Comprehensive Cell Biology and Microbiology: Characteristics, Structures, and Functions

What is glycocalyx?

A gelationous, sticky substance surrounding some cells, made of polysaccharides or polypeptides.

What is the function of a capsule?

Protects the cell from drying out and may prevent recognition by host defense systems.

What is flagella?

A stiff rotating structure in prokaryotic cells; flexible whip in eukaryotic cells.

What are the types of flagella arrangements?

Peritrichous, Single Polar, Tufts of Polar, Endoflagella

What are fimbriae?

Sticky, proteinaceous projections used by bacteria to adhere to surfaces.

What are pili?

Longer than fimbriae, used for attachment and DNA transfer between bacteria.

What is the function of the cell wall?

Provides strength, rigidity, and maintains cell shape.

What are the characteristics of life?

Growth, Reproduction, Responsiveness, Metabolism

Do we classify viruses as alive?

No, only prokaryotic microorganisms are considered alive.

What are the components of all cells?

Cytoplasm, Plasma Membrane, Genetic Material, Ribosomes

What is the size difference between prokaryotes and eukaryotes?

Prokaryotes lack a membrane-bound nucleus and have a single circular chromosome; eukaryotes have a complex nuclear membrane and are larger.

What are the two types of glycocalyces?

Capsule and Slime layer

What is the function of a slime layer?

Protects cells from drying out and allows attachment to surfaces.

What is the cytoplasmic membrane?

Separates the cell's content from the environment and controls substance passage.

What is the nucleoid?

Region containing the bacterial chromosome, a single circular strand of DNA.

What are endospores?

Dormant survival structures produced by some bacteria, highly resistant to extreme conditions.

How are bacterial cell shapes categorized?

By morphology: Cocci (spherical), Bacilli (rod-shaped), Spirilla (spiral).

What are the differences between gram-positive and gram-negative bacteria?

Gram-positive has a thicker peptidoglycan layer; gram-negative has an outer membrane and a thinner peptidoglycan layer.

What is peptidoglycan?

A strong, rigid structure found only in bacteria, composed of sugars and amino acids.

What is a gram stain?

A staining technique to distinguish bacterial cell wall types.

What are the results of a gram stain?

Gram-positive: purple; Gram-negative: pink.

Why are gram-negative bacteria harder to treat?

They have an outer membrane and LPS, which can trigger severe immune responses.

What happens when gram-negative bacteria are killed?

Releases lipid A, triggering fever and inflammation.

What is the role of LPS?

It acts as an endotoxin that can activate immune responses.

What is the structure of bacterial cell walls?

Gram-positive has a thick peptidoglycan layer; gram-negative has a thin layer with an outer membrane.

What types of molecules move by which transport methods?

Various methods exist for nutrient uptake and waste removal.

What is facilitated diffusion?

The movement of substrates from high to low concentration gradient without energy.

What is passive transport?

Transport that does not require energy.

Why is passive transport not frequently used by prokaryotes?

Because nutrients poor environments do not create a favorable gradient.

What is passive diffusion?

The movement of small molecules from high to low concentration without energy.

What is active transport?

Transport that requires energy and uses proteins to move molecules against the electrochemical gradient.

What is the role of ATP in active transport?

ATP hydrolysis is used to create ADP and provide energy for transport.

What is osmosis?

The diffusion of water across a membrane.

What causes osmotic pressure?

Differences in the concentration of solutes on opposing sides of a membrane.

What happens in isotonic solutions?

The concentration of water is the same inside and outside the cell, allowing for balanced movement.

What occurs in hypotonic solutions?

Water concentration is greater outside the cell, causing water to enter and potentially burst the cell.

What occurs in hypertonic solutions?

Water concentration is greater inside the cell, causing water to exit and the cell to shrivel.

What is the function of the nucleus?

It contains most of the cell's DNA and has a double membrane with nuclear pores.

What are ribosomes?

Sites of protein synthesis found in all cells, with prokaryotic ribosomes being smaller (70S) and eukaryotic ribosomes being larger (80S).

What is the function of mitochondria?

They convert O2 and nutrients into energy and produce most of the ATP in eukaryotic cells.

What is the plasma membrane?

A lipid bilayer that facilitates transport and cell communication.

What is the cytoplasm?

A gel-like, water-based fluid that occupies most of the cell volume and contains organelles.

What is the rough endoplasmic reticulum?

It contains ribosomes and is involved in protein synthesis and transport.

What is the smooth endoplasmic reticulum?

It is involved in lipid synthesis and degradation and does not have ribosomes.

What are lysosomes?

Organelles that contain enzymes to destroy old or damaged cells and pathogens.

What are cilia?

Motile hair-like structures that extend from the cell surface and help in movement and cleansing.

What is the function of flagella?

