Micro Exam 2

metabolism

* the sum of chemical reactions in a cell (how well do you break things down and build the stuff you want)
* All cells need to synthesize new parts (cell walls, membranes, ribosomes) and harvest energy to power those reactions (build or break down molecules) - metabolism can effect this
* Is the sum of anabolism and catabolism

catabolism

* processes that degrade compounds to release energy (breaking down reaction)
* exergonic energy required

anabolism

* assemble subunits of macromolecules (building reactions)
* Use ATP to drive reactions
* endergonic energy required

exergonic reactions

reactants have more free energy than products (energy is released in reaction)

endergonic reactions

products have more free energy than reactants (reaction requires input of energy)

metabolic pathway

series of chemical reactions that converts starting compound to an end product

enzymes

* biological catalysts that speed up the rate in which chemical reactions occur
* specific enzymes are required for each step of a metabolic pathway
* without enzymes, energy-yielding reactions would occur too slowly

enzyme-substrate relationship

* enzymes are highly specific for substrate (molecule that needs to be broken or built)
* enzymes are not changed by a reaction so a single molecule can be reused
* enzymes are used to break large molecules into smaller ones or to build large molecules from its subunit
* enzymes typically end in -ase


1. active site on surface of enzyme binds substrate(s) weakly (shape of active site determines what it can or cannot do
2. this causes the enzyme shape to change slightly, induced fit
3. resulting enzyme-substrate complex destabilizes existing bond or allows new ones to form

precursor metabolites

* intermediates of catabolism that can be used in anabolism (in between stage of breaking down that can be used in building)
* serve as carbon skeletons for building macromolecules
* an in between stage molecule of respiration, we are going to use it to build something, based off of cells needs

photosynthesis

* conversion of radiant energy into chemical energy
* Only plants, algae, and several groups of bacteria can perform
* What goes in → CO₂, H₂O, and light
* What comes out → glucose

DNA structure

* forms a double-stranded helix made of a deoxyribose sugar molecule, a phosphate group, and nucleotides (A, C, T, and G)


* Strands are complementary; held together by hydrogen bonds between nucleobases
* Strands are anti-parallel = oriented in the opposite direction
* A→T and C→G

RNA structure

* usually forms a single strand of ribose sugar
* uracil in place of thymine
* synthesized from a DNA template strand
* RNA molecule is transcript
* base-pairing rules apply except A→U

DNA replication

* occurs solely to make a copy of DNA before a cell divides (binary fission/mitosis)
* occurs before binary fission or mitosis
* DNA is copied to make more DNA
* replication is semiconservative; DNA contains one original, one newly synthesized strand
* DNA gyrase, topoisomerase, and helicases initiate DNA replication.

transcription

* converts DNA into RNA
* RNA polymerase is the enzyme responsible to make RNA

translation

* converts RNA to proteins
* ribosomes are responsible for translation

natural selection

* organisms adapt to ever-changing environments; it is the driving force of evolution; bacteria have 2 general mechanisms to adjust to new circumstances


1. regulation of gene expression
2. genetic change

genetic change

* occurs in a single organism


* there are two mechanisms:


1. mutation (vertical gene transfer)
2. horizontal gene transfer

vertical gene transfer

passing genetic information to offspring (all mutations are passed this way)

horizontal gene transfer

movement of DNA from one organism to another (passing genetic info to neighbors; bacteria are the only ones who can do this)

evolution

entire populations of organisms change over time

spontaneous mutations

* genetic changes that result from normal processes
* mutation that occurs because the organisms “machinery” messes up

induced mutations

something from the environment causes a mutation

mutagen

agent that induces change (chemical agent, radiation)

proofreading

DNA polymerases checks accuracy

* can back up, remove incorrect nucleotide
* inserts correct nucleotide
* very efficient but not perfect

mismatch repair

* fixes errors missed by DNA polymerases

recombinants

organism that acquires genes from other cells by horizontal gene transfer

transformation

* “naked” (exposed) DNA taken up from the environment; this is DNA not within a cell or virus
* originates from cells that have burst
* recipient cell must be competent (ability to undergo transformation)

transduction

* bacterial DNA transfer by a virus
* virus infects bacteria and cuts bacterial DNA into small pieces, then the bacterial cell enzymes create more viruses
* results when a fragment of bacterial DNA enters the virus protein coat, producing a transducing particle
* transducing particle may attach to another bacterial cell and inject the DNA it contains

conjugation

* DNA transfer during cell-to-cell contact
* requires direct contact with a cell and uses a sex pilus to transfer DNA, the recombinant cell is the one receiving the DNA

virus

* non-cellular infectious agents that require live organisms as hosts; it is the actual genetic material that causes infection
* made up of DNA or RNA contained within a basic protective protein coat

virion

* carries the infective form of the virus
* virions are the virus contained within a capsule
* not active in the environment, until they find a host and inject the virus (genetic material) into the host causing infection
* virion attaches to a cells receptor then injects the virus into the cell
* virions can only attach to cells where their spikes can fit into the receptor

bacteriophages

viruses that infect bacteria

capsids

a protein shell that protects the virus (genetic material)

enveloped viruses

* surrounded by a lipid bilayer that was obtained from the host cell as it exits the cell; only certain viruses are enveloped
* non-enveloped (naked) viruses are more resistant to disinfectants

spikes

made of proteins that attach to receptor sites on host cells

ssRNA

single stranded RNA

dsRNA

double stranded RNA

ssDNA

single stranded DNA

dsDNA

double stranded DNA

persistent infections

infections that remain and can be either:

* Chronic or Latent

chronic infections

continuous production of low levels of virus particles

latent infections

viral genome remains silent in host cell; can reactivate to cause productive infection

acute infections

* rapid onset; short duration


* burst of virions released from infected host cells
* immune system gradually eliminates virus

reverse transcriptase

evolved enzymes that allow RNA viruses to infect our bodies; makes DNA from RNA

viroids

RNA molecules that are infectious in plants

prions

* are proteinaceous infectious agents, composed solely of protein
* linked to slow, fatal human diseases; animal diseases
* usually transmitted by the consumption of brains
* prion proteins accumulate in neural tissue and give rise to transmissible spongiform encephalopathies (holes in the brains)
* ground beef can carry prions