Bacterial Structure and Function Quiz

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Questions and Answers

What is the primary function of flagella in bacteria?

DNA transfer between cells

Movement in liquid environments (correct)

Protection from immune system

Attachment to surfaces

What type of movement do bacteria perform when they swim in a zigzag pattern in search of nutrients?

Random walk (correct)

Linear motion

Tumble movement

Directional swimming

Which structure allows bacteria to stick to various surfaces, including epithelial tissue?

Flagella

Fimbria (correct)

Glycolax

Pili

What is the main role of pili in bacterial cells?

Gene transfer between cells Signup and view all the answers

What is a well-organized layer of uniform thickness around a bacterium called?

Capsule Signup and view all the answers

Which type of glycolax layer is described as poorly defined?

Slime layer Signup and view all the answers

What significant defense mechanism do pathogenic bacteria often rely on?

Capsule formation Signup and view all the answers

What does the ability of a bacterium to be motile depend on?

Presence of flagella Signup and view all the answers

What is a characteristic feature of prokaryotic cells?

Absence of a nuclear membrane Signup and view all the answers

What type of DNA structure is typically found in prokaryotic cells?

Circular chromosomes Signup and view all the answers

Which of the following is true regarding eukaryotic cells compared to prokaryotic cells?

Eukaryotic cells contain membrane-bound organelles Signup and view all the answers

How is the chromosome structure in eukaryotic cells typically characterized?

Multiple and linear Signup and view all the answers

Which of the following organisms are classified as eukaryotes?

Algae Signup and view all the answers

Which component is absent in prokaryotic cells?

Nucleolus Signup and view all the answers

What is the primary method of cell division in prokaryotic cells?

Binary fission Signup and view all the answers

What is the primary purpose of a microscope?

To examine objects that are too small to be seen by the naked eye Signup and view all the answers

What structure helps maintain the shape and provides protection in most bacteria?

Cell wall Signup and view all the answers

Which type of microscope is commonly referred to as a biological microscope?

Compound Microscope Signup and view all the answers

What is the typical highest magnification of a compound microscope?

1000x Signup and view all the answers

What component of a compound microscope contains a power lens of either 10X or 15X?

Eyepiece Signup and view all the answers

What should be avoided when focusing a microscope?

Having the objective lens touch the slide Signup and view all the answers

How many objective lenses does a standard compound microscope typically have?

Three, four, or five Signup and view all the answers

Which of the following samples can be examined using a compound microscope?

Tissues Signup and view all the answers

What purpose does the diopter adjustment serve in a microscope?

It corrects for differences in the viewer's eyesight Signup and view all the answers

What type of anaerobes can tolerate oxygen but cannot use it?

Aerotolerant Anaerobes Signup and view all the answers

Which classification of bacteria has flagella distributed evenly around the cell?

Peritrichous Signup and view all the answers

Which type of bacteria is known for producing spores within the bacterial cell?

Endospore forming bacteria Signup and view all the answers

What is the optimum pH for growth of Alkaliphiles?

8.2 Signup and view all the answers

Which of the following bacteria are classified as Acidophiles?

Thiobacillus Signup and view all the answers

Halophiles require which type of environment for optimal growth?

High osmotic pressure Signup and view all the answers

Which of the following is an example of a monotrichous bacterium?

Vibrio cholerae Signup and view all the answers

What function does the glycolax perform aside from protection?

Allows bacteria to stick to surfaces Signup and view all the answers

What is the primary component of the bacterial cell wall?

Peptidoglycan Signup and view all the answers

What type of bacteria do not produce spores?

Non-spore forming bacteria Signup and view all the answers

How can bacteria be classified based on their cell wall structure?

By the thickness of peptidoglycan layer Signup and view all the answers

What is a key characteristic of gram negative bacteria?

They have a second outer membrane Signup and view all the answers

What role do lipopolysaccharides (LPS) play in gram negative bacteria?

