Flashcards in Chapter 3 Deck (245):
Today we know that all living things contain both ______ and ________ chemicals & that many ________ chemicals can be made from ______ chemicals by laboratory processes
Organic and inorganic
organic chemicals made from inorganic chemicals
All living things share at lease 4 processes of life
Living things can grow; that is they can?
Increase in size
Organisms normally have the ability to reproduce themselves. Reproduction means that they increase in?
Number, producing more organisms organized like themselves. Reproduction may be accomplished asexually (alone) or sexually with gametes (sex cells).
Reproduction is an increase in?
Growth is an increase in?
Growth and reproduction often occur
All living things respond to their environment, meaning?
They have the ability to change internal and/or external properties in reaction to changing conditions around or within them. Many organisms also have the ability to move toward or away from environmental stimuli-a response called taxis
Metabolism can be defined as the ability of organisms to?
Take in nutrients from outside themselves and use the nutrients in a series of controlled chemical reactions to provide the energy and structures needed to grow, reproduce, and be responsive
Cells store metabolic energy in the?
Chemical bonds of adenosine triphosphate, or ATP.
Which organisms does growth occur
Bacteria, archaea, & eukaryotes
Does Not occur in viruses
Which organisms does reproduction occur?
Bacteria, archaea, & eukaryotes
Host cell replicates the viruse
Which organism does responsiveness occur?
Bacteria, archaea, & eukaryotes
Reaction to host cells seen in some viruses
Which organism does metabolism occur
Bacteria, archaea, & eukaryotes
Viruses use host cell's metabolism
Which organism have a cellular structure (membrane bound structure capable of growth, reproduction, responsiveness, & metabolism)
Present in bacteria, archaea & eukaryotes.
Viruses lack cytoplasmic membrane or cellular structure
There are many different kinds of cells
Some are free-living, independent organisms; others live together in colonies or form the bodies of multicellular organisms. Cells also exist in various sizes, from the smallest bacteria to bird eggs, which are the largest of cells
All cells may be described as either
Prokaryotes or eukaryotes
Scientists categorize organisms based on shared characteristics into groups called
The distinctive feature of prokaryotes is that they?
Can make proteins simultaneously to reading the genetic code because the typical prokaryote does not have a membrane surrounding its genetic material (DNA). It does not have a nucleus
Bacteria and archaea differ fundamentally in such ways as the type of?
Liquids in their cytoplasmic membranes and in the chemistry of their cell walls
The cells of algae, protozoa, fungi, animals, & plants are
Eukaryotes are usually what compared to prokaryotes
Larger & more complex than prokaryotes, which are typically 1.0 micrometers in diameter or smaller as compared to 10-100 micrometers for eukaryotic cells
Many cells have special external features that enable them to respond to other cells and their environment. In bacteria, these features include
Glycocalyces, flagella, fimbriae, & pili.
Some cells have a gelatinous sticky substance that surrounds the outside of the cell. This substance is known as?
Glycocalyx (glycoclyces) meaning sugar cup. It may be composed of polysaccharides, polypeptides, or both. These chemicals are produced inside the cell & are extruded onto the cell's surface.
What is a capsule? (Bacterial)
When the glycocalyx of a bacterium is composed of organized repeating units of organic chemicals firmly attached to the cell surface.
What is a slime layer? (bacterial)
When the glycocalyz of a bacterium is loose, water-soluble
Bacterial capsules and slime layers protect the cells from?
Desiccation (drying) & from being devoured; it may also help attach cells to one another & to surfaces in the environment
The presence of bacterial glycocalyx is a feature of numerous?
Pathogenic bacteria. Their glycocalyces play an important role in the ability of these cells both to survive & to cause disease.
The slime layers of bacterial glycocalyces are often?
Sticky (viscous), providing one means by which bacteria attach to surfaces. For example they enable oral bacteria to colonize the teeth, where they produce acid and cause decay.
Because chemicals in many capsules of glycocalyces are similar to those normally found in the body, they may prevent bacteria from?
Being recognized or devoured by defensive cells of the host. For example, the capsules of Streptococcus pneumoniae & Klebsiella pneumonia enable these prokaryotes to avoid destruction by defensive cells in the respiratory tract & to cause pneumonia. Unencapsulated strains of these same bacterial species do not cause disease, because the body's defensive cells destroys them
A cell's motility may enable it to?
Flee from a harmful environment or move toward a favorable environment such as one where food or light is available. The most notable structures responsible for such bacterial movement are flagella
Flagella (singular flagellum) are?
Long structures that extend beyond the surface of a cell and its glycocalyx and propel the cell through its environment.
Do all bacteria have flagella?
Not all bacteria have flagella, but for those that do, the flagella are very similar in composition, structure, and development
Bacterial flagella are composed of three parts
1) A long, thin filament
2) A hook
3) A basal body
Describe the long thin filament of bacterial flagella
It is a long hollow shaft, about 20 nm in diameter, that extends out into the cells environment. Composed of many identical globular molecules of a protein called flagellin. The cell extrudes molecules of flagellin through the hollow core of the flagellum, to be deposited in a clockwise helix at the lengthening tip. No membrane covers the filament.
Bacterial flagella sense external?
Wetness, inhibiting their own growth in dry habitats
Describe the hook of bacterial flagella
At the long, thin filaments base, a filament inserts into a curved structure, the hook, which is composed of a different protein.
Describe the basal body of bacterial flagella
Composed of different proteins, anchors the filament & hook to the cell wall and cytoplasmic membrane by means of a rod and a series of either two or four rings of integral proteins. Together the hook, rod, and rings allow the filament to rotate 360 degrees
Differences in the proteins associated with bacterial flagella vary enough to allow classification of
Species into groups (strains) called serovars
Bacterial flagella that cover the surface of the cell are termed
Bacterial flagella only at the ends
Some spiral-shaped bacteria (spirochetes) have flagella at both ends that spiral tightly around the cell instead of protruding into the surrounding medium. These flagella, called?
Endoflagella, form an axial filament that wraps around the cell between its cytoplasmic membrane & an outer membrane. Rotation of endoflagella evidently causes the axial filament to rotate around the cell, causing the spirochete to corkscrew through its medium. Some scientists think the corkscrew motility of these pathogens allows them to invade human tissues
Treponema pallidum, the agent of syphilis, and Borrelia burgdorferi, the cause of lyme disease, are notable?
Although the precise mechanism by which bacterial flagella move is not completely understood, we do know that they?
Rotate 360 degrees like boat propellers rather than whipping from side to side
What propels the spiral bacterium through the environment?
The flow of hydrogen ions or sodium ions through the cytoplasmic membrane near the basal body propelling the bacterium through the environment at about 60 cell lengths per second
Bacteria flagella rotate at more than ______ rpm and can change direction from?
counterclockwise to clockwise
Bacteria move with a series of "_____" punctuated by "_______". Explain
Counterclockwise flagellar rotation produces runs, which are movements of a cell in a single direction for some time. If more than one flagellum is present, the flagella align and rotate together as a bundle. Tumbles are abrupt, random changes in direction resulting from clockwise flagellar rotation where each flagellum rotates independently. Both runs and tumbles occur in response to stimuli
What sends signals to bacteria flagella?
Receptors for light or chemicals on the surface of the cell sends signals which they then adjust their speed and direction of rotation
A bacterium can position itself in a more favorable environment by varying the?
Number & duration of runs & tumbles
The presence of favorable stimuli increases what in bacteria?
The number of runs and decreases the number of tumbles; as a result, the cell tends to move toward an attractant.
The presence of unfavorable stimuli does what to bacteria?
Increase the number of tumbles, which increases the likelihood that it will move randomly in another direction, away from the repellant
In bacteria, movement in response to a stimulus is termed
Taxis. The stimulus may either be light (phototaxis) or a chemical (chemotaxis)
Movement toward a favorable stimulus is termed
Positive taxis, whereas movement away from an unfavorable stimulus is negative taxis.
Movement toward a nutrient would be positive/negative phototaxis/chemotaxis
Many bacteria have rodlike proteinaceous extensions called
fimbriae and pili
Bacteria use fimbriae which is sticky, bristlelike projections to
Adhere to one another & to substances in the environment. There may be hundreds of fimbriae per cell, and they are usually shorter than flagella
Neisseria gonorrhoeae is an example of?
A bacterium with fimbriae, it causes gonorrhea. Such pathogens must be able to adhere to their hosts if they are to survive and cause disease. The bacterium is able to colonize the mucous membrane of the reproductive tract by attaching with fimbriae. Nesseria cells that lack fimbriae are nonpathogenic
Bacteria may use fimbriae to move?
Across a substrate or toward another bacterium via a process similar to pulling an object with a rope. The bacterium extrudes a fimbria, which attaches to the substrate or to another bacterium; then the bacterium retracts the fimbriae, pulling itself toward the attachment point
Bacterium fimbriae aslo serve an important function in biofilms which are
Slimy masses of microbes adhering to a substrate by means of fimbriae and glycocalyces. Some fimbriae act as electrical wires, conducting electrical signals among cells in a biofilm. At least 99% of bacteria in nature exist in biofilms
A special type of fimbriae is
Pilus, also called conjugation pills. Pili are longer than other fimbriae & usually shorter than flagella. Typically only one to a few pili are present per cell in bacteria that have them.
Conjugation pili mediate the transfer of?
DNA from one cell to the other via a process termed conjugation
The cells of most prokaryotes are surround by a cell wall that provides
Structure & shape to the cell & protects it from osmotic forces. In addition, a cell wall assists some cells in attaching to other cells or resisting antimicrobial drugs.
Cell walls give bacterial cells characteristic shapes.
1) Spherical cells, called?
2) Rod shaped cells called?
1) Spherical cells are called cocci and may appear in various arrangements, including singly or in chains (streptococci, clusters (staphylococci), or cuboidal packets (sardine) depending on the planes of cell division.
2) Rod shaped cells called bacilli typically appear singly or in chains
Bacterial cell walls are composed of?
Peptidoglycan which is a complex polysaccharide. Peptidoglycan is in turn composed of two types of regularly alternating sugar molecules, called N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM), which are structurally similar to glucose. Millions of NAG & NAM molecules are covalently linked in chains in which NAG alternates with NAM
What are the glycan portions of peptidoglycan?
The chains of NAG alternating with NAM
Chains of NAG & NAM are attached to other chains by?
Crossbridges of four amino acids (tetrapeptides)
Peptidoglycan covers the?
Entire surface of a cell, which must insert millions of new subunits if it is to grow and divide
Scientists describe two basic types of bacterial cell walls as?
Gram-positive cell walls or Gram-negative cell walls
We distinguish Gram positive/negative cell walls by?
