Cell Biology 2025 Final Exam Study Guide

These flashcards cover key vocabulary terms and concepts related to cell communication and signaling pathways as outlined in the Cell Biology 2025 lecture notes.

Intercellular Signaling

Communication between cells, typically involving signaling molecules.

US28

similar in structure to human chemokine receptor CCR1, signals constitutively, binds to varous chemokines, can activate many different g proteins

examples of disabilities when loss of function mutations resulting in nonfunctional signal pathways

retinitis pigmentosa which is a progressive degeneration of the retina. caused by mutations in rhodopsin’s ability to activate g protein

Example of disability when gain of function mutations may create a constitutively activated g protein

some benign thyroid tumors are caused by mutation in a receptor so the receptor is always on even if not binding

Certain polymorphisms in g protein related genes may result in what?

increased susceptibility to asthma or high blood pressure, as well as decreased susceptibility to HIV

How are cancers promoted?

by deregulation of signaling pathways

HCMV symptoms in immunocompromised patients

visual impairment blindness, pnemonia with low blood oxygen, gastrointestinal ulcerations and bleeding, effects on liver, hepatits, brain encephalitis, behavioral changes, seizures, and coma

What cancers have promoted development in HCMV?

Colon cancer and malignant glioblastoma

desensitization

by blocking active receptors from turning on additional G proteins

Arrestins

proteins that compete with G proteins to bind GPCRs

How to accelerate termination of the response?

accelerated by regulators of G-protein signaling (RGSs)

How to terminate response?

Desensitization, arrestin proteins, acceleration by RGSs

Signaling pathways

consist of a series of proteins. Each protein in a pathway alters the conformation of the next which is usually altered by phosphorylation

Extracellular messengers include:

Small molecules such as amino acids and their derivatives, gases such as NO and CO, steroids, Eicosanoids (lipids derived from fatty acids), various peptides and proteins

Extracellular Messenger receptors include:

G-protein coupled receptors (GPCRs), Receptor protein-tyrosine kinases (RTKs), ligand gated chanels, steroid hormone receptors, specific receptors like B- and T-cell receptors

What do cells need to respond to in order to survive?

External stimuli (environment) via cell signaling

Autocrine Intercellular Signaling

A type of intercellular signaling where a cell produces signaling molecules that bind to receptors on its own surface, influencing its own behavior.

Paracrine Intercellular Signaling

A form of intercellular signaling where signaling molecules released by a cell affect nearby target cells. Nearby cells that have receptors bind to signal

Endocrine Intracellular Signaling

“Hormone signaling” through bloodstream to long distances to affect distant target cells.

Transcription Factors

Proteins that regulate gene expression by binding to specific DNA sequences.

What is Protein Phosphorylation?

The addition of a phosphate group to a protein, often regulating its activity.

What can protein phosphorylation do?

Can activate or inactivate an enzyme, increase or decrease protein-protein interactions, induce a protein to move from one compartment to another, or act as a signal that initiates protein degradation

Protein Kinase

An enzyme that catalyzes the transfer of phosphate groups to specific substrates, usually proteins. Regulate diverse activities as hormone action, cell division, and gene expression

Extracellular Messengers

Signaling molecules such as hormones or neurotransmitters that are released into the extracellular space to send signals to target cells. Transmit messages between cells. Ex. cytokines

G-Protein Coupled Receptor (GPCR)

A large family of cell surface receptors that detect molecules outside the cell and activate internal signal transduction pathways. Very specific structure. Several color receptors, odorant receptors, and taste receptors for bitter and some sweet flavors

How many transmembrane domains do GPCRs have and what to they interact with?

GPCRs have 7 transmembrane domains and interact with G proteins.

Rhodopsin

A light-sensitive receptor protein involved in visual phototransduction. photosensitive protein for black-and-white vision that is also a GPCR.

What is a Trimeric G Protein?

A G protein composed of three subunits (alpha, beta, gamma) that transduces signals from GPCRs. Bound to GDP when inactive and exchanges GDP for GTP upon activation.

What do trimeric G proteins do?

Transmits signals from receptor to effector and can exist in multiple forms.

What are Second Messengers?

Intracellular signaling molecules that relay signals received at receptors on the cell surface.

What do Second Messengers do?

Amplify the response to a single extracellular ligand and can be made over and over again

cAMP

Cyclic adenosine monophosphate, a second messenger important in many biological processes. released into the cytoplasm after receptor binding of a ligand.

What is cAMP produced in response to and what does it do?

extracellular signal and activates protein kinase A (PKA) to regulate various cellular functions

What is cAMP involved in?

Fatty acid formation, glycogen formation, glycogen breakdown, DNA synthesis, differentiation, RNA synthesis, protein synthesis, assembly/disassembly of microtubules

c-di-GMP

A second messenger that regulates various cellular processes, including biofilm formation and motility in bacteria, by influencing the activity of other signaling molecules. Acts like a switch inside cell that turns certain behaviors off or on

Effector

Something that carries out a response after reviving a signal

Phosphodiesterase

An enzyme that breaks down cyclic nucleotides such as cAMP and cGMP or c-di-GMP or c-di-AMP.

Diguanylate Cyclase

An enzyme that converts GTP to cyclic di-GMP, a second messenger involved in bacterial signaling. Joins two GTP molecules in a circular form.

What does Diguanylate do in high levels?

regulates biofilm formation, reduces motility, increases production of extracellular polysaccharides

What does Diguanylate Cyclase so in low levels?

gives more motility and less biofilm

Adenylyl Cyclase

An enzyme that converts ATP to cyclic AMP, a key second messenger. Affects heart rate, energy metabolism, hormone secretion, and memory and learning

How can a signal be amplified?

Signaling cascades or second messengers.

What is the target for cholera toxin?

GPCRs and G-proteins

Cytokines

Signaling proteins that mediate and regulate immunity, inflammation, and hematopoiesis. Secreted by cells of the immune system.

Chemokines

A subset of cytokines that induce chemotaxis in nearby responsive cells. Act as chemoattractants, stimulating the migration of lymphocytes into inflamed tissues

What is chemotaxis?

movement toward or away from a particular substance

IL-6 – STAT Pathway

A signaling pathway that involves the cytokine IL-6 and leads to activation of STAT transcription factors.

What does IL-6 STAT pathway do?

It is a crucial role in immune responses, inflammation, and regulation of various functions

Steps in IL-6 STAT Pathway

1. IL-6 shows up when there is inflammation or infection

2. IL-6 attaches to a receptor on the surface of certain cells (lock + key)

3. receptor changes shape and activates helper proteins called JAK

4. JAKS add a chemical tag to protein called STAT3 which turns it on

5. Activated STAT3 goes into cell’s nucleus and turns on specific genes that tell the cell what to do

Human Cytomegalovirus (HCMV)

A common virus that can cause disease in individuals with weakened immune systems, particularly problematic in infants and organ transplant recipients. Family B-herpesviruses. 80-90% of the population carries it and they are usually asymptomatic. genome encodes 4 chemokine receptors

Symptoms of HCMV Infection

Jaundice, purple splotches/rash, small birth weight/size, enlarged spleen, poorly functioning liver, pneumonia, seizures, delayed manifestations