Chapter 4 Cell Structure Flashcards

A complete set of 100 vocabulary flashcards covering key terms, cell structures, organelles, cellular transport, and intercellular junctions from Chapter 4 Cell Structure.

Cell

The smallest unit of a living thing and the basic structural and functional building block of all organisms.

Organism

An individual living entity, which may be unicellular (such as bacteria) or multicellular (such as a human).

Tissue

A group of interconnected cells of one kind that perform a shared function within an organism.

Microscope

An optical instrument used to magnify objects that are too small to be seen with the naked eye.

Micrograph

A photograph taken of an image produced through a microscope.

Light microscope

A microscope that passes visible light through a specimen and a lens system to magnify objects up to approximately 400 times (or 1,000 times with oil immersion).

Magnification

The process of enlarging the apparent size of an object.

Resolving power

The ability of a microscope to distinguish two adjacent structures as separate entities; higher resolution improves image clarity and detail.

Electron microscope

A microscope that uses a beam of electrons focused by lenses to provide higher magnification (up to $100{,}000\times$) and resolution ($50$ picometers) than light microscopes.

Scanning electron microscope (SEM)

An electron microscope that moves a beam of electrons back and forth across a cell's surface to render detailed cell surface characteristics.

Transmission electron microscope (TEM)

An electron microscope in which an electron beam penetrates the specimen to provide detailed visualization of internal cellular structures.

Antony van Leeuwenhoek

A 17th-century Dutch lens maker who first observed single-celled organisms, bacteria, and protozoa using handcrafted microscopes.

Animalcules

The term coined by Antony van Leeuwenhoek to describe the microscopic single-celled organisms he observed under his lenses.

Robert Hooke

The experimental scientist who coined the term "cell" in his 1665 publication Micrographia after observing box-like structures in cork tissue.

Unified cell theory

A fundamental biological principle stating that all living organisms are composed of one or more cells, the cell is the basic unit of life, and new cells arise from existing cells.

Matthias Schleiden and Theodor Schwann

The botanist and zoologist who jointly proposed the unified cell theory in the late 1830s.

Rudolf Virchow

A scientist who made important contributions to the unified cell theory by proposing that all cells arise from pre-existing cells.

Cytotechnologist

A laboratory medical professional trained to examine microscopic cellular samples to detect subtle normal and abnormal cellular changes.

Pathologist

A medical doctor who interprets and diagnoses changes in body tissues and fluids caused by disease.

Pap smear

A clinical screening test in which cells scraped from the uterine cervix are microscopically examined by a cytotechnologist for signs of cervical cancer or microbial infection.

Prokaryote

A simple, predominantly single-celled organism belonging to the domains Bacteria or Archaea that lacks a membrane-bound nucleus and membrane-bound organelles.

Eukaryote

An organism whose cells possess a membrane-bound nucleus, multiple membrane-bound organelles, and multiple rod-shaped chromosomes.

Four common components of all cells

The four structures shared by all prokaryotic and eukaryotic cells: plasma membrane, cytoplasm, DNA, and ribosomes.

Nucleoid

The central region of a prokaryotic cell where its single, circular chromosome of DNA is localized.

Prokaryotic Cell Structure

The generalized structural arrangement of a bacterium, including a cell wall, plasma membrane, nucleoid region, ribosomes, and optional features like a capsule, pili, or flagella.

Peptidoglycan

The primary structural polymer that makes up the rigid cell wall of most bacteria.

Capsule

A polysaccharide outer layer surrounding many prokaryotes that prevents dehydration and aids attachment to environmental surfaces.

Flagellum

A long, hair-like cellular projection extending from the plasma membrane that rotates or whips to provide cell locomotion.

Pili

Hair-like surface appendages on bacteria used to transfer genetic material to another bacterial cell during conjugation.

Conjugation

The process by which one bacterium transfers genetic material directly to another through cell-to-cell contact via pili.

Fimbriae

Proteinaceous surface structures used by bacteria to attach to host cells or other substrates.

Microbiologist

A scientist who studies microscopic organisms such as bacteria, viruses, algae, fungi, and protists.

Bioremediation

The technological use of selected or genetically engineered microbes to clean up environmental pollutants from soil or water.

Surface area-to-volume ratio

A mathematical relationship in which a cell's volume increases as the cube of its radius while its surface area increases only as the square of its radius, limiting transport efficiency in larger cells.

Cell Size and Surface Area-to-Volume Ratio

A visual principle demonstrating that smaller cells maintain a higher surface area-to-volume ratio, facilitating effective diffusion across the plasma membrane compared to larger cells.

Organelle

A specialized, membrane-enclosed compartment or structure within a eukaryotic cell that carries out specific metabolic processes.

Plasma membrane

A phospholipid bilayer embedded with proteins and cholesterol that separates the interior of the cell from its surrounding environment and regulates passage of substances.

Phospholipid

A major membrane lipid molecule composed of a glycerol backbone, two fatty acid tails, and a phosphate-containing head.

