1. The Cell+khan

Flagella

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. Composed of a filament, a basal body, and a hook

Eukaryotic cells

reproduce by mitosis, allowing for the formation of two identical daughter cells.

Some bacteria are symbiotes

meaning that both humans and the bacteria benefit from the relationship. Examples include the bacteria in the human gut that produce vitamin K and biotin (vitamin B), and which also prevent the overgrowth of harmful bacteria.

Other bacteria are pathogens

meaning that they provide no advantage or benefit to the host, but rather cause disease. They may live intracellularly or extracellularly.

Lysosomes

membrane-bound structures containing hydrolytic enzymes that are capable of breaking down many different substrates, including substances ingested by endocytosis and cellular waste products. The lysosomal membrane sequesters these enzymes to prevent damage to the cell.

Prokaryotes do not contain any membrane-bound organelles, and their genetic material is organized into a single circular molecule of DNA concentrated in an area of the cell called the

nucleoid region.

Bacteria that require oxygen for metabolism are termed

obligate aerobes

Plasmids may also 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.

Bacterial characteristics - Gram staining

positive if purple, pink if not.

Cilia are

projections from a cell that are primarily involved in movement of materials along the surface of the cell; for example, they line the respiratory tract and are involved in movement of mucus.

kinetochores

protein structures located on the centromeres that serve as attachment points for specific fibers of the spindle apparatus

Transformation

results from the integration of foreign genetic material into the host genome. This foreign genetic material most frequently comes from other bacteria that, upon lysing, spill their contents in the vicinity of a bacterium capable of transformation.

autolysis

self-digestion occurring in plant and animal tissues, particularly after they have ceased to function properly

outer membrane

serves as a barrier between the cytosol and the inner environment of the mitochondrion.

rough ER (RER)

studded with ribosomes, which permit the translation of proteins destined for secretion directly into its lumen.

Connective tissue

supports the body and provides a framework for the epithelial cells to carry out their functions. example: Bone, cartilage, tendons, ligaments, & adipose tissue

conjugation

In bacteria, the direct transfer of DNA between two cells that are temporarily joined.

bacteriophages

(viruses that infect bacteria) can accidentally trap a segment of host DNA during assembly. When the bacteriophage infects another bacterium, it can release this trapped DNA into the new host cell. This transferred DNA can then integrate into the genome, giving the new host additional genes.

Mitochondria

Membrane-bound cellular organelles in which the reactions of aerobic respiration and ATP synthesis occur. They contain some of their own genes and replicate independently of the nucleus via binary fission.

9+2 structure

cilia and flagella structure. 9 pairs of microtubules in circle with 2 microtubules in middle. only seen in eukaryotic motility organelles

cell/plasma membrane (prokaryote)

composed of phospholipids, similar to that of a eukaryote.

hook

connects the filament and the basal body so that, as the basal body rotates, it exerts torque on the filament, which can thereby spin and propel the bacterium forward.

Protista (eukaryotes)

-mostly aquatic, plants (phosynthesizing), fungi (nonphotosynthesis), and animals (protozoa)

Cell theory

1) All living things are composed of cells. 2) The cell is the basic functional unit of life. 3) Cells arise only from preexisting cells. 4) Cells carry genetic information in the form of deoxyribonucleic acid (DNA). This genetic material is passed on from parent to daughter cell. (exception: Viruses are small structures that contain genetic material, but are unable to reproduce on their own. This violates the third and fourth tenets of the cell theory because virions can only replicate by invading other organisms and because they may contain ribonucleic acid (RNA) as their genetic information.)

bacterial growth curve

1) In a new environment, the bacteria first adapt to the new local conditions during the lag phase 2) As the bacteria adapt, growth increases, causing an exponential increase in the number of bacteria in the colony during the exponential/log phase 3) As the number of bacteria in the colony grows, resources are often reduced. The reduction of resources slows reproduction in the stationary phase 4) 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.

KEY CONCEPT 2

Bacteria contain a cell wall, the composition of which is different in gram-positive and gram negative bacteria. The human immune system can respond to the components of the cell wall, inciting an inflammatory response.

Epithelial tissue

A body tissue that covers the surfaces of the body, inside and out. They provide a means for protection against pathogen invasion and desiccation. In certain organs, epithelial cells are involved in absorption, secretion, and sensation. one side faces a lumen (the hollow inside of an organ or tube) or the outside world, while the other side interacts with blood vessels and structural cells.

