The Cell Flashcards

Question

What are the dynamic properties of actin filaments? Does polymerization require energy?

Answer 1

- assemble (polymerize) and disassemble (depolymerize) by noncovalent, reversible, additions/loss of actin monomers at the ends of filaments - polymerization requires energy by ATP hydrolysis, releasing energy to the filaments that creates a type of dynamic activity called treadmilling

Answer 2

Cytoplasmic streaming is the directed flow of cytosol (the liquid component of the cytoplasm) and organelles around fungal and plant cells. This movement aids in the delivery of organelles, nutrients, metabolites, genetic information, and other materials to all parts of the cell. Cytoplasmic streaming occurs as myosin-coated organelles move along actin filaments in the cytoskeleton of the cell, causing the cytosol to move as well.

Answer 3

1. All living things are composed of cells 2. The cell is the basic functional unit of life 3. Cells arise only from pre-existing cells 4. Cells carry genetic information only in the form of DNA→genetic material is passed from parent to daughter cell

Answer 4

``` Environmental factors (radiation, light, or chemicals) can cause the provirus to LEAVE the genome and revert to a lytic cycle. The prophage exits the bacterial chromosome to initiate the lytic cycle. The virus remains dormant until host conditions deteriorate, perhaps due to depletion of nutrients; then, the endogenous phages (known as prophages) become active. At this point they initiate the reproductive cycle, resulting in lysis of the host cell. As the lysogenic cycle allows the host cell to continue to survive and reproduce, the virus is reproduced in all of the cell’s offspring. ```

Answer 5

Each Golgi stack has two distinct ends, or faces. The cis face of a Golgi stack is the end of the organelle where substances enter from the endoplasmic reticulum for processing, while the trans face is where they exit in the form of smaller detached vesicles. Consequently, the cis face is found near the endoplasmic reticulum, from whence most of the material it receives comes, and the trans face is positioned near the plasma membrane of the cell, to where many of the substances it modifies are shipped. The chemical make-up of each face is different and the enzymes contained in the lumens (inner open spaces) of the cisternae between the faces are distinctive. Proteins, carbohydrates, phospholipids, and other molecules formed in the endoplasmic reticulum are transported to the Golgi apparatus to be biochemically modified during their transition from the cis to the trans poles of the complex. Enzymes present in the Golgi lumen modify the carbohydrate (or sugar) portion of glycoproteins by adding or subtracting individual sugar monomers. In addition, the Golgi apparatus manufactures a variety of macromolecules on its own, including a variety of polysaccharides.

Answer 6

A high-frequency recombination cell (Hfr cell) (also called an Hfr strain) is a bacterium with a conjugative plasmid (for example, the F-factor) integrated into its chromosomal DNA. The integration of the plasmid into the cell's chromosome is through homologous recombination.

Answer 7

Bacteria perform ESSENTIAL functions for human beings, including the production of VITAMIN K in the intestine. Vitamin K is required for the production of PLASMA PROTEINS necessary for blood clotting. Beneficial bacteria in the human intestine produce about 75% of the vitamin K the body absorbs each day, with the other 25% coming from dietary sources. Newborn infants are not yet COLONIZED by bacteria and so cannot produce vitamin K and therefore lack CLOTTING factors, putting them at risk for hemorrhage (bleeding). When babies are born they are given injections of vitamin K to aid in production of clotting factors until they have been colonized by bacteria.

Answer 8

o Eukaryotic cells contain a true nucleus enclosed in a membrane, while prokaryotic cells do not contain a nucleus o Prokaryotic cells are SMALLER and simpler than eukaryotic

Answer 9

o The mitochondria are capable of killing the cell by release of enzymes from the ETC; this release kick-starts a process known as APOPTOSIS, or programmed cell death o Mitochondrial outer membrane permeabilization is often required for activation of the caspase proteases that cause apoptotic cell death; caspase proteases dismantle cells and signal efficient phagocytosis of cell corpses

Answer 10

Bovine Spongiform Encephalopathy (BSE/MAD COW) Creutzfeldt-Jakob Disease, Classic (CJD) Familial Fatal Insomnia

Answer 11

Extremophiles are organisms that thrive in physically or geochemically EXTREME conditions that are detrimental to MOST life on earth--these organisms are most commonly found in HARSH environments with extremely high temperatures, high salinity, or NO LIGHT

Answer 12

BACTERIA ARCHAEA EUKARYA

Answer 13

After the bacteria have exceeded the ability of the environment to support the number of bacteria, a death phase occurs as resources in the environment have been depleted. At death phase (decline phase), bacteria die. This could be caused by lack of nutrients, environmental temperature above or below the tolerance band for the species, or other injurious conditions.

Answer 14

The envelope is very sensitive to heat, detergents, and desiccation, making enveloped viruses easier to kill. Viruses that do not have an envelope are more resistant to sterilization and are likely to persist on surfaces for an extended period of time.

Answer 15

Because the integration of the genetic material of the virus into the HOST CELLS GENOME allows for the cell to be infected INDEFINITELY--the only way to cure the infection is to kill the infected cell itself.

Answer 16

o Microtubules are HOLLOW polymers of tubulin proteins; they are cylindrical tubes built by the assembly of dimers of alpha tubulin and beta tubulin *Microtubules are the largest scaffold proteins with a diameter of 25 nm o Microtubules radiate throughout the cell, providing the primary pathway along which motor proteins like KINESIN and DYNEIN carry vesicles • Motor proteins like kinesin and dynein are classic examples of NONENZYMATIC proteins, along with binding proteins, cell adhesion molecules, IG, and ion channels • Motor proteins often travel along cytoskeletal structures to accomplish their function o Microtubules act as a scaffold to determine CELL SHAPE and provide a set of tracks for cell organelles and vesicles to move on o When arranged in geometric patterns inside flagella and cilia, they are used for locomotion

Answer 17

The sugar component consists of alternating residues of β-(1,4) linked N-acetylglucosamine and N-acetylmuramic acid. Attached to the N-acetylmuramic acid is a peptide chain of three to five amino acids. The peptide chain can be cross-linked to the peptide chain of another strand forming the 3D mesh-like layer

Answer 18

o Membranes of eukaryotic cells consists of a PHOSPHOLIPID BILAYER • Surfaces are HYDROPHILIC (water-lovng)→can electrostatically interact with the aqueous environment inside & outside the cell • Inner portions are HYDROPHOBIC→hydrophobicity helps provide a highly selective BARRIER between the interior of the cell and the EXTERNAL environment

Answer 19

o In this theory, a bacterium (which is aerobic) is engulfed by an ancestral eukaryote (anaerobic), and multiplies within it (primitive mitochondria formed) o CHLOROPLASTS: engulfed cyanobacterium becomes an endosymbiont and multiplies; new cells can make ATP using energy from SUNLIGHT o The prisoner prokaryotes might have provided crucial nutrients (in the case of the primitive chloroplast) or helped to exploit oxygen for extracting energy (in the case of the primitive mitochondrion); the prokaryotes, in turn, would have received PROTECTION and a steady environment in which to live

Answer 20

o It separates the nucleus from the cytoplasm and thus allows for COMPARTMENTALIZATION of transcription (formation of hnRNA from TNA, which is then processed to form mRNA), and TRANSLATION (mRNA made into a peptide/protein)

Answer 21

o Lipids cause water to arrange in an ordered, unfavorable cage-like structure. Forcing lipids into a bilayer reduces this effect • The formation of a phospholipid bilayer is PRIMARILY driven by an increase in entropy of surrounding water molecules • Lipids cause water to arrange in an ordered, unfavorable, cage-like structure called a CLATHRATE cage o Several intermolecular forces contribute to and subtract from the favorability of a phospholipid bilayer • These include STRONGER Van der Waals forces between hydrophobic phospholipid tails (favorable), INCREAED entropy of water molecules (favorable), decreased entropy of phospholipid molecules (unfavorable), and stabilization by hydrogen bonds (favorable) • Systems tend towards increased entropy; a disordered state is MORE favorable than an ordered state *Phospholipids are amphipathic molecules with two hydrophobic fatty acids and a hydrophilic phosphate-containing group linked to glycerol. When placed in an aqueous solution, water forms a shell around the hydrophobic lipid, a situation that not only prevents water from making hydrogen bonds with other water molecules, but also reduces freedom of movement, making the water molecules more ordered.

