Eukaryotic and Prokaryotic Cells

Cell walls

-A non-living extracellular layer which provides support and protection. -Both Prokaryotic and Eukaryotic Cells

Ribosomes

-Composed of RNA and protein, are the site of all protein synthesis. -Both Prokaryotic and Eukaryotic Cells

Peroxisomes

-Contain enzymes involved in hydrogen peroxide metabolism. -Eukaryotic cells

Plasmids

-Extrachromosomal loops of DNA carrying genes not essential to cell function. -Prokaryotic cells

Histones

-Homogeneous proteins associated with linear strands of chromatin. -Eukaryotic cells

Pili

-Made of protein pilin, allow for attachment and genetic exchange. -Prokaryotic cells

Thylakoids

-Membranous structures with enzymes for ATP synthesis via photophosphorylation. -Both Prokaryotic and Eukaryotic cells

Nucleoid

-Not bounded by a membrane, contains one circular chromosome. -Prokaryotic cells

Golgi complex

-Primary site of packaging, secretion, and polysaccharide synthesis. -Eukaryotic cells

Glycocalyx :)

-Reservoir of stored food which aids in attachment and pathogenicity. -Prokaryotic cells

Exospores undergo a process called ___________________________ when they find an environment suitable for their growth, and have been subjected to the proper "triggering" stimuli.

Germination

A ____________________________ is a layer of material found outside the prokaryotic cell wall, and is usually composed of protein or polysaccharide. If this layer is dense and well organized it is called a capsule and if it is lose it is called a slime layer. What functions are associated with this layer? _____________________________________________________ __________________________________________________________________________.

Glycocalyx/ The glycocalyx (capsule or slime layer) serves as a reservoir of stored food, it aids in attachment to smooth surfaces, it provides protection from predators, desiccation or phagocytosis by white blood cells. In the case of pathogenic bacteria, the glycocalyx aids pathogenicity by protecting the cells against host defenses. Glycocalyx materials plus cells form biofilms that render cells resistant to chemical damage.

A membranous organelle known as the ________________________________ is involved in storage, the synthesis of polysaccharides, and the assembly of complex organic compounds (glycoproteins, glycolipids, etc.). What other functions are associated with this organelle? ___________________________________________________________________________

Golgi apparatus (body or complex)/ Assembly of complex molecules, sorting, packaging and secretion.

Cyanobacteria such as Anabaena often form specialized cell types that carry out specific functions. Specialized cells called _______________________ contain enzymes involved in nitrogen fixation, while thick-walled, granular-looking cells called ____________________ are highly resistant to cold and desiccation thus allowing bacteria to survive cold winters and/or dry summers.

Heterocysts/ akinetes

Histone

Histones are a type of homogeneous protein found in chromatin (e.g., within the nuclei of eukaryotic cells). DNA molecules wrapped around core histone proteins (octomers), form the nucleosomes that combine to form chromatin. Histones help to maintain the structural integrity of DNA, help regulate transcription, and are involved in DNA repair.

Single-celled organisms digest the "food" materials they consume by bringing them into contact with digestive enzymes called ___________________________. These enzymes are stored within organelles called _______________________________. Organelles containing enzymes involved in hydrogen peroxide metabolism are referred to as ___________________.

Hydrolase enzymes or hydrolases/ lysosomes/ peroxisomes

The cell membranes of some prokaryotic cells appear to fold inward forming structures known as ______________________________. Like the cristae of mitochondria, these would contain enzymes involved in phosphorylation. Most investigators now believe these membrane folds are actually artifacts formed during the preparation of cells for electron microscopy.

Mesosomes

Some bacteria contain cytoplasmic inclusions called _____________________________ that serve as a source of intracellular phosphate (a sort of energy reserve). Bacteria living in water environments often contain inclusions called gas vacuoles. What function do these serve?

Metachromatic granules/ They are used to regulate buoyancy of cells in water.

Most eukaryotic cells contain many tubular protein complexes called _____________________ that provide structural support and allow for intracellular motion. These tubular structures appear to be arranged in a characteristic pattern (nine groups of two plus an additional two in the middle) within locomotor structures called ______________ and _____________________.

