BSCI331 Exam 2 Study

mRNAs

messenger RNAs, code for proteins

rRNAs

ribosomal RNAs. form the basic structure of the ribosome and catalyze protein sythesis

tRNAs

transfer RNAs central to protein synthesis as ada[tprs between mRNA and amino acids

snRNAs

small nuclear RNAs, function in a vareity of nuclear processes, including the splicing pre-MRNA

Protein Domain

A region of the protein that folds essentially independently of other regions

Irreversible Inhibitors

Covalently bind to an amin o acid reside and usually lower vmax by inactivating and removing active enzyme molecules

Rare in nature but not in industry

Aspirin is an irreverisible inhibitor of the enzymes cox-1 and cox-2 by acetylating the serine in the active site

Competitive inhibitor

Reversibly bind to active site and compete with substrate can be displaced b.High [S]

Increases Km - lower affinity, but does not reduce VMAX

Noncompetitive inhibitor

Reversibly bind away from actve site to cause change in enzyme structure that ;pwers ctaalytic efficiency

Lowers Vmax and does NOT increase Km. Do not affect substrate binding

KM And VMAX for inhibitors

Irreversible Inhibitor - Lowers VMAX usually

Competitive Inhibitor - Increases KM, VMAX stays same

Non Competitive - Vmax goes down, KM does not increase

What is VMAX?

Vmax is the rate where the enzyme is saturated with the substrate

What is KM?

Km is the Michaelis constant and is equal to the approximate equal to the dissociation constant for enzyme substrate complex

Three ways that enzymes stabilize the the transition state

1) Enzymes binds to two substrate molecules and orient them precisely to encourage a reaction to occur between them

2) Binding of substrate to enzyme rearranges electron sin the substrate creating partial negative and positive charges that favor a reaction

3) Enzymes strain the the bound substrate, forcing the transition state to favor a reaction

What do Multi enzyme complexes do?

They make the reaction more faster and more efficieint. KEY: It prevents the difussion of the product from one enzyme to the next or it faciliattes the product of one enzyme interacting as the subtrate for the next enzyme

Exceptions to the central dogma (DNA → RNA → protein)

Retroviruses which have an RNA genome but take their RNA and reverse transcribe to DNA and that DNA is then inserted into the host cell genome and replicated with the cell.
(RNA to DNA to RNA to Protein )

Cellular biological Exceptions

1) Telomeres -> Telomere is created by copying RNA molecule to DNA (DNA —→ RNA ——> DNA ). Telomere is example of reverse transcripttase. It DEFINATELY violates the Central DOgma. But there is no information content in the sequence of the Telomere.

“Jumping genes” → Number of classes of transposons -

• Retrotransposons —→ Structure gets transcribed into RNA intermediate which gets reverse transcribe into DNA. Within the reverse transposon there is a gene for reverse transcriptase (Gene → >RNA translated to a protein —> Protein and reverse transcribed into → DNA)

Gene gets transcribe into RNA that RNA can be translated to a protein, and that protein reverse transcribes that RNA into RNA

(DNA —→ RNA —→ DNA ) Life cycle of HIV

A lot of viruses don’t violate the central dogma but certain Retroviruses like HIV violate the central dogma. Since viruses are not cells. they rely on ells for replication can not indepdemyt;u/ Ebery gene in vriuses, arises from cellular gene. So reverse transcriptase in retroviruses provbably arises from tertro transposons or telomerase

Prions don’t violate the central dogma. They do not go backwards.

How do antibiotics inhibit eukaryotic cells?

Antibiotics entire purpose is to prevent protein synthesis or what we call translation and teh reason why is because without proteins the bacteria cannot thrive and grow and so antibitics want to intervene here and the reason why it doesn’t target humans and only prokaruotic is becuaase our ribosomal subunits are 80s vs their 70s and the only stipulation is that the mitochondria is derived from teh endoysmbiotic theory so they may also be affected.