Answer 22

Both eukaryotes and Archaea start TRANSLATION with METHIONINE, contain RNA POLYMERASES, and associate their DNA with HISTONES. Due to the similarities of Archaea with eukaryotes, it is believed that hey share a COMMON ORIGIN

Answer 23

Viroids can BIND to a large number of RNA sequences and will silence genes in the plant genome. This prevents synthesis of necessary proteins and can subsequently cause METABOLIC and STRUCTURAL DERANGEMENTS in the plant cell.

Answer 24

The (F+) cell replicates its F factor and donates the copy to the recipient, converting it from an (F-) cell to an (F+) cell. This process enables the cell obtaining the new plasmid (in this case the F plasmid) to then transfer copies to OTHER CELLS. This method of genetic recombination allows for RAPID acquisition of antibiotic resistance or virulence factors throughout a colony because other plasmids can also be passed through the conjugation bridge.

Answer 25

Viruses may be as small 20nm or as large as 300nm. | Prokaryotes are 1-10 um, and eukaryotes are about ten times larger.

Answer 26

Results from the integration of foreign genetic material into the host GENOME. Genetic material often comes from other bacteria that, upon lysing, spill their contents in the vicinity of a bacterium capable of transformation. Many gram-negative RODS are capable of transformation.

Answer 27

A bacterium, virus, or other microorganism that can cause disease.

Answer 28

1. LAG PHASE 2. EXPONENTIAL PHASE/LOG PHASE 3. STATIONARY PHASE 4. DEATH PHASE

Answer 29

As the number of bacteria in the colony grows, resources are often reduced. The reduction of resources slows reproduction, and the stationary phase results. The stationary phase is often due to a growth-limiting factor such as the depletion of an essential nutrient, and/or the formation of an inhibitory product such as an organic acid. Stationary phase results from a situation in which growth rate and death rate are equal. The number of new cells created is limited by the growth factor and as a result the rate of cell growth matches the rate of cell death. The result is a “smooth,” horizontal linear part of the curve during the stationary phase.

Answer 30

The bacterial form of MATING (sexual reproduction). Two cells form a CONJUGATION BRIDGE between them that allows the transfer of genetic material. The transfer is UNIDIRECTIONAL and goes from the donor male (+) to the recipient female (-).

Answer 31

o Saturated fatty aids have NO carbon-carbon double bonds (they are SATURATED with HYDROGEN) o Unsaturated fatty acids have one to three double bonds along the backbone carbon chain—these double bonds introduce KINKS in the carbon chain which have important consequences on the fluid nature of the lipid membranes (increase fluidity) o Unsaturated fatty acids have LOWER melting points than saturated fatty acids

Answer 32

o During mitosis, the centrioles migrate to opposite poles of the dividing cell and organize the MITOTIC SPINDLE • Basically, the centrosomes move to opposite sides of the cell and begin the initiation of several types of microtubules, some that anchor the centrosomes in the cell at a specific position, and thus positioning the mitotic spindle apparatus • The second type of microtubule, the KINETOCHORE microtubule, attaches to the kinetochore, which is a protein found on the centromere of the sister chromatid o The microtubules emanating from the centrioles attach to the chromosome via complexes called KINETOCHORES and can exert force on the sister CHROMATIDS, pulling them apart o Basically, this entire apparatus of the centrosome and centriole, as well as the microtubules emanating from these structures, comprise the mitotic spindle

Answer 33

o hnRNA: heterogeneous nuclear RNA→it is the ORIGINAL product of transcription, so no post-transcriptional modifications have occurred→not all of hnRNA becomes an mRNA product o Pre-mRNA is an incompletely processed single strand of mRNA synthesized from a DNA template; all pre-mRNAs are hnRNAs but NOT all hnRNAs are pre-MRNAs o HnRNAs are all of the RNA in the nucleus while pre-mRNAs are those RNAs that will become mRNAs after post-transcriptional processing

Answer 34

o Microfilaments are made up of solid polymerized rods of actin • They are resistant to COMPRESSION and FRACTURE, and thus provide protection for the cell—they form a band beneath the plasma membrane which provides mechanical strength to the cell •Actin filaments can use ATP to generate force for movement by interacting with MYOSIN (i.e. during muscle contraction) o Microfilaments can also carry out CELLULAR MOVEMENTS including gliding, contraction, cytoplasmic streaming, and cytokinesis *Microfilaments are solid rods made of a protein known as actin. When it is first produced by the cell, actin appears in a globular form (G-actin). In microfilaments, however, which are also often referred to as actin filaments, long polymerized chains of the molecules are intertwined in a helix, creating a filamentous form of the protein (F-actin). All of the subunits that compose a microfilament are connected in such a way that they have the same orientation. Due to this fact, each microfilament exhibits polarity, the two ends of the filament being distinctly different. This polarity affects the growth rate of microfilaments, one end (termed the plus end) typically assembling and disassembling faster than the other (the minus end). *Also have role in extension of pseudopods in amoebae

Answer 35

o Viruses violate the third and fourth tenets of cell theory: that cells come from pre-existing cells, and that genetic information in the form of DNA goes from parent to daughter cells (viruses may have RNA) o Viruses are unable to reproduce on their own→they can only replicate by invading other organisms and taking over that cells machinery

Answer 36

o Connective tissue supports the body and provides a framework for the epithelial cells to carry out their functions o Connective tissues are the main contributors to the STROMA or SUPPORT STRUCTURE o Bone, cartilage, tendons, ligaments, adipose tissue, lymph and blood are all examples of connective tissues o Connective tissues develop from the MESODERM o Most cells in connective tissues produce and secrete materials such as COLLAGEN and ELASTIN to form the extracellular matrix • Elastin is a protein found in connective tissue that has the actual property of being ELASTIC and is responsible for allowing tissues in the body to “snap back” to their original shape after being stretched or contraction • COLLAGEN: the main structural protein in the extracellular space in the various connective tissues in animal bodies; it is the most abundant protein in mammals

Answer 37

Gram-positive cell walls contain a THICK LAYER of peptidoglycan, a polymeric substance made of amino acids and sugars. In addition to peptidoglycan, gram-positive cell walls also contain LIPOTEICHOIC ACID--function unknown. Potentially this acid that activates the immune system of humans

Answer 38

Because actin polymerization is reversible, filaments can depolymerize by the dissociation of actin subunits, allowing actin filaments to be broken down when necessary. Thus, an apparent equilibrium exists between actin monomers and filaments, which is dependent on the concentration of free monomers. The rate at which actin monomers are incorporated into filaments is proportional to their concentration, so there is a critical concentration of actin monomers at which the rate of their polymerization into filaments equals the rate of dissociation. At this critical concentration, monomers and filaments are in apparent equilibrium.

