MCAT BIOLOGY

prokaryotic organisms; prokaryotes lack a true nucleus and membrane-bound organelles

not considered living organisms, since they cannot carry out metabolism outside of a host cell

viruses that infect bacteria

lack chlorohyll but are eukaryotic organisms and therefore have membrane-bound organelles

• ex: methogens (prokaryotes that produce methane)
• extreme halophilies - live at high concentrations of NaCl
• extreme thermophiles - live where super hot

• phospolipids arranged in lipid bilayer
• philic head with phobic tail

gram-positive and gram-negative

thick cell wall - peptidoglycan

thin layer of peptidoglycan between layers of periplasm and coated with lipopolysaccarde and proteins

cannot survive in the presence of oxygen

can survive with or without oxygen

require oxygen to survive

• photosynthetic, using light energy to produce their own nutrient molecules.
• Photosynthetic bacteria use the plasma membrane as the site of photosynthesis

use energy derived from inorganic molecules such as ammonia (NH3) or hydrogen sulfide (H2S) to drive nutrient production

uses light to generate energy but must obtain their carbon in organic form (glucose)

must consume organic molecules both as an energy source and as a source of carbon

there is no seperate membrane-bound nucleus

nucleus, where splicing of introns takes place before leaving the nucleus

DNA taken up from the enviorment and integrated into the bacterial genome

genetic material is passed from one bacterial cell to another via a virus .... recombination of bacterial DNA

• genetic information is directly transferred from one bacterial cell to another via temportany connection known as a conjugation bridge
• Cells containing F plasmid are called F+, cells lacking F plasmid are called F-
• F+ cells extends sex pilli to recipeient F- cell to form the conjugation bridge

DNA from any part of the host's chromosome becomes a part of the viral genome, replacing the viral genome

DNA from a specific part of the host's chromosomes becomes part of the viral genome, usually replacing some viral genes

when part of the plasmid intergrates into the chromosome

• they can express genes and reproduce only within a living host cell
• Viruses are unable to survive outside of a host cell, since they lack the structures necessary for independent activity and reproduction

• Reverse transcriptase
• Since animal cells do not contain this, viruses must carry the enzyme with them
• Since the virus integrates in the genome of the host, it can escape immune detection

virus that infects bacteria

Lytic- viral DNA is translated and transcribed, weakening the cell wall where it bursts

Lysogenic-viral DNA becomes integrated into bacterial genome in prophage form, where it lies dormant, until its activated and starts the lytic cycle

chiton

in the membranes of myelinated cells composing the human nervous system

• four ringed structure
• hormones, vitamin A, cholestrol which is important for membrane fluidity

 

structural component of membranes

store metabolic energy, provide thermal insulation, and padding

regulate metabolic activities

serve as local hormones

a single chain

• beta-pleated sheet or alpha-helix - a,helix and the beta-pleated sheets are the secondary structure and contribute to the conforllIation of the protein. All proteins have a pri- mary structure and most have a secondary structure.
• Beta-pleated sheets: connecting segments of the two strands of the sheet can lie in the same direction (parallel) or in opposite directions (al/liparallel)
• Alpha-helix: single chain twisted

The tertiary structure refers to the three dimensional shape formed when the peptide chain curls and folds

1.2.3. 4. 5.covalent disulfide bonds between two cysteine an1ino acids on djfferent parts of the chain;electrostatic (ionic) interactions mostly between acidic and basic side chains;hydrogen bonds;van der Waals forces;hydrophobic side chains pushed away from water (toward center of protein)