The use of the Gram staining procedure
Gram-positive bacterial cell walls have a?
Relatively thick layer of peptidoglycan that also contains unique chemicals called teichoic acids. Some acids are covalently linked to lipids, forming lipoteichoic acids that anchor the peptidoglycan to the cytoplasmic membrane. Teichoic acids have negative electrical charges, which help give the surface of a Gram-positive bacterium a negative charge & may play a role in the passage of ions through the wall. The thick cell wall of a Gram-positive bacterium retains the crystal violet dye used in the Gram staining procedure, so the stained cells appear purple under magnification
Some additional chemicals are associated with the walls of some Gram-positive bacteria. For example, species of Mycobacterium, which include the causative agents of tuberculosis and leprosy, have walls with up to 60% of?
Mycolic acid which is a waxy lipid. Mycolic acid helps these cells survive desiccation and makes them difficult to stain with regular water-based dyes. Researchers have developed a special staining procedure called the acid-fast stain to stain these Gram-positive cells that contain large amounts of waxy lipids
Gram-negative cell walls have
Only a thin layer of peptidoglycan, but outside this layer is an asymmetric bilayer membrane. The inner leaflet of the outer membrane is composed of phospholipids and proteins, and the other leaflet is made of lipopolysaccharide (LPS). Integral proteins called porins form channels through both leaflets of the outer membrane, allowing glucose & other monosaccharides to move across the membrane. The outer membrane is protective, allowing Gram-negative bacteria such as E. coli to better survive in harsh environments
What is lipopolysaccharide?
A union of lipid with a sugar. The lipid portion of LPS is known as lipid A
The Gram-negative outer membrane can also be impediment to the treatment of disease. For example, the outer membrane may prevent the movement of penicillin to the underlying peptidoglycan, thus?
Rendering the drug ineffectual against many Gram-negative pathogens
For a Gram-negative bacterial cell wall between the cytoplasmic membrane and the outer membrane is a?
Periplasmic space which contains the peptidoglycan and periplasm, the name given to the gel between the membranes of these Gram-negative cells. Periplasm contains water, nutrients, and substances secreted by the cell, such as digestive enzymes and proteins involved in specific transport. The enzymes function to catabolize large nutrient molecules into smaller molecules that can be absorbed or transported into the cell.
After the Gram staining procedure, Gram-negative cells appear?
Gram positive cells appear
Gram-negative appear pink/red
Gram-positive appear purple
The erroneous idea the lipid A is inside Gram-negative cells led to the use of the term _______ for this chemical. A dead cell releases lipid A when the outer membrane disintegrates, and lipid A may trigger fever, vasodilation, inflammation, shock, and blood clotting in humans. Because killing large numbers of Gram-negative bacteria with antimicrobial drugs releases large amounts of lipid A, which might threaten the patient more than the live bacteria, any internal infection by Gram-negative bacteria is cause for concern.
A few bacteria, such as ______ _______ lack cell wall entirely. In the past, these bacteria were often mistaken for viruses because of their small size and lack of walls. However, they do have other features of prokaryotic cells, such as prokaryotic ribosomes
Beneath the glycocalyx and the cell wall is a
Cytoplasmic membrane. May also be referred to as the cell membrane or a plasma membrane
Cytoplasmic membranes are about 8nm thick and composed of
Phospholipids and associated proteins. Some bacterial membranes also contain sterol-like molecules, called hopanoids, that help stabilized the membrane
The structure of a cytoplasmic membrane is referred to as a phospholipid bilayer. A phospholipid molecule is bipolar; that is?
The two ends of the molecule are different. The phosphate-containing heads of each phospholipid molecule are hydrophilic, the hydrocarbon tails are hydrophobic
About half of a bacterial cytoplasmic membrane is composed of what along with the phospholipids?
Integral proteins inserted. Some proteins penetrate the entire bilayer; others are found only in half of the bilayer. In contrast, peripheral proteins are loosely attached to the membrane on one side or the other
A cytoplasmic membrane does more than separate the contents of the cell from the outside environment. It also controls the?
Passage of substances into & out of the cell. Nutrients are brought into the cell, & wastes are removed. Also functions in producing molecules for energy storage and for harvesting light energy in photosynthetic bacteria.
In its function of controlling the contents of the cell, the cytoplasmic membrane is selectively permeable; that is
It allows some substances to cross it while preventing the crossing of others.
A phospholipid bilayer is naturally impermeable to most substances. Large molecules cannot cross through it; ions & molecules with an electrical charge are repelled by it; and hydrophilic substances cannot easily cross its hydrophobic interior. However, cytoplasmic membranes, unlike plain phospholipid bilayers in a scientist's test tube, contain proteins, & these proteins allow?
Substances to cross the membrane by functioning as pores, channels, or carriers
Movement across the cytoplasmic membrane occurs either by?
Passive or active processes.
Describe passive/active processes
Do not require the expenditure of a cell's metabolic energy store, whereas active processes require the expenditure of cellular energy, either directly or indirectly.
Selectively permeable cytoplasmic membranes have an ability to maintain a?
What is a concentration gradient
Membranes enable a cell to concentrate chemicals on one side of the membrane or the other. The difference in concentration of a chemical on the two sides of a membrane is its concentration gradient (chemical gradient)
Because many of the substances that have concentration gradients across cell membranes are electrically charged chemicals, a corresponding what exists?
Electrical gradient, or voltage, exists across the membrane. For example, a greater concentration of negatively charged proteins exists inside the membrane, & positively charged sodium ions are more concentrated outside the membrane. One result of the segregation of electrical charges by a membrane is that the interior of a cell is usually electrically negative compared to the exterior. This tends to repel negatively charged chemicals & attract positively charged substances into cells
In passive processes, the electrochemical gradient provides the source of?
Energy; the cell does not expend its energy reserve. Passive processes include diffusion, facilitated diffusion, and osmosis
What is diffusion?
1) The net movement of a chemical down its concentration gradient (from higher to lower)
2) Requires no energy output by the cell
3) Can occur in absence of cells or their membranes
4) Only chemicals that are small or lipid soluble can diffuse through the lipid portion of the membrane
What can and cannot freely diffuse through the cytoplasmic membrane?
Can- Oxygen, carbon dioxide, alcohol, & fatty acids
Cannot- Glucose & proteins
What is facilitated diffusion?
The phospholipid bilayer blocks the movement of large or electrically charged molecules, so they do not cross the membrane unless there is a pathway for diffusion. Some of the integral proteins act as channels or carriers to allow certain molecules to diffuse down their concentration gradients into or out of the cell. The proteins facilitate the process by providing a pathway for diffusion. Cell expends no energy in this type of movement, electrochemical gradients provide the energy
Some channel proteins allow the passage of a range of chemicals that have the right size or electrical charge. Other channel proteins known as _______ are more specific, carrying only certain substrates. A _______ has a binding site that is selective for one substance
When discussing simple and facilitated diffusion, we considered a solution in terms of the solutes (dissolved materials) it contains, because it is those solutes that move into and out of the cell. In contrasts, with osmosis it is useful to consider the concentration of the solvent, which in organisms is always?
Osmosis is the special name given to the?
Diffusion of water across a selectively permeable membrane, that is, across a membrane that is permeable to water molecules, but not to solutes that are present, such as proteins, amino acids, salts, or glucose. Because these solutes cannot freely penetrate the membrane, they cannot diffuse, no matter how unequal their concentrations on either side of the membrane may be. Instead, what diffuses is the water, which crosses from the side of the membrane that contains a higher concentration of water (lower concentration of solute) to the side that contains a lower concentration of water (higher concentration of solute). Osmosis continues until equilibrium is reached, or until the pressure of water is equal to the force of osmosis
We commonly classify solutions according to their concentrations of solutes. When solutions on either side of the membrane have same concentration of solutes the two solutions are said to be?
When concentrations of solutions are unequal, the solution with the higher concentration of solutes is said to be?
Solution with lower concentration of solutes is?
Isotonic means equal
Higher concentration of solutes is hypertonic
Lower concentration is hypotonic
Osmosis refers to the movement of the?
Down its concentration gradient from a hypotonic solution to a hypertonic.
A cell placed in a hypertonic solution will?
Lose water and shrivel
Water will move into a cell that is placed in a hypotonic solution because?
The cell has a higher solutes-to-water concentration. As water moves into the cell, water pressure against its cytoplasmic membrane increases, & the cell expands. One function of the cell wall, such as the peptidoglycan of bacteria, is to resist further osmosis and prevent cells from bursting
Active processes require?
The cell the expend energy stored in ATP molecules to move materials across the cytoplasmic membrane against their electrochemical gradient. ATP may be utilized directly during transport, or indirectly at some other site and at some other time
Active processes in bacteria include
Active transport by means of carrier proteins and a special process termed group translocation
Active transport is
Like facilitated diffusion, it utilizes transmembrane permease proteins; however, the functioning of active transport proteins requires the cell the expend ATP to transport molecules across the membrane. Some such proteins are referred to as gated channels or ports because they are controlled. When the cell is in need of a substance, the protein becomes functional (the gate "opens"). At other times, the gate is "closed"
If only one substance is transported at a time, the permease is called?
They simultaneously transport two chemicals, but in opposite directions; one going into the cell and one going out of the cell.
What are symports
Two substances move together in the same direction across the membrane by means of a single carrier protein
Active transport moves substances
Against their electrochemical gradient
In active transport, typically the protein acts as?
An ATPase-an enzyme that breaks down ATP into ADP and inorganic phosphate during transport, releasing energy that is used to move the chemical against its electrochemical gradient across the membrane
What is coupled transport
With symports and antiports, one chemical's electrochemical gradient may provide the energy needed to transport the second chemical. For example H+ moving into a cell down its electrochemical gradient by facilitated diffusion provides energy to carry glucose into the cell, against the glucose gradient. The two processes are linked by a symport. However, cellular energy may still be utilized for transport because the H+ gradient can be previously established by the active pumping of H+ to the outside of the cell by an H+ uniport. The use of ATP is thus separated in time & space from the active transport of glucose, but ATP was still expended
What is group translocation
An active process that occurs only in some bacteria. The substance being actively transported across the membrane is chemically changed during transport. The membrane impermeable to the altered substance, trapping it inside the cell. This type of transport is very efficient even if the external concentration of the chemical being transported is low
The substance is chemically altered during transport; found only in some bacteria.
Example of group translocation is the accumulation of glucose inside a bacterial cell. Explain
As glucose is transported across the bacterial cell membrane, it is phosphorylated (phosphate group added). Glucose is changed into glucose-6 phosphate, a sugar that cannot cross back out but can be utilized in the ATP producing metabolism of the cell. Other carbohydrates, fatty acids, purines, and pyrimidines are also brought into bacterial cells by group translocation.
