All steroid hormones are derived from ___ and differ only in the ring structure and side chains attached to it.
cholesterol
All steroid hormones are ___soluble but ___ insoluble
lipid
water
steroid hormones bind to ___ receptors
intracellular (they are lipid soluble= can freely move through the lipid bilayer)
•While ___hormones are encoded by specific genes, ___ hormones are synthesized from the enzymatic modification of cholesterol.
peptide
steroid
•There are far fewer different types of ___ hormones than ___ hormones.
steroid
peptide
•The regulation of ___ involves control of the enzymes which modify cholesterol into the steroid hormone of interest.
steroidogenesis
•The first enzymatic step in the production of ANY steroid hormone begins with enzymatic modification of ___
cholesterol
cholesterol can be made within the cells from ___
acetyl CoA
(de novo synthesis).
A key rate-limiting enzyme for production of cholesterol in the cell from acetyl CoA is ___
HMG-CoA reductase.
There is negative feedback regulation of ___ activity by cholesterol, so that high intracellular cholesterol inhibits de novo synthesis.
HMG-CoA reductase
•Cholesterol is also taken up by the cell in the form of ___
low density lipoprotein (LDL).
•LDL is a complex composed of cholesterol, ___ , ___, and proteins
phospholipids, triglycerides
(proteins and phospholipids make LDL soluble in blood).
•LDL is taken into cells via LDL receptors, and broken down into ___ and then ___
esterified cholesterol,
free cholesterol
two ways cell get cholesterol
from outside cell (LDL)
make it in cell from acetyl CoA
All steroid hormones derive from the ___within the cell.
free cholesterol
•A series of enzymatic steps in the ___ convert cholesterol into all of the other steroid hormones and intermediates.
mitochondria and ER
what is the rate limiting step of steroid synthesis
The rate-limiting step in this process is the transport of free cholesterol from the cytoplasm into mitochondria.
the process of transport of free cholesterol from the cytoplasm into mitochondria is carried out by ___
Steroidogenic Acute Regulatory Protein (StAR)
1st step of cholesterol breakdown into other hormones is ___
CYP11A into pregnenolone
•Steroid hormones are not water soluble so have to be carried in the blood complexed to specific binding ___.
globulin proteins
•Corticosteroid binding globulin (CBG) carries ___
cortisol
steroid hormones have to be carried through blood because they are hydrophobic
•Sex steroid binding globulin (SHBG) carries ___ and ___
testosterone and estradiol
steroid hormones have to be carried through blood because they are hydrophobic
Glucocorticoids
cortisol is the major representative in most mammals – produced by adrenal cortex
class of steroid hormone
Mineralocorticoids
; aldosterone being most prominent – produced by adrenal cortex
class of steroid hormone
Androgens
such as testosterone – produced by testis
class of steroid hormone
Estrogens
, including estradiol and estrone – produced by ovary
type of steroid hormone
Progestogens (also known a progestins)
such as progesterone – produced by ovary and adrenal cortex
class of steroid hormone
Steroid hormones are classified chemically by number of ___.
carbons
what are the most common number of carbons for steroid hormones?
C18 (ovarian)
C19 (testicular)
C21 (adrenal cortical)
