Cell Junctions, Motor Proteins, and Signaling Pathways

Microtubule

Organelle or vesicle transport

Microtubule and microfilament

Motor proteins

Microtubule

Cilia and flagella

Microfilament

Lamellipodia and filopodia

Microfilament

Muscle contraction

Myosin

Lamellipodia movement

Dynein

Cilia beating

Kinesin and Dynein

Movement of organelles and vesicles along microtubules

Dynein

Flagella

Myosin

Muscle contraction

Motor proteins

They convert chemical energy into motion.

Muscle contractions

Involve shrinking and lengthening of actin and myosin filaments.

None of the above

Processes of motility that do NOT require ATP

Heterophilic interaction

Leukocytes express carbohydrates on their plasma membrane that bind to selectins on the endothelial cells.

Tight junction

A mutation in ZO-1 or Claudin would result in a poor tight junction.

Desmosomes

Most beneficial junction for skin cells exposed to mechanical stress.

Intermediate Filaments

Cytoskeletal structure responsible for stress resistance in skin cells.

Integrin

A mutation in a gene preventing a cell from binding to collagen is most likely in a gene that encodes this type of protein.

Cadherin mutation

Could result in disorganization of the cells of a developing embryo.

Endocytosis of E-cadherins

Best molecular explanation for epithelial-mesenchymal transition (EMT).

Integrins

The extracellular matrix contains all the following proteins EXCEPT this.

Plasmodesmata

Plant cells contain these structures that span cell walls to connect multiple cells.

Plasmodesmata connection

Most similar to a gap junction.

Autoimmune disorder symptom

Improper migration to cells to the correct destinations.

Cortisol

A hormone produced at the adrenal glands that travels throughout the bloodstream.

Receptors

They exclusively initiate signaling by binding downstream second messengers.

Ligand binding

Ligands typically bind non-covalently to allow reversible signaling.

Unit affinity (Kd)

The ligand concentration at which 50% of receptors are bound.

Ligand A vs Ligand B

If Ligand A and Ligand B were applied together at the same concentration, Ligand A would outcompete Ligand B for the receptor.

Decrease responsiveness to ligand

Downregulate expression of the receptor for the ligand or prevent the receptor from binding to downstream second messengers.

Kinase

An enzyme that adds phosphate groups to molecules.

Leukocyte interaction

An example of heterophilic interaction.

Mutation in tight junction

A mutation in ZO-1 or Claudin would result in a poor tight junction.

Junction for mechanical stress

Desmosomes are most beneficial to withstand mechanical stress.

Cytoskeletal structure for junctions

Intermediate filaments are responsible for the structural integrity in junctions.

Cadherin

A type of cell adhesion molecule that helps cells stick to each other.

Integrin

A transmembrane receptor that facilitates cell-extracellular matrix adhesion.

Selectin

A type of cell adhesion molecule that binds to carbohydrates on the surfaces of other cells.

Proteoglycan

A protein that is heavily glycosylated and is a major component of the extracellular matrix.

Epithelial-mesenchymal transition (EMT)

A process where epithelial cells lose their characteristics and gain migratory properties.

Cortisol

A steroid hormone produced by the adrenal glands that regulates various functions in the body.

Ligand

A molecule that binds to a receptor to initiate a signaling pathway.

Receptor

A protein that receives and transmits signals from ligands.

Antibodies

Proteins produced by the immune system to identify and neutralize foreign objects.

Fibronectin

A glycoprotein that helps cells attach to the extracellular matrix.

Collagen

A structural protein that provides strength and support in connective tissues.

Plasmodesmata

Channels that allow communication and transport between plant cells.

Tight junction

A type of junction that prevents leakage of materials between cells.

Gap junction

A specialized intercellular connection that allows direct communication between cells.

Desmosome

A structure that anchors adjacent cells together.

Adherens junction

A junction that connects the actin cytoskeleton of one cell to that of another.

Juxtracrine

A type of signaling where cells communicate through direct contact.

Autocrine

A type of signaling where a cell targets itself.

Paracrine

A type of signaling where a cell targets nearby cells.

Downregulate

To decrease the expression or activity of a receptor.

Enzyme

A biological catalyst that speeds up chemical reactions.