Cytoplasm is the
General term used to describe the gelatinous material inside a cell. It is semitransparent, fluid, elastic, & aqueous. It is composed of cytosol, inclusions, ribosomes, and in many cells, a cytoskeleton. Some bacteria cells produce internal, resistant, dormat forms called endospores
What is contained in the cytosol (liquid portion of the cytoplasm)?
Mostly water, dissolved & suspended substances, including ions, carbohydrates, proteins (mostly enzymes), lipids, and wastes.
The cytosol of prokaryotes contains the cells?
DNA in a region called the nucleoid
The site of some chemical reactions for example enzymes within the cytosol function to produce amino acids and degrade sugar
What are inclusions?
Deposits, called inclusions, that are often found within bacterial cytosol. May include reserve deposits of lipids, starch, or compounds containing nitrogen, phosphate, or sulfur
Many bacteria store carbon and energy in molecules of glycogen, which is a polymer of glucose molecules, or as a lipid polymer called?
Long chains of polyhydroxybutyrate (PHB) accumulate as inclusion granules in the cytoplasm. Slight chemical modification of PHB produces?
A plastic that can be used for packaging & other applications. PHB plastics are biodegradable, breaking down in a landfill in a few weeks rather than persisting for years as petroleum-based plastics do
Some bacteria, notably Bacillus and Clostridium are characterized by the ability to produce unique structures called
Endospores, which are important for many reasons including their durability and potential pathogenicity. They are not reproductive structures. They constitute a defensive strategy against hostile or unfavorable conditions
Many aquatic cyanobacteria contain inclusions called gas vesicles that store?
Gases in protein sacs. The gases buoy the cells to the surface and into the light needed for photosynthesis
A vegetative cell normally transforms itself into an endospore only when one or more nutrients such as what are limited in supply?
Carbon or nitrogen
The process of endospore formation called sporulation, requires 8-10 hours and proceeds in 8 steps
1) DNA replicated
2) DNA aligns along cell's long axis
3) Cytoplasmic membrane invaginates to form forespore
4) Cytoplasmic membrane grows and engulfs foreshore within a second membrane. Vegetative cell's DNA disintegrates
5) A cortex of calcium & dipicolinic acid is deposited between the membranes
6) Spore coat forms around endospore
7) Endospore matures: completion of spore coat & increase in resistance to head & chemicals by unknown process
8) Endospore released from original cell
During the process of sporulation (endospore formation) two membranes, a thick layer of peptidoglycan and a spore coat form?
Around a copy of the cell's DNA and a small portion of cytoplasm
During endospore formation (sporulation) the cell deposits large quantities of dipicolinic acid, calcium, and DNA-binding proteins within the endospore while removing most of the water. Depending on the species, a cell forms an endospore either?
Centrally, subterminally (near one end), or terminally (at one end). Sometimes an endospore is so large it swells the vegetative cell
What are some conditions that endospores can survive
4) lethal chemicals
The ability to survive harsh conditions makes endospores the most?
Resistant and enduring cells
Endospore formation is a serious concern to food processors, health car professionals, and governments because?
They are resistant to treatments & inhibit other microbes, & because endospore forming bacteria produce deadly toxins that cause such fatal diseases as anthrax, tetanus, and gangrene
Nonmembranous organelles in bacteria include
Ribosomes and the cytoskeleton
Sites of protein synthesis in cells
Describe ribosomes in bacteria cells
They have thousands of ribosomes in their cytoplasm. The subunits of prokaryotic 70S ribosomes are a smaller 30S subunit and a larger 50S subunit, the 30S subunit contains polypeptides and a single rRNA molecule; whereas the 50S subunit has polypeptides and 2 rRNA molecules
Prokaryote ribosomes are ___S in contrast, the larger ribosomes of eukaryotic cells are ___S
Prokaryotic cells are 70S
Eukaryotic cells are 80S
All ribosomes are composed of?
Two subunits, each of which is composed of polypeptides and molecules of RNA called ribosomal RNA (rRNA)
How can antibacterial drugs stop protein synthesis in bacteria without affecting protein synthesis in a patient?
Many antibacterial drugs act on bacterial 70S ribosomes or their subunits without deleterious effects on the larger 80S ribosomes of eukaryotic cells
Most cells contain an internal network of fibers called a _________, that plays a role in forming a cell's basic shape
Does bacteria have a cytoskeleton?
Yes but a very simple one
Archaeal cells have external structures similar to those seen in bacteria. These include?
Glycocalyces, flagella, and fimbriae. Some archaea have another kind of proteinaceous appendage called a hamus.
Difference between bacterial and archeal glycocalyces
Archeal glycocalyces function at a minimum in the formation of biofilms (adhering cells to one another, to other types of cells, & to inanimate surfaces in the environment). Organized glycalyces (capsules) of bacteria and bacterial biofilms are often associated with disease, there is no link between archeal capsules or biofilms & disease.
