Chapter 2: Cell and Tissue Characteristics

Vocabulary flashcards covering cell structure, organelles, membrane transport, cell signaling, cell division, tissues, and cell junctions based on Chapter 2 lecture notes.

Protoplasm

The living substance of a cell consisting of all materials inside the cell membrane essential for life, including water, protein, lipids, and electrolytes. Includes the cytoplasm and nucleoplasm.

Cytoplasm

The living material or semifluid substance outside the nucleus that surrounds organelles and supports cellular metabolism.

Nucleoplasm

The living material located inside the nucleus of a cell.

Major structures of a human (eukaryotic) cell

Includes cell boundary or plasma membrane, nucleus, cytoplasm, and organelles.

Plasma Membrane

A selectively permeable cell boundary composed of lipids, carbohydrates, proteins, phospholipids, and glycolipids that regulates passage of substances and participates in cell signaling.

Cell signaling

Allows a cell to receive, interpret, and respond to messages from its environment or from other cells. Provides receptors for hormones and other biologically active substances. Participates in the electrical events that occur in nerve and muscle cells, and aids in the regulation of cell growth and proliferation. Examples include hormones, cytokines, growth factors, and neurotransmitters.

Nuclear Envelope

A double membrane surrounding the nucleus that separates nuclear contents from the cytoplasm.

Nuclear Pore

Openings in the nuclear envelope that regulate the movement of RNA, proteins, and other molecules in and out of the nucleus.

Chromatin

The complex of DNA and histone proteins inside the nucleus that condenses to form chromosomes during cell division.

Euchromatin

The active, less condensed form of chromatin.

Heterochromatin

The inactive, highly condensed form of chromatin.

Nucleolus

A dense, dark-staining structure within the nucleus that serves as the site of ribosomal RNA (rRNA) synthesis and ribosome assembly.

Messenger RNA (mRNA)

RNA synthesized from genetic information transcribed from DNA that travels to ribosomes in the cytoplasm to direct protein synthesis.

Ribosomal RNA (rRNA)

The RNA component of ribosomes that is essential for protein production.

Transfer RNA (tRNA)

RNA that transports amino acids to ribosomes so that mRNA can be translated into amino acids to synthesize proteins.

Cytosol

The fluid portion of the cytoplasm and site of metabolic reactions.

Mitochondria

Organelles responsible for ATP (energy) production, known as the powerhouse of the cell.

Ribosomes

Cellular structures involved in protein synthesis by translating mRNA.

Rough Endoplasmic Reticulum

An organelle with attached ribosomes involved in protein processing and the transport of newly synthesized proteins.

Smooth Endoplasmic Reticulum

An organelle free of ribosomes that functions in lipid synthesis, detoxification, and $\text{Ca}^{2+}$ storage (calcium ions).

Golgi Apparatus

An organelle that modifies and packages proteins and lipids.

Lysosomes

Organelles responsible for intracellular digestion and recycling through phagocytosis.

Peroxisomes

Organelles involved in cellular detoxification, fatty acid oxidation, and neutralizing free radicals.

Cytoskeleton

A network of protein filaments and tubules that provides structural support and shape to the cell, facilitates movement, and transport within the cell.

Microtubules

Cytoskeletal elements that develop and maintain cell form, participate in intracellular transport, form structures for complex cytoplasmic organelles, and contain cilia (nose hairs), flagella (sperm cells), centrioles, and basal bodies.

Microfilaments

Structures of the cytoskeleton that aid in cell motility and muscle contraction.

Centrosome

A cytoplasmic structure containing centrioles that functions in forming the mitotic spindle during cell division.

Tay-Sachs Disease

An autosomal recessive lysosomal storage disorder caused by hexosaminidase A deficiency, leading to GM2 ganglioside accumulation in the nervous system and eye. Causes progressive destruction of neurons in the brain and spinal cord with a higher population risk in Ashkenazi Jewish descent. The prognosis is considered progressive and fatal usually by early childhood (around age 4-5). Includes normal development at birth, developmental regression by 3-6 months, hypotonia, spasticity, seizures, blindness, deafness, and a cherry-red spot on the macula without hepatosplenomegaly (important distinction).

Hexosaminidase A

A lysosomal enzyme required to degrade debris in nerves; its absence leads to GM2 ganglioside accumulation in Tay-Sachs disease.

GM2 Ganglioside

The glycolipid substance that accumulates in the nervous system and eyes of patients with Tay-Sachs disease.

Hypotonia

A neuromuscular condition characterized by reduced muscle tone.

Spasticity

A neuromuscular condition that causes muscles to stiffen or tighten uncontrollably, resisting normal stretching and fluid movement.

Autocrine Signaling

Cell communication that occurs when a cell releases a chemical into the extracellular fluid that affects its own activity, such as cancer cells producing growth factors.