Phosphorylation

The addition of a phosphate group to a molecule, often used to regulate activity.

Kinase

An enzyme that catalyzes the transfer of phosphate groups from high-energy donor molecules, such as ATP, to specific substrates.

G-protein

A molecular switch that transmits signals from a variety of stimuli outside a cell to its interior.

Phosphatase

An enzyme that removes a phosphate group from its substrate, often reversing the action of kinases.

G-protein coupled receptors

Membrane proteins that transmit signals through seven transmembrane domains and interact with G-proteins.

PKA

Protein Kinase A, an enzyme that is activated by cyclic AMP and phosphorylates various target proteins.

cAMP

Cyclic adenosine monophosphate, a second messenger important in many biological processes.

PLC

Phospholipase C, an enzyme that cleaves phosphatidylinositol 4,5-bisphosphate (PIP2) into IP3 and DAG.

IP3

Inositol trisphosphate, a second messenger that triggers calcium release from the endoplasmic reticulum.

DAG

Diacylglycerol, a second messenger that activates protein kinase C.

β-arrestin

A protein that regulates G-protein coupled receptor signaling and mediates receptor desensitization.

mAchR

Muscarinic acetylcholine receptor, a type of G-protein coupled receptor that responds to acetylcholine.

G1 phase

The first phase of the cell cycle, where the cell grows and prepares for DNA replication.

G0 phase

A resting phase where the cell is not actively preparing to divide.

G2 phase

The second gap phase of the cell cycle, where the cell prepares for mitosis.

Interphase

The phase of the cell cycle where the cell is not dividing and DNA is replicated.

Autophosphorylation

The process by which a kinase phosphorylates itself, often critical for its activation.

Epinephrine

A hormone that increases heart rate and energy availability, acting through adrenergic receptors.

Crosstalk

Interactions between different signaling pathways that can affect cellular responses.

Ligand

A molecule that binds to a receptor to initiate a signaling cascade.

Receptor dimerization

The process where two receptor molecules bind together, often necessary for receptor activation.

Calcium signaling

A signaling mechanism that involves the release of calcium ions to trigger various cellular processes.

Transmembrane proteins

Proteins that span the entire membrane of a cell and play a role in signaling.

Heterotrimeric G-proteins

G-proteins composed of three different subunits (alpha, beta, gamma) that transmit signals from receptors.

Anaphase and Metaphase

Dynamic instability of microtubules is key

Interphase stages

A cell that is in interphase could be in G1, S, or G2

Centrosome of MTOCs

Contains centrioles

Chromatids at prophase

An adult human stem cell has a total of 48 chromosomes, resulting in 96 chromatids at prophase during mitosis

Checkpoint during the cell cycle

Determines the previous stage is complete before beginning the next stage and that each stage occurs at the correct time

Cyclin concentration during DNA replication

Reaches a peak during DNA replication and then falls once in G2; likely a G1-S cyclin

G1-S checkpoint influences

All of these influence the G1-S checkpoint EXCEPT whether chromosomes are attached to the mitotic spindle

Protein Ras

Is a proto-oncogene and a GTPase

Growth factors and cell division

Stimulate cell division by ultimately relieving transcription factor E2F from inhibition

Complete activation of the MPF

Requires M-Cdk to be bound to m-cyclin and for inhibitory phosphates to be removed via a phosphatase

Inducing a cell to skip G2 phase

Injection of M-cyclin

Regulating Cdk activity

Each of the following is involved in regulating Cdk activity EXCEPT none of these regulate Cdk activity

Raf and MEK relationship

Raf is to MEK, as MEK is to MAPK

Destruction-inducing protein

A cell expresses a protein on the surface that leads to its destruction; likely a death receptor

Apoptosis definition

Describes organized cell death

Cytochrome C release

Released from mitochondria during indirect apoptosis

Bcl2 injection consequence

A cell that probably should have undergone apoptosis will survive

Characteristics of cancer cells

Can survive without anchoring, resistant to apoptotic-inducing factors, and resistant to density-dependent inhibition

Cancer cell mitosis

A cancer cell undergoes mitosis faster than a normal cell

Carcinogens and DNA damage

Can damage DNA by point mutation, chromosomal translocation, insertion or deletion, and transposition