Form endotoxins when the cell is destroyed Signup and view all the answers

What is the purpose of a differential stain in microbiology?

To differentiate between gram positive and gram negative cells Signup and view all the answers

What happens to bacteria without a proper cell wall structure in unfavorable conditions?

They could burst due to osmotic pressure Signup and view all the answers

What color do gram positive bacteria appear after gram staining?

Purple Signup and view all the answers

What characteristic must agar have to be a suitable solidifying agent?

Gel at a concentration of 1% Signup and view all the answers

Which of the following is a disadvantage of liquid media?

It cannot guarantee purity of growth. Signup and view all the answers

Which component acts as a stimulant for bacterial growth in culture media?

Yeast extract Signup and view all the answers

What is the primary purpose of carbohydrates in media?

To serve as a carbon and energy source Signup and view all the answers

What is a unique property of gelatin compared to agar?

Can be liquefied by bacteria at 37°C Signup and view all the answers

Which mineral is specifically mentioned as essential for enzymatic activities of bacterial growth?

Magnesium Signup and view all the answers

How does solid media differ from liquid media?

Forms visible colonies at the site of inoculation Signup and view all the answers

Which of the following statements about agar is false?

It is derived from animal protein. Signup and view all the answers

Study Notes

Microscopy

A microscope is a laboratory instrument used to examine objects too small to see with the naked eye
Microscopy is the science of investigating small objects and structures using a microscope
Microscopic means being invisible to the naked eye unless aided by a microscope

Types of Microscopes

Compound Microscope
Stereo Microscope
Inverted Microscope
Metallurgical Microscope
Polarizing Microscope

Compound Microscopes

Also referred to as a biological microscope
Used in laboratories, schools, wastewater treatment plants, veterinary offices, and histology/pathology
Samples viewed under a compound microscope must be prepared on a microscope slide using a cover slip to flatten the sample
Can view blood cells, cheek cells, parasites, bacteria, algae, tissue, and thin sections of organs
Common magnifications are 40x, 100x, 400x, and sometimes 1000x
Microscopes advertising magnification above 1000x offer empty magnification with low resolution and should not be purchased

Microscope Parts

Eyepiece: The lens the viewer looks through to see the specimen. Usually contains a 10x or 15x power lens.
Diopter Adjustment: Useful for correcting vision differences between the two eyes.
Body Tube (Head): Connects the eyepiece to the objective lenses.
Arm: Connects the body tube to the base of the microscope.
Coarse Adjustment: Brings the specimen into general focus.
Fine Adjustment: Fine tunes focus and increases detail of the specimen.
Nosepiece: A rotating turret that houses the objective lenses
Objective Lenses: The lenses closest to the specimen. Standard microscopes have 3-5 objective lenses ranging from 4x to 100x power.
Specimen/Slide: The specimen is the object being examined and is placed on a glass slide.
Stage: The flat platform where the slide is placed.
Stage Clips: Metal clips that hold the slide in place.
Stage Height Adjustment: Moves the stage left/right or up/down.
Aperture: The hole in the middle of the stage that allows light from the illuminator to reach the specimen.
On/off switch: Controls the illuminator. Older microscopes used mirrors, most now use a low-voltage bulb.
Illumination: The light source for the microscope
Condenser: Gathers and focuses light from the illuminator onto the specimen.
Iris Diaphragm: Adjusts the amount of light that reaches the specimen.
Base: Supports the microscope and houses the illuminator.

Cells

All living things are made of cells
Cells are the smallest units that can be alive
Life on Earth is classified into five kingdoms
Each kingdom has its own kind of cell
There is a key division between prokaryotic and eukaryotic cells

Prokaryotes

Lacking well-defined nuclei and membrane-bound organelles.
Chromosomes composed of a single closed DNA circle
Typical prokaryotic cells range from 0.1 to 5.0 micrometers in diameter.
Common bacteria are prokaryotic and are found everywhere on Earth.
The majority of prokaryotic DNA is found in a central region called the nucleoid.
Most are surrounded by a rigid cell wall made of peptidoglycan (a polymer). This helps cell shape and prevents dehydration.
Many bacteria also have a capsule (carbohydrate layer) that helps with adhesion to surfaces.

