Chapter 6: A Tour of the Cell Flashcards
Light Microscope (LM)
Optical instrument with lenses that refract (bend) visible light to magnify images of specimens
Organelle
- Membrane-enclosed structures
- Have specialized functions
- Suspended in the cytosol of eukaryotic cells
Electron Microscope (EM)
Microscope that uses magnets to focus an electron beam on or through a specimen, resulting in practical resolution that is 100-fold greater than that of a light microscope using standard techniques
Scanning Electron Microscope (SEM)
Microscope that uses an electron beam to scan the surface of a sample, coatec with metal atoms, to study details of its topography (surface)
Transmission Electron Microscope (TEM)
- Microscope that passes an electron beam through very thin sections stained with metal atoms
- Primarily used to study the internal ultrastructure of cells
Cell Fractionation
Disruption of a cell and separation of its parts by centrifugation at successively higher speeds
Cytosol
Semifluid portion of the cytoplasm
Eukaryotic Cell
- Type of cell with a membrane-enclosed nucleus and membrane-enclosed organelles
- Examples of organisms with these cells include fungi, protists, plants, and animals
Prokaryotic Cell
- Type of cell lacking a membrane-enclosed nucleus and membrane-enclosed organelles
- Only found in the domains Bacteria and Archaea
Cytoplasm
- Contents of the cell bounded by the plasma membrane
- In eukaryotes, the portion exclusive of the nucleus
Plasma Membrane
- Membrane at the boundary of every cell that acts as a selective barrier
- Regulates the cell’s chemical composition
Nucleus
Organelle of a eukaryotic cell that contains the genetic material in the form of chromosomes, made up of chromatin
Nuclear Envelope
- In a eukaryotic cell
- Double membrane that surrounds the nucleus
- Perforated with pores that regulate traffic with the cytoplasm
- Outer membrane is continuous with the endoplasmic reticulum
Chromosome
- Cellular structure consisting of one DNA molecule and associated with protein molecules
- Eukaryotic cell usually has many while prokaryotic cell has one
Chromatin
- Complex of DNA and proteins that makes up eukaryotic chromosomes
- Not visible under a microscope when in its dispersed form (when the cell is in interphase)
Nucleolus
- Specialized structure in the nucleus
- Consists of chromosomal regions containing ribosomal RNA (rRNA) genes along with ribosomal proteins imported from the cytoplasm
Ribosome
- Complex of rRNA and protein molecules that functions as a site of protein synthesis in the cytoplasm
- Consists of a large and a small subunit
- In eukaryotic cells, each subunit is assembled in the nucleolus
Endomembrane System
- Collection of membranes inside and surrounding a eukaryotic cell, related through either direct physical contact or by the transfer of membranous vesicles
- Includes the plasma membrane, nuclear envelope, the smoot and rough endoplasmic reticulum, the Golgi apparatus, lysosomes, vesicles, and vacuoles
Vesicle
A membranous sac in the cytoplasm of a eukaryotic cell
Endoplasmic Reticulum (ER)
- Extensive membranous network in eukaryotic cells
- Continuous with the outer nuclear membrane and composed of ribosome-studded (rough) and ribosome free (smooth) regions
Smooth Endoplasmic Reticulum (Smooth ER)
The portion of the endoplasmic reticulum that is free of ribosomes
Rough Endoplasmic Reticulum (Rough ER)
The portion of the endoplasmic reticulum with ribosomes attached
Glycoprotein
A protein with one or more covalently attached carbohydrates
Transport Vesicle
- Small membranous sac in a eukaryotic cell’s cytoplasm
- Carries molecules produced by the cell
Golgi Apparatus
- Organelle in eukaryotic cells consisting of flat membranous sacs
- Modifies, stores, and routes products of the endoplasmic reticulum and synthesizes some products (notably no cellulose carbohydrates)
Lysosome
- Membrane-enclosed sac of hydrolytic enzymes
- Found in the cytoplasm of animal cells and some protists
Phagocytosis
- Type of endocytosis
- Large particulate substances or small organisms are taken up by a cell
- Carried out by some protists and by certain immune cells of animals
Vacuole
Membrane-bound vesicle whose specialized function varies in different kinds of cells
Food Vacuole
Membranous sac formed by phagocytosis of microorganisms or particles to be used as food by the cell
Contractile Vacuole
Membranous sac that helps move excess water out of certain freshwater protists
Central Vacuole
-In a mature plant cell, a large membranous sac with diverse roles in growth, storage, and sequestration of toxic substances
Mitochondria
- Organelles in eukaryotic cells
- Serve as the site of cellular respiration
- Use oxygen to break down organic molecules and synthesize ATP
Chloroplast
- An organelle found in plants and photosynthetic protists
- Absorbs sunlight and uses it to drive the synthesis of organic compounds from carbon dioxide and water
Endosymbiont Theory
- Theory that mitochondria and plastids, including chloroplasts, originated as prokaryotic cells engulfed by an ancestral eukaryotic cell
- The engulfed cell and its host cell then evolved into a single organism
Crista
Infolding of the inner membrane of a mitochondrion that houses electron transport chains and molecules of the enzyme catalyzing the synthesis of ATP (ATP synthase)
Mitochondrial Matrix
Compartment of mitochondria enclosed by the inner membrane and containing enzymes and substrates for the citric acid cycle, as well as ribosomes and DNA
Thylakoid
- Flattened, membranous sac inside a chloroplast
- Often exist in stacks called grana that are interconnected
- Their membranes contain molecular “machinery” used to convert light energy to chemical energy
Granum
- Stack of membrane-bounded thylakoids in the chloroplast
- Function in the light reactions of photosynthesis
Stroma
- Dense fluid within the chloroplast surrounding the thylakoid membrane and containing ribosomes and DNA
- Involved in the synthesis of organic molecules from carbon dioxide and water
Plastid
- One of a family of closely related organelles that includes chloroplasts, chromoplasts, and amyloplasts
- Found in cells of photosynthetic eukaryotes
Peroxisome
Organelle containing enzymes that transfer hydrogen atoms from various substrates to oxygen, producing then degrading hydrogen peroxide
Cytoskeleton
- Network of microtubules, microfilaments, and intermediate filaments
- Extend throughout the cytoplasm and serve a variety of mechanical transport and signaling functions
Motor Protein
Protein that interacts with cytoskeleton elements and other cell components, producing movement of the whole cell or parts of the cell
Microtubule
- Hollow rod composed of tubulin proteins that makes up part of the cytoskeleton in all eukaryotic cells
- Found in cilia and flagella
Centrosome
- Structure in the centrosome of an animal cell that functions as a microtubule-organizing center and is important during cell division
- Has two centrioles
Centriole
A structure in the centrosome of an animal cell composed of a cylinder of microtubule triplets arranged in a “9+1” pattern
-There are two in a centrosome
Flagellum
Long cellular appendage specialized for locomotion
Cilium
Short appendage containing microtubules in eukaryotic cells
Basal Body
- Eukaryotic structure consisting of a “9+0” arrangement of microtubule triplets
- May organize the microtubule assembly of a cilium or flagellum
- Structurally very similar to a centriole
Dynein
In cilia and flagella, a large motor protein extending from one microtubule doublet to the adjacent doublet
Microfilament
Cable composed of actin proteins in the cytoplasm of almost every eukaryotic cell, making up part of the cytoskeleton and acting alone or with myosin to cause cell contraction
-Also known as an actin filament
Actin
Globular protein that links into chains, two of which twist helically about each other, forming microfilaments in muscle and other kinds of cells
Cortex
Outer region of cytoplasm in a eukaryotic cell, lying just under the plasma membrane, that has a more gel-like consistency than the inner regions due to the presence of multiple microfilaments
Myosin
Type of motor protein that associates into filaments that interact with actin filaments to cause cell contractions
Pseudopodia
Cellular extension of amoeboid cells used in moving and feeding
Cell Wall
- Protective layer external to the plasma membrane in plant cells, bacteria, fungi, and some protists
- Protects the cell and helps maintain its shape
Cytoplasmic Streaming
Circular flow of cytoplasm, involving interactions of myosin and actin filaments, that speeds the distribution of materials within cells
Intermediate Filament
Component of the cytoskeleton that includes filaments intermediate in size between microtubules and microfilaments
Primary Cell Wall
In plants, a relatively thin and flexible layer that surrounds the plasma membrane of a young cell
Middle Lamella
In plants, a thin layer of adhesive extracellular material, primarily pectins, found between primary walls of adjacent young cells
Secondary Cell Wall
In plant cells, strong and durable matrix that is often deposited in several laminated layers around the plasma membrane and provides protection and support
Extracurricular Matrix (ECM)
The meshwork surrounding animal cells, consisting of glycoproteins, polysaccharides, proteoglycans synthesized and secreted by cells
Collagen
- Glycoprotein in the extracellular matrix of animal cells that forms strong fibers, found extensively in connective tissue and bone
- Most abundant protein in the animal kingdom
Proteoglycan
- Large molecule consisting of a small core protein with many carbohydrate chains attached
- Found in the extracellular matrix of animal cells
FIbronectin
Extracurricular glycoproteins secreted by animal cells that help them attach the extracellular matrix
Integrin
In animal cells, a transmembrane receptor protein with subunits that interconnects the extracellular matrix and the cytoskeleton
Plasmodesma
An open channel through the cell wall that connects the cytoplasm of adjacent plant cells, allowing water, small solutes, and some large molecules to pass between cells
