MCB3020 Asghari Exam 1

What is the role of microbes in maintaining temperature on earth? (Role of microbes in CO2 and CH4 recycling)

- Without the help of microbes to break down organic materials, the progress of life on Earth would be constrained by the fixed amount of materials available to produce biomass

- Impact on atmospheric CO2 and CH4 levels, which impacts global climate change

- These greenhouse gases accumulate in the atmosphere, forming a "blanket" that traps heat

- The Earth would be uninhabitable without these gases, but the accumulation of gases in the atmosphere cause global temperatures to gradually increases

- Microbes both consume and produce these gases, so they are deeply involved in carbon recycling

Top 3 causes of death

heart disease, cancer, stroke

aristotle

Greek philosopher who proposed the idea of spontaneous generation

spontaneous generation

suggests that living things could spontaneously arise from nonliving things

Louis Pasteur

A French chemist, who disproved the theory of spontaneous generation through the "swan neck flask experiment"

- germ theory of disease

Robert Hooke

coined the term "cell"

Antony can Leeuwenhoek

invented first microscope, first person to actually visualize microbes

Edward Jenner

developed first vaccine - the smallpox vaccine

Ignaz Semmelewis

dutch physician who advocated hand-washing

John Snow

father of epidemiology

Robert Koch

- stated Koch's postulates: criteria designed to establish a causal relationship between a microbe and disease

- one microbe, one disease idea

Paul Ehrlich

Pharmacist who mixed and matched chemicals in order to find "magic bullets" for a disease - chemicals that selectively killed the disease without harming human cells

Alexander Fleming

Discovered penicillin, first antibiotic

Frederick Griffith

discovered genetic transformation

James Watson and Francis Crick

discovered the structure of DNA

List and explain the impact of microbes on the environment (slide 4)

flow of energy, primary producers, regulation of temp, symbiosis

cell

fundamental unit of life

microbe

An organism invisible to the naked eye, especially one that causes disease

hallmarks of the cell

Cell membrane, Genetic material, Self-replication, Regulation, Similar macromolecules, Energy use

nonliving infectious agents

viruses, viroids, prions

viruses

non-living biological entities that have infectious properties - acellular: do not share the hallmark of cells

prions

Infectious proteins that cause several brain diseases: scrapie in sheep, mad cow disease in cattle, and Creutzfeldt-Jacob disease in humans

viroids

plant pathogens composed of infectious RNA

List extreme conditions at which microbes can thrive

- Microbes can live in nearly every extreme condition imaginable

- Extremely salt conditions, extreme heat or cold, and extremely acidic or extremely basic conditions

- Microbes can live with or without oxygen

Where in human body bacteria may be found?

human skin, mouth, intestines

prokaryote domains and kingdoms

- domain Archaea and domain Bacteria

- kingdom monera

eukaryote domains and kingdoms

- domain eukarya

- kingdom protista, fungi, plantae, and animalia

do viruses have kingdoms

viruses do not belong to any of the kingdoms or domains because they are acellular and nonliving

List membrane-bound organelles found in eukaryotes but not in prokaryotes.

Nucleus, endoplasmic reticulum, Golgi apparatus, lysosomes, mitochondria and chloroplasts

List the six major bio elements

-carbon

-hydrogen

-oxygen

-nitrogen

-phosphourus

-sulfur

List the bio elements present in each of the four polymers

- Lipids (fatty acids): contain C, H, O

- Polysaccharides: contain C, H, O

- Proteins: contain C, H, O, N (and sometimes S)

- Nucleic acids: contain C, H, O, N, and P

chemical bonds

the attractive forces that hold atoms together

ionic bonds

Formed when one or more electrons are transferred from one atom to another

covalent bonds

Bonds created by sharing electrons with other atoms to fill their outer shells

hydrogen bonds

Very weak bonds; occurs when a hydrogen atom in one molecule is attracted to the electrostatic atom in another molecule

role of water in biological activities

Hydrogen bonding between water molecules gives water a high boiling point, makes it a good temp buffer and makes it an excellent solvent

water activity (aw)

A quantitative measure of water availability in a habitat

osmosis

The movement of water across a selectively permeable membrane from an area of higher concentration to an area of lower concentration.

osmolarity

describes the concentration of solute particles in a solution

osmotolerant

where an organism is able to grow in a wide range of solute concentrations or water activity

halophiles

organisms that thrive in high salt concentrations

exergonic reaction

describes a reaction that releases energy on net because the free energy of the products is greater than the free energy of the reactants

endergonic reaction

describes a reaction that requires energy on net because the free energy of the products is less than the free energy of the reactants

spontaneous

describes a reaction that releases free energy (exergonic)

nonspontaneous

describes a reaction that absorbs free energy (endergonic)

hydrolysis

Breaking down complex molecules by the chemical addition of water

- catabolic

dehydration reaction

A chemical reaction in which molecules combine by removing water

hydrolytic reaction

reactions which use water and in which chemical bonds are broken

condensation reaction

a chemical reaction in which two or more molecules combine to produce water or another simple molecule

- anabolic

What is the role of enzymes in chemical reactions?

