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BIO111: Microbiology > Chapter 7 > Flashcards

Flashcards in Chapter 7 Deck (65):
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Biosynthesis

processes that synthesize and assemble macromolecule subunits, use ATP energy.

1

DNA

Deoxyribonucleic Acid
Deoxyribose sugar
Bases - Adenine, Thymine, Guanine, Cytosine

2

DNA Structure

Double Helix
Sugar-phosphate chains on outside
Complementary base pairing (A-T, G-C) with hydrogen bonds
Two strands run antiparallel

3

Antiparallel strands

One strand of DNA runs one way the other side runs the opposite direction. 5 prime and 3 prime ends

4

RNA structure

Ribonucleic acid
ribose sugar
Bases A,G,C,U
Single strand
Three types: mRNA, tRNA, rRNA

5

DNA replication

DNA is copied in binary fission to give two exact copies of chromosome to the dividing cell

6

What does semiconservative mean in terms of DNA replication

-Only one strand is "conserved" from original
-One strand is the template and the other is the copy

7

New DNA strand is only made from ...

5' to 3'

8

Nucleotides are only added to which end of the DNA strand

3'

9

Starting Replication envolves what two areas

Origin of replication
Replication fork

10

Origin of replication

Specific DNA sequence that is recognized by enzymes as the starting point
-Unwinding of DNA (unzipping) starts here

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Replication fork

where unwinding occurs

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Two different DNA stands

Leading strand and Lagging strand

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Leading strand

the new DNA strand that is made continuously toward the replication fork 5' to 3'

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Lagging Strand

the new DNA strand that is made in pieces AWAY from the replication fork

15

Leading Strand
(process)

1. Helicase unzips DNA
2. Gyrase relaxes twisting of unwinding strands
3. Primase adds RNA primer at origin of replication
4. DNA polymerase adds nucleotides to 3' end of new DNA through complementary base pairing
5. goes in direction of unwinding parent DNA

16

Lagging Strand
(process)

1. Primase starts near the replication fork
2. DNA polymerase adds neucleotides in 5' to 3' direction AWAY from unwinding and replication fork
3. DNA polymerase detaches and goes back to replication fork and a new primer to make a new Okazaki fragment
4. RNA Primers are removed by DNA polymerase
5. Fragments are joined by DNA ligase

17

Lagging strand is formed in pieces called...

Okazaki fragments

18

Prokaryote DNA replication vs Eukaryote

Prokaryote will only have one point of origin, where eukaryotes can have several replication bubbles to speed up the process

19

Protein Synthesis Overview

Transcription - DNA to mRNA
Translation - mRNA to protein using tRNA and ribosomes

20

Transcription Steps
(protein synthesis)

Initiation
Elongation
Termination

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Initiation
(Transcription-Protein)

1. Sigma factor on RNA polymerase recognizes promoter on DNA
2. RNA polymerase binds to promoter
3. RNA polymerase unwinds DNA

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Elongation
(transcription - protein)

RNