U2 Chapter 6: A Tour of the Cell Flashcards
Light Microscope (LM)
Visible light is passed through the specimen and then through glass lenses, the lenses refract (bend) the light in such a way that the image of the specimen is magnified as it is projected into the eye or into a camera
Magnification
The ratio of an object’s image size to its real size
Resolution
A measure of the clarity of the image; it is the minimum distance two points can be separated and still be distinguished as separate points
Organelles
The membrane-enclosed structures within eukaryotic cells
Electron Microscope (EM)
Focuses a beam of electrons through the specimen or onto its surface
Scanning Electron Microscope (SEM)
Useful for detailed study of the topography of a specimen where the electron beam scans the surface of the sample, usually coated with a thin film of gold
- the result is an image of the specimen’s surface that appears 3D
Transmission Electron Microscope (TEM)
Used to study the internal structure of cells where the TEM aims an electron beam through a very thin section of the specimen, much as a light microscope aims light through a sample on a slide
Cell Fractionation
Technique for studying cell structure and dunction which takes cells apart and separates major organelles and other subcellular structures from one another
Differential Centrifugation
The piece of equipment that is used for this task is the centrifuge, which spins test tubes holding mixtures of disrupted cells at a series of increasing speeds
Cytosol
Semifluid and jellylike substance where subcellular components are suspended
Eukaryotic Cell
Most of the DNA is in an organelles called the nucleus, which is bounded by a double membrane
Prokaryotic Cell
The DNA is concentrated in a region that is not membrane-enclosed nucleoid
Cytoplasm
Interior in all cells
- for eukaryotic cells, this term refers only to the region between the nucleus and the plasma membrane
Nucleus
Contains most of the genes in the eukaryotic cell (some genes are located in mitochondria and chloroplasts)
Nuclear Envelope
Encloses the nucleus, separating its contents from the cytoplasm
Nuclear Lamina
A netlike array of protein filaments (in animal cells, called intermediate filaments) that maintains the shape of the nucleus by mechanically supporting the nuclear envelope
Chromosomes
Structures that carry the genetic information that DNA units are organized into
Chromatin
Complex DNA and proteins making up chromosomes
Nucleolus (plural for nucleoli)
Appears through the electron microscope as a mass of densely stained granules and fibers adjoining part of the chromatin
Ribosomes
Complexes made of ribosomal RNAs and proteins, are the cellular components that carry out protein synthesis
Endomembrane System
Different membrane-bounded organelles of the eukaryotic cell, which includes the nuclear envelope, the endoplasmic reticulum, the Golgi apparatus, lysosomes, various kinds of vesicles and vacuoles, and the plasma membrane
Vesicles
Sacs made of membrane for membrane transfer segments
Endoplasmic Reticulum (ER)
Extensive network of membranes that it accounts for more than half the total membrane in many eukaryotic cells
Smooth ER
Named because its outer surface lacks ribosomes
Rough ER
Studded with ribosomes on the outer surface of the membrane and thus appears rough through the electron microscope
Transport Vesicles
Vesicles in transit from one part of the cell to another
Golgi Apparatus
After leaving the ER, many transport vesicles travel to the GB where it is a warehouse for receiving, sorting, shipping, and even some manufacturing
- products of the ER, such as proteins, are modified and stored and then sent to other destinations
Lysosome
Membranous sac of hydrolytic enzymes that many eukaryotic cells use to digest (hydrolyze) macromolecules
- lysosomal enzymes work best in the acidic environment found in lysosomes
Phagocytosis
Amoebas and many other unicellular protists eat by engulfing smaller organisms or food particles
Vacuoles
Large vesicles derived from the endoplasmic reticulum and Golgi apparatus
- vacuolar membrane is selective in transporting solutes; as a result, the solution inside a vacuole differs in composition from the cytosol
Types of Vacuoles
- food vacuoles: formed by phagocytosis, have already been mentioned
- contractile vacuoles: many unicellular protists living in fresh water have this to pump excess water out of the cell, thereby maintaining a suitable concentration of ions and molecules inside the cell
- central vacuoles: in mature plant cells and developed by the coalescence of smaller vacuoles where the solutions called the cell sap is the main repository of inorganic ions (including potassium and chloride)
Mitochondria
Sites of cellular respiration, the metabolic process uses oxygen to drive the generation of ATP by extracting energy from sugars, fats, and other fuels
Chloroplasts
Found in plants and algae, are the sites of photosynthesis where chloroplasts convert solar energy to chemical energy by absorbing sunlight and using it to drive the synthesis of organic compounds such as sugars from carbon dioxide and water
Endosymbiont Theory
States that an early ancestor of eukaryotic cells (a host cell) engulfed an oxygen using non-photosynthetic prokaryotic cell and eventually the engulfed cell formed a relationship with the host cell in which it was enclosed, becoming an endosymbiont (a cell living within another cell)