They are used for movement in eukaryotic cells.

What is the composition of fungal cell walls?

Fungal cell walls are composed of chitin.

What are algae?

Eukaryotic photoautotrophs with cell walls made of glycoproteins and polysaccharides.

What is endocytosis?

The process where cells engulf solid (phagocytosis) or liquid (pinocytosis) nutrients.

What is exocytosis?

The process where cells export substances out of the cell.

What does virulence mean?

It measures a pathogen's ability to cause disease.

What is an attenuated virus?

A weakened virus that cannot cause disease.

What is pathogenicity?

The ability of a microorganism to cause disease.

How do viruses compare in size to other organisms?

Viruses are much smaller than bacteria and eukaryotic cells.

What are some characteristics of viruses?

They are acellular, obligate intracellular parasites, have no metabolism, and cannot produce ATP.

What components are always seen in viruses?

Viruses consist of genetic material (DNA or RNA) and a protein coat.

What is the protein shell of a virus called?

Capsid

What are the three shapes of virus capsids?

Icosahedral, Helical, Complex

What types of genetic material can a viral genome have?

DNA or RNA

What are the characteristics of single-stranded viral genomes?

Circular, Sense (+) or Antisense (-)

What are the characteristics of double-stranded viral genomes?

Segmented, Linear, Continuous, or Ambisense

What is an envelope in the context of viruses?

A lipid bilayer made from the host cell upon exit

What is the first step of viral infection?

Attachment of a virus to its host cell

What receptors does Influenza bind to for attachment?

Sialic Acid

What receptor does SARS-CoV-2 bind to?

ACE2 receptor

What is the second step of viral infection?

Penetration: Virus enters the host cell

What occurs during the uncoating step of viral infection?

Viral genes are released into the host cell

What is biosynthesis in viral infection?

Viral genome contains instructions for making new virions

What happens during the assembly step of viral infection?

New virions are created and prepped for release

How are mature viruses released from the host cell?

By sudden rupture or gradual extrusion through the cell membrane

What is the difference between bacterial and viral infections regarding antibiotics?

Bacterial infections often respond to antibiotics; viral infections do not

What does a gram stain identify?

It only works for bacteria, not viruses

What is tropism in relation to viruses?

The ability of a virus to bind to certain cells and infect certain animals

How do enveloped and non-enveloped viruses differ in entering host cells?

Non-enveloped viruses use endocytosis; enveloped viruses use membrane fusion

Why are antiviral drugs hard to produce?

They target host cell machinery, making it difficult to avoid harming host cells

Why is it harder to treat slower-growing bacteria?

Many antibiotics target actively growing cells, which slow-growing bacteria do less often

What are the optimal growth conditions for psychrophiles?

-5 to 15 °C

What is sterilization?

The removal or destruction of all microbes, including viruses and bacterial endospores

What does disinfection refer to?

The use of agents to eliminate most pathogens but not necessarily all

What is pasteurization?

Use of heat to kill pathogens and reduce spoilage microorganisms in food and beverages

What does the suffix '-static' indicate?

Inhibits microbial metabolism and growth but does not kill microbes

What does the suffix '-cide' indicate?

Agents that destroy or permanently inactivate a microbe

Why does altering the cell wall kill bacteria?

It prevents the cell from counteracting osmotic effects, leading to bursting

Why does damaging the plasma membrane kill bacteria?

It causes cellular contents to leak out

Why does damaging proteins kill bacteria?

It disrupts their structure, leading to loss of function and cell death

Why does damaging nucleic acids kill bacteria?

It can produce fatal mutations and halt protein synthesis

How long can endospores survive in 70% alcohol?

Over 20 years.

What is Mycobacterium known for?

Cell walls contain large amounts of wax, protecting them from drying and water-based chemicals.

What is the significance of Mycobacterium tuberculosis?

It causes tuberculosis.

What are protozoan cysts?

Dormant state of protozoa that remain until they find a suitable host.

What are prions?

Infectious agents composed of proteins without nucleic acid.

What happens when cellular prion protein (c-prp) misfolds?

It causes other c-prp to misfold into the prion form.

What diseases are associated with prions?

Creutzfeldt-Jacob disease, scrapie, mad cow disease, and wasting disease.

What is the most effective sterilization method?

Autoclaving, as it uses higher temperatures than boiling.

What are typical autoclave conditions?

121°C at 15 psi for 15 minutes.

Is refrigeration bacteriostatic or bactericidal?

Refrigeration is bacteriostatic; it slows microbial metabolism and growth.

What is the effect of slow freezing on microbes?

More effective than quick freezing as ice crystals puncture cell membranes.

How does filtration kill bacteria?

By trapping particles larger than the pore size used.

What is desiccation?

The process of drying that inhibits microbial growth.