F factor

A fertility factor in bacteria; a DNA segment that confers the ability to form pili for conjugation and associated functions required for the transfer of DNA from donor to recipient. It may exist as a plasmid or be integrated into the bacterial chromosome.

basement membrane

A layer of collagen fibers that separates epithelial tissue from connective tissue (example of epithelial cells in digestive tract) - they are actual connective tissue.

organelles

A membrane-enclosed structure with a specialized function within a cell.

cytoskeleton

A network of fibers that holds the cell together, helps the cell to keep its shape, and aids in movement, helps with transport of substances within cell

chromosomes

A threadlike, gene-carrying structure found in the nucleus. Each chromosome consists of one very long DNA molecule and associated proteins.

7. Living things adapt to their environment.

Adaptation and evolution happen through unintentional changes (mutations) that are advantageous to an entire species. Viruses definitely adapt to their surroundings. Unlike the previous requirement, which required an immediate response, adaptation is a process that takes place over time. A virus can live in two different phases - the lytic phase (where the virus actively replicates in a host cell) and the lysogenic phase (where the viral DNA incorporate itself into the cell's DNA and multiples whenever the cell multiplies). Sometimes a host does not have enough energy or supplies to support the virus to actively replicate, so it will switch to the lysogenic phase. The virus can eventually reenter the lytic phase when conditions are right. This ability to adapt is what makes human immunodeficiency virus (HIV) as hard to treat as it is. HIV mutates quickly because it makes frequent mistakes while replicating its genome. Because the virus is constantly changing, it makes it very hard to design drugs and vaccines against it. One drug might prevent a large number of virions from replicating, but just a few will be unaffected. Those surviving virions will continue to infect more cells, making copies of the resistant strains. Verdict: Pass

obligate anaerobes

Anaerobes that cannot survive in an oxygen-containing environment; the presence of oxygen leads to the production of reactive oxygen-containing radicals in these species, which leads to cell death.

eukaryotic cells

Contain a nucleus and other organelles that are bound by membranes.

genes

DNA segments that serve as the key functional units in hereditary transmission.

histones

Globular protein that assist in DNA packaging in eukaryotes. Histones form octamers around which DNA is wound to form a nucleosome.

1. Living things must maintain homeostasis

Homeostasis is all about balance - can something control its internal temperature, or its internal contents? In earlier drafts of criteria for life, the requirement was that living things must be made of cells. Viruses are not made out of cells. A single virus particle is known as a virion, and is made up of a set of genes bundled within a protective protein shell called a capsid. Certain virus strains will have an extra membrane (lipid bilayer) surrounding it called an envelope. Viruses do not have nuclei, organelles, or cytoplasm like cells do, and so they have no way to monitor or create change in their internal environment. This criterion asks whether an individual virion is capable maintaining a steady-state internal environment on its own. Though some have argued that the capsid and envelope help virions resist change in their environment, the general consensus is that viruses do not pass this first requirement for life. Verdict: Fail

2. Living things have different levels of organization.

Life is a complicated idea, and live organisms reflect that complexity in their structure. Smaller building blocks come together to make a larger product. Viruses certainly do this. They have genes made from nucleic acids and a capsid made of smaller subunits called capsomeres. Verdict: Pass

4. Living things grow.

Living things grow. They use energy and nutrients to become larger in size or more complex. Viruses manipulate host cells into building new viruses which means each virion is created in its fully-formed state, and will neither increase in size nor in complexity throughout its existence. Viruses do not grow. Verdict: Fail

KEY CONCEPT 1

Not all cells have the same relative distribution of organelles. Form will follow function. Cells that require a lot of energy for locomotion (such as sperm cells) have high concentrations of mitochondria. Cells involved in secretion (such as pancreatic islet cells and other endocrine tissues) have high concentrations of RER and Golgi apparatuses. Other cells, such as red blood cells, which primarily serve a transport function, have no organelles at all.

3. Living things reproduce.

One of the basic urges in nature is for a species to pass on its genetic information. Viruses definitely multiply. While our immune system could certainly handle a single virion, it's the hundreds of thousands of virions created in a short period of time that harm our cells. Viruses must use host cells to create more virions. Since viruses don't have organelles, nuclei, or even ribosomes, they don't have the tools they need to copy their genes, much less create whole new virions. Instead, viruses enter living cells and then hijack the host's cellular equipment to copy viral genetic information, build new capsids, and assemble everything together. We use the term replicate, instead of reproduce, to indicate viruses need a host cell to multiply. Verdict: Maybe

Peroxisomes

Organelles in both plants and animals that break down peroxide, a toxic byproduct of cell respiration

facultative anaerobes.

