Chapter 03: Cell Biology

Comprehensive vocabulary flashcards covering the major cell structures, membrane transport mechanisms, organelles, gene expression processes, and cell cycle stages from Seeley's Anatomy & Physiology, 13th Edition (Chapter 03: Cell Biology).

Cell

Basic unit of life and is composed of a plasma membrane and cytoplasm which includes a nucleus and cytoplasmic organelles.

Plasma (Cell)Membrane

The outer boundary of the cell that encloses and supports cell contents, regulates the movement of substances into and out of the cell, and allows communication and attachment with the external environment.

Nucleus

Directs cells activities

Cytoplasm

The cellular material located outside the nucleus but inside the plasma membrane, composed of cytosol, the cytoskeleton, cytoplasmic inclusions, and organelles.

Cell Communication

When cells produce and receive electrical and chemical signals.

Gametes

Cells that specialize in the transmission of genetic information to the next generation

Light Microscope

Has the resolution of about .1 µm; Can examine tissues and cells with the assistance of stains

Electron Microscope

Has the resolution of about .1 nm;

Scanning Microscope (SEM)

Electron microscope that can see three dimensional surface features

Transmission Microscope (TEM)

Electron Microscope that can view internal structures.

Atomic Force Microscope (AFM)

Electron microscope that scans samples, has a very high resolution and reveals surface topography.

Cytosol

The fluid portion of the cytoplasm consisting of water with dissolved molecules, ions, and suspended proteins, especially enzymes.

Membrane Potential

An electrical charge difference across the plasma membrane caused by the cell's regulation of ion movement, resulting in a positive charge outside and a negative charge inside.

Glycocalyx

The collection of carbohydrates combined with lipids (glycolipids) and proteins (glycoproteins) located on the outer surface of the plasma membrane.

Membrane Phospholipids

Bilayer with polar heads facing water in the interior and exterior of the cell (hydrophillic); non polar tails facing each other on the interior of the membrane (hydrophobic).

Membrane Cholesterol

Interspersed among the phospholipids in the cell membrane, it provides stability to the membrane and determines the membranes fluid nature.

Fluid-Mosaic Model

A model of membrane structure depicting phospholipids as a dynamic fluid bilayer with interspersed cholesterol and proteins, allowing molecular distribution and membrane fusion.

Integral Membrane Proteins

Membrane proteins that penetrate deeply into the lipid bilayer, frequently extending from one membrane surface to the other and often forming channels.

Peripheral Membrane Proteins

Proteins attached to integral proteins at either the inner or outer surfaces of the lipid bilayer, or bound to the polar heads of phospholipids.

Marker Molecules

Cell-surface glycoproteins and glycolipids that allow cells to identify one another, distinguish self from foreign cells, and facilitate intercellular communication.

Cadherins

Integral attachment proteins that anchor cells to other neighboring cells.

Integrins

Integral attachment proteins that function in pairs to anchor cells to extracellular molecules and facilitate communication between the extracellular matrix and cytoplasm.

Saturation

The condition where the rate of substance movement across a membrane reaches a plateau because all binding sites on available transport proteins are occupied.

Channel Proteins

Integral membrane proteins that can form tiny channels through membrane. Determines the size, shape and charge of what can move through. Hydrophobic regions face outward while hydrophilic regions remain inward and line the tunnel. The charge of the hydrophilic tunnel determines the types of ions that can move through.

Leak Ion channels

Nongated ion channels that are constantly open and responsible for resting plasma membrane permeability to specific ions.

Gated Ion Channels

Open or closed by certain stimuli

Ligand-gated ion channels

Membrane channels that open or close in response to the binding of specific chemical signals, such as acetylcholine, to receptor sites.

Voltage-gated ion channels

Membrane channels that open or close in response to changes in electrical charge differences across the plasma membrane.

Transporters (Carrier Protiens)

Integral proteins move ions from one side of the membrane to the other.