Paracrine Signaling

Cell communication in which signaling molecules act on nearby target cells, such as epidermal growth factor (EGF) stimulating adjacent cells.

Endocrine Signaling

Cell communication that relies on hormones carried in the bloodstream to reach target cells throughout the body, such as cortisol affecting metabolism and immune response.

Synaptic Signaling

Cell communication in the nervous system where neurotransmitters act specifically on adjacent nerve cells, such as GABA inhibitory signaling in the brain.

Interphase

The phase of the cell cycle comprising the $G_1$, S, and $G_2$ phases during which the cell grows and prepares for division.

$G_0$ Phase

The resting phase of the cell cycle where cells are metabolically active but not dividing; maintained permanently by cells like neurons and cardiac muscle.

$G_1$ Phase

The first gap phase where the cell grows in size, synthesizes proteins and organelles, and checks size, nutrients, and DNA damage before DNA replication.

S Phase

The synthesis phase of the cell cycle where DNA replication occurs, duplicating each chromosome into sister chromatids and then duplicating centrosomes.

$G_2$ Phase

The second gap phase during which the cell undergoes further growth, produces proteins needed for mitosis, and checks that DNA replication is complete and undamaged.

M Phase

The mitotic phase of the cell cycle consisting of nuclear division (mitosis) and cytoplasmic division (cytokinesis).

Prophase

The initial stage of mitosis where chromosomes condense and spindle fibers form between centrioles as they move apart.

Metaphase

The stage of mitosis where the microtubule spindle apparatus attaches to chromosomes and aligns them along the metaphase plate.

Anaphase

The stage of mitosis in which sister chromatids separate and are pulled toward opposite poles of the cell.

Telophase

The stage of mitosis where chromatids arrive at each pole, new nuclear membranes form around them, and nuclear division concludes.

Cytokinesis

The division of the cytoplasm resulting in the formation of two genetically identical daughter cells.

Somatic Cells

All the body cells of an organism except reproductive (sex) cells. Key characteristics include diploid ($2n$) body cells (excluding gametes) that form tissues and organs (skin, muscle, liver, nerve cells) and divide by mitosis for growth, repair, and maintenance. Mutations affect only the individual not the offspring. Cancer arises from uncontrolled cell division of somatic cells.

Cell Metabolism

Processes by which fats, proteins, and carbohydrates from the foods we eat are converted into energy in the form of ATP.

Catabolism

The metabolic process of breaking down stored nutrients and body tissues to produce energy (ATP) through aerobic (in mitochondria) or anaerobic (in cytoplasm) pathways.

Anabolism

A constructive metabolic process in which more complex molecules are built from simpler ones.

Simple Diffusion

Passive transport where molecules move from high to low concentration directly through the lipid bilayer without requiring energy. Examples include oxygen and carbon dioxide.

Facilitated Diffusion

Passive transport moving substances down a concentration gradient with high to low concentration using specific carrier or channel proteins without energy. Examples include glucose and ions.

Osmosis

The passive diffusion of water through aquaporins or the cell membrane from an area of low solute concentration to high solute concentration without the use of energy.

Primary Active Transport

Energy-requiring movement of molecules against their concentration gradient directly using ATP such as the $\text{Na}^+/\text{K}^+$ ATPase pump.

Secondary Active Transport

Transport mechanism that uses energy derived from an ion gradient, which is energy produced from one reaction to create another reaction.

Vesicular (Bulk) Transport

The process by which substances are transported into or out of a cell within vesicles, allowing for the movement of large molecules or particles.

Endocytosis

A vesicular transport process by which cells surround and engulf material from their surroundings into intracellular vesicles.

Phagocytosis

The active vesicular transport process by which cells engulf and destroy microorganisms (solids) such as pathogens or cell debris, using their plasma membrane to form vesicles.

Pinocytosis

An active vesicular transport process in which a cell engulfs extracellular fluid and dissolved substances by forming small vesicles.

Ligand Channels

Channels that open and close when chemicals bind to the channels.

Exocytosis

The secretion of intracellular substances into the extracellular space through the fusion of vesicles with the plasma membrane.

Membrane Potential

The electrical charge difference across a cell’s plasma membrane that relies on ion transfer. Essential for nerve impulses, muscle contraction, and cardiac rhythm.

Diffusion Potential

The electrical voltage created across a membrane when ions move down their concentration gradient, such as $\text{K}^+$ exiting the cell.

Equilibrium Potential ($E_x$)

The membrane voltage at which net ion movement stops because the electrical gradient balances the concentration gradient, calculated via the Nernst equation.