Microtubules/ cilia/ flagella

Almost all types of eukaryotic cells carry organelles called ____________________________ that evolved from prokaryotic organisms (Proteobacteria), acquired through endocytosis. These organelles have inner folded membranes called cristae, that carry enzymes involved in _______ synthesis (something eukaryotic membranes cannot do), lack cholesterol, and have a 60:40 protein to lipid ratio. These organelles have additional features characteristic of prokaryotic cells; what are they? ___________________________________________________________

Mitochondria/ ATP/ They have 70S ribosomes and ccc-DNA.

All single-celled eukaryotic microorganisms contain one or more centrally located structures called _______________________________ that serve to control all cellular activities (they are sometimes referred to as the "brains" of these cells). The protoplasm within these structures is largely composed of a thread-like material called _______________________________ that is made up of _____________________________ and protein.

Nuclei (singular = nucleus) / chromatin/ DNA

The chromosome of a prokaryotic cell is not contained within a nucleus with a nuclear membrane, but is contained within a region known as the nuclear region (area, body) or _____________________. Many bacteria also contain one or more small extrachromosomal loops of DNA known as ____________________________. These generally carry genetic information that is not essential to the survival of the cell under most circumstances.

Nucleoid/ plasmids

A dark staining body within the nucleus is known as the __________________________ and serves as the site of _________________________________ synthesis, and the assembly of 60s and 40s subunits.

Nucleolus/ ribosomal RNA (r-RNA)

Eukaryotic cells typically contain a large number of membrane bound structures called ___________________________________ that carry out specific functions and are supported by a fluid-like material called the ___________________________.

Organelles/ cytosol

The rigid cell walls of typical Gram positive and Gram negative bacteria are composed of a unique organic material known as ________________________________. In Gram positive cells this layer is quite thick, while in Gram negative cells it is thin.

Peptidoglycan

Prokaryotic cells that have flagella distributed fairly evenly all over their cell surfaces are said to have a ____________________________ flagellar arrangement. If a cell has flagella located at both ends it is said to have a polar or ___________________________ flagellar arrangement.

Peritrichous (Such cells are also polytrichous, but peritrichous is a better answer.)/ amphitrichous

Gram positive bacteria have thicker cell walls and are generally more resistant to ___________ ____________________________ than are ordinary Gram negative bacteria. The Gram negative cells have an outer membrane associated with their cell wall and so are more resistant to _________________ than are Gram positive cells.

Physical factors (heat, drying, radiation, pressure)/ chemicals

Many types of Gram negative bacteria are covered with thin, hair- like structures called _________________________ that serve to attach the bacteria to various surfaces including other cells.

Pili and fimbriae/ Note - In some texts these terms are used interchangeably, but pili and fimbriae do differ in both structure and function. Fimbriae are more numerous per cell, shorter, and are used for attachment to various surfaces while pili are few in number (1-2 per cell), longer, and are used for bringing bacteria together during genetic exchange. They are sometimes called sex pili.

Describe three ways in which the flagella of prokaryotic cells differ from the flagella of eukaryotic cells.

Prokaryotic flagella are made of flagellin proteins, they are not membrane bound, and they move by spinning (they have rotary motion). Eukaryotic flagella are made up of microtubules that are arranged in 9 sets of 2 with 2 in the center. These are inside the cell membrane, so are surrounded by a layer of membrane. They move with a back-and-forth or whip-like motion.

Ribosome

Ribosomes are granular bodies each made up of two sub-units composed of nucleic acid (r-RNA) and protein. Ribosomes are the site of protein synthesis within cells. They may or may not be considered organelles. They are not surrounded by membranes.

Gram negative bacteria such as Escherichia coli sometimes produce one or more thin, tube-like structures called ______________________ from proteins called pilins. Cells making these structures can attach to other cells, then pull them close for the cell-to-cell transfer of DNA.

Sex pili

A complex membranous organelle that serves as a transport system, a site for storage and for lipid synthesis is called the _____________________________________. Sometimes this structure is made "rough" by the presence of small granular bodies called ribosomes. These serve as the site for _____________________________ synthesis within the cell.