Uniporters

Carrier proteins that transport a single specific ion or molecule across the plasma membrane.

Symporters

Carrier proteins that move two different ions or molecules across the membrane simultaneously in the same direction (cotransport).

Antiporters

Carrier proteins that move two different ions or molecules across the membrane simultaneously in opposite directions (countertransport).

ATP-Powered Pumps

Transport proteins that utilize the hydrolysis of $\text{ATP}$ to $\text{ADP}$ and phosphate to actively move specific ions or molecules against their concentration gradient.

Receptor Proteins

Proteins or glycoproteins in membranes with an exposed receptor site on the outer cell surface. Can attach to specific chemical signal molecules and act as an intracellular communication system. Ligand can attach only yo cells with that specific receptor.

G protein complex

A membrane-associated signaling complex consisting of alpha ($\alpha$), beta ($\beta$), and gamma ($\gamma$) subunits that activates upon exchanging bound $\text{GDP}$ for $\text{GTP}$ in response to receptor activation.

Enzymes

Acts as catalysts to reactions on the surface of the plasma membrane.

Passive Membrane Transport

Diffusion, Osmosism and Facilitated Diffusion

Active Membrane Transport

ATP is used to move from lower concentration to higher concentration.

Osmosis

The diffusion of water across a selectively permeable membrane from an area of low solute concentration (high water concentration) to an area of high solute concentration (low water concentration). {Type of Passive Transport}

Osmotic Pressure

The precise force required to prevent the net movement of water across a selectively permeable membrane by osmosis.

Hyperosmotic solution

A solution that has a greater concentration of solute particles and a higher osmotic pressure compared to another solution.

Hypoosmotic solution

A solution that has a lower concentration of solute particles and a lower osmotic pressure compared to another solution.

Isotonic solution

A solution having a solute concentration equal to that inside the cell, causing no net water movement and allowing the cell to maintain its normal volume and shape.

Hypertonic solution

A solution with a higher solute concentration than the cell interior, causing water to leave the cell by osmosis and resulting in cell shrinkage (crenation).

Facilitated diffusion

A passive, carrier- or channel-mediated transport process that moves large, polar, or charged molecules down their concentration gradient without requiring $\text{ATP}$.

Sodium-potassium ($\text{Na}^+-\text{K}^+$) pump

An ATP-powered transport protein that actively moves $3\,\text{Na}^+$ out of the cell and $2\,\text{K}^+$ into the cell against their concentration gradients per $\text{ATP}$ hydrolyzed.

Secondary active transport

A transport mechanism that utilizes the potential energy stored in an established ionic concentration gradient (such as $\text{Na}^+$) to co-transport another substance (such as glucose) against its gradient.

Phagocytosis

A type of endocytosis in which a cell engulfs solid extracellular particles to form a large internal membrane-bound vesicle.

Pinocytosis

A type of endocytosis that involves the non-specific uptake of extracellular fluid and dissolved solutes into small vesicles.

Receptor-mediated endocytosis

A selective endocytic process where specific extracellular ligands bind to plasma membrane receptors, prompting the inward budding and pinching off of a vesicle.

Exocytosis

A process where secretory vesicles fuse with the plasma membrane to release their contents into the extracellular fluid.

Transcytosis

The transport of a substance across a cell through a sequence of endocytosis on one cell surface followed by exocytosis on the opposite surface.

Microtubules

Hollow cytoskeletal cylinders of about $25\,\text{nm}$ diameter made of tubulin subunits, providing an internal scaffold, facilitating intracellular transport, and forming centrioles, spindle fibers, cilia, and flagella.

Actin filaments

Cytoskeletal fibers of about $8\,\text{nm}$ diameter (microfilaments) that provide structural support to microvilli, enable cell motility, and allow cellular contractility.

Intermediate filaments

Rope-like cytoskeletal protein fibers of about $10\,\text{nm}$ diameter that furnish cells with mechanical strength, particularly in nerve cell extensions.

