BAMS Molecules and Cells Flashcards
Ligand
generic name for any chemical messenger that interacts with a receptor. Receptor/ligand interactions are highly specific. Only cells that express the correct receptor can bind to the ligand
Plasma membrane
phospholipid bilayer that functions as a barrier between intracellular and extracellular environments
Can hydrophilic or hydrophobic molecules more easily enter cells? Why?
Hydrophobic core of phospholipid bilayer prevents hydrophilic molecules from diffusing across the cell membrane
Molecular structure of most ligands, and the relevance of this
Large and hydrophilic so they must interact with cell surface receptors rather than intracellular receptors
e.g. hormones, cytokines, peptides, growth factors
Example of a hydrophobic molecule that would diffuse across cell membrane and interact with intracellular receptors
Steroid hormones
Stages of signal transduction pathway
Stage 1 - receptor ligation
Stage 2 - signal transduction
Stage 3 - cell response
Stage 2 of the signal transduction pathway
Signal transduction
Recruitment of second messengers to deliver the message from the activated receptor at the plasma membrane to effector proteins
Functions of stage 2 of the signal transduction pathway
Stage 2 - signal transduction
1. Deliver the signal from the activated receptor to the effector proteins
2. Amplify the signal
Example of signal transduction
Phosphorylation cascade
Enzymes that add phosphates to proteins
Kinases
Enzymes that remove phosphates from proteins
Phosphatases
Signal transduction pathways deliver signals to effector proteins where?
Either in the nucleus or cytoplasm
Effector molecules in the nucleus
Transcription factors - their function is to regulate gene expression
Function of transcription factors
Regulate gene expression
Process of making genes functional
DNA transcribed into mRNA by RNA polymerases, guided by transcription factors to promoter sequences
mRNA translated into proteins
What determines activity of transcription factors
- Phosphorylation/dephosphorylation
- Ligand binding
What can disrupted cell communication pathways often result in?
Disease
What component of the signal transduction is most commonly targeted by drugs for a therapeutic benefit?
Receptors
Insulin
Hormone important in the regulation of blood sugar levels
Describe the process triggered by eating a lot of sugar
Glucose absorbed from the digestive tract and blood sugar levels increase
Activation of receptors that monitor blood glucose
Release of insulin into bloodstream from beta cells in the pancreas
Insulin binds to receptors on target cells
Target cells take up and metabolise glucose from bloodstream
Acids
Molecules or ions which tend to give up protons when in solution
Bases
Molecule or ions which tend to accept protons when in solution
HX <–> H+ + X- What is the conjugate acid and conjugate base?
HX is conjugate acid
X- is conjugate base
Acid dissociation constant formula
Ka = [H+][X-]/[HX]
