Chapter 5 - Cells: The Working Units of Life Flashcards
Cell Theory
Cells are the fundamental units of life; all organisms are composed of cells; all cells come from preexisting cells; modern cells evolved from a common ancestor
Size of a cell
Cells are small because of a high surface area-to-volume ratio; larger organisms have more cells rather than larger cells
Magnification
Increases apparent size
Resolution
Clarity of magnified object; minimum distance 2 objects an be apart and still be seen as 2 objects
Light Microscopes
Use glass lenses and light; resolution is 0.2 micrometers
Electron Microscopes
Use electromagnets to focus an electron beam; resolution is 0.2 nanometers
Plasma Membrane
Outer surface of every cell; made of a phospholipid bilayer with embedded proteins and other molecules; functions as a selective barrier; cell needs a high surface area-to-volume ratio for efficient transfer of substances
Prokaryotic Cell
Enclosed by a plasma membrane; DNA contained in a region called the nucleoid; cytoplasm consists of cytosol (liquid) plus filaments and particles
Cytosol
Water mixed with dissolved ions, small molecules and soluble macromolecules; the liquid component of the cytoplasm
Eukarotic Cell
Membrane enclosed cell with organelles and a nucleus; DNA is located in the nucleus
Cell Wall
Most prokaryotes have a rigid cell wall outside the plasma membrane; some bacteria have a slimy polysaccharide capsule that surrounds the cell wall
Flagella
Prokaryotes use long stringlike structures to mobilize and are made of the protein flagellin
Pili
Short hairlike structures projecting from the surface on some bacteria (prokaryotes) that help attach to other cells or exchange DNA
Cell Fractionation
A process in which organelles are separated from one another after cells are broken open and their contents are suspended in an aqueous medium. The medium is placed in a tube and spun in a centrifuge where heavier particles sediment at the bottom of the tube
What do animal cells not have?
Chloroplasts, tonoplast, central vacuole and plamodesmata
What do plant cells not have?
Lysosomes, centrioles and flagella
Endomembrane System
Composed of the plasma membrane, nuclear envelope, endoplasmic reticulum (rough and smooth), golgi apparatus, and lysosomes
Nucleus
Largest organelle surrounded by a double membrane (nuclear envelope and nuclear lamina) that contains most of the genetic material including chromosomes and the nucleolus
Nuclear Lamina
Network of protein fibers on “nuclear” side of membrane within the inner and outer double membrane of the nucleus; maintains the shape of the nucleus
Nucleolus
Concentrated region in the nucleus where ribosome components (rRNA) are synthesized from DNA; not an organelle because it is not surrounded by a membrane
Endoplasmic Reticulum (ER)
Network of interconnected membranes in the cytoplasm
Rough ER
Newly made proteins enter RER lumen (interior compartment inside the folds of the RER) where they are modified, folded and transported to other areas; site of first glycosilation of proteins, (carbohydrates attached to the newly synthesized proteins); contains attached ribosomes
Smooth ER
Tubular structure attached to the RER; main function: site where lipids and steroids are synthesized;
also chemically modifies small molecules that may be toxic (drugs, pesticides, etc); site of glycogen degradation in animal cells (mobilization of glucose from glycogen in liver)
Ribosomes
Sites of protein synthesis; not considered an organelle because they exist in both prokaryotic and eukaryotic cells; consists of ribosomal RNA (rRNA) and more than 50 different protein molecules
Attached Ribosomes
Cell structure located attached to the walls of the RER; produce proteins that are transported out of the cell
Free Ribosomes
Cell structure located in the cytoplasm; synthesize proteins that are released directly into the cytoplasm for use by the cell
Golgi Apparatus
Cell structure that consists of flattened sacs (cisternae) and small membrane-enclosed vesicles; receives proteins from RER and further modifies them; concentrates, packages and sorts proteins; UPS packaging center of the organelles
Lumen
Internal components inside the RER; liquid space
Cis/Trans Region of the Golgi Apparatus
Cis region is nearest to the nucleus (faces the rough ER) that receives vesicles; trans region lies closest to the plasma membrane (faces the outer membrane) where vesicles bud of and move to the plasma membrane or other organelles
Primary Lysosomes
Originate from the golgi apparatus; contain digestive enzymes which hydrolyze macromolecules into monomers
Secondary Lysosomes
Primary lysosomes fuse with phagosomes to initiate digestion/hydrolysis of macromolecules
Autophagy
Lysosome engulfs another organelle or some cytosol recycling cell’s own materials
Phagocytosis
Materials/food molecules are enclosed from outside the cell that are engulfed in a vesicle called a phagosome; the phagosome moves through the cell and fuses with a primary lysosome to initiate digestion
Mitochondria
Double membraned organelle that are considered the powerhouse of the cell that convert fuel molecules into ATP (cellular respiration); contains enzymes, DNA and ribosomes
Chloroplast
Double membraned organelle in plant cell that is the site photosynthesis, converting light energy into food
Thylakoids
Circular compartments in the chloroplast that contrain chlorophyll that harvest light energy for photosynthesis
Grana
Stacks of thylakoids–circular compartments of inner membrane
Stroma
Fluid in which grana are suspended inside a chloroplast
Peroxisome
Single membranes organelle that collects and breaks down toxic by-products of metabolism such as peroxide (H2O2)
Cytoskeleton
Meshwork of filaments that supports and maintain cell shape; holds organelles in position, enable movement organelles; composed of microtubules, microfilaments and intermediate filaments
Microtubules
Long hollow cylinders made up of the protein tubulin (dimer of alpha and beta tubulin); thickest of the 3 components of the cytoskeleton; forms a rigid internal skeleton in some cells; can change length rapidly by adding or losing dimers; facilitates cell motility (cilia or flagella), chromosome movements in cell division and organelle movements
Cilia
Many microtubules that are short and move with a stiff power stroke and flexible recovery stroke; 9 + 2 array: 9 fused pairs of microtubules called doublets form an outer cylinder and one pair of unfused microtubules runs up the center
Flagella
Microtubules that are longer that are usually singular or in pairs where movement is snakelike; 9 + 2 array: 9 fused pairs of microtubules called doublets form an outer cylinder and one pair of unfused microtubules runs up the center
Movement of Cilia/Flagella
Results from the sliding of the microtubule doublets past one another; dynein binds to microtubule doublets and allows them to slide; nexin can cross-link the doublets and prevent them from sliding, causing the cilium to bend
Kinesin
The motor protein that moves vesicles or organelles from one part of the cell to another; binds to a vesicle and “walks” it allong by changing shape
Centrioles
Cylindrical cell structure that forms the anchoring site for microtubules attached to chromosomes during cell division/mitosis; located in the centrosome and is composed of 9 sets of triplet microtubules (9 x 3 conformation); usually found in a pair
Basal Body
Organelle of barrel-like microtubule structures located at the surface of the cell that anchor cilia or flagella attached to the cell
Nexin
Interdoublet linkage in cilia or flagella microtubule structure; cross-links the doublets and appears to limit how far the doublets can slide. This causes the cilium or flagellum to bend.
Microfilaments
2 intertwined strands of actin protein; actin has a positive and negative end that polymerizes to form long helical chains; thinnest of the 3 kinds of filaments; maintains/alters cell shape, helps cells to move in muscle contractions and cell motility (including moving whole cell or just the cytoplasm in the cell)
Myosin
Motor protein associated with actin filaments in muscle cells that result in muscle contraction