Compare archeal flagella with bacterial flagella
Archeal flagella same qualities as bacterial flagella:
1) Use flagella to move through environment at slower speed
2) Superficially similar to bacterial flagella; consists of basal body, hook, & filament, each composed of protein
3) Rotate like propellers
1) Half the thickness of bacteria flagella (10-14 nm)
2) Lack central channel; grow w/addition of subunits at base of filament rather than the tip
3) Proteins in flagella share common amino acid sequences that are different than bacterial sequences
4) Sugar molecules attached to filaments unlike bacteria
5) Powered w/energy stored in molecules of ATP, bacteria use flow of H+ across membrane
6) Rotate together, bacteria operate independently
Archeal cell walls are composed of?
Specialized proteins or polysaccharides. Lack peptidoglycan, which is common to all bacterial cell walls.
Gram-negative archeal cells have an?
Outer layer of protein rather than an outer lipid bilayer as seen in Gram-negative bacteria. They still appear pink when Gram stained.
Gram-positive archaea have a?
Thick cell wall and Gram stain purple, like Gram-positive bacteria
Archael cells are typically what type of shape?
Spherical or rod shaped
Archael cytoplasmic membranes are composed of
Lipids that lack phosphate groups & have branched hydrocarbons linked to glycerol by ether linkages rather than the ester linkages seen in bacterial membranes. Ether linkages are stronger than ester linkages which allows them to live in extreme environments such as boiling water & in hypersaline lakes. The archaeal cytoplasmic membrane maintains electoral and chemical gradients in the cell. Also functions to control the import & export of substances from the cell using membrane proteins as ports & pumps
Describe the cytoplasm of archaea cells
Like bacteria, they have 70S ribosomes, a fibrous cytoskeleton, & a circular DNA suspended in a liquid cytosol. They also do not have membranous organelles.
They differ in several ways from bacteria:
1) Ribosomes have different proteins more like those of eukaryotic cells
2) Use different metabolic enzymes to make RNA & use genetic code similar to the code used by eukaryotes
Some eukaryotes have _______, which are similar to those of prokaryotes
Animal and most protozoan cells lack cell walls, but they have?
Sticky carbohydrate glycocalyces that are anchored to their cytoplasmic membranes via covalent bonds to membrane proteins and lipids
The functions of eukarotic glycocalyces include
Helping to anchor animal cells to each other, strengthening the cell's surface, providing some protection against dehydration, & functioning in cell-cell recognition & communication
Glycocalyces are absent in eukaryotic cells that have?
Cell walls, such as plants and fungi
The eukaryotic cells of fungi, agae, & some protozoa have cell walls. Glycocalyces are absent from these cells with cell walls; instead, the cell wall takes on one of the functions of glycocalyx by providing?
Protection from the environment. The wall also provides shape & support against osmotic pressure. Most of these cell walls are composed of various polysaccharides, but not the peptidoglycan seen in the walls of bacteria
Fungi also have walls of polysaccharides, including?
Cellulose, chitin, and/or glucomannan
The walls of algae are composed of a variety of?
Polysaccharides or other chemicals, depending on the type of algae. These chemicals include, cellulose, proteins, agar, carrageenan, silicates, algin, calcium carbonate, or a combination of these substances
All eukaryotic cells have cytoplasmic membranes. A eukaryotic cytoplasmic membrane, like those of bacteria, is a?
Fluid mosiac model of phospholipids & proteins, which act as recognition molecules, enzymes, receptors, carriers, or channels.
Channel proteins for facilitated diffusion are more common in?
Eukaryotes than in prokaryotes
Eukaryotic cytoplasmic membranes may differ from prokaryotic cytoplasmic membranes in several ways
1) Contain steroid lipids (sterols)
2) May contain small, distinctive assemblages of lipids & proteins that remain together as a functional group & do not flow independently amidst other membrane components (membrane rafts)
Eukaryotic cells frequently attach chains of sugar molecules to the outer surfaces of lipids and proteins in their cytoplasmic membranes; prokaryotic cells don't do this. Sugar molecules may act in?
Intercellular signaling, cellular attachment, and in other roles
Like its prokaryotic counterpart, a eukaryotic cytoplasmic membrane controls the movement of materials into and out of a cell, by what type of processes?
Both passive processes (simple diffusion, facilitated diffusion, & osmosis) and active transport. Eukaryotic membranes DO NOT perform group translocation. Many perform another type of active transport -endocytosis
What is endocytosis
Involves physical manipulation of the cytoplasmic membrane around the cytoskeleton
When does endocytosis occur?
When the membrane distends to form pseudopodia (false feet) that surround a substance, bringing it into the cell
Endocytosis is termed phagocytosis when?
If a solid is brought into the cell , and it is termed pinocytosis if only liquid is brought into the cell
Nutrients brought into the cell by endocytosis are then enclosed in a?
Some eukaryotes also use pseudopodia as a means of locomotion. Explain
The cell extends a pseudopod, & then the cytoplasm streams into it, a process called amoeboid action
Exocytosis, another solely eukaryotic process, is?