- act as catalysts

- Enzymes decrease the activation energy needed for a reaction to begin

carbohydrates

lipids

nucleic acids

proteins

folding

occurs when a polypeptide consisting of a string of amino acids begins to take a three-dimensional shape, due to different types of chemical bonds

denaturation

occurs when exposure to heat or chemicals disrupts the normal folding and confirmation of the protein, causing it to unravel and lose its function

primary structure

refers to the amino acid sequence that makes up the backbone of the protein

secondary structure

long peptides form into regular structural units, such as the alpha helix and beta pleated sheet

- result from hydrogen bonding

tertiary structure

refers to the bonds between the variable R groups of amino acids (the side chains)

- Peptide bonds, hydrogen bonds, ionic bonds, disulfide bridges, and hydrophobic interactions all play a role in proper protein folding

quaternary structure

highest level of protein structure, formed by the combination of multiple polypeptides into functional units

- Van der waals forces

- ex. hemoglobin

amphipathic molecule

A molecule that has both a hydrophilic region and a hydrophobic region

- ex. phospholipids

magnification

refers to how large the image is compared to the actual specimen

refractive index

ratio of velocity of light in a vacuum to its velocity in the medium

resolution

refers to the crispness or detail of the image produced

oil immersion

technique in which they place a drop of oil between the objective lens and the glass cover

- Technique used to reduce or eliminate the problem of some of the light no passing through the objective lens

smear

a thin layer of cells attached to a microscope slide

smear preparation

necessary if a scientist wishes to use one of the many staining techniques

steps of smear prep

1. place a thin film of the specimens on the slide

2. allow specimen to air-dry

3. fix the specimen on the slide by passing the slide over Busnen burner

4. flood the specimen with a stain, rine, and dry

simple stains

application of a single dye

- provides info about shape, size and arrangement

- positive and negative stains

positive stains

Bacterial cell surfaces typically have a negative charge, so the application of a stain with a positive charge cause the stain to adhere to the cell surface

- use basic dyes

negative stains

Will not adhere to the cell surface; rather, it will fill in the spaces around the bacterium, providing a contrast that allowed scientists to see unstained bacteria against a dark background

- acidic dyes

differential stains

involves application of two or more dyes to differentiate among cells

- gram stain

- acid fast stain

- structural stain

gram-positive bacteria

thicker peptidoglycan layer in their cell walls - turn blue/purple

gram-negative bacteria

- thinner peptidoglycan layer in their cell walls - turn red/pink

- extra cell membrane

acid-fast stain

uses a harsh acid to identify mycobacteria: bacteria with a thick, waxy-coated cell wall

structural stains

used to identify and highlight the structures of a bacterial cell to allow visualization of endospores, capsules, and flagella under light microscopes

capsule stain

- well-organized layer of polysaccharides and other materials that is found outside the cell walls of many bacteria

- negative stain

- makes bacterium resistant to phagocytosis

flagellum stain

lash-like appendage that conveys motility to certain prokaryotic cells

Define and describe the importance of wet mount

A wet mount is placing a drop of liquid on a slide, placing the specimen in the liquid, then placing a cover slip over the slide.

This simple technique allows you to observe the morphology and motility of a bacterium and it is useful for observing living specimens.

Explain the steps involved in Gram staining procedure

1. Apply the primary stain, such as crystal violet

2. Apply a mordant, such as iodine

3. Apply a decolorizer, such as alcohol

4. Apply a counterstain, such as safranin

What is the significance of acid-fast staining procedure?

Identification of a bacterium as a mycobacterium is important because this group of bacteria includes organisms that cause tuberculosis and leprosy

Which microscope uses the differences in refractive index and cell density to visualize live cells?

Phase-contrast microscope uses the different densities of the various cellular components to produce a more detailed image of the cell

- Advantage is that you can see the details within the cell, even with an unstained specimen

Gram-positive, coccus (round shaped) bacteria:

usually either Streptococcus (found in chains) or Staphylococcus (found in clusters)

Gram-negative, coccus (round shaped) bacteria:

Neisseria gonorrhoeae, the bacterium that cause gonorrhea

Gram-positive, bacillus (rod-shaped) bacteria:

usually either Bacillus (which causes anthrax) or Clostridium (which causes gangrene, botulism, tetanus and other diarrheal diseases)

Gram-negative, bacillus (rod shaped) bacteria:

include E. coli (which causes a number of problems, including urinary tract infections) and Salmonella

Spirochete-shaped bacteria

cause Lyme disease and syphilis

Vibrio-shaped bacteria

cause cholera

Gram negative cell envelopes

- Peptidoglycan cell walls with fewer layers

- Lipopolysaccharide present

- Have additional membrane that lies outside the peptidoglycan cell wall - outer membrane: plays a role in defense and immunity

Gram positive cell envelopes

- Peptidoglycan cell walls with many layers

- Have teichoic acids in their cell walls

- Provide additional rigidity to the cell wall

What is the significance of periplasmic space?

Contains enzymes that break down nutrients, as well as special proteins that facilitate the transfer of nutrients to the plasma membrane

phospholipids

- amphipathic molecules that make up the majority of the membrane

- Consist of a hydrophilic head and hydrophobic tails that naturally arrange into a bilayer

membrane proteins

facilitate cell signaling and membrane transport

hopanoids

a steroid-like molecule that strengthens prokaryotic membranes, much like cholesterol does in eukaryotic membranes

- impact membrane fluidity

glycoproteins

sugars attached to proteins on cell surface

- play role in signaling

glycolipids

sugars attached to lipids on cell surface

- play role in signaling

Define the importance of the interaction between ligand and receptor molecules

- Ligand: a molecule that binds to another molecule

- In the context of cell signaling, a ligand is a signal molecule that binds to a receptor on the surface of the cell, triggering some kind of change

What are steroids? Give examples. What is their role in function of cell membrane?

- Steroids: class of organic compounds with a characteristic molecular structure containing three six carbon rings and one five carbon ring

- In eukaryotic cells

- Ex. cholesterol

- They embed within the cell membrane to help maintain membrane integrity and impact the membrane's fluidity

simple diffusion

concentration gradient allows molecules to simply move fro one side of the membrane to another

facilitated diffusion

- form of passive transport in which molecules move down their concentration gradient (high to low)

- Does not require energy but does require carrier proteins