Smooth endoplasmic reticulum/ protein

Sporulation

Sporulation is the process by which endospores are made within certain types of bacteria. It involves forespore formation and covering formation and may be stimulated by a variety of factors. Note - this term is also applied to spore formation as it occurs in other types of organisms (fungi, algae, etc.).

Organelle

The term organelle means "little organ", but refers to structures found within cells. These structures have specific functions and may be more or less numerous depending on the type of cell being studied. Some texts indicate that organelles must be membrane bound; others indicate that they may or may not be membrane bound.

Cyanobacteria are photosynthetic prokaryotes that contain membranous vesicles called ___________________________ . These are usually located parallel to the cell membrane, but appear to be separate from it. They contain enzymes involved in the formation of ___________________ via photophosphorylation.

Thylakoids/ ATP

Microtubules are made up of proteins called _________________________ arranged in linear strands (protofilaments) that can be taken apart or assembled as needed. Microtubule associated proteins such as _______________________________ can move materials along these strands and play a major role in intracellular transport.

Tubulin proteins or tubulins/ kinesin and dynein (Some kinesins move particles toward the plus ends and dyneins move particles toward the minus ends of protofilaments.)

Structures known as __________________________________ or as periplasmic flagella occur within the periplasmic space of spirochete bacteria.

Axial filaments or endoflagella

____ Histones ____ ____ Ribosomes ____ ____ Cell walls ____ ____ Glycocalyx ____ ____ Thylakoids ____ ____ Peroxisomes ____ ____ Nucleoid ____ ____ Golgi complex ____ ____ Pili ____ ____ Plasmids ____ A. Contain enzymes involved in hydrogen peroxide metabolism. B. Made of protein pilin, allow for attachment and genetic exchange. C. Homogeneous proteins associated with linear strands of chromatin. D. Reservoir of stored food which aids in attachment and pathogenicity. E. Extrachromosomal loops of DNA carrying genes not essential to cell function. F. Composed of RNA and protein, are the site of all protein synthesis. G. A non-living extracellular layer which provides support and protection. H. Primary site of packaging, secretion, and polysaccharide synthesis. I. Not bounded by a membrane, contains one circular chromosome. J. Membranous structures with enzymes for ATP synthesis via photophosphorylation.

C/E, F/B, G/B, D/P, J/B, A/E, I/P, H/E, B/P, E/P. Note - Some prokaryotic cells have histone-like proteins or histones, but histones are more likely to be found in eukaryotic cells. Some eukaryotic cells may have a glycocalyx, and a few contain plasmids, but these structures are more common to prokaryotes.

A layer of organic material (glycocalyx) found outside the cell wall of a prokaryotic cell may be a dense, well-organized ___________________________ or a loosely organized ____________________________. This layer is produced only under certain circumstances and may serve a variety of functions. It may aid in attachment and in pathogenicity, may protect the cell against dehydration, and serves as a _________________________________.

Capsule/ slime layer/ reservoir of stored food materials

The cytoplasmic region of a prokaryotic cell contains no membrane bound organelles, but does contain ribosomes and a variety of inclusions. ________________________________ are inclusions which contain enzymes involved in "fixing" carbon dioxide into organic compounds.

Carboxysomes

The cells of most "plant-like" microorganisms (algae and fungi) are surrounded by rigid layers of non-living material known as _______________________________. What functions do these layers of material serve? ___________________________________________________

Cell walls Cell walls provide protection against changes in osmotic pressure and predators. They also give cells a characteristic shape significant to their function. (We use the unique shapes of cells as a means of identifying and categorizing them, but cell shapes have functional significance to organisms.)

Some eukaryotic cells contain bodies called ______________________________ that are made up of microtubules arranged in nine groups of three. These give rise to spindle fibers and aid in chromosome separation during mitosis and meiosis.

Centrioles

Most microbiologists believe the organelles called ______________________________ and __________________________ were originally prokaryotic cells that were taken in by, and formed symbiotic relationships with larger eukaryotic cells. What evidence is available to support this theory? __________________________________________________

Chloroplasts mitochondria These organelles have inner folded membranes that lack cholesterol and are involved in ATP synthesis (like those of prokaryotes), they also contain 70s ribosomes and have DNA in closed loops. Like bacteria, they can reproduce themselves by means of binary fission. Antimicrobial agents that kill or inhibit the growth of bacteria also cause damage to mitochondria and chloroplasts.