Other bacteria can toggle between metabolic processes, using oxygen for aerobic metabolism if it is present, and switching to anaerobic metabolism if it is not

transformation

Process in which one strain of bacteria is changed by a gene or genes from another strain of bacteria

apoptosis

Programmed cell death

high frequency of recombination

Sex factor of F+ host plasmid may be integrated into whole host circular genome. So during conjugation, the donor will attempt to transfer a copy of its entire genome. The bridge usually breaks before this is finished. Cells that have undergone this behaviour called Hfr.

prokaryotic cells

Small, simple, no nucleus, no membrane-bound organelles, single loop of DNA (nucleosome), no cellulose, cytoplasm, cell membrane, cell wall (made of carbs), somtimes have cilia or flagella (movement).

cleavage furrow

The area of the cell membrane that pinches in and eventually separates the dividing cell

stroma

The fluid of the chloroplast surrounding the thylakoid membrane; involved in the synthesis of organic molecules from carbon dioxide and water. Contributor to connective tissues.

cytosol

The soluble portion of the cytoplasm, which includes molecules and small particles, such as ribosomes, but not the organelles covered with membranes.

intermembrane space

The space between the inner and outer membranes

A subset of plasmids called episomes

are capable of integrating into the genome of the bacterium

Archaea (prokaryotes)

They are extremohpiles and have 3 types. They are thermophiles, halophiles, and methanogens. single-celled organisms that are visually similar to bacteria, but contain genes and several metabolic pathways that are more similar to eukaryotes than to bacteria. They are notable for their ability to use alternative sources of energy. While some are photosynthetic, many are chemosynthetic and are able to generate energy from inorganic compounds, including sulfur- and nitrogen-based compounds, such as ammonia. They divide by binary fission or budding. They have different cell wall membranes.

5. Living things use energy.

This criterion is somewhat tricky. Creating new virion units is a major undertaking, from building nucleic acids to putting capsids together - that costs a lot of energy. However, all the energy that goes into this construction comes from, you guessed it, the host. While viruses will definitely benefit from the use of energy, they are latching onto the host's metabolism to get to it (maybe they're vampires?). Verdict: Maybe

transduction

Transfer of bacterial DNA by phages from one bacterium to another

aerotolerant anaerobes

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

6. Living things respond to stimuli.

Whether viruses respond to their environment is one of the trickiest questions to answer. A response to a stimulus is defined by an almost immediate reaction to some change in the environment. While they don't change behaviors in response to touch or sound or light the way that humans, bacteria, or sea sponges might, there has not been enough research done to definitively say that viruses do not respond to anything. Verdict: Unknown

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.

Intermediate filaments

a diverse group of filamentous proteins, including keratin and desmin. They are involved in cell-cell adhesion or maintenance of the overall integrity of the cytoskeleton. Intermediate filaments are able to withstand a tremendous amount of tension, making the cell structure more rigid. In addition, intermediate filaments help anchor other organelles, including the nucleus. The identity of the intermediate filament proteins within a cell is specific to the cell and tissue type.

nuclear membrane/envelope

a double membrane that maintains a nuclear environment separate and distinct from the cytoplasm.

Gram-positive cell walls consist of a thick layer of peptidoglycan

a polymeric substance made from amino acids and sugars. In addition to its structural and barrier functions, the cell wall may also aid a pathogen by providing protection from a host organism's immune system. It also contains lipoteichoic acid which activates the human immune system. remains purple

endoplasmic reticulum (ER)

a series of interconnected membranes that are actually contiguous with the nuclear envelope. The single membrane of the endoplasmic reticulum is folded into numerous invaginations, creating complex structures with a central lumen.

actin filaments

a thin type of protein filament composed of actin proteins that forms part of the cytoskeleton and supports the plasma membrane and plays a key role in cell strength, shape and movement

Plasmids

carry DNA that is not necessary for survival of the prokaryote—and therefore is not considered part of the genome of the bacterium—but may confer an advantage such as antibiotic resistance. Contain extrachromsomal material

ability of a cell to detect chemical stimuli and move toward or away from them is called

chemotaxis.

Other bacteria that use fermentation, or some other form of cellular metabolism that does not require oxygen, are called

anaerobes

The microtubules emanating from the centrioles attach to the chromosomes via complexes called kinetochores

and can exert force on the sister chromatids, pulling them apart.

pseudostratified epithelia

appear to have multiple layers due to differences in cell height, but are, in reality, only one layer.

