Bio 006 - Cell Communication II & Immune System I

Signal Reception

Step 1 of Cell Communication:

Ligand binds to receptor, changing its shape.

Signal Transduction

Step 2 of Cell Communication:

Chain reaction of relay molecules transmitting signals.

Cellular Response

Step 3 of Cell Communication:

Change occurs within the cell due to signaling.

Ligand

Signaling molecule that binds to receptors.

Receptor

Protein that binds to a ligand.

G Protein-Coupled Receptors

• Made of alpha-helices

• Loops serve as binding sites

• GDP = inactive, GTP = active

• Receptors that interact with G proteins.

  • which binds to GDP (guanosine diphosphate) OR GTP (guanosine diphosphate)

Receptor Tyrosine Kinases

• Receptors that form dimers upon ligand binding.

• Each has a set of tyrosines (amino acids)

• When BOTH RTKs receive the signal, they snap together

Ion Channel Receptors

• Channel proteins that open in response to ligands.

• Usually closed, but open when a signal molecule binds

• Specifically let in ions such as Na+ or Ca2+

GDP

Inactive form of G protein, binds to G protein.

GTP

Active form of G protein, replaces GDP.

Membrane Receptors

Receptors located in the cell membrane.

Cytoplasmic Receptors

Receptors located in the cytoplasm or nucleus.

Phosphorylation

Addition of phosphate group to proteins.

Relay Molecules

Transmit signals from receptors to cellular targets in Signal Transduction

• protein

• Small non-protein molecules or ions

Monomer

Individual unit of receptor tyrosine kinases.

Tyrosines

Amino acids phosphorylated in receptor tyrosine kinases.

Ion Channel

Protein that allows ions to pass through cell membrane.

Na+

Sodium ion, can enter through ion channels.

Ca2+

Calcium ion, can enter through ion channels.

Hormone Receptors

Cytoplasmic receptors that bind hormones.

Conformational Change

Structural change in a receptor after ligand binding.

Cyclic AMP

A common secondary messenger in cells. Used as a Non-Protein Relay Molecule.

Calcium ions

Important ions in cellular signaling processes. Used as a Non-Protein Relay Molecule.

Cellular Response

Outcome of signal transduction pathway activation.

Signal Transduction Pathway

Regulates cellular activities based on signals.

Regulating Transcription

Altering gene expression to produce proteins.

Transcription

Copying DNA into mRNA for protein synthesis. Which the ribosomes then translate into protein

Hormones

Chemical messengers that regulate cellular functions.

Regulating Cytoplasmic Activities

Modifying the use of existing proteins in cells.

Epinephrine

Hormone that activates enzymes in response to stress.

(an example of Regulating Cytoplasmic Activities)

Amplification

Increasing the strength of a cellular response.

Response Variation Factors

Elements affecting how cells respond to signals.

• Is the response being amplified?

• How many steps in the relay?

• Is the response different across cell types?

• How efficient is the response?

• When does it stop?

Host

Organism infected by a pathogen.

• can have immune systems to fight

Pathogen

Disease-causing organism (germ), such as bacteria or viruses (can be prokaryotic & eukaryotic).

Immune System

Defense mechanism against pathogens in organisms.

Innate Immunity

General defense system without memory of pathogens.

Adaptive Immunity

Specific defense that learns and remembers pathogens. Expands overtime.

Physical Barriers

First line of defense against pathogens, like skin.

CRISPR

Bacterial system for cutting foreign DNA.

Defense Mechanisms

Strategies to surround and alert cells to pathogens.

Cleanup Crews

Cells that eliminate pathogens and debris.

Self vs Non-Self Recognition

Immune cells identify body cells versus invaders. Inside mammals.

Mammalian Immune System

Complex barriers and memory cells for defense.

Physical Barriers

First line of defense against pathogens.

complementary

Signal and receptor are ____________: they fit one another in a specific way

dimers

Two monomers bonded together in receptor activation in receptor tyrosine kinases

microbes

Are only pathogens if they make you sick.

bacteria

Keep a DNA log of bacteriophages that have previously attacked