Week 5 - Cellular Communications (RAH Y1 - Cell Biology)

What is cell communication?

The process by which cells send, receive and respond to signals.

Why do cells need to communicate?

To coordinate their activities, respond to changes and maintain a stable internal environment.

What is homeostasis?

The maintenance of a relatively stable internal environment.

How does cell communication help maintain homeostasis?

It allows cells to detect changes and coordinate responses that help keep internal conditions stable.

What is a signalling molecule?

A molecule that carries a message from one cell to another or within a cell.

What is a ligand?

A signalling molecule that binds to a specific receptor.

What is a receptor?

A protein that recognises and binds a specific signalling molecule and helps trigger a cellular response.

What is the difference between a ligand and a receptor?

A ligand is the signalling molecule; a receptor is the protein that recognises and binds it.

Why are receptors specific?

Their structure allows them to bind only particular ligands or groups of compatible ligands.

What happens when a ligand binds to its receptor?

The receptor is activated or changes activity, initiating a response in the cell.

Can every cell respond to every signalling molecule?

No. A cell generally needs the appropriate receptor to respond to a particular signal.

What is extracellular signalling?

Communication involving signals that act outside a cell, often by binding to receptors on target cells.

What is intracellular signalling?

Communication and signal processing that occur inside a cell.

What is the extracellular matrix (ECM)?

A network of molecules outside cells that provides structural support and helps cells interact and communicate.

What are the main functions of the extracellular matrix?

It supports cells, helps organise tissues and influences cell attachment, behaviour and signalling.

What is collagen?

A structural protein in the extracellular matrix that provides strength and support.

What are proteoglycans?

ECM components made of proteins attached to carbohydrate chains that help form and maintain the surrounding matrix.

What is fibronectin?

An extracellular matrix protein that helps cells attach to the matrix and connects matrix components with cell-surface receptors.

What are integrins?

Cell-surface receptors that connect the extracellular matrix to the cell and help transmit signals.

How can the extracellular matrix affect cell behaviour?

By interacting with cell receptors and influencing signals that affect cell activities.

What are glycoproteins?

Proteins with carbohydrate chains attached to them.

What are glycolipids?

Lipids with carbohydrate chains attached to them.

How do glycoproteins and glycolipids help cells recognise one another?

Their carbohydrate patterns can act as identifying markers on cell surfaces.

What is cell recognition?

The ability of cells to identify and distinguish particular cells or molecules through specific surface markers and interactions.

What is direct cell-to-cell signalling?

Communication in which neighbouring cells pass signals directly between one another, for example through cell connections.

What is autocrine signalling?

A cell releases a signalling molecule that acts on the same cell that released it.

What is paracrine signalling?

A cell releases a signal that acts on nearby cells.

What is endocrine signalling?

Communication in which hormones travel through the bloodstream to act on distant target cells.

What is the key difference between paracrine and endocrine signalling?

Paracrine signals act locally on nearby cells; endocrine hormones travel through the blood to distant cells.

Which type of signalling acts on the cell that released the signal?

Autocrine signalling.

Which type of signalling acts on nearby cells?

Paracrine signalling.

Which type of signalling commonly uses the bloodstream to reach distant target cells?

Endocrine signalling.

What is a cell junction?

A specialised connection between cells that helps them seal together, attach to one another or communicate.

What is the main function of tight junctions?

They seal adjacent cells together and help prevent substances leaking between them.

What is the main function of desmosomes?

They provide strong attachment between cells and help tissues resist mechanical stress.

What is the main function of gap junctions?

They form channels between neighbouring animal cells, allowing certain small molecules and ions to pass directly between them.

Which cell junction helps prevent leakage between adjacent cells?

Tight junctions.

Which cell junction provides mechanical strength between adjacent cells?

Desmosomes.

Which cell junction allows direct communication between neighbouring animal cells?

Gap junctions.

What are plasmodesmata?

Channels through plant cell walls that connect the cytoplasm of neighbouring plant cells.

What is the function of plasmodesmata?

They allow materials and signals to pass between neighbouring plant cells.

How are plasmodesmata and gap junctions similar?

Both provide direct connections that allow communication between neighbouring cells.

How are plasmodesmata and gap junctions different?

Plasmodesmata connect plant cells through their cell walls; gap junctions connect neighbouring animal cells.

What are the three main stages of cell signalling?

Reception, transduction and response.

What happens during reception?

A signalling molecule binds to its specific receptor.

What happens during signal transduction?

The signal is passed along or converted into intracellular signals that relay the message.

What happens during the response stage?

The cell produces a specific effect in response to the signal.

What is signal transduction?

The process of transmitting a signal from a receptor through a cell to produce a response.

Why is signal transduction important?

It connects the detection of an external signal to the appropriate response inside the cell.

Can a signalling pathway produce more than one cellular effect?

Yes. Signals can affect different processes depending on the cell and the signalling pathway involved.

What is a target cell?

A cell that can respond to a particular signalling molecule because it has the appropriate receptor.

What is synaptic signalling?

Communication between a nerve cell and a target cell across a synapse using chemical messengers.

What is a synapse?

A specialised junction where a nerve cell communicates with another cell.

What is a neurotransmitter?

A chemical messenger released by a nerve cell that transmits a signal to a target cell.

How does a neurotransmitter generally communicate across a chemical synapse?

It is released by a nerve cell, crosses the synaptic gap and binds to receptors on the target cell.

What is acetylcholine?