Answer 39

Vapor pressure lowering is a colligative property of solutions. The vapor pressure of a pure solvent is greater than the vapor pressure of a solution containing a non volatile liquid. This lowered vapor pressure leads to boiling point elevation. The force that is driving the solvent molecules to the vapour phase is the difference between the entropy of the liquid and the vapour phases: when the molecule escape the liquid there is an entropy gain. Adding a non-volatile solute will increase the entropy of the liquid phase without having an effect on the entropy of the vapour phrase (given that the solute is non-volatile). This will lower the difference in entropy between the two phases, which is the driving force that make vaporisation happen, therefore there will be a lower number of solvent particles in the vapour phase and a consequent lower vapour pressure. Another reason could be because molecules in solution, like NaCl, will break up and these ions will attract water molecules so water will be surrounding these ions or other polar molecules (like if sugar is added), so they will be less likely to escape because they are attracted to the solute. Another reason: since some of the solute molecules will take up spaces at the surface of the liquid, this will limit the number of solvent molecules at the surface. Since only solvent molecules located at the surface can escape (evaporate), the sheer presence of the solute lowers the number of solvent molecules coming and going and therefore lowers the equilibrium vapor pressure.

Answer 40

If the osmotic concentration of two solutions are equal, the solutions are ISOTONIC. When solutions have unequal osmotic concentrations, the solution with the higher concentration of solutes is HYPERTONIC, while the solution with the lower concentration of solutes is HYPOTONIC.

Answer 41

In the LYTIC CYCLE, bacteriophages make MAXIMAL use of the cell's machinery with little regard for the survival of the host cell. Once the host is SWOLLEN with new virions, the cell LYSES, and other bacteria can be infected. Bacteria in the lytic phase are termed VIRULENT.

Answer 42

The Cell wall forms the outer barrier of the cell and serves to protect the organism from its environment. It provides STRUCTURE and CONTROLS the movement of solutes into and out of the bacterium. This allows the cell to maintain CONCENTRATION GRADIENTS relative to the environment. The cell wall may also aid a pathogen by providing protection from a host organism’s immune system.

Answer 43

A form of genetic recombination that requires a VECTOR, a virus that caries genetic material from one bacterium to another. Viruses are OBLIGATE INTRACELLULAR PATHOGENS so they need host cell machinery to reproduce themselves; because of this, bacteriophages can trap a segment of host bacterial DNA during viral assembly. Then when that virus infects another bacterium, it can release this trapped DNA into the NEW host cell, and then that transferred DNA can integrate into the genome, giving the host new additional genes.

Answer 44

Bacteriophages are viruses that specifically target BACTERIA. They do not ENTER bacteria but rather inject their GENETIC MATERIAL, leaving the remaining structure outside the infected cell.

Answer 45

The three most common bacterial cell shapes are cocci (spherical, from the Greek word for seed/berry), bacilli (rod-shaped, from the Greek word for staff), and spirilla (curved shape, from spiral), and Vibrio – comma-shaped.

Answer 46

Flagella are LONG, WHIPLIKE structures that can be used for propulsion. Bacteria may have ONE, TWO, or MANY flagella depending on the species. They can be used to move TOWARD food or AWAY from toxins or immune cells.

Answer 47

o The residual attractive or repulsive forces between molecules or atomic groups that do not arise from covalent or ionic bonds o Includes forces between permanent dipoles, forces between a permanent dipole and a corresponding induced dipole, or forces between instantaneously induced dipoles

Answer 48

o Establishing a structural framework for the body o Transporting fluids and dissolved materials from in the body o Provides protection for delicate organs o Supports, surrounds, and interconnects other tissue types

Answer 49

o The ER is a series of interconnected membranes that are actually CONTIGUOUS (touching) with the nuclear envelope o The single membrane of the ER is folded into numerous invaginations, creating complex structures with a central lumen o ROUGH ER: studded with ribosomes, which permit the translation of proteins destined for secretion directly into its lumen o SMOOTH ER: lacks ribosomes and is utilized primarily for lipid synthesis and the detoxification of certain drugs and poisons • The smooth ER also transports proteins from the rough ER to the Golgi Apparatus

Answer 50

o They are a diverse group of filamentous proteins, including KERATIN and DESMIN o Many intermediate filaments are involved in cell-cell adhesion or maintenance of the overall integrity of the cytoskeleton o Intermediate filaments are able to withstand a tremendous amount of TENSION, making the cell structure more RIGID • They provide TENSILE STRENGTH for the cell • Nuclear lamins, another type of intermediate filament, form a meshwork that stabilizes the INNER MEMBRANE of the NUCLEAR ENVELOPE o Intermediate filaments help anchor other organelles, including the nucleus o The identity of the intermediate filament proteins within a cell is specific to the CELL and to the TISSUE TYPE • Ex: neurofilaments strengthen the long axons of neurons

Answer 51

o During mitosis, the CLEAVAGE FURROW is formed from microfilaments, which organize as a RING at the site of division between the two new daughter cells o As the actin filaments within the ring contract, the ring becomes smaller, eventually PINCHING OFF the connection between the two daughter cells

Answer 52

Anaerobes that CANNOT survive in oxygen-containing environments. The presence of oxygen leads to the PRODUCTION of reactive oxygen-containing radicals in these species, which leads to cell death.

Answer 53

o Centrioles are found in a region of the cell called the centrosome; there are a pair of centrioles per centrosome and are arranged at a 90-degree angle to one another • They are the ORGANIZING CENTERS for microtubules, and are structured as NINE TRIPLETS of microtubules with a HOLLOW CENTER (so a total of 27 microtubules per centriole)

Answer 54

A close and often long-term interaction between two different biological species. The term symbiosis applies to any type of persistent biological interaction (in other words mutualistic, commensalistic, or parasitic).

Answer 55

Mutualism is the way two organisms of different species exist in a relationship in which each individual benefits from the activity of the other.