Eukaryotes

Contain complex cells or single cells with complex structures.
Genetic material organized into chromosomes in the nucleus
Usually much larger than prokaryotes (10-100 μm).
Contain organelles (other structures with membranes)
Eukaryotic DNA is put in bundles called chromosomes. These are separated by a microtubular spindle during cell division.
Most eukaryotes reproduce sexually.
The number of chromosomes is usually typical for each species.

Prokaryotic vs. Eukaryotic Cells (Table)

Feature	Prokaryotic Cell	Eukaryotic Cell
Nuclear Membrane	Absent	Present
Chromosome	Single, circular	Multiple
DNA	Circular	Linear
Nucleolus	Absent	Present
Cell Division	Mitosis (fission)	Mitosis or meiosis
Ribosomes	70s	80s
Chloroplasts	Absent	Present
Mitochondria	Absent	Present
Cell Organelles	Absent	Present
Cell Wall	Usually present, contains peptidoglycan	Usually present, varies
Flagella	Simple arrangement	Complex arrangement
Average Size	0.2-2um	10-100um
Plasma Membrane	No carbohydrates, lacks sterols	Sterols and carbohydrates present
Number of Cells	Generally unicellular	Generally multicellular

Bacteria Cell Shapes

Cocci (round)
Bacilli (rod-shaped)
Coccobacillus (oval-shaped)
Vibrio (comma-shaped)
Spirillum/Spirochete (corkscrew/spiral-shaped)

External Features of Bacteria

Flagella: Long filamentous appendages that function as a propeller for movement in liquid environments
Fimbriae: Smaller appendages that allow bacteria to attach to surfaces.
Pili: Long appendages that function similarly to fimbriae, often used for bacterial conjugation (sharing DNA)
Glycocalyx: Carbohydrate and protein matrix that forms when cells are in harsh environments or need to adhere to a surface.

Cell Wall Structure

Bacteria have a cell wall structure that protects their cellular membrane from damage in unfavorable conditions.
The cell wall helps the bacteria withstand/resist the hypotonic environment.
Bacteria are often surrounded by peptidoglycan.

Gram Stain

Shows the difference between gram-positive and gram-negative bacteria.
Bacteria with thick peptidoglycan layers in their walls stain purple.
Bacteria with thin layers will clear of stain after a rinse and stain pink with Saffranin.

Bacterial Internal Structures

Mesosomes: Convoluted invaginations in the cytoplasmic membrane. Play a role in cell division and secretion
Nucleoid: The region containing the DNA contained within the cytoplasm of the cell (no membraneous envelope)
Ribosomes: Located throughout the cytoplasm. The site of protein synthesis. Important for conveying genomic code.
Cytoplasmic inclusions: Sources of reserved food for the cell (e.g., glycogen, volutin)

Bacterial Taxonomy and Classification

Taxonomy is the science or study of classifying living organisms.
It groups living organisms into categories (e.g. kingdom, phylum, etc.).
The original taxonomy system used in biology is called binomial nomenclature and is credited to Carolus Linnaeus. It is an accepted system for communication about organisms around the world.
The system involves two parts and includes the genus name in the first, capitalised part and a specific epithet (a descriptor) in a second, non-capitalised part.

Mechanisms of Drug Resistance in Bacteria

Spontaneous mutations in DNA.
Transfer of DNA (e.g. through plasmids) from one bacterium to another (resistance properties often encoded on these).

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Description

Test your knowledge on bacterial structures and their functions in this quiz. Topics include flagella, pili, and the differences between prokaryotic and eukaryotic cells. Gauge your understanding of how bacteria navigate and adhere to surfaces.