Membranes of eukaryotic cells

consist of a phospholipid bilayer. This membrane is unique in that its surfaces are hydrophilic, electrostatically interacting with the aqueous environments inside and outside of the cell, while its inner portion is hydrophobic, which helps to provide a highly selective barrier between the interior of the cell and the external environment

Golgi Apparatus

consists of stacked membrane-bound sacs in which cellular products can be modified, packaged, and directed to specific cellular locations.

All bacteria

contain a cell membrane and cytoplasm, and some have flagella or fimbriae

cuboidal cells

cube-shaped

Bacteria (prokaryotes)

diverse environments, prokaryotic flagella (flagellin), circular double stranded DNA, no membrane bound organelles, chemotaxis is used to get to nutrients or get away from toxins

Together, the cell wall and the cell membrane are known as the

envelope

Most cells in connective tissues produce and secrete materials such as collagen and elastin to form the

extracellular matrix

filament is a hollow, helical structure composed of

flagellin.

Squamous cells

flat and scalelike.

cell wall (prokaryote)

forms the outer barrier of the cell. 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.

Centrioles

found in a region of the cell called the centrosome. They are the organizing centers for microtubules and are structured as nine triplets of microtubules with a hollow center. During mitosis, they migrate to opposite poles of the dividing cell and organize the mitotic spindle.

Transposons

genetic elements capable of inserting and removing themselves from the genome. If it is inserted within a coding region of a gene, that gene may be disrupted.

stratified epithelia

have multiple layers

Simple epithelia As their names imply,

have one layer of cells;

Gram negative bacteria

have outer membranes containing phospholipids and lipopolysaccharides. turns pink

microtubules

hollow polymers of tubulin proteins. They radiate throughout the cell, providing the primary pathways along which motor proteins like kinesin and dynein carry vesicles. Microtubules are small tubes made from the protein tubulin. These tubules are found in cilia and flagella, structures involved in cell movement. They also help provide pathways for secretory vesicles to move through the cell, and are even involved in cell division as they are a part of the mitotic spindle, which pulls homologous chromosomes apart.

Binary fission

is a simple form of asexual reproduction seen in prokaryotes. The circular chromosome attaches to the cell wall and replicates while the cell continues to grow in size. Eventually, the plasma membrane and cell wall begin to grow inward along the midline of the cell to produce two identical daughter cells. This is a rapid process.

Transduction

is the only genetic recombination process that requires a vector—a virus that carries genetic material from one bacterium to another.

Spherical bacteria,

known as cocci, include common pathogens such as Streptococcus pyogenes.

spiral-shaped bacteria

known as spirilli, include such species as Treponema pallidum, which causes syphilis.

smooth ER (SER)

lacks ribosomes and is utilized primarily for lipid synthesis and the detoxification of certain drugs and poisons. It also transports proteins from the RER to the Golgi apparatus.

Rod-shaped bacteria

like Escherichia coli, are known as bacilli.

Nuclear pores

located in the nuclear membrane allow for selective two-way exchange of material between the cytoplasm and the nucleus.

columnar cells

long and thin.

Conjugation

the bacterial form of mating (sexual reproduction). It involves two cells forming a conjugation bridge between them that allows for the transfer of genetic material. The transfer is unidirectional, from the donor male (+) to the recipient female (-). The bridge is made from appendages called sex pili that are found on the donor male. To form the pili, bacteria must contain plasmids known as sex factors that contain the necessary genes.

cytokinesis

the division of materials between daughter cells.

parenchyma

the functional parts of the organ, formed by epithelial cells. Epithelial cells are highly diverse and serve numerous functions depending on the identity of the organ in which they are found. For example, nephrons in the kidney, hepatocytes in the liver, and acid producing cells of the stomach are all composed of epithelial cells.

mitochondrial matrix

the space inside the inner membrane

microfilaments

thinner, solid rods of protein that enable the cell to move or change shape when protein subunits slide past one another, composed of actin subunits. Microfilaments are the thinnest part of the cytoskeleton, and are made of actin [a highly-conserved protein that is actually the most abundant protein in most eukaryotic cells]. Actin is both flexible and strong, making it a useful protein in cell movement. In the heart, contraction is mediated through an actin-myosin system.

prokaryotic ribosomes contain 30S and 50S subunits,

whereas eukaryotic ribosomes contain 40S and 60S ribosomes.

The inner membrane

which is thrown into numerous infoldings called cristae, contains the molecules and enzymes necessary for the electron transport chain. The cristae are highly convoluted structures that increase the surface area available for electron transport chain enzymes.