Answer 56

The Golgi enzymes catalyze the addition or removal of sugars from cargo proteins (glycosylation), the addition of sulfate groups (sulfation), and the addition of phosphate groups (phosphorylation). Cargo proteins are modified by enzymes (called resident enzymes) located within each cisterna.

Answer 57

Peptidoglycan is a POLYMER consisting of SUGARS and amino acids that forms a mesh-like layer outside of plasma membranes of bacteria, forming the cell wall. Peptidoglycan serves a structural role in the bacterial cell wall, giving structural strength, as well as counteracting the osmotic pressure of the cytoplasm. Peptidoglycan is composed of numerous glycan (sugar‐based) polymers that are covalently crosslinked to one another by short peptide side‐chains, creating a single bag‐like macromolecule called the sacculus.

Answer 58

The bridge is made from appendages called SEX PILI that are found on the DONOR MALE.

Answer 59

Also called intrinsic proteins, have one or more segments that are embedded in the phospholipid bilayer. Most integral proteins contain residues with hydrophobic side chains that interact with fatty acyl groups of the membrane phospholipids, thus anchoring the protein to the membrane. Most integral proteins span the entire phospholipid bilayer. These transmembrane proteins contain one or more membrane-spanning domains as well as domains, from four to several hundred residues long, extending into the aqueous medium on each side of the bilayer. In all the transmembrane proteins examined to date, the membrane-spanning domains are α helices or multiple β strands. In contrast, some integral proteins are anchored to one of the membrane leaflets by covalently bound fatty acids, as discussed later. In these proteins, the bound fatty acid is embedded in the membrane, but the polypeptide chain does not enter the phospholipid bilayer.

Answer 60

o Polarized in the sense that ONE SIDE faces a LUMEN (the hollow inside of an organ or tube) or the outside world, with the OTHER SIDE interacts with blood vessels and structural cells o Small intestine: one side of the cell will be involved in the absorption of nutrients from the LUMEN, while the other side will be involved in releasing those nutrients into circulation for USE in the rest of the body

Answer 61

o Its three principle shapes are squamous, columnar and cuboidal (squamous are wider than they are tall, cuboidal are cube-shaped, and columnar are taller than they are wide) o Cuboidal are cube-shaped o Columnar are long and thin o Squamous are flat and scale-like

Answer 62

Viruses are composed of GENETIC MATERIAL, a protein COAT (CAPSID), and sometimes an envelope containing LIPIDS. The genetic material may be circular or linear, single-stranded or double-stranded, DNA or RNA. If an envelope IS present, it will surround the protein capsid--the envelope is composed of phospholipids and virus-specific proteins.

Answer 63

1. The viral invasion may initiate cell death (APOPTOSIS) which will release the virions--eukaryotic cells tend to trigger apoptosis when attacked 2. LYSIS: host cell may lyse because its filled with a lot of virions--disadvantage because the virus can no longer use the host cell to carry out its life cycle 3. EXTRUSION: virus leaves by fusing with the plasma membrane--favorable because this process allows the host cell to survive and the virus to continue to USE the host cell to create more viral progeny--a virus in this state is said to be an a PRODUCTIVE CYCLE

Answer 64

Freezing-point depression describes the process in which adding a solute to a solvent decreases the freezing point of the solvent. Examples include salt in water, alcohol in water, or the mixing of two solids such as impurities in a finely powdered drug. The resulting solution or solid-solid mixture has a lower freezing point than the pure solvent or solid. This phenomenon is what causes sea water, (a mixture of salt (and other things) in water) to remain liquid at temperatures below 0 °C (32 °F), the freezing point of pure water. Freezing-point depression is a COLLIGATIVE PROPERTY.

Answer 65

o Lysosomes are membrane-bound structures containing hydrolytic enzymes that are capable of breaking down many different substrates, including substances ingested by ENDOCYTOSIS and cellular waste products o Lysosomal membrane sequesters these enzymes to PREVENT damage to the cell

Answer 66

o Molecules that are non-polar diffuse through membranes more quickly than molecules that are polar o Molecules that are SMALL diffuse through membranes more quickly than molecules that are LARGE

Answer 67

o Larger cells o Often multicellular o Always have nucleus and other membrane-bound organelles o DNA is linear and associated with proteins to form CHROMATIN o Ribosomes are LARGE (80S) o Motility by flexible waving cilia or flagellae (made of TUBULIN) o Cell division by mitosis or MEIOSIS o Reproduction is asexual or sexual o Have common metabolic pathways

Answer 68

o Endosymbiotic Theory; Mitochondria look very similar to bacteria; possibility that mitochondria and bacteria are evolutionarily related o Mitochondria and Bacteria have in common: • Similar SIZE range • Protein-encoding and RNA-encoding DNA • 70 S ribosomes; mitochondria have bacterial-sized ribosomes; in eukaryotes, ribosomes are larger, while mitochondria have bacteria that are smaller and 70 S in size • Respiratory electron transport chains; can find those in a variety of aerobic bacteria • Electron Transport-Coupled ATP synthesis; idea of coupling gradient to synthesis of ATP; chemiosmotic model is also seen in BACTERIA

Answer 69

o PERIPHERAL PROTEIN o Hormones move through the circulatory system, acting as signaling molecules to specific organs/cells o A steroid is NOT a membrane protein o An integral protein can not easily leave the cell membrane and would therefore be a POOR SIGNALING MOLECULE o Lipid-bound proteins remain within the phospholipid bilayer by the fatty acid tails of phospholipids—they would be poor signaling molecules (they are proteins located on the surface of the cell membrane that are covalently attached to lipids embedded within the cell membrane) o Peptide hormones like INSULIN and GROWTH HORMONE interact with integral protein receptors in cell membranes; these hormones can be considered peripheral membrane proteins

Answer 70

o Cilia and flagella share the same structure, composed of NINE pairs (total of 18) of microtubules forming an OUTER ring, with TWO microtubules in the CENTER • 9+2 structure→seen only in eukaryotic organelles of motility • bacterial flagella have a different structure with a different chemical composition

Answer 71

Peripheral membrane proteins, or extrinsic proteins, do not interact with the hydrophobic core of the phospholipid bilayer. Instead they are usually bound to the membrane indirectly by interactions with integral membrane proteins or directly by interactions with lipid polar head groups.

Answer 72

There are two basic types of transmembrane proteins: alpha-helical and beta-barrels. Alpha-helical proteins are present in the inner membranes of bacterial cells or the plasma membrane of eukaryotes, and sometimes in the outer membranes. This is the major category of transmembrane proteins.

Answer 73

o Epithelial tissue, connective tissue, muscle, and nervous tissue

Answer 74

Genetic elements capable of inserting or removing themselves from the genome. Transposons are found in both prokaryotes and eukaryotes. Potential problem: if transposon is inserted within a coding region of a gene, that gene may be disrupted.

