Chapter 28 Flashcards
Describe Pasteur’s experiment determining the source of bacterial cells
First experiment, flasks with sterilized broth were exposed to indoor or outdoor air. > Flasks become contaminated with microbial growth. Second experiment, the neck of the flask was curved so that microbes could not enter the broth from the air. > Flasks had no microbial growth. He demonstrated that the bacteria did not arise spontaneously.
Describe Miller-Urey experiment
Proposed energy sources included heat from volcanoes, radioactivity from isotopes, electrical discharges from lightning, and solar radiation. Miller placed a mixture of methane (CH4), ammonia (NH3), hydrogen (H2), and water into a closed system. He heated the mixture and provided an electric spark. After a week’s run, he discovered that amino acids and other organic acids had been produced.
The origin of life from nonliving matter to life - Stage 1: monomers
Early Earth contained water vapor, hydrogen gas, methane, and ammonia. Methane and ammonia are better reducing agents in the absence of oxygen. Thus, early Earth had a reducing atmosphere in which redox reactions could have driven the abiotic synthesis of organic monomers from inorganic molecules in the presence of strong energy sources. (amino acids and nucleotides)
The origin of life from nonliving matter to life - Stage 2: polymers
Protein-first hypothesis > Amino acids in oceans could have collected in shallow puddles along rock shores. > The solar heat could have caused them to form proteinoids. > Their enzymatic activity may have provided an advantage over others. RNA-first hypothesis is the contrasting belief that only RNA would be needed to progress toward the formation of the first cell. > The discovery of catalytic RNA in the 1980s supports this hypothesis. > If RNA evolved first, it could have functioned as both genes and enzymes. > It was an “RNA world” 4 billion years ago, according to supporters. (DNA, RNA, proteins)
The origin of life from nonliving matter to life - Stage 3: protobionts
Protobionts (or protocells) would have emerged before the first true cell. > Possess an outer membrane, which helps regulate and maintain cellular activities. > Fatty acids likely formed the first membranes, as they can form micelles, small spheres consisting of a single layer of fatty acids. > Vesicles are larger than micelles and are surrounded by a bilayer of fatty acids. > First protobiont was likely a type of vesicle. (cell membrane)
The origin of life from nonliving matter to life - Stage 4: Living cells
The central dogma of genetics states that DNA directs protein synthesis and information flows from DNA to RNA to protein.
What are the 6 stages of the lifecycle of animal viruses?
1: Attachment 2: Entry 3: Replication 4: Biosynthesis 5: Assembly 6: Budding
How do antibiotics work?
Inhibit protein synthesis by bacteria. > Erythromycin and tetracyclines. Inhibit cell wall biosynthesis. > Penicillins and cephalosporins.
What components make up a virus?
Capsid (outer portion comprised of proteins). > Encloses nucleic acid core and sometimes additional viral enzymes. > May be surrounded by a lipid envelope. > May have spikes for attachment to a host cell. Nucleic acid core (DNA or RNA). > Genome can be single- or double-stranded DNA or single- or double-stranded RNA.
What are similarities and differneces between Domain Archaea and Domain Bacteria?
Domain Bacteria and domain Archaea are both prokaryotes. > Molecular and cellular differences separate the two. Prokaryotes are single-celled organisms that lack a nucleus and the membrane-bound cytoplasmic organelles found in eukaryotic cells. > Archaea and bacteria are not closely related even though both are prokaryotes. > Eukarya are more closely related to archaea than to bacteria based on a number of criteria.
What is a viroid?
are strands of RNA that can reproduce inside a cell.
What is a prion?
are protein molecules that cause other proteins to become prions.
What are gram stains used for and what does gram-negative and gram-positive mean?
A method used to classify bacteria is based on differences in cell walls. The result is used to select antibiotics to treat infections. Gram-positive bacteria have a thick layer of peptidoglycan and stain purple. Gram-negative bacteria have a thin or lacking layer of peptidoglycan and stain pink.
What are the three mechanisms of horizontal gene transfer in bacteria?
Conjugation: donor cell passes DNA to a recipient cell by way of a sex pilus. Transformation: bacterium takes up DNA from environment released by dead bacteria. Transduction: viruses carry portions of bacterial DNA from one bacterium to another.
