Chapter 4

Prokaryotic Cells

Cells that typically lack membrane-enclosed organelles, including a nucleus.

Eukaryotic Cells

Cells that have a membrane-bound nucleus and other organelles.

Peptidoglycan

A polymer found in the cell walls of prokaryotes but absent in eukaryotic cell walls.

Glycocalyx

A gelatinous covering in prokaryotic cells that can protect against phagocytosis and aid in adherence.

Flagella

Long filamentous appendages in bacteria that rotate to propel the cell.

Axial Filaments

Structures in spirochetes that enable movement by wrapping around the cell.

Fimbriae

Hair-like structures that help bacteria adhere to surfaces.

Pili

Appendages involved in twitching motility and DNA transfer in bacteria.

Gram-positive Bacteria

Bacteria with thick peptidoglycan layers and teichoic acids in their cell walls.

Gram-negative Bacteria

Bacteria with a thin peptidoglycan layer and an outer membrane containing lipopolysaccharides.

Mycoplasma

A genus of bacteria that naturally lack cell walls.

Nucleoid

The region in prokaryotic cells where the DNA is located.

Functions in housing genetic material and controlling cellular activities, such as replication and transcription

Ribosomes

Cellular structures where protein synthesis occurs; prokaryotic ribosomes are 70S.

Translating mRNA into polypeptides

Endospores

Resting structures formed by some bacteria that allow survival in adverse conditions.

Organelles

Specialized membrane-enclosed structures found in eukaryotic cells.

Mitochondria

Organelles responsible for ATP production in eukaryotic cells.

Chloroplasts

Organelles that contain chlorophyll and are involved in photosynthesis.

Endoplasmic Reticulum (ER)

A network of membranes in eukaryotic cells involved in protein and lipid synthesis.

Golgi Complex

An organelle that modifies, sorts, and packages proteins for secretion.

Centrosome

A structure in eukaryotic cells that organizes microtubules and is involved in cell division.

Endosymbiotic Theory

The theory that eukaryotic cells evolved from symbiotic prokaryotes living within other prokaryotic cells.

Compare the cell structure of prokaryotes and eukaryotes

Prokaryotes: no nucleus, simpler structure, lack membrane-bound organelles, single circular chromosomes, cell walls

Eukaryotes: Nucleus present, larger, more complex, contain membrane- bound organelles, multiple linear chromosomes

Bacteria

unicellular and more multiply by binary fission

Identify the three basic chapes of bacteria

Cocci: Spherical shape

Bacilli: Rod-shaped

Spirilla: Spiral or corkscrew-shaped

Describe the structure and function of glycocalyx

Structure: Sticky, gelatinous layer outside the cell wall, made of polysaccharides or polypeptides. Can be a capsule (organized, firmly attached, or a slime layer (loose, unorganized)

Function: Protects cells from dehydration, phagocytosis, and aids in attachment to surfaces, helping with biofilm formation, and virulence

Acid-Fast Bacteria

Thick, waxy lipid layer (mycolic acid) in the cell wall, resists decolorization

Archaea

No peptidoglycan, cell walls made of pseudopeptidoglycan or proteins, can survive in extreme environments

Compare and contrast archaea and mycoplasmas.

Arechaea:

• Lack peptidoglycan in cell walls, often have pseudopeptidoglycan or protein-based walls.

• Can survive in extreme environments (high salt, heat, or acidity).

• Distinct evolutionary lineage, no known pathogenic species.

Mycoplasmas:

• Lack cell wall entirely, relying on sterols in the cell membrane for stability

• Smallest known bacteria, flexible and pleomorphic

• Many are pathogenic to humans, causing diseases like pneumonia

Comparison:

Both lack typical bacterial cell walls but differ in their environments, evolutionary origins, and pathogenicity.

Protoplast

A gram-positive bacterium that has had its cell wall entirely removed by enzymes (like lysozyme) but remains intact with only the plasma membrane

Spheroplast

A gram-negative bacterium with a partially removed cell wall (peptidogycan layer is damaged, but outer membrane remains), typically after treatment with enzymes or antibiotics

L form

Bacteria that have lost their cell walls naturally or due to mutations, and can grow and divide without a cell wall, either temporarily or permanently. Can revert to a walled form under certain conditions.