Answer 75

o Small cells o Always unicellular o No nucleus or any membrane-bound organelles, such as mitochondria • Instead has NUCLEAR BODY: the region of the cytoplasm that contains the DNA o DNA is CIRCULAR, without proteins o Ribosomes are small (70S) o Motility by rigid rotating flagellum (made of flagellin) o Cell division is by BINARY FISSION o Reproduction is always asexual o Huge variety of metabolic pathways

Answer 76

Peroxisomes are small, membrane-enclosed organelles that contain enzymes involved in a variety of metabolic reactions, including several aspects of energy metabolism. Peroxisomes originally were defined as organelles that carry out oxidation reactions leading to the production of hydrogen peroxide. Because hydrogen peroxide is harmful to the cell, peroxisomes also contain the enzyme catalase, which decomposes hydrogen peroxide either by converting it to water or by using it to oxidize another organic compound. A variety of substrates are broken down by such oxidative reactions in peroxisomes, including uric acid, amino acids, and fatty acids. In addition to providing a compartment for oxidation reactions, peroxisomes are involved in lipid biosynthesis. In animal cells, cholesterol and dolichol are synthesized in peroxisomes as well as in the ER. In the liver, peroxisomes are also involved in the synthesis of bile acids, which are derived from cholesterol.

Answer 77

Treponema pallidum, the cause of syphilis Borrelia burgdorferi, the cause of Lyme disease Leptospira interrogans, the cause of Weil’s syndrome

Answer 78

In biology/ecology, parasitism is a non-mutual symbiotic relationship between species, where one species, the parasite, benefits at the expense of the other, the host. Unlike predators, parasites typically do not kill their host, are generally much smaller than their host, and will often live in or on their host for an extended period. Both are special cases of consumer-resource interactions. Parasites show a high degree of specialization, and reproduce at a faster rate than their hosts. Parasites increase their own fitness by exploiting hosts for resources necessary for their survival, e.g. food, water, heat, habitat, and transmission

Answer 79

The ability of a cell to DETECT chemical stimuli and move toward or away from them

Answer 80

Viroids are classically thought of as PLANT pathogens, but a few examples of human viroids do exist, including the hepatitis D virus (HDV). HDV is innocuous ALONE, but when coinfected with hep. B virus (HBV), HDV is able to exert its silencing function on human hepatocytes.

Answer 81

They cannot reproduce independently and must express and replicate genetic information WITHIN a host cell because they lack ribosomes to carry out protein synthesis.

Answer 82

X-axis: TIME Y-axis: log of number of bacteria The bacterial growth curve is an example of a semilog plot. The fact that the y-axis is logarithmic means that a straight line (as seen during the exponential phase) actually represents an exponential increase in the number of bacteria, not a linear increase.

Answer 83

When the virus does not LYSE the bacterium, and instead integrates its viral DNA into the HOST GENOME as a PROVIRUS or PROPHAGE, which begins the lysogenic cycle. The virus will be REPLICATED as the bacterium reproduces because it is now apart of the host's genome. Via the lysogenic cycle, the bacteriophage's genome is not expressed and is instead integrated into the bacteria's genome to form the prophage. Since the bacteriophage's genetic information is incorporated into the bacteria's genetic information as a prophage, the bacteriophage replicates passively as the bacterium divides to form daughter bacteria cells. In this scenario, the daughter bacteria cells contain prophage and are known as lysogens.

Answer 84

It modifies proteins and lipids (fats) that have been built in the endoplasmic reticulum and prepares them for export outside of the cell or for transport to other locations in the cell. Proteins and lipids built in the smooth and rough endoplasmic reticulum bud off in tiny bubble-like vesicles that move through the cytoplasm until they reach the Golgi complex. The vesicles fuse with the Golgi membranes and release their internally stored molecules into the organelle. Once inside, the compounds are further processed by the Golgi apparatus, which adds molecules or chops tiny pieces off the ends. When completed, the product is extruded from the GA in a vesicle and directed to its final destination inside or outside the cell. Among the most important duties of the Golgi apparatus is to sort the wide variety of macromolecules produced by the cell and target them for distribution to their proper location. Specialized molecular identification labels or tags, such as phosphate groups, are added by the Golgi enzymes to aid in this sorting effort.

Answer 85

Bacteria that REQUIRE oxygen for metabolism

Answer 86

It is a form of ASEXUAL REPRODUCTION seen in prokaryotes. The circular chromosome attaches to the cell wall and replicate while the cell continues to GROW in size. Then the plasma membrane and cell wall begin to grow INWARD along the midline of the cell to produce TWO identical daughter cells. Because this is a relatively simple process compared to mitosis, binary fission is quite rapid. E. Coli can replicate every 20 minutes under ideal growth conditions.

Answer 87

A class of relationships between two organisms where one organism benefits from the other without affecting it. It is a non-harmful coexistence

Answer 88

Infection with one strain of phage generally makes the bacterium less susceptible to superinfection (simultaneous infection) with other phages. Because the provirus is relatively innocuous, there may be some evolutionary advantage to this association.

Answer 89

After infection, TRANSLATION of viral genetic material must occur in order for the virus to reproduce. This means that the viral genome has to migrate to the correct location in the cell. 1. Viral DNA must go to the nucleus in order to be transcribed into mRNA. Can then go to cytoplasm to make proteins 2. Positive-sense RNA viruses stay in cytoplasm where they are translated to proteins 3. Negative-sense RNA requires synthesis of a complementary strand via RNA replicase, which can THEN be translated to form proteins 4. RETROVIRUSES ultimately make DNA and that DNA must go to the nucleus, insert itself in the genome, and from there make RNA

Answer 90

o Mitochondria are the POWER PLANTS of the cell, in reference to their important metabolic functions o Structurally, contain TWO membranes, the OUTER and INNER membranes o OUTER membrane: serves as a barrier between the cytosol and the inner environment of the mitochondrion o INNER membrane: has numerous infoldings called CRISTAE & contains the molecules and enzymes necessary for the Electron Transport Chain (ETC) • The cristae are highly convoluted structures that INCREASE the SURFACE AREA available for ETC enzymes o Intermembrane space: the space between the inner and outer membranes o Matrix: the space inside the inner membrane o The pumping of protons FROM the mitochondrial matrix TO the intermembrane space establishes the proton-motive force • Protons will flow through ATP synthase to generate ATP during oxidative phosphorylation

Answer 91

Enveloped viruses fuse with the plasma membrane of a cell, allowing the entry of the virion into the host cell. Sometimes a host cell may misinterpret the binding of a virus to the membrane as nutrients or other useful molecules and will actually bring the virus into the cytoplasm via endocytosis. Bacteriophages use tail fibers to anchor themselves to the cell membrane and then inject their viral genome into the host bacterium using the tail sheath. Some tail fibers even have enzymatic activity, allowing for both penetration of the cell wall and the formation of pores in the cell membrane.

