Chapter 27 Flashcards
What are the most common shapes of prokaryotics?
Spherical (Cocci), Rod-shaped
Bacilli), and Spiral (Spirilla
What were the first organisms to inhabit earth?
Prokaryotics that lived 3.5 billion years ago.
What is a key feature of nearly all prokaryotic cells?
The cell wall, which maintains cell shape, protects the cell, and prevents it from bursting in a hypotonic environment.
What do the bacterial cell walls of prokaryotics contain?
Prokaryotic cells walls contain peptidoglycan a polymer composed of modified sugars cross-linked by short polypeptides.
What is the gram stain technique?
Gram staining is a common technique used to differentiate two large groups of bacteria based on their different cell wall constituents. Gram positive bacteria stains violet due to the presence of a thick layer of peptidoglycan in their cell walls, which retains the crystal violet these cells are stained with.
Why is Gram Staining an important medical tool?
It can quickly determine if a patients infection is due to gram-negative or gram-positive bacteria.
The lipid portions of the lipopolysaccharides in the walls of many gram-negative bacteria are toxic causing what?
Fever or Shock
Which is more resistant to antibiotics? Gram negative or postitive bacteria?
Gram-Negative bacteria because the outer membrane impedes entry of the drugs
Can Gram-Positive bacteria be resistant to antibiotics?
Yes there are some forms that are.
The cell wall of many prokaryotes is surrounded by what?
A sticky layer of polysaccharide or protein, This layer is called a capsule if it is dense and well-defined. or a slime layer if it is not well organised.
What do stick layers of the prokaryotic cell wall enable prokaryotes to do?
Both kinds of sticky outer layers enable prokaryotes to adhere to their substrate or to other individuals in a colony. Some also protect against dehydration and some shield pathogenic prokaryotes from attacks by their host’s immune system.
What are endospores?
a resistant asexual spore that develops inside some bacteria cells.
When do certain bacteria develop endospore resistant cells?
When they lack water or essential nutrients
How do endospores form?
When the original cell produces a copy of its chromosome it surrounds that copy with a multilayered structure, forming the endospore. Water is removed from the endospore and its metabolism halts, the cell then lyses releasing the endospore.
How do you kill endospores?
They are very durable and can survive boiling water so killing them requires heating lab equipment to 121.c under high pressure.
What are fimbriaes?
Hairlike protein containing appendages that allow some prokaryotes to attach to surfaces or to other cells.
How does the bacteria that causes gonorrhoea use fimbriae?
It uses fimbriae to fasten itself to the mucous membranes of its host
What are pili?
A pilus is a thin, rigid fiber made of protein that protrudes from the cell surface. The primary function of pili are to attach a bacterial cell to specific surfaces or to other cells (They pull two cells together prior to DNA transfer from one cell to the other)
What is taxis?
The directional movement away or towards and stimulus
What is the most common structure that enables prokaryotes to move?
Flagella
What is flagella in the prokaryotic cell?
Flagella are primarily used for cell movement and are found in prokaryotes as well as some eukaryotes. The prokaryotic flagellum spins, creating forward movement by a corkscrew shaped filament. A prokaryote can have one or several flagella, localised to one pole or spread out around the cell.
Are flagella analogous or homologous structures?
Analogous structures
What are analogous structures?
Analogous structures are similar structures that evolved independently in two living organisms to serve the same purpose.
What are homologous structures?
Homologous structures are organs or skeletal elements of animals and organisms that, by virtue of their similarity, suggest their connection to a common ancestor
What is the bacterial flagellum?
Bacterial flagella are helically shaped structures containing the protein flagellin. Bacterial flagella are complex and well honed organelles that provide swimming and swarming motilities and also play a central role in adhesion, biofilm formation, and host invasion
How many different types of proteins are the bacterial flagellum composed of?
42
How did the bacterial flagellum evolve?
Evidence indicates that the bacterial flagellum originated as simpler structures that were modified in a step-wise fashion over time.
How many of the flagellum’s proteins appear to be necessary for it to function?
Only half
What is exaptation?
Where structures originally adapted for one function to take on new functions through descent with modification. For example, a trait can evolve because it served one particular function, but subsequently it may come to serve another.
Which cells are more simple? Prokaryotic or eukaryotic?
Prokaryotic cells
Do prokaryotic cells have specialised membranes?
Yes
Where and what are the specialised membranes of prokaryotic cells?
They are usually infolding’s of the plasma membrane and recent discovery’s indicate that some prokaryotic’s can store metabolic by products in simple compartments that are made out of proteins, these compartments do not have a membrane.
In most cases which cell has more DNA? Prokaryotic or eukaryotic cells?
Eukaryotic cells
What type of chromosomes do prokaryotic cells tend to have?
Circular chromosomes.
What type of chromosomes do eukaryotic cells tend to have?
Linear chromosomes
Do prokaryotic have a nucleus?
no, their chromosome is located in the nucleoid
What are plasmids?
A plasmid is a small, circular, double-stranded DNA molecule that is distinct from a cell’s chromosomal DNA. Plasmids naturally exist in bacterial cells
Are ribosomes bigger in eukaryotic or prokaryotic cells?
Eukaryotic
What is a benefit of the difference of the ribosomes of eukaryotic cells being bigger than the ribosomes of prokaryotic cells?
These differences allow certain antibiotics, such as erythromycin and tetracycline, to bind to ribosomes and block protein synthesis in prokaryotes but not in eukaryotes. As a result, people can use these antibiotics to kill or inhibit the growth of bacteria without harming themselves.
What is binary fission?
In the process of binary fission, an organism duplicates its genetic material, or deoxyribonucleic acid (DNA), and then divides into two parts (cytokinesis), with each new organism receiving one copy of DNA.