Microvilli

Fingerlike projections of the plasma membrane on absorptive cells, such as those lining the small intestine, that dramatically increase surface area for absorption.

Cytoplasm

The total region of a cell between the plasma membrane and the nuclear envelope, comprising cytosol, cytoskeleton, and suspended organelles.

Cytosol

The gel-like water-based medium inside the cytoplasm in which cellular components and organelles are suspended.

Nucleus

The prominent eukaryotic cell organelle that houses chromosomal DNA and directs ribosome and protein synthesis.

Nuclear envelope

A double-membrane structure punctuated by protein-lined pores that surrounds the nucleus and separates nucleoplasm from cytoplasm.

Nucleoplasm

The semi-solid gel-like fluid enclosed within the nuclear envelope containing the chromatin and nucleolus.

Chromosome

A distinct linear structure within the eukaryotic nucleus composed of DNA wrapped around proteins (chromatin) that contains genetic material.

Chromatin

The unwound, thread-like complex of DNA wrapped around histone proteins that condenses to form chromosomes during cell division.

Nucleolus

A dense region inside the nucleus responsible for synthesizing ribosomal RNA (rRNA) and assembling ribosomal subunits.

Ribosomes

Large cellular complexes of RNA and proteins that perform protein synthesis by translating messenger RNA sequences into amino acid chains.

Polyribosomes

Clusters of multiple ribosomes simultaneously translating a single messenger RNA strand into identical proteins.

Messenger RNA (mRNA)

The single-stranded RNA molecule transcribed from nuclear DNA that delivers genetic instructions for protein synthesis to ribosomes.

Mitochondria

Double-membrane eukaryotic organelles often termed "powerhouses" because they generate ATP via cellular respiration.

Adenosine triphosphate (ATP)

The primary energy currency of the cell, storing short-term chemical energy needed to drive cellular work.

Cellular respiration

The metabolic process in mitochondria that consumes oxygen and glucose to synthesize ATP while releasing carbon dioxide as a waste byproduct.

Cristae

The inner membrane folds of a mitochondrion that increase surface area for electron transport and ATP synthesis.

Mitochondrial matrix

The fluid-filled internal space enclosed by the inner membrane of a mitochondrion.

Peroxisome

A single-membrane organelle that carries out oxidation reactions to break down fatty acids and amino acids, safely converting toxic hydrogen peroxide byproduct into water and oxygen.

Glyoxysomes

Specialized peroxisomes in plant cells that convert stored fats into carbohydrates for germinating seedlings.

Vesicles

Small, membrane-bound sacs involved in cellular storage and transport that can readily fuse with the plasma membrane or other cellular membrane systems.

Vacuoles

Membrane-bound storage and transport compartments that are larger than vesicles and whose membranes do not fuse with other cellular membranes.

Centrosome

The microtubule-organizing center located near the nucleus in animal cells, consisting of a pair of perpendicular centrioles.

Centriole

A cylindrical organelle structure composed of nine triplets of microtubules arranged in a ring, two of which sit perpendicular to each other inside a centrosome.

Centrosome and Centrioles

A microtubule-organizing center containing two perpendicular centriole cylinders, each formed by nine microtubule triplets bound by nontubulin proteins.

Lysosome

An acidic animal cell organelle containing digestive enzymes that breaks down proteins, lipids, nucleic acids, carbohydrates, and worn-out organelles.

Cell wall

A rigid outer covering surrounding the plasma membranes of plant, fungal, and protistan cells that maintains cell shape, provides structural support, and resists mechanical stress.

Cellulose

A structural polysaccharide made of long, unbranched chains of $\beta$-1,4-linked glucose units that forms the major organic component of plant cell walls.

Chloroplast

A double-membrane plant cell organelle containing thylakoids and chlorophyll that performs photosynthesis to manufacture sugars.

Photosynthesis

The biochemical process carried out in chloroplasts using sunlight energy, water, and carbon dioxide to yield glucose and oxygen.

Thylakoid

A flattened, fluid-filled membranous sac inside a chloroplast where the light-dependent reactions of photosynthesis occur.

Granum

A stack of thylakoid membranes suspended within the stroma of a chloroplast.

Stroma

The fluid enclosed by the inner membrane of a chloroplast surrounding the grana where sugar synthesis takes place.

Chlorophyll

The green pigment contained in thylakoid membranes that captures solar energy to power photosynthesis.

Endosymbiosis

An evolutionary theory stating that eukaryotic organelles such as mitochondria and chloroplasts originated as free-living prokaryotic cells engulfed by ancestral eukaryotic host cells.

Central vacuole

A large fluid-filled plant organelle that stores cell sap, regulates water balance, provides turgor pressure against the cell wall, and supports cell expansion.

Endomembrane system

A group of eukaryotic membranes and organelles (nuclear envelope, lysosomes, vesicles, ER, Golgi apparatus, and plasma membrane) that work together to synthesize, modify, package, and transport lipids and proteins.

