Unit 1 - Cells

Signal molecule

A 'messenger' molecule moving between cells that binds to a specific receptor on the outer surface of the plasma membrane.

Receptor protein

A membrane protein that has a binding site for a signal molecule on the outer face of the plasma membrane.

Signal transduction

The process of relaying the message from a signal molecule within a cell, often involving amplification of the signal.

Amplification

The process by which the initial small signal is enhanced multiple times through the activation of a series of enzymes.

Phosphorylation

The process of adding a phosphate group to an enzyme, converting it from an inactive to an active form.

Signal reception

The initial step where a signal molecule interacts with its receptor, causing a change in shape.

Transduction process

A relay of interactions among molecules that occurs after the signal is received, leading to a cellular response.

Cellular response

The outcomes of signal transduction which can include enzyme activation, cytoskeleton rearrangement, or gene activation.

Cytoskeleton rearrangement

A cellular response in which the structure of the cytoskeleton is altered, often resulting in changes to cell shape or movement.

Gene activation

A cellular response that involves the activation of a gene or set of genes, leading to changes in protein synthesis.

Signalling molecules

Chemical messengers used by cells to communicate.

Local signalling

Communication between nearby cells.

Paracrine signalling

Local regulators that affect nearby target cells.

Synaptic signalling

Nerve cells communicate by releasing neurotransmitters across a synapse.

Endocrine signalling

Hormonal signaling, where hormones travel through the bloodstream to target cells.

Cell signaling stages

Three stages: Reception, Transduction, Response.

Reception

The stage where a target cell receives a signaling molecule.

Transduction

The process of relaying the signal within the cell, often involving a cascade of reactions.

Cellular response

The final outcome after the signal is processed, leading to a specific action by the cell.

G protein-coupled receptors

Receptors that activate G proteins in response to signal binding.

Phosphorylation cascade

A series of enzyme-catalyzed phosphorylation events that amplify a cellular signal.

Kinase enzymes

Enzymes that add phosphate groups to proteins to activate or deactivate them.

Signal amplification

The process of increasing the strength of a signal through a cascade of reactions.

Neurotransmitter

Chemical messengers released by neurons to transmit signals across synapses.

Signal molecule

A chemical that binds to a receptor on a target cell to initiate signaling.

Target cell

A cell that is affected by a signaling molecule.

Secretory vesicles

Vesicles that transport signaling molecules to the cell membrane for release.

Cell-cell recognition

The ability of cells to recognize and respond to specific signals.

Extracellular fluid

Fluid outside the cell where signaling molecules are found.

Cyclic AMP

A secondary messenger involved in signal transduction pathways.

Adenylyl cyclase

An enzyme that converts ATP to cyclic AMP.

Transcription factor

Proteins that regulate the transcription of specific genes.

Intracellular receptors

Receptors located inside the cell, activated by lipophilic signal molecules.

Growth factor

Signaling molecules that stimulate cell growth and differentiation.

Response to growth factors

Activation of specific genes that promote cell division and growth.

Testosterone receptor

An intracellular receptor that activates gene transcription in response to testosterone.

Plasmodesmata

Channels between plant cells that allow communication and transport.

Gap junctions

Connections between animal cells allowing direct communication.

Cell junctions

Structures that connect adjacent cells and facilitate communication.

Mitosis

A process of cell division that results in two daughter cells.

Cancer cells

Cells that grow uncontrollably due to disrupted signaling pathways.

Signal transduction pathway

A series of molecular events initiated by the binding of a signaling molecule to its receptor.

Relay molecules

Proteins that transmit signals from receptors to target molecules within the cell.

Active protein kinase

A phosphorylated enzyme that catalyzes the phosphorylation of other proteins.

Inactive protein kinase

A non-phosphorylated enzyme that does not catalyze reactions.

Phosphorylase kinase

An enzyme activated by phosphorylation that catalyzes glycogen breakdown.

Glycogen phosphorylase

An enzyme that breaks down glycogen into glucose.

Glucose 1-phosphate

A product of glycogen breakdown used in metabolism.

Receptor protein

A protein that binds to signaling molecules and initiates signaling pathways.

Hormone-receptor complex

The combination of a hormone and its specific receptor, triggering a cellular response.

Nucleus

The compartment in eukaryotic cells where DNA is located and gene transcription occurs.

Signal transduction amplification

The process of magnifying a signal as it is processed within a cell.

Direct contact signalling

A form of communication requiring physical contact between cells.

