Class Notes (836,128)
Canada (509,645)
Biology (6,817)
Lecture 9

Lecture 9 Notes.docx

7 Pages
Unlock Document

Biology 2382B
Robert Cumming

Cell Biology Lecture 9 Notes – Basic Principles of cell signaling and GPCR system Basic Elements of cell signaling:  Signal or signaling molecule (ligand, first messenger) o Small molecules (epinephrine, acetylcholine, steroids), peptides, hormones, & light secreted by signaling cells o First messenger – molecule brings first message to the cell to do something  Receptors – recognize the signal o Cell-surface receptors o Intracellular receptors  Intracellular signaling and effector proteins o Receptors activated and instigate a sequence of events in the cell o G proteins, protein kinases (phosphorylate amino acids – serine, tyrosine, thymine) and phosphates  Second messengers o Small molecules such as Ca2+, cAMP, cGMP, IP3, DAG, NO  All cells receive and respond to signals from their environment – cells and environment must communicate Four forms of intercellular signaling:  Signaling molecules can be delivered to the cell by different mechanisms  Endocrine = signaling to distant cells o Signaling molecules are synthesized & secreted by signaling cells (endocrine cells) & are transported through circulatory system to target cells o The hormone generally refers to signaling molecules that mediate endocrine signaling  Paracrine = signaling to nearby cells o The signaling molecules released by a cell affect only those target cells in close proximity o E.g. neurotransmitters  Autocrine = signaling to cell itself o Cells respond to substances that they themselves release o Have receptor & recognize signal & develop response to signal molecule o E.g. tumour cells – express receptors for different growth factors  Signaling by PM-attached proteins o Signal molecules are membrane attached proteins o Make a cell complex – not like a cell-adhesion – cell complex just based on interactions between signal molecule and the cell Ligand-receptor interactions:  Binding specificity is based on the molecular complementarity (molecular recognition) between the interacting surfaces of a receptor (binding interface) and ligand (non-covalent forces) o Surfaces that interact tightly = complementary to each other  Interactions trigger a conformational change in the receptor – becomes active  Very often signaling molecules (ligands) induce receptor dimerization The Dissociation Constant:  R + L  RL at equilibrium we have a simple equilibrium-binding equation: K d [R][L]/[RL] o Kdis the measure of affinity of a receptor to its ligand o Kdis ligand concentration required to bind 50% of cell surface receptors o The lower the Kd, the lower the ligand concentration required to occupy 50% of the cell surface receptors  Ligand binding to a receptor usually can be viewed as a simple reversible reaction Nuclear-receptor superfamily:  Specific type of receptors that are NOT located in the membrane – cytoplasm or nucleus  Transcription factors that are activated once they bind their appropriate ligand  Focus only on the domains of the general primary structure  Lipid-soluble molecules/ hormones bind to intracellular receptors which constitute the nuclear receptor superfamily of transcription factors o Steroid hormones are extracellular & are used by intracellular receptor to mediate cell response – are synthesized by adrenal glands  Ligand binding domain – binds to specific hormones  DNA binding domain – binding the specific DNA sequence (response element)  Variable region – significant difference between transcription factors – have one of several activation domains within the variable region Gene activation by a nuclear receptor:  GR is a steroid hormone – can diffuse through PM and get inside the cell because is lipid soluble o Is a potent anti-inflammatory/ immuno-suppressive reagent & others  The characteristic nucleotide sequences of the DNA sites that bind nuclear receptors are called response elements o The receptor binds to a response element of the target gene and stimulate
More Less

Related notes for Biology 2382B

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.