Nuclear envelope

A double membrane structure bounding the nucleus, consisting of an outer and an inner membrane separated by a space and perforated by nuclear pores.

Nucleolus

A dense, non-membrane-bound region within the nucleus where ribosomal RNA ($\text{rRNA}$) is transcribed and assembled with proteins into ribosomal subunits.

Chromatin

The dispersed, thread-like complex of $\text{DNA}$ and histone proteins found throughout the nucleoplasm during interphase.

Nucleosomes

Structural units of chromatin consisting of a length of $\text{DNA}$ wrapped around a core complex of histone proteins.

Rough endoplasmic reticulum

A membranous network of flattened cisternae studded with ribosomes on its cytoplasmic surface, primarily responsible for synthesizing and modifying proteins.

Smooth endoplasmic reticulum

A tubular membranous network continuous with the rough ER that lacks ribosomes; specializes in lipid synthesis, cellular detoxification, and calcium ion storage.

Golgi apparatus

A series of flattened membrane-enclosed cisternae that receives transport vesicles at its cis face, modifies and packages proteins and lipids, and buds off secretory vesicles from its trans face.

Lysosomes

Membrane-bound digestive vesicles formed at the Golgi apparatus containing hydrolytic enzymes that digest phagocytized materials and break down worn-out organelles (autophagy).

Peroxisomes

Membrane-bound organelles containing oxidative enzymes that break down fatty acids and amino acids, producing hydrogen peroxide ($\text{H}_2\text{O}_2$) which is decomposed into water and oxygen by catalase.

Proteasomes

Non-membranous, barrel-shaped protein complexes with inner enzymatic surfaces that degrade and recycle damaged or unwanted cellular proteins.

Cristae

Infoldings of the inner mitochondrial membrane that house the enzyme complexes of the electron transport chain involved in $\text{ATP}$ synthesis.

Centrosome

A specialized region near the nucleus serving as the primary center of microtubule formation; contains two centrioles oriented perpendicularly to each other.

Cilia

Motile appendages extending from cell surfaces composed of a $9+2$ microtubule doublet arrangement that use $\text{ATP}$ and dynein arms to move substances across cell surfaces.

Microvilli

Non-motile, cylindrical extensions of the plasma membrane supported internally by actin filaments, serving to increase total surface area for absorption.

Transcription

The nuclear process wherein $\text{RNA}$ polymerase synthesizes a complementary strand of messenger $\text{RNA}$ ($\text{mRNA}$) using a $\text{DNA}$ template strand.

Introns

Non-coding sequences within a gene and pre-$\text{mRNA}$ that are excised by spliceosomes prior to translation.

Exons

Protein-coding segments of a pre-$\text{mRNA}$ molecule that are retained and spliced together to form mature, functional $\text{mRNA}$.

Codon

A sequence of three consecutive nucleotides on an $\text{mRNA}$ molecule that specifies a particular amino acid or signals translation termination.

Start codon

The specific $\text{mRNA}$ codon $\text{AUG}$, which codes for methionine and initiates the process of translation.

Stop codons

The $\text{mRNA}$ triplets $\text{UAA}$, $\text{UGA}$, and $\text{UAG}$, which do not code for any amino acid and cause termination of translation.

Translation

The cytoplasmic process occurring on ribosomes where the base sequence of $\text{mRNA}$ directs the assembly of specific amino acids into a polypeptide chain using $\text{tRNA}$ and $\text{rRNA}$.

Polyribosome

A cluster of multiple ribosomes simultaneously engaged in translating the same single $\text{mRNA}$ strand to produce multiple identical polypeptides.

$\text{G}_0$ phase

A non-dividing, resting phase of the cell cycle entered by cells that are not actively preparing for division or that do not divide.

Apoptosis

Genetically programmed cell death that regulates cell numbers and removes damaged, redundant, virus-infected, or potentially cancerous cells without triggering inflammation.