Electrical signal

A signal that may trigger the release of neurotransmitters in synaptic signaling.

Endomembrane System

A network of membranes involved in the synthesis, modification, and transport of proteins and lipids.

Endoplasmic Reticulum (ER)

An extensive membrane system continuous with the nuclear membrane; involved in protein and lipid synthesis.

Rough ER

The portion of the endoplasmic reticulum studded with ribosomes, involved in protein synthesis.

Smooth ER

The portion of the endoplasmic reticulum without ribosomes, involved in lipid synthesis and detoxification.

Functions of Rough ER

Protein synthesis, glycosylation, and membrane synthesis.

Functions of Smooth ER

Ca2+ ion storage, lipid synthesis, and detoxification.

Glycosylation

The process of adding carbohydrates to proteins or lipids, occurring primarily in the ER.

Glycoprotein

A protein that has carbohydrate chains covalently attached to it.

Golgi Apparatus

An organelle that modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles.

Exocytosis

The process of transporting material out of the cell by vesicle fusion with the plasma membrane.

Vacuoles

Membrane-bound organelles in plants and fungi that store ions and organic molecules, derived from ER and Golgi.

Lysosome

An organelle containing digestive enzymes to breakdown waste materials and cellular debris.

Mitochondrion

An organelle that generates ATP, the energy currency of the cell, through cellular respiration.

Cytosol

The liquid component of the cytoplasm in which organelles are suspended and metabolic processes occur.

SRP (Signal Recognition Particle)

A ribonucleoprotein that recognizes a signal peptide and directs the ribosome to the ER.

Polypeptide

A chain of amino acids linked by peptide bonds, which makes up proteins.

Signal Peptide

A short amino acid sequence that directs the transport of a protein to the ER.

Ribosomes

Molecular machines that synthesize proteins by translating mRNA into polypeptides.

Protein Secretion Pathway

The route taken by proteins from synthesis in the ER to export from the cell.

Hydrophobic Signal Peptide

A portion of protein that connects to SRP and facilitates the targeting of proteins to the ER.

Lysosomal Storage Disorder

A genetic disorder caused by enzyme deficiencies in lysosomes, leading to the accumulation of waste.

Phagocytosis

The process by which a cell engulfs large particles or microorganisms.

Autophagy

The mechanism by which cells degrade and recycle their own components.

Central Vacuole

A large vacuole found in plant cells that maintains turgor pressure and stores nutrients.

Peroxisome

An organelle that contains enzymes for breaking down fatty acids and detoxifying harmful substances.

Nuclear Envelope

A double membrane that encases the nucleus and separates it from the cytoplasm.

Protein Transport Vesicle

A small membrane-bound sac that transports proteins from the ER to the Golgi apparatus.

Membrane Glycoproteins

Proteins with attached carbohydrate groups that extend through or outside of the plasma membrane.

Trans Face of Golgi

The side of the Golgi apparatus where vesicles bud off to transport proteins.

Cis Face of Golgi

The side of the Golgi apparatus where incoming vesicles fuse to deliver proteins.

Polysaccharide

Carbohydrates formed by the polymerization of monosaccharides.

Hydrolytic Enzymes

Enzymes that catalyze the breakdown of complex molecules by hydrolysis.

Signal Recognition Particle (SRP) Role

Binds to ribosome and directs it to the ER for protein translation completion.

Secretory Protein

Proteins that are synthesized for export from the cell.

Endomembrane System Components

Includes the ER, Golgi apparatus, lysosomes, vacuoles, and plasma membrane.

Animal Cell Components

Includes nucleus, mitochondria, rough and smooth ER, Golgi apparatus, and lysosomes.

Plant Cell Components

Includes cell wall, chloroplasts, central vacuole, and similar organelles as animal cells.

Cell Membrane

A biological membrane that separates and protects the interior of all cells from the outside environment.

Functional Importance of Lysosomes

Essential for breaking down waste, cellular debris, and recycling old organelles.

Bacterial cells do not have a __________.

nucleus

Eukaryotic cells contain a __________ that is a distinct feature compared to prokaryotic cells.

genuine nucleus

Mitochondria and chloroplasts in eukaryotic cells resemble __________ cells.

bacterial

The essential functions are carried out by the major __________ in a eukaryotic cell.

organelles

Prokaryotic cells lack __________-enclosed organelles.

membrane

The cytoskeleton provides __________ and support to cells.

structure

In structure, prokaryotic cells possess a __________ that contains their DNA.

nucleoid