Answer 92

An Hfr cell can transfer a portion of the bacterial genome. Despite being integrated into the chromosomal DNA of the bacteria, the F factor of Hfr cells can still initiate conjugative transfer, without being excised from the bacterial chromosome first. Due to the F factor's inherent tendency to transfer itself during conjugation, the rest of the bacterial genome is dragged along with it. Therefore, unlike a normal F+ cell, Hfr strains will attempt to transfer their entire DNA through the mating bridge, in a fashion similar to the normal conjugation. Interestingly, in a typical conjugation, the recipient cell also becomes F+ after conjugation as it receives an entire copy of the F factor plasmid; but this is not the case in conjugation mediated by Hfr cells. Due to the large size of bacterial chromosome, it is very rare for the entire chromosome to be transferred into the F - cell as time required is simply too long for the cells to maintain their physical contact. Therefore, as the conjugative transfer is not complete (the circular nature of plasmid and bacterial chromosome requires complete transfer for the F factor to be transferred as it may be cut in the middle), the recipient - cells do not receive the complete F factor sequence, and do not become F + due to its inability to form a sex pilus.

Answer 93

Archaea are single-celled organisms that are VISUALLY similar to bacteria but contain genes and several metabolic pathways that are more similar to eukaryotes than bacteria. Archaea are resistant to many antibiotics.

Answer 94

o Epithelial cells most often constitute the PARENCHYMA, or the FUNCTIONAL parts of the organ o Ex: nephrons in the kidney, hepatocytes in the liver, and acid-producing cells of the stomach are all composed of epithelial cells o Epithelial cells are very diverse and serve NUMEROUS functions depending on the organs they are in

Answer 95

They are being OXIDIZED as their electrons are given over to the electron transport chain. o This process allows PROTONS to be pumped from the mitochondrial matrix into the intermembrane SPACE; however its entirely possible that the protons are NOT remaining there; the outer membrane has HUGE pores so the protons could be leaving the mitochondria; the point is that there is a large LACK of protons in the mitochondrial matrix due to this electron transport chain process, which is pumping them OUT of the matrix Creating a very LOW concentration of protons in mitochondrial matrix; also movement of CHARGED molecules in only ONE DIRECTION (out of the matrix), which is an electrogenic process that generates a charge across the inner membrane will generate the energy necessary to make ATP molecules Electrons ultimately going down electron transport chain through cofactors and complexes to ultimately reduce OXYGEN, and FOUR electrons at a time, is generating H2O

Answer 96

Osmotic pressure is the minimum pressure which needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane. It is also defined as the measure of the tendency of a solution to take in water by osmosis. Osmotic pressure is defined as the external pressure required to be applied so that there is no net movement of solvent across the membrane. Osmotic pressure is a colligative property, meaning that the osmotic pressure depends on the molar concentration of the solute but not on its identity.

Answer 97

POSITIVE SENSE: implies that the RNA genome may be DIRECTLY translated to functional proteins by the ribosomes of the host cell, just like mRNA. NEGATIVE SENSE: these require synthesis of an RNA strand complementary to the negative-sense RNA strand, which can THEN be used as a template for protein synthesis. Negative sense RNA viruses must carry an RNA replicase in the virion to ensure that the complementary strand is synthesized.

Answer 98

Bacteria that use FERMENTATION or some other form of cellular metabolism that DOES NTO REQUIRE OXYGEN

Answer 99

During lag phase, bacteria adapt themselves to growth conditions. It is the period where the individual bacteria are maturing and not yet able to divide. During the lag phase of the bacterial growth cycle, synthesis of RNA, enzymes and other molecules occurs.

Answer 100

They are composed of polymers of glucose. They are important for carbon and energy storage.

Answer 101

A subset of plasmids that are capable of integrating into the genome of the bacterium.

Answer 102

o The intracellular solute concentration, the extracellular solute concentration, and the presence of aquaporins o Osmotic pressure is a colligative property (colligative properties of solutions are properties that depend on the concentration of solute molecules or ions, the ratio of solute to solvent concentration, but NOT upon the identity of solute or the solvent) • Colligative properties include freezing point depression, boiling point elevation, vapor pressure lowering, and osmotic pressure o Aquaporins are channel proteins that allow water to follow through a membrane o The polarity and molecular weight of the solutes do not affect osmosis; the rate of osmosis depends on the ratio of intracellular to extracellular concentration as well as the presence of aquaporins in the cell membrane

Answer 103

o Structures involved in the movement of the cell itself, such as the movement of SPERM cells through the reproductive tract o Composed of microtubules

Answer 104

Virulence factors are molecules produced by pathogens (bacteria, viruses, fungi and protozoa) that contribute to the pathogenicity of the organism. Plasmids often carry additional VIRULENCE FACTORS or traits that increase how pathogenic a bacterium is, such as TOXIN PRODUCTION, PROJECTIONS that allow the bacterium to attach to certain kinds of cells, or evasion of the host's immune system.

Answer 105

o Cholesterol DECREASES fluidity at high temperatures and INCREASES fluidity at LOW temperatures o The fluidity of cell membranes is determined in large part by how well the fatty acid tails of phospholipids can interact with each other via Van der Waals forces • The closer the fatty acids can pack together the less fluid the membrane becomes o At LOW temperatures, phospholipids are packed CLOSELY together→cholesterol inserts within the hydrophobic region of the membrane, separating phospholipids and decreasing the strength of Van der Waals forces among fatty acid tails o At HIGH temperatures, phospholipids are already fairly well-separated from each other→cholesterol fills in these gaps, pulling phospholipids CLOSER together and increasing the strength of Van der Waals forces among fatty acid tails

Answer 106

The flagella are composed of a FILAMENT, a basal body, and a HOOK. The FILAMENT: a hollow, helical structure composed of flagellin. BASAL BODY: a complex structure that anchors the flagellum to the cytoplasmic membrane and is also the MOTOR of the flagellum, rotating at rates up to 300 Hz. HOOK: connects the filament to the basal body so that, as the basal body rotates, it exerts torque on the filament, which can thereby SPIN and propel the bacterium forwards.

Answer 107

Prions cause disease by triggering MISFOLDING of other proteins, usually involving the conversion of a protein from an alpha-helical structure to a Beta-pleated sheet. This misfolding DRASTICALLY reduces the solubility of the protein, as well as the ability of the cell to degrade the misfolded protein. Eventually protein AGGREGATES FORM, and the function of the cell is reduced. The misfolded proteins themselves are non-functional.

Answer 108

RUBISCO!!! The most abundant protein in the world is RuBisCO, which is an enzyme that catalyzes the first step in carbon fixation. RuBisCO is found in plants, algae, cyanobacteria and certain other bacteria. Carbon fixation is the main chemical reaction responsible for inorganic carbon entering the biosphere. In plants, this is part of photosynthesis, in which carbon dioxide is made into glucose.

Answer 109

“The overall structure of flagella is similar in both gram-positive and gram-negative bacteria, but there are slight differences due to the different physical structure and chemical composition of the envelope in gram-positive and gram-negative bacteria.”