Resting Membrane Potential (RMP)

The steady voltage across a resting cell membrane (typically $-70\,\text{mV}$ in neurons), primarily generated by $\text{K}^+$ leak channels and the $\text{Na}^+/\text{K}^+$ pump. The cell is not sending a signal just “waiting”.

Action Potential

A rapid, temporary change in membrane potential used for cellular signaling between neurons and muscles, involving depolarization, repolarization, hyperpolarization, and return to resting potential.

Depolarization

The process during an action potential where the membrane potential becomes more positive due to the influx of sodium ions ($\text{Na}^+$).

Repolarization

The process during an action potential where the membrane potential returns to a more negative value, mainly due to the efflux of potassium ions ($\text{K}^+$).

Hyperpolarization

The process during an action potential where the membrane potential becomes slightly more negative than the resting potential.

Epithelial Tissue

An avascular (has few/no blood vessels) tissue that attaches to a basement membrane. Forms sheets that function to cover the body’s outer surface, line internal surfaces, and form glandular tissue.

Simple Layer Classification

All cells touch the basement membrane.

Stratified Layer Classification

Only the basal layer touches the basement membrane.

Pseudostratified Layer Classification

Appears multilayered but is actually one layer.

Transitional Epithelium Layers

Multiple layers that change shape from cuboidal to squamous.

Simple Squamous Epithelium

A single layer of thin, flat cells located in the air sacs of lungs and lining of heart/blood/lymphatic vessels that allows passage of materials by diffusion and filtration. Also secretes a lubricating substance.

Simple Cuboidal Epithelium

A single layer of boxy, cube-shaped cells located in ducts and secretory portions of small glands and in kidney tubules that functions in secretion and absorption.

Simple Columnar Epithelium

A single layer of tall cells where smooth, nonciliated tissues are in the digestive tract and bladder, while ciliated tissues are in the respiratory/reproductive tracts such as bronchi, uterine tubes, and uterus that function in absorption and secretion of mucus and enzymes.

Pseudostratified Columnar Epithelium

A single-layered epithelium that appears multilayered, with ciliated tissue lining the trachea and upper respiratory tract, where ciliated tissues move to secrete mucus.

Stratified Squamous Epithelium

Multiple layers of flattened cells lining the esophagus, mouth, and vagina that protect against abrasion.

Stratified Cubodial Epithelium

Multiple layers of cube-shaped cells, located in glandular ducts such as sweat glands, salivary glands, and mammary glands, primarily function as protective tissue.

Stratified Columnar Epithelium

Multiple layers of column-shaped cells, found in the ducts of certain glands and the male urethra, providing protection and secretion.

Transitional Epithelium

A stratified epithelium lining the bladder, ureters, and urethra whose cells shift shape between cuboidal and squamous to allow the urinary organs to expand and stretch.

Connective or Supportive Tissue

The most abundant tissue of the body that connects and binds or supports various tissues.

Loose or Areolar Tissue

A type of connective tissue that is under the skin, around organs and blood vessels.

Adipose Tissue

Found under the skin and around organs.

Reticular Tissue

Forms a soft internal skeleton (stroma) for organs like the spleen and lymph nodes.

Dense Connective Tissue

Fibers in multiple directions (dermis of skin, joint capsules)

Supportive Tissue

Includes cartilage and bone.

Hyaline Cartilage

A type of supportive connective tissue that provides smooth surfaces for joint movement and flexibility, found in areas such as the nose, trachea, and ends of long bones.

Elastic Cartilage

A type of supportive connective tissue that maintains shape while allowing great flexibility, found in structures like the ear and epiglottis.

Fibrocartilage

A tough type of supportive connective tissue that provides strength and absorbs shock, commonly found in intervertebral discs, the pubic symphysis, and menisci of the knee.

Muscle Tissue

Contains actin and myosin filament that provides locomotion and movement of skeletal structures, pumping blood through the heart, and contraction of blood vessels and visceral organs.

Cardiac Muscle

A specialized type of muscle tissue that is found only in the heart. It is involuntary and striated, enabling rhythmic contractions to pump blood throughout the body.

Skeletal Muscle

A type of striated muscle tissue attached to bones that facilitates voluntary movement. It is under conscious control and enables actions such as walking and lifting.

Smooth Muscle

A type of muscle tissue that is non-striated and involuntary. It is found in the walls of hollow organs and blood vessels, aiding in processes like digestion and blood circulation.

Nervous Tissue

Tissues that provide the means for controlling body function and for sensing and moving about the environment.

Neurons

Specialized cells in nervous tissue that transmit electrical impulses, facilitating communication between different body parts and the brain.

Neuroglial Cells

Cells in nervous tissue that support and protect neurons.

Ependymal Cells

Specialized glial cells of the central nervous system that line the ventricles of the brain and the central canal of the spinal cord, involved in the production and circulation of cerebrospinal fluid.