The reverse of endocytosis in that it enables substances to be exported from the cell. Not all eukaryotic cells can perform endocytosis or exocytosis
Glycocalyx of archaea and bacteria
Archaea: Polypeptide or polysaccharides or both
Bacteria: Polypeptide or polysaccharides or both
Flagella of archaea and bacteria
Archaea: Present in some, 10-14 nm in diameter,grow at base, rotate both counterclockwise and clockwise as bundles
Bacteria: Present in some, 20 nm in diameter, grows at tip, rotate counterclockwise in bundles to cause runs, rotate independently clockwise to cause tumbles
Fimbriae of archaea and bacteria
Archaea: Proteinaceous, used for attachment & in formation of biofilms
Bacteria: Proteinaceous, used for attachment, gliding motility, & in formation of biofilms
Pili of archaea and bacteria
Archaea: None discovered
Bacteria: Present in some, proteinaceous, used in bacterial exchange in DNA
Hami of archaea and bacteria
Archaea: Present in some, used for attachment
Cell walls of archaea and bacteria
Archaea: Present in most, composed of polysaccharides (not peptidoglycan) or proteins
Bacteria: Present in most, composed of peptidoglycan (a polysaccharide)
Cytoplasmic membrane of archaea and bacteria
Archaea: Present in all, membrane lipids made with ether linkages, some have single lipid layer
Bacteria: Present in all, phospholipids made with ester linkages in bilayer
Cytoplasm of archaea and bacteria
Archaea: Cytosol contains circular DNA molecule and 70S ribosomes, ribosomal proteins similar to eukaryotic ribosomal proteins
Bacteria: Cytosol contains at least a circular DNA molecule and 70S ribosomes with bacterial proteins
Substances are surrounded by pseudopodia and brought into the cell. There are two types
Two types are phagocytosis involves solid substances; and pinocytosis involves liquids
Vesicles containing substances are fused with cytoplasmic membrane, dumping their contents to the outside
Wastes and secretions are examples of?
The cytoplasm of eukaryotic cells is what compared to prokaryotic cells?
More complex. The most distinctive feature difference is the presence of numerous membranous organelles in eukaryotes
Some eukaryotes are flagellated. Flagella of eukaryotes differs structurally and functionally from flagella of prokaryotes.
Eukaryotes flagella is within the cytoplasmic membrane, they are internal structures that push the cytoplasmic membrane out around them. Their basal bodies are in the cytoplasm. The shaft of these flagella is composed of molecules of a globular protein called tubulin arranged in chains to form hollow microtubules
The filaments of eukaryotic flagella are anchored in the cytoplasm by a?
Basal body, but no hook connects the two parts, as in prokaryotes.
What is the function of eukaryotic flagella
Rather than rotating like prokaryotes flagella, those of eukaryotes undulate rhythmically. Some push the cell through the medium, others pull the cell through the medium
Other eukaryotic cells move by means of motile, internal, hair-like structures called ____, which extend the surface of the cell and are shorter and more numerous than flagella
Cila of eukaryotic cells are composed of?
Primarily of tubulin microtubules, which are arranged in a "9+2" arrangement of pairs in their shafts and a "9+0" arrangement of triplets in their basal bodies
A single cell may have hundreds or even thousands of motile cilia. Such cilia heath rhythmically, much like a swimmer doing a butterfly stroke. Coordinated beating of cilia propels?
Single-celled eukaryotes through their environment. Cilia are also used within some multicellular eukaryotes to move substances in the local environment past the surface of the cell. For example, such movement of cilia helps cleanse the human respiratory tract of dust and microorganisms
What are three nonmembranous organelles found in eukaryotes
Ribosomes and cytoskeleton (both of which are also present in prokaryotes) and centrioles (which are present only in certain kinds of eukaryotes)
The cytosol of eukaryotes, like that of prokaryotes, is a?
Semitranspartent fluid composed of water containing dissolved & suspended proteins, ions, carbohydrates, lipids, and wastes.
Within the cytosol of eukaryotic cells are ribosomes that are larger than prokaryotic ribosomes; instead of 70S ribosomes, eukaryotic ribosomes are?
80S and are composed of 60S and 40S subunits. In addition to the 80S ribosomes found w/in the cytosol, many eukaryotic ribosomes are attached to the membranes of the endoplasmic reticulum
Eukaryotic cells contain an extensive cytoskeleton composed of an?
Internal network of fibers and tubules. The eukaryotic cytoskeleton acts to anchor organelles & functions in cytoplasmic streaming & in movement of organelles w/in the cytosol.
The cytoskeleton in some cells enables the cell to?
Contract, move the cytoplasmic membrane during endocytosis & amoeboid action, & produce the basic shapes of the cells
The eukaryotic cytoskeleton is made up of?
Tubulin microtubules (also found in flagella and cilia), thinner microfilaments composed of actin, and intermediate filaments composed of various proteins
Animal cells and some fungal cells contain two _______, which lie at right angles to each other near the nucleus, in a region of the cytoplasm called the?
Plants, algae, & most fungi (and prokaryotes) lack centrioles, but usually have a region of cytoplasm corresponding to a?
Centrioles are composed of?
Nine triplets of tubulin microtubules arranged in a way that resembles the "9+0" arrangement seen at the base of eukaryotic flagella and cilia
Centrosomes play a role in?
Mitosis (nuclear division), cytokinesis (cell division), & the formation of flagella and cilia
Eukaryotic cells contain a variety of organelles that are surround by phospholipid bilayer membranes similar to the cytoplasmic membrane. These include?
2) Endoplasmic reticulum
3) Golgi body
9) Other chloroplasts
Prokaryotic cells lack these structures
The _______ is usually spherical to ovoid and is often the largest organelle in a cell
The control center of the cell
Nucleus, because it contains most of the cell's genetic instructions in the form of DNA. Cells that lose their nuclei, such as mammalian red blood cells, can survive for only a few months
The semiliquid portion of the nucleus is called
Within the nucleoplasm (liquid portion of the nucleus) may be one or more
Nucleoli, which are specialized regions where RNA is synthesized. The nucleoplasm also contains chromatin, which is a threadlike mass of DNA associated with special proteins called histones that play a role in packaging nuclear DNA
During mitosis (nuclear division) chromatin becomes?
