Chapter 3 Flashcards
Hans Christian Joachim Gram
Danish physician microscopically examining the lungs of patients who died of pneumonia.
Who did Gram work under?
Carl Friedlander
What was Carl Friedlander trying to figure out?
He was trying to identify the cause of pneumonia by studying patients who had died of it.
What was Gram’s task under Friedlander?
Gram’s task was to stain the infected lung tissue to make the bacteria easier to see under the microscope.
What did Gram notice about his staining methods?
One of the methods he developed did not stain all bacteria equally; some types retained the first dye applied in this multi step procedure, whereas others did not.
What did Gram’s staining method reveal?
Gram’s staining method revealed that two different kinds of bacteria were causing pneumonia, and these types retained the dye differently.
Gram stain
Important staining method that efficiently identifies two large distinct groups of bacteria: Gram positive and Gram negative.
What are the two large distinct groups of bacteria?
- Gram positive
- Gram negative
What is a key test in the initial identification of a bacterium?
Gram stain
Why are the similarities and differences of prokaryotes and eukaryotes important to know from a human health standpoint?
Bacterial cell components are particularly relevant because some are targets for antibacterial medications used to treat infectious diseases.
By interfering with the function of components unique to bacteria, or at least more accessible to antibacterial medications, we can selectively kill or inhibit bacteria without harming the patient.
What do “alarm systems” in the body do?
Recognize compounds unique to bacteria or certain microbial groups, alerting the body’s defenses when invaders are present.
What are the advantages of prokaryotic cells being smaller than eukaryotic cells?
Their small size gives the cells a high surface area to volume ratio, making it easier for them to take in nutrients and excrete waste products
What are the disadvantages of prokaryotes being small?
Their small size makes them vulnerable to a variety of threats, including predators, parasites and competitors.
Eukaryotes v Prokaryotes
Eukaryotic cells are much more complex than prokaryotic cells.
Many cellular processes of eukaryotes take place within membrane bound compartments.
Eukaryotes are defined by the presence of what?
The nucleus
Cell envelope
Surface layer of the prokaryotic cell
The layer surrounding the contents of the cell
What does the cell envelope consist of
- Cytoplasmic membrane
- The cell wall
- Capsule (if present)
Capsule
Bacterial cells often have them.
Is a layer that helps protect the cell or allows it to attach to certain surfaces.
Archaeal cells rarely have…
Capsules
Cytoplasm
A thick substance filled with nutrients ribosomes, and enzymes.
Is the contents of the cell, excluding the nucleus.
What is the cytoplasm filled with?
Nutrients
Enzymes
Ribosomes
What is the fluid portion of the cytoplasm called
Cytosol
Nucleoid
Gel like region in the cytoplasm where the cell’s chromosome is found.
Cytoplasmic membrane or plasma membrane
Is a thin delicate structure that surrounds the cytoplasm and defines the boundary of the cell.
Serves as a crucial permeability barrier between the cell and its external environment.
The structure of the prokaryotic cytoplasmic membrane
A phospholipid belayer embedded with proteins.
The phospholipid molecules are arranged in opposing layers so that their hydrophobic tails face in, toward the other layer and their hydrophilic heads face outward, interacting freely with aqueous solutions.
What are the roles of the proteins embedded in the membrane
- selective gates allowing nutrients to enter the cell and wastes to exit.
- -sensors of environmental conditions, providing the cell with a mechanism to monitor and adjust to its surroundings.
- Some are enzymes that catalyze essential chemical reactions.
Fluid mosaic model
Model that describes the nature of the cytoplasmic membrane.
The various proteins embedded are not stationary, they are constantly drifting laterally in the phospholipid bilayer.
How do Archaeal cytoplasmic membranes differ from bacterial membrane?
They are chemically distinct.
The hydrophobic tails of Archaeal membrane phospholipids are not fatty acids.
The phospholipids are connected to the glycerol component of the hydrophilic head by a different type of chemical linkage.
Describe the permeability of the cytoplasmic membrane
Selectively permeable.
Selectively permeable
Describing material that allows only certain molecules to pass through it.