Plasma (Cytoplasmic) Membrane

• encloses the cytoplasm and is a lipid bilayer with peripheral and integral proteins (the fluid mosaic model)

• selectively premeable

• contain enzymes for metabolic reactions, such as nutrient breakdown, energy production, and photosynthesis

• Mesosomes, irregular infoldings of the plasma membrane, are artifacts, not true cell structures

• Plasma membranes can be destroyed by alcohols and polymyxins

Simple diffusion

molecules and ions move until equilibrium is reached

Facilitated diffusion

substances are transported by transporter proteins across membranes from areas of high to low concentration

Osmosis

movement of water from areas of high to low concentration across selectively permeable membrane until equilibrium is reached

Active transport

materials move from areas of low to high concentration by transporter proteins, and cell must expend energy

Group translocation

energy is expended to modify chemicals and transport them across the membrane

Identify the functions of four inclusions.

Storage Granules: Store nutrients (like glycogen and polyhydroxybutyrate) for energy and carbon sources

Gas Vacuoles: Provide buoyancy to aquatic bacteria, allowing them to maintain optimal positions in water columns

Magnetosomes: Contain magnetic particles that help bacteria orient themselves along magnetic fields, aiding in navigation

Phosphate Granules (Volutin): Store inorganic phosphate, which can be used for ATP production and other metabolic processes

Sporulation

process of forming endospores. Involves DNA replication, formation of a protective spore coat, and dehydration, allowing the bacterium to endure unfavorable conditions

Endospore Germination

process by which an endospore returns to a vegetive state when conditions become favorable, allows bacterium to resume growth and reproduction

Nucleus

Houses DNA, regulates gene expression, and coordinates cellular activities like growth and reproduction

Peroxisomes

contain enzymes for breaking down fatty acids and detoxifying harmful substances

Which of the following organelles most closely resembles a prokaryotic cell?

mitochondrion
cell wall
vacuole
nucleus

mitochondrion

Functions of the glycocalyx include all of the following EXCEPT

protection against dehydrations
binary fission
source of nutrition
biofilm formation

binary fission

Which of the following is NOT found or observed to occur in both mitochondria and prokaryotes?

70s ribosomes
ATP-generating mechanism
Binary fission
Cell wall

cell wall

Which of the following statements is correct about passive diffusion?

It involves movement of molecules down a concentration gradient and may require a transport protein
It may require a transport protein
It is a process in which molecules move from a region of lower concentration to one of higher concentration
It requires an expenditure of energy by cell

It involves movement of molecules down a concentration gradient and may require a transport protein

The DNA found in most bacterial cells

is linear in structure
is circular in structure
is surrounded by a nuclear membrane
utilizes histones for chromosomal packaging

is circular in structure

Cell may frequently find themselves in an environment with very low extracellular concentrations of substances needed in higher amounts inside the cell. To obtain these needed items, such cells would be most likely to engage in

active transport
osmosis
facilitated diffusion
simple diffusion

active transport

Where are phospholipids most likely found in a eukaryotic cell?

the plasma membrane
ribosomes
the plasma membrane and organelles
metachromatic granules

the plasma membrane and organelles

Which of the following statements is TRUE?

Endospores allow a cell to survive environmental changes by producing a dormant period with no growth.
Endospores are easily stained in a Gram stain
A cell produces one endospore and keeps growing
Endospores are for reproduction

Endospores allow a cell to survive environmental changes by producing a dormant period with no growth

Which structure protects bacteria from being phagocytized?

slime layer
cell wall
cell membrane
capsule

capsule

The terms “run” and “tumble” are generally associated with:

cell wall fluidity
clustering properties of certain rod-shaped bacteria
taxic movements of the cell in response to attractants or repellents
cell membrane synthesis

taxic movements of the cell in response to attractants or repellents