BIOL2108H - Endocrine System

NAD+/NADH and FAD/FADA2 act differently as electron carriers

-NADH has to transfer both electrons simultaneously, while FADH2 can transfer one electron at a time

-NADH carriers “higher energy” electrons than FADH2

-this is why NADH passes electrons to complex I and FADH2 passes electrons to complex II

-around 2.5 ATP per NADH vs around 1.5 ATP per FADH2

oxygen important in cellular respiration

-oxygen is required as the final electron acceptor

-without enough O2, cannot harvest ATP during the ETC

-instead, just get 2 ATP from glycolysis and regenerate NAD+ (quick (inefficient) way of getting energy from glucose. so cells do this if pyruvate is ubiblding faster than can be used (fast-twitch muscle). red blood cells lack mitochondria and also do this

fermentation

-lactate is transported back to liver

-converted back to glucose for later energy via cellular respiration

main idea 1 summary

when oxygen is limiting, anaerobic fermentation can provide some energy from glucose

recall

glucose in our blood can be used immediately or stored

2 communication systems in our bodies

nervous and endocrine system

hormones

-glands manufacture specific hormones

-hormones travel through bloodstream

-hormones interact with target cells to trigger specific responses

endocrine glands

secret hormones as messengers to target cells

receptors

-hormones need to bind to receptors on target cells to cause a response

-receptors are hormone-specific proteins

-not all cels have receptors for every hormone

3 types of hormones

amine, peptide, lipid (steroids) hormones

amine hormones

small, polar, epinephrine (adrenaline), melatonin

peptide hormones

large, polar, insulin, oxytocin, prolactin

lipid hormones

variable, nonpolar, testosterone, estrogen

polar/nonpolar

hormone transport and hormone receptors depend on if its polar or nonpolar

hydrophilic (polar) hormone

-diffuse in and out of the blood stream

-cannot diffuse across cell membrane, instead binds to an extracellular receptor

hydrophobic (nonpolar) hormone

-need carrier proteins in blood

-diffuse across cell membrane and bind to receptor inside the target cell (intracellular). hormone-receptor complex travels to nucleus and alters DNA transcription (signal transport)

when hormone binds to receptor

signal transport or signal transduction

signal transport

movement of molecule across a membrane

hormones regulate gene expression

since all cells have identical DNA, regulation of gene expression helps cells differentiate

signal transduction

-movement of signal across a membrane (hormone → second messenger

-hydrophilic polar: binds to receptor outside the target cell (extracellular)

-triggers a cascade of second messenger molecules

-immediate cellular response

-can also alter DNA transcription for longer-term response

target and strength of hormone responses is controlled

-aren’t on/off switch

-receptors only on target cells

-change the amount of hormone and the number of receptors

-block/inhibit binding to receptors

-amplifying or counteracting hormones