Many types of fresh-water protozoa contain osmoregulatory organelles called _______________________. These structures serve to pump excess water out of cells, but also play a role in intracellular circulation and excretion.

Contractile vacuoles

Both mitochondria and chloroplasts contain inner membranes that are involved in ATP synthesis. In mitochondria these inner membranes form folds called ____________________, while in chloroplasts they are arranged in flat, membranous vesicles called _______________.

Cristae/ thylakoids

_____________________________ may be defined as the science or study of cells.

Cytology

Bacteria in the genera Bacillus and Clostridium often form dormant structures known as ______________________ . These contain high levels of DNA, calcium and dipicolinic acid but very little RNA and almost no water. They are metabolically inactive and resistant to both physical and chemical damage. What is the overall function of these structures?

Endospores/ They allow the population to survive periods of unfavorable conditions. The vegetative cells of the population may die, but the spores survive and give rise to new cells when conditions improve.

Some types of Gram positive bacteria produce dormant structures called __________________________ that allow these cells to survive periods of unfavorable conditions. These dormant structures are highly resistant to environmental factors such as _______________________________________ and may live in a nearly inactive state for hundreds or thousands of years.

Endospores/ heat, drying, radiation, pressure changes and toxic chemicals

Many microorganisms (both eukaryotic and prokaryotic cells) are motile by means of locomotor structures called __________________________________. In eukaryotic cells, these structures are surrounded by membrane, contain a cytoskeleton made of __________________________, and move with a whip-like motion.

Flagella/ microtubules

Describe two ways (other than size) in which Eukaryotic cells differ from prokaryotic cells.

Eukaryotic microorganisms contain at least one true nucleus surrounded by a nuclear membrane or envelop, prokaryotic cells do not (they have a nucleoid or nuclear region that is not membrane bound). Eukaryotic cells contain many membrane bound organelles while prokaryotic cells do not (prokaryotes often contain inclusions, but these are not surrounded by unit membrane). Eukaryotic cells contain two or more linear chromosomes while prokaryotic cells typically contain a single circular chromosome (many prokaryotes also contain plasmids and some contain more than one circular chromosome). Eukaryotic cells contain 80s ribosomes (60s and 40s subunits) while prokaryotes contain 70s ribosomes (50s and 30s subunits). The cell membranes of eukaryotic cells contain about 25% cholesterol, while the cell membranes of ordinary bacteria contain little or no cholesterol. Eukaryotic cells make most of their ATP in association with internal organelles (mitochondria and chloroplasts), while prokaryotes make their ATP in their cytoplasm, or in association with their cell membranes. In general, eukaryotic cells are larger than prokaryotic cells, but there are some exceptions.

Glycocalyx

The glycocalyx, also known as a capsule or slime layer, is a layer of poly- saccharide or sometimes protein that is deposited outside the cell wall of some bacteria. It can serve as a reservoir of stored food, as a means of attachment to smooth surfaces, as a protection against phagocytosis by white blood cells or other predatory cells, and to prevent desiccation (drying out). Biofilms are made up of cells suspended in glycocalyx materials.

Explain how endospores differ from vegetative cells in terms of their composition and function. Include information about nucleic acids, water, calcium, dipicolinic acid, resistance to environmental factors, metabolic activity levels and longevity.

Vegetative cells contain considerable water, RNA and enzymes and their metabolic activities occur at a rapid rate. Endospores contain little or no water and so lack metabolic activity. They contain mostly DNA and very little RNA, but also have high levels of calcium and dipicholinic acid within their cytoplasm. Endospores can remain viable (alive) much longer than typical vegetative cells (evidence is now available that indicates they can survive within amber for millions of years), they do not reproduce, and they tend to be extremely resistant to environmental factors such as heat, radiation, pressure and toxic chemicals; much more so than are vegetative cells. While vegetative cells typically have a single membrane and wall, endospores have multiple layers of covering material (cortex, spore coat, inner and outer spore membranes). These help provide extra protection against damage.