Answer 110

UNABLE to use oxygen for metabolism, but are not harmed by its presence in the environment

Answer 111

Phages that replicate only via the lytic cycle are known as virulent phages while phages that replicate using both lytic and lysogenic cycles are known as temperate phages

Answer 112

Archaea have a SINGLE CIRCULAR CHROMOSOME, divide by BINARY FISSION or BUDDING, and overall share a SIMILAR STRUCTURE to bacteria.

Answer 113

The sarcoplasmic reticulum is a specialized type of smooth ER that regulates the calcium ion concentration in the cytoplasm of striated muscle cells.

Answer 114

o Stromal cells are connective tissue cells of any organ | o They are cells that SUPPORT the function of the parenchymal cells of that organ

Answer 115

o Unlike simple diffusion, the rate of facilitated diffusion is LIMITED by the number of transport proteins in the membrane o Simple diffusion is the passage of a substance across a membrane without the aid of an integral membrane protein o Facilitated diffusion is a PASSIVE PROCESS, meaning it does NOT require a source of energy, such as ATP—since there is no external source of energy, facilitated diffusion cannot transport ligands against a concentration gradient o Facilitated diffusion of a substance requires a specific integral membrane protein, which may not be found in all cell-types o When a specific protein becomes saturated with ligand molecules, the rate of facilitated diffusion cant get any higher • Simple diffusion is not limited in any way • Therefore, unlike simple diffusion, the rate of facilitated diffusion is limited by the number of transport proteins in the membrane

Answer 116

o FORM WILL FOLLOW FUNCTION o Cells that require a lot of energy for locomotion (i.e. sperm cells) have high concentrations of mitochondria o Cells involved in secretion (pancreatic islet cells and other endocrine tissue) have high concentrations of RER and Golgi o RBC serve a transport function and therefore have NO ORGANELLES AT ALL

Answer 117

o TO STORE ELECTRICAL AND CHEMICAL POTENTIAL ENERGY o During an action potential, sodium and potassium ions move across the membrane through sodium and potassium channels, not sodium potassium pumps o Sodium-potassium pumps increase the concentration of sodium OUTSIDE the cell and increase the concentration of POTASSIUM inside the cell o Sodium-potassium pumps create an electrochemical gradient between the inside and outside of the cell. This produces electrical and chemical potential energy to be used in action potentials

Answer 118

As already discussed, proteins are translocated across the ER membrane as unfolded polypeptide chains while their translation is still in progress. These polypeptides, therefore, fold into their three-dimensional conformations within the ER, assisted by the molecular chaperones that facilitate the folding of polypeptide chains. The formation of disulfide bonds between the side chains of cysteine residues is an important aspect of protein folding and assembly within the ER. In the ER, however, an oxidizing environment promotes disulfide (S—S) bond formation, and disulfide bonds formed in the ER play important roles in the structure of secreted and cell surface proteins. Disulfide bond formation is facilitated by the enzyme protein disulfide isomerase which is located in the ER lumen. The ER is also the site of protein folding, assembly of multisubunit proteins, disulfide bond formation, the initial stages of glycosylation, and the addition of glycolipid anchors to some plasma membrane proteins. Indeed, the primary role of lumenal ER proteins is to catalyze the folding and assembly of newly translocated polypeptides.

Answer 119

o The nuclear envelope is perforated with holes called NUCLEAR PORES that regulate the passage of molecules between the NUCLEUS and the CYTOPLASM, permitting some to pass through the membrane but not others o Building blocks for building DNA and RNA are allowed into the nucleus, as well as molecules that provide the energy to construct genetic material

Answer 120

Bacteria constitute a LARGE domain of prokaryotic microorganisms. The cell structure is simpler than that of other organisms as there is no nucleus or membrane bound organelles. Instead their control centre containing the genetic information is contained in a single loop of DNA. The bacterial cell is surrounded by a cell membrane This membrane encloses the contents of the cell and acts as a barrier to hold nutrients, proteins and other essential components of the cytoplasm within the cell. As they are prokaryotes, bacteria do not usually have membrane-bound organelles in their cytoplasm, and thus contain few large intracellular structures. Some have flagella or fimbriae (similar to cilia)

Answer 121

SINGLE STRANDED DNA

Answer 122

o The nuclear envelope is a DOUBLE-LAYERED membrane that encloses the contents of the nucleus during most of the cell’s lifecycle, and connects with the ROUGH endoplasmic reticulum o The envelope is perforated with tiny holes called NUCLEAR PORES o Perinuclear space: the space between the layers o The inner surface of the nuclear envelope has a protein lining called the NUCLEAR LAMINA, which binds to chromatin and other nuclear components o During mitosis or cell division, the nuclear envelope disintegrates, and then REFORMS as the two cells complete their formation

Answer 123

o The nucleolus is a membrane-less organelle WITHIN the nucleus where ribosomal RNA (rRNA) is synthesized o During cell division, the nucleolus disappears

Answer 124

1. LYTIC CYCLE | 2. LYSOGENIC CYCLE

Answer 125

In order to infect a cell, the virus has to bind to specific receptors on the host cell. Without the proper receptors, a cell is essentially invisible to the virus. Once the virus binds the correct receptor, the virus and the cell are brought into close enough proximity to permit additional interactions.

Answer 126

Gram Positive and Gram Negative. The type of cell wall is determined by the GRAM STAINING PROCESS with a CRYSTAL VIOLET STAIN, followed by a counterstain with a substance called SAFRANIN. If the envelope (cell wall + plasma membrane) absorbs the crystal violet stain, it will appear DEEP PURPLE, and the cell is said to be gram positive. If the envelope does NOT absorb the crystal violet stain but absorbs the SAFRANIN counterstain, then the cell will appear PINK-RED, and the cell is said to be gram-negative.

Answer 127

Osmosis is the spontaneous net movement of solvent molecules through a semi-permeable membrane into a region of higher solute concentration, in the direction that tends to equalize the solute concentrations on the two sides. Although water molecules are POLAR, they are small enough to pass through the plasma membrane FREELY, and so this special case of diffusion is called osmosis.

Answer 128

As the bacteria adapt, growth increases, causing an exponential increase in the number of bacteria in the colony during the exponential phase, which can also be called the log phase. The number of new bacteria appearing per unit time is proportional to the present population. The actual rate of this growth depends upon the growth conditions, which affect the frequency of cell division events and the probability of both daughter cells surviving.

Answer 129

Gram-negative cell walls are very THIN, and contain peptidoglycan in MUCH smaller amounts. These bacteria also have OUTER MEMBRANES containing PHOSPHOLIPIDS and LIPOPOLYSACCHARIDES

Answer 130

o Cilia are projections from a cell that are primarily involved in MOVEMENT of materials along the surface of the cell o Example: Cilia line the respiratory tract and are involved in movement of mucus o They are composed of microtubules

Answer 131

The antibiotic PENICILLIN targets the enzyme that catalyzes the cross-linking of peptidoglycan. If a gram-positive cell cannot cross-link its cell wall, it no longer serves as an effective barrier. The bacterium becomes susceptible to OSMOTIC damage and LYSES. Most bacteria have become resistant to penicillin, but a few bacteria, like Streptococcus pyogenes (Strep throat & skin infections) and Treponema pallidum (causes syphilis) are still sensitive to this antibiotic.