Mitochondrial Matrix
Enclosed by the inner membrane, the matrix contains many different enzymes as well as the mitochondrial DNA and ribosomes
- enzymes in the matrix catalyze some of the steps of cellular respiration
- proteins that function in respiration, including the enzyme that makes ATP are built into the inner membrane
Thylakoids
Inside the chloroplasts, membranous system in the form of flattened interconnected sacs
Granum (plural, grana)
Thylakoids are staked like poker chips, granum is each individual stack
Stroma
The fluid outside the thylakoids and contains the chloroplast DNA and ribosomes as well as many enzymes
Plastids
Pivotal subcellular organelles that have evolved to perform specialized functions in plant cells, including photosynthesis and the production and storage of metabolites
- Amyloplast: a colorless organelle that stores starch (amylose) particularly in roots and tubers
- Chromoplast: has pigments that give fruit and flowers their orange and yellow hues
Peroxisome
A specialized metabolic compartment bounded by a single membrane
- Contains enzymes that remove hydrogen atoms from various substrates and transfer them to oxygen (O2), producing hydrogen peroxide (H2O2) as a by-product
Cytoskeleton
A network of fibers extending throughout the cytoplasm
Motor Protein
A class of molecular motors that can move along the cytoplasm of animal cells. They convert chemical energy into mechanical work by the hydrolysis of ATP. Flagellar rotation, however, is powered by a proton pump
Microtubules
Hollow rods constructed from globular proteins called tubulins
Centrosome
Microtubules grow out from this and it is a region that is often located near the nucleus
Centrioles
Within the centrosome as a pair, each composed of nine sets of triplet microtubules arranged in a ring
Flagella
A motility organelle that enables movement and chemotaxis. Bacteria can have one flagellum or several, and they can be either polar (one or several flagella at one spot) or peritrichous (several flagella all over the bacterium)
Cilia
To move water relative to the cell in a regular movement of the cilia. This process can either result in the cell moving through the water, typical for many single-celled organisms, or in moving water and its contents across the surface of the cell
Basal Body
Structurally very similar to a centriole with microtubule triplets in a “9+0” pattern
- a highly conserved cellular organelle discovered over one hundred years ago
Dynein
Large motor proteins that are attached along each outer microtubule doublet
- has two “feet” that “walk” along the microtubule of the adjacent doublet, using ATP for energy
Microfilaments
Thin solid rods that are also called actin filaments because they are built from molecules of actin, a globular protein
Cortex
Outer cytoplasmic layer of a cell, the semisolid consistency of a gel, in contrast with the more fluid state of the interior cytoplasm
Myosin
Thousands of actin filaments and thicker filaments are made of this and they interact to cause contractions in muscle cells
Pseudopodia
The cell crawls along a surface by extending cellular extensions
Cytoplasmic Streaming
A circular flow of cytoplasm within cells
- especially common in large plant cells, speeds the movement of organelles and the distribution of materials within the cell
Intermediate Filaments
Larger in diameter of microfilaments, but smaller than that of microtubules
- only found in the cells of some animals, including vertebrates
- specialized for bearing tension (like microfilaments)
- create cell cohesion and prevent the acute fracture of epithelial cell sheets under tension
Cell Wall
Surrounds the plasma membrane of plant cells and provides tensile strength and protection against mechanical and osmotic stress. It also allows cells to develop turgor pressure, which is the pressure of the cell contents against the cell wall
Primary Cell Wall
The cellulose-containing layer laid down by cells that are dividing and growing. To allow for cell wall expansion during growth, primary walls are thinner and less rigid than those of cells that have stopped growing
Middle Lamella
Serves as a cementing layer between the primary walls of adjacent cells
Secondary Cell Wall
Mainly composed of cellulose, hemicelluloses (xylem and glucomannan) and lignin, and are deposited in some specialized cells, such as tracheary elements, fibers and other sclerenchyma cells
Extracellular Matrix (ECM)
3D network consisting of extracellular macromolecules and minerals, such as collagen, enzymes, glycoproteins and hydroxyapatite that provide structural and biochemical support to surrounding cells
Collagen
Most abundant glycoprotein in the ECM of most animal cells, forms strong fibers outside the cells
Proteoglycans
Where collagen fibers are embedded in a network woven out of proteoglycans secreted by cells
- this molecule consists of a small core protein with many carbohydrate chains covalently attached , so that it may be up to 95% carbohydrate
Fibronectin
A ubiquitous extracellular matrix (ECM) glycoprotein that plays vital roles during tissue repair
Integrins
Principal receptors used by animal cells to bind to the extracellular matrix
Plasmodesmata
Intercellular pores connecting adjacent plant cells allowing membrane and cytoplasmic continuity and are essential routes for intercellular trafficking, communication and signaling in plant development and defense
