Chapter 3 Flashcards
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
1) Growth
2) Reproduction
3) Responsiveness
4) Metabolism
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?
Reproduction-number
Growth-size
Growth and reproduction often occur
Simultaneously
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
Taxa
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
Eukaryotic
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
Peritrichous
Bacterial flagella only at the ends
Polar
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?
spirochetes
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?
100,000
counterclockwise to clockwise
Bacteria move with a series of “_____” punctuated by “_______”. Explain
“runs”
“tumbles”
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
Positive 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.
endotoxin
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
Mycoplasma pneumoniae
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?
Concentration gradient
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
Permeases
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?
Water
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?
Solvent