Answer 132

The most abundant protein in your body is collagen. Around 25% to 35% of protein in your body is collagen. It is the most common protein in other mammals, too. Collagen forms connective tissue. It is found primarily in fibrous tissue, such as tendons, ligaments and skin. Collagen is a component of muscle, cartilage, bone, blood vessels, the cornea of the eye, intervertebral discs and the intestinal tract.

Answer 133

Both retroviruses and transduction are under investigation as methods of gene therapy. It is theorized that retroviruses and transduction methods can deliver functional versions of missing or altered genes, so that the correct proteins can be synthesized and certain disease states can be alleviated.

Answer 134

HIV must bind to a receptor called CCR5 on white blood cells in order to infect them. Some people lack this receptor and are thus immune to HIV. There was recently a case in which an HIV-positive man with leukemia received a bone marrow transplant from a donor that lacked CCR5. Not only was his leukemia cured, but this transplant also resulted in remission of his HIV infection because the white blood cells from his newly acquired bone marrow were not susceptible to HIV infection.

Answer 135

LIPOPOLYSACCHARIDES are the part of gram-negative bacteria that triggers an immune response in human beings. The inflammatory response to lipopolysaccharides is MUCH STRONGER than the response to lipteichoic acid of gram-positive bacterial cells.

Answer 136

Small plant pathogens consisting of very SHORT circular single-stranded RNA.

Answer 137

Retroviruses are enveloped single-stranded positive sense RNA viruses in the family RETROVIRIDAE. Usually the virion contains two identical RNA molecules. These viruses carry an enzyme known as REVERSE TRANSCRIPTASE which synthesizes DNA from single-stranded RNA. The DNA will then integrate itself into the HOST CELL GENOME, where it is replicated and transcribed as if it were the host cell's OWN DNA. This new DNA is then incorporated into the host cell genome by an integrase enzyme, at which point the retroviral DNA is referred to as a provirus.

Answer 138

Prokaryotes use a 70S ribosome with 30S (small subunit) and 50S (large subunit) components. Eukaryotes use an 80S ribosome with 40S (small subunit) and 60S (large subunit) components.

Answer 139

o FACILITATED DIFFUSION THROUGH A CARRIER PROTEIN o Glucose is too large and polar to move quickly through the cell membrane by simple diffusion o Typically the concentration of glucose OUTSIDE the cell is higher than INSIDE the cell o Since glucose is moving DOWN a concentration gradient by entering the cell, the process does NOT REQUIRE ATP

Answer 140

In addition to a capsid, bacteriophages contain a tail sheath and tail fibers. The TAIL SHEATH can act like a SYRINGE, injecting genetic material into the bacterium. The TAIL FIBERS help the bacteriophage to recognize and connect to the correct host cell.

Answer 141

After hijacking a cell’s machinery, a virus will replicate and produce viral progeny, called virions, which can be released to infect additional cells.

Answer 142

This implies that prokaryotes and eukaryotes carry out protein synthesis in slightly different ways. The differences allow scientists to TARGET BACTERIAL RIBOSOMES with antibiotics, like tetracyclines, aminoglycosides and macrolides, while leaving the eukaryotic ribosomes largely unaffected.

Answer 143

A genetic structure in a cell that can replicate independently of the chromosomes, typically a small circular DNA strand in the cytoplasm of a bacterium or protozoan. Plasmids are often used in the laboratory manipulation of genes. Plasmids are known as extrachromosomal (extragenomic) material. DNA acquired from external sources may be carried on small circular structures known as plasmids. Plasmids carry DNA that is NOT necessary for the survival of the prokaryote, so it isn't considered part of the GENOME of the bacterium, but may be important because it confers an ADVANTAGE like antibiotic resistance.

Answer 144

To from the PILI, bacteria must contain PLASMIDS known as SEX FACTORS that contain the necessary genes. The best-studied sex factor is the FERTILITY FACTOR (the F factor) in E. Coli. Bacteria with the F factor are (F+), and those without are (F-).

Answer 145

o The paw of a polar bear must be able to tolerate low temperatures o For a cell to function at low temperatures, it must increase membrane fluidity o Membrane fluidity can be increased by the presence of unsaturated phospholipids

Answer 146

1. Centrioles migrate to opposite poles of the dividing cell during cell division and organize the mitotic spindle 2. Centrioles are responsible for forming FLAGELLA and CILIA; one of the centrioles (mother centriole) develops the BASAL BODY and these specialized structures mobilize the cell 3. Position of centrioles determine placement of nucleus and other organelles--the microtubules from centrioles help create cell scaffold

Answer 147

When a cell is replicating or undergoing mitosis, the centrioles DUPLICATE and a pair of centrioles will land on either side of the cell at opposite poles.

Answer 148

(1) a central mitotic spindle — a bilaterally symmetrical bundle of microtubules with the overall shape of a football, but divided into opposing halves at the equator of the cell by a plate of metaphase chromosomes — and (2) a pair of asters — a tuft of microtubules at each pole of the spindle.

Answer 149

In each half of the spindle, a single centrosome at the pole organizes three distinct sets of microtubules, whose (−) ends all point toward the centrosome. One set, the astral microtubules, forms the aster; they radiate outward from the centrosome toward the cortex of the cell, where they help position the mitotic apparatus and later help to determine the cleavage plane during cytokinesis. The other two sets of microtubules compose the spindle. The kinetochore microtubules attach to chromosomes at specialized attachment sites on the chromosomes called kinetochores. The third set, polar microtubules, do not interact with chromosomes but instead interdigitate with polar microtubules from the opposite pole.

Answer 150

Anaphase is characterized by the shortening of kinetochore microtubules, which pulls the chromosomes toward the poles. During anaphase the two poles move farther apart, bringing the chromosomes with them into what will become the two daughter cells. Movement towards the pole is due to microtubule disassembly at the (+) end of the microtubule, which is the end that is connected to the kinetochore. Movement of chromosomes during anaphase is NOT due to motor proteins. There is no depolymerization at the (-) end, which is where the microtubules connect to the centriole (anchored to the MTOC)

Answer 151

Basal body is an organelle that forms the base of either a cilium or flagella. Basal bodies are MTOC in cells that have cilia or flagella. Cilia are hair-like projections that come out of cell. Flagella are tail like projections coming out of cell and helping it move (i.e. sperm cell). Microtubules are arranged in a (9+2) arrangement with nine pairs in the outer ring and a single pair (2 microtubules) in the middle. Between the pairs of microtubules we have a protein called NEXIN that connects the microtubules and helps to keep them in their place. Coming OUT of the microtubules we have this protein called DYNEIN--dynein breaks down ATP and helps the microtubules move past each other and that's what drives the movement of flagella and cilia

Answer 152

Microtubules play an important role of internal transport in neurons.