What are the molecules that freely pass through the phospholipid bilayer?
O2
CO2
N2
Small hydrophobic compounds
Water
Aquaporins
Pore forming membrane proteins that specifically allow water to pass through.
Some cells facilitate water passage this way.
Simple diffusion
Movement of solutes from a region of high concentration to one of low concentration; does not involve transport proteins.
Molecules that freely pass through the phospholipid bilayer move in and out of the cell by simple diffusion.
What do direction and speed of simple diffusion depend on
Speed and direction of movement depend on the relative concentration of molecules on each side of the membrane-the greater the difference in concentration, the higher the rate of diffusion.
How long does simple diffusion occur?
The molecules continue to pass through at a diminishing rate until their concentration is the same on both sides of the membrane.
Osmosis
Is the diffusion of water across a selectively permeable membrane
When does osmosis occur?
It occurs when the concentrations of solute (dissolved substances) on two sides of the membrane are unequal.
What occurs during osmosis?
Water moves down its concentration gradient from high water concentration (low solute concentration) to low water concentration (high solute concentration)
What are the three terms used to describe osmosis?
- Hypotonic
- Hypertonic
- Isotonic
Important biological consequences of osmosis
Page to read again.
What is the energy currency of the cell
ATP
Role of cytoplasmic membrane in energy transformation
Cytoplasmic membrane of prokaryotes play a crucial role in transforming energy converting the energy of food or sunlight into ATP.
Electron Transport Chain
Group of membrane embedded electron carriers that pass electrons from one to another and in the process, create a proton motive force.
Is a series of protein complexes.
Net result of ETC
Net result is that protons are moved out of the cell.
This creates an electrochemical gradient across the membrane- positively charged protons are concentrated immediately outside the membrane, whereas negatively charges hydroxide ions remain inside the cell
The charged ions attract each other so they stay close to the membrane.
Net result of ETC
Net result is that protons are moved out of the cell.
This creates an electrochemical gradient across the membrane- positively charged protons are concentrated immediately outside the membrane, whereas negatively charges hydroxide ions remain inside the cell
The charged ions attract each other so they stay close to the membrane.
Proton motive force
Form of energy generated as an electron transport chain moves protons across a membrane to create a chemiosmotic gradient.
Transport systems
Mechanism used to transport nutrients and other small molecules across the cytoplasmic membrane
Efflux pumps
A transporter that moves molecules out of the cell
Moves waste products and other toxic substances out of the cell.
What do efflux pumps have to do with anti microbial medications?
Some efflux pumps are particularly important because bacterial cells use them to remove antimicrobial medications that have entered, thereby allowing the bacterium to withstand the effects of the medication.
The three categories that transport systems can be separated into:
- Facilitated diffusion
- Active transport
- Group translocation
Facilitated diffusion
Is a form of passive transport-energy is not required.
The molecules are transported from one side of the membrane to the other until their concentration is the same on both sides
Active transport
This moves compounds against a concentration gradient, a process that requires energy (think of swimming upstream).
Why do prokaryotes routinely use active transport?
Prokaryotes routinely use active transport because nearly every organic molecule taken in by a cell moves against a concentration gradient.
What form is energy is used for active transport?
The energy used is either:
1. In the form of proton motive force
2. ATP
What do transporters that use proton motive force as energy source do?
Transporters that use proton motive force as an energy source allow a proton into the cell and simultaneously being along or remove another substance.
What do transporters that use ATP as an energy source do?
Transporters that use ATP as an energy source rely on specific binding proteins located immediately outside the cytoplasmic membrane to deliver molecules to the transport complex.
Group translocation
This process chemically alters a molecule during its passage through the cytoplasmic membrane.
Most well known example of group translocation:
A phosphate group is added to a sugar such as glucose-a modification called phosphorylation.
Phosphorylation
A phosphate group is added to a sugar such as glucose
Exoenzyme
Extracellular enzymes used to break down the macromolecules into their component subunits , those subunits can be transported into the cell.
Why would cells need exoenzymes?
Because macromolecules such as proteins and polysaccharides are too big to be moved across the membrane by other processes.