Visible as chromosomes
Surrounding the nucleus is a?
Double membrane called the nuclear envelope, which is composed of two phospholipid bilayer, for a total of four phospholipid layers
The nuclear envelop contains
Nuclear pores that function to control the import & export of substances through the envelope
Continuous with the outer membrane of the nuclear envelope is a netlike arrangement of flattened hollow tubules called
Endoplasmic reticulum (ER)
The endoplasmic reticulum functions as a?
Transport system & is found in two forms: smooth ER and rough ER
The smooth ER (SER) play a role in?
Lipid synthesis as well as transport
Rough ER is rough because?
Ribosomes adhere to its outer surface. Proteins produced by ribosomes on the RER are inserted into the lumen (central canal) of the RER and transported throughout the cell
A golgi body is like a?
Shipping department of a cell: it receives, processes, & packages large molecules for export from the cell. It packages secretions in sacs called secretory vesicles, which then fuse with the cytoplasmic membrane before dumping their contents outside the cell via exocytosis
Golgi bodies are composed of?
A series of flattened hollow sacs that are circumscribed by a phospholipid bilayer. Not all eukaryotic cells contain Golgi bodies
Lysosomes, peroxisomes, vacuoles, & vesicles are membranous sacs that function to?
Store & transfer chemicals within eukaryotic cells.
Large vacuoles are found in plant and algal cells that store
Starch, lipids, and other substances in the center of the cell
Lysosomes, which are found in animal cells, contain
Catabolic enzymes that damage the cell if they are released from their packaging into the cytosol. The enzymes are used during during the self destruction of old, damaged, and diseased cells, and to digest nutrients that have been phagocytized. For example, white blood cells utilized the digestive enzymes in lysosomes to destroy phagocytized pathogens
Peroxisomes are vesicles derived from the?
ER, they contain oxidase and catalase, which are enzymes that degrade poisonous metabolic wastes (such as free radicals and hydrogen peroxide) resulting from some oxygen-dependent reactions
Peroxisomes are found in?
All types of eukaryotic cells but especially prominent in the kidney & liver cells of mammals
Mitochondria are spherical to elongated structures found in most eukaryotic cells. Like nuclei, they have two membranes, each composed of a phospholipid bilayer. The inner membrane is folded into numerous cristae that increase the inner membrane's surface area. Often called the power house of the cell because?
Their cristae produce most of the ATP in many eukaryotic cells
The powerhouse of the cell
The interior matrix of a mitochondrion contains
70S ribosomes and a circular molecule of DNA. This DNA contains genes for some RNA molecules & for a few mitochondrial polypeptides that are manufactured by mitochondrial ribosomes; most mitochondrial proteins are coded to nuclear DNA & synthesized by cytoplasmic ribosomes
Light-harvesting structures found in photosynthetic eukaryotes
Mitochondria & chloroplasts are semiautonomous; that is they
Divide independently of the cell but remain dependent on the cell for most of their proteins
This theory suggests that eukaryotes formed from the union of small aerobic prokaryotes with larger anaerobic prokaryotes. The smaller prokaryotes were not destroyed by the larger cells, instead became internal parasites that remained surrounded by a vesicular membrane of the host
Capsules protect cells from?
Slime layers enable?
Capsules protect cells from phagocytosis by other cells
Slime layers enable cells to stick to each other and to surfaces in their environment
Bacterial flagella may be?
Polar (single or tufts) or cover the cell (peritrichous)
Endoflagella, which are special flagella of spirochete, form an
Axial filament, located in the periplasmic space
May also use these to pull themselves across a surface or to conduct signals to neighboring cells
Thick layer of peptidoglycan
Has a thin layer of peptidoglycan & an external wall membrane with a periplasmic space between. This wall membrane contains lipopolysaccharide (LPS), which contains lipid A.
What can happen during an infection with Gram-negative bacteria?
Lipid A can accumulate in the blood, causing shock, fever, and blood clotting
What type of process depends on the electrochemical gradient and occurs within the membrane that allow certain substances to pass through the membrane
Include reserve deposits of lipids, starch, or compounds containing nitrogen, phosphate, or sulfur
True or False: A living organism must reproduce to be considered alive
A "9+2" arrangement of microtubules is seen in?
Svedbergs are an expression of?
Sedimentation rate during high-speed centrifugation
The cell walls of bacteria are composed of?
Bacterial flagella are anchored to the cell by a?
A Gram-negative cell is moving uric acid across the cytoplasmic membrane against its chemical gradient. What statement is true?
The acid moves by an active process such as active transport
Gram-positive bacteria 3 main points
1) have a thick cell wall, which retains crystal violet dye
2) contain teichoic acids in their cell walls
3) Appear purple after Gram staining
Dormant, resistant cells
Inclusions have been found to contain
Dipicolinic acid is an important component of?
Long whip, made of tubulin in eukaryotes, made of flegellin in bacteria
Responsible for motility in spirochetes
Made of tubulin in eukaryotes
Bristlelike projections found in quantities of 100 or more, numerous grappling hook projections
Responsible for conjugation, extensions not used for cell motility
The centriole contains microtubules in "___" arrangment
Functions as the transport system within a eukaryotic cell
Packages large molecules for export from a cell