A neurotransmitter involved in communication between nerve cells and target cells, including roles in muscle control.

What is dopamine?

A neurotransmitter important in brain signalling, including the control and coordination of movement.

What is serotonin?

A neurotransmitter involved in signalling processes associated with functions such as mood and other aspects of nervous system activity.

Why are neurotransmitters important?

They allow nerve cells to communicate with other cells and coordinate body functions.

What is endocrine signalling mainly associated with?

Hormones released into the bloodstream that affect distant target cells.

What is a hormone?

A chemical messenger released by cells that influences the activity of target cells with suitable receptors.

How can hormones affect target cells?

They bind to specific receptors and initiate signalling pathways that change cell activity.

What are steroid hormones?

Lipid-based hormones that can pass through cell membranes and bind to receptors inside target cells.

How does steroid hormone signalling differ from signalling by many water-soluble hormones?

Steroid hormones can cross the cell membrane and bind intracellular receptors, whereas many water-soluble hormones bind to receptors on the cell surface.

Why can steroid hormones cross cell membranes?

Their lipid-based structure allows them to pass through the lipid bilayer.

What is a G-protein-coupled receptor (GPCR)?

A cell-surface receptor that activates a G protein when an appropriate ligand binds.

What happens when a ligand activates a GPCR?

The receptor activates a G protein, which helps relay the signal to downstream components inside the cell.

What is the role of a G protein in signalling?

It helps transmit a signal from an activated GPCR to other components of the signalling pathway.

What is an ion channel receptor?

A receptor that controls an ion channel, allowing particular ions to cross the cell membrane when the channel opens.

How can ion channel receptors change cell activity?

By allowing ions to move across the membrane, changing the electrical or chemical conditions of the cell.

What is an enzyme-linked receptor?

A cell-surface receptor associated with enzyme activity that can initiate intracellular signalling when activated.

What is the main difference between GPCRs and ion channel receptors?

GPCRs relay signals through G proteins; ion channel receptors regulate the passage of ions across the membrane.

What is receptor activation?

The change in a receptor's activity after it binds an appropriate signalling molecule.

Why must signalling pathways be regulated?

To ensure cell responses occur at the right time and intensity and do not continue unnecessarily.

What can happen if cell communication goes wrong?

Cell activities may become poorly controlled, contributing to disease or abnormal tissue function.

What is receptor affinity?

The strength or tendency with which a ligand binds to its receptor.

How might altered ligand-receptor interactions affect a cell?

They may change how strongly or effectively a cell responds to a signal.

What is Type 1 diabetes?

A condition in which the body produces little or no insulin because insulin-producing pancreatic beta cells are destroyed.

What is insulin?

A hormone that helps regulate blood glucose levels.

What is the role of insulin in glucose regulation?

It signals insulin-responsive tissues to increase glucose uptake, helping lower blood glucose levels.

What happens to insulin production in Type 1 diabetes?

Insulin production becomes very low or absent because insulin-producing beta cells are destroyed.

Why does blood glucose rise in Type 1 diabetes?

Without sufficient insulin, insulin signalling is impaired and glucose uptake by insulin-responsive tissues is reduced.

How does Type 1 diabetes illustrate the importance of cell communication?

It shows that when a hormone signal is missing, target cells cannot respond normally and the body's regulation of blood glucose is disrupted.

What is cancer in terms of cell behaviour?

A disease involving abnormal cell growth and division that is not properly controlled.

Why is communication between cells important for controlling cell growth?

Signals help regulate cell division, survival and other activities; disrupted signalling can contribute to uncontrolled growth.

What is p53?

A protein that helps protect cells by responding to DNA damage and regulating the cell cycle and cell survival.

Why is p53 often described as a tumour suppressor?

It can prevent damaged cells from continuing to divide, helping reduce the risk of cancer.

What can p53 do when DNA damage is detected?

It can stop or slow the cell cycle to allow repair, or trigger apoptosis if the damage cannot be repaired.

What is apoptosis?

Programmed cell death, a controlled process by which a cell is eliminated.

Why is apoptosis important?

It removes cells that are damaged or no longer needed, helping maintain healthy tissues.

What may happen if p53 does not work properly?

Damaged cells may escape normal growth controls and survive or divide, increasing the risk of cancer.

How are DNA damage, p53 and cancer connected?

p53 helps stop damaged cells dividing or triggers their death; failure of this protection can allow cancer to develop.

What is Parkinsonism?

A group of movement-related symptoms associated with disruption of the brain systems that control movement; Parkinson's disease is one cause.

Which neurotransmitter is particularly associated with Parkinson's disease?

Dopamine.

How does dopamine loss affect movement in Parkinsonism?

It disrupts signalling in brain circuits involved in movement, making movements slower and less well coordinated.

What happens to dopamine signalling in Parkinson's disease?

Dopamine-producing nerve cells in a key brain region are lost, reducing dopamine signalling.

Why is dopamine important for movement?

It helps regulate brain circuits that initiate and coordinate movement.

What role does acetylcholine play in the Parkinsonism lecture example?

Acetylcholine is another neurotransmitter involved in movement-control circuits and is discussed in relation to its balance with dopamine.

How does the balance between dopamine and acetylcholine relate to Parkinsonism?

Loss of dopamine disrupts the balance between these signalling systems, contributing to impaired movement control.

Why is Parkinsonism an example of faulty cell communication?

Changes in neurotransmitter signalling disrupt communication in brain circuits responsible for coordinating movement.