Endoplasmic reticulum (ER)

An interconnected network of membranous tubules and sacs that modifies proteins and synthesizes lipids.

Lumen

The hollow inner space enclosed by the membranes of the endoplasmic reticulum tubules, also known as the cisternal space.

Rough endoplasmic reticulum (RER)

The portion of the ER studded with ribosomes on its cytoplasmic surface that modifies proteins synthesized by those ribosomes and produces membrane phospholipids.

Smooth endoplasmic reticulum (SER)

The region of the ER lacking ribosomes that synthesizes lipids, carbohydrates, and steroid hormones, detoxifies medications and poisons, and stores calcium ions.

Sarcoplasmic reticulum

A specialized smooth ER in muscle cells that stores and releases calcium ions to trigger coordinated muscle contractions.

Cardiologist

A medical physician who specializes in the diagnosis, treatment, and prevention of diseases of the heart and blood vessels.

Golgi apparatus

An endomembrane organelle composed of stacked, flattened membranous sacs (cisternae) that sorts, tags, packages, and distributes lipids and proteins.

Cis face

The receiving side of the Golgi apparatus nearest the endoplasmic reticulum where transport vesicles fuse.

Trans face

The exit or shipping side of the Golgi apparatus from which sorted and packaged secretory vesicles bud off toward their cellular destinations.

Lowe disease

An inherited genetic disorder (oculocerebrorenal syndrome) caused by a deficiency in a Golgi enzyme, affecting development in the eyes, brain, and kidneys.

Geneticist

A scientist or clinical specialist who studies inheritance, conducts DNA research, or counsels individuals on genetic conditions and testing options.

Macrophage

A large phagocytic white blood cell that engulfs foreign microorganisms, cellular debris, and pathogens as part of the immune system.

Phagocytosis Process

A cellular process in which a cell invaginates its plasma membrane to engulf a foreign particle or bacterium into a vesicle, which then fuses with a lysosome for destruction.

Cytoskeleton

A network of internal protein fibers in the cytoplasm (microfilaments, intermediate filaments, and microtubules) that provides structural support, maintains cell shape, and facilitates movement.

Microfilaments

The narrowest cytoskeletal fibers (about $7$ nm in diameter), composed of two intertwined strands of actin that enable cellular movement, contractility, and cell shape maintenance.

Actin

A globular protein that polymerizes to form intertwined microfilament strands that serve as tracks for motor proteins like myosin.

Myosin

A motor protein that interacts with actin filaments using ATP to generate force and cellular movements, such as muscle contraction.

Cytoplasmic streaming

The continuous circular movement of cytoplasm driven by actin and myosin within large plant cells.

Intermediate filaments

Fibrous cytoskeletal elements ($8$ to $10$ nm in diameter) composed of intertwined protein strands that bear tension, maintain cell shape, and anchor the nucleus and organelles in place.

Keratin

A tough fibrous protein found in intermediate filaments that reinforces hair, nails, and the outer layer of skin.

Microtubules

The widest cytoskeletal fibers ($25$ nm in diameter), formed of polymerized ̴̵̶̷̸̡̢̧̨̛̠̖̗̘̙̜̝̞̟̠̣̤̥̦̩̪̫̬̭̮̯̰̱̲̳̹̺̻̼͇͈͉͍͎̑̀̂̃̄̅̆̇̈̉̊̋̌̍̎̏̐̑̒̓̔̽̾̿̀́͂̓̈́͆͊͋͌̕̚ͅ͏͓͔͕͖͙͚͐͑͒͗͛ͣͤͥͦͧͨͩͪͫͬͭͮͯ͘͜͟͢͝͞͠͡ͰͱͲͳʹ͵Ͷͷ͸͹ͺͻͼͽ;Ϳ΀΁΂΃΄΅Ά·ΈΉΊ΋Ό΍ΎΏΐΑΒΓΔΕΖΗΘΙΚΛΜΝΞΟΠΡ΢ΣΤΥΦΧΨΩΪΫάέήίΰα ext{--}eta$$ tubulin dimers that resist compression, transport organelles, and split chromosomes during cell division.

9 + 2 array

The structural arrangement of microtubules found in eukaryotic flagella and cilia, consisting of an outer ring of nine microtubule doublets surrounding two central single microtubules.

Cilia

Short, hair-like cell projections present in large numbers that move whole cells or sweep materials across the extracellular surface of tissues.

Extracellular matrix (ECM)

A meshwork of secreted proteins (mainly collagen) and carbohydrates (proteoglycans) surrounding animal cells that holds cells together, provides tissue strength, and transmits cellular signals.

Collagen

The most abundant glycoprotein in the extracellular matrix of animal tissues, forming strong interwoven fibrous networks.

Desmosome Structure

An intercellular spot-weld junction formed by cadherin proteins linked to keratin intermediate filaments, holding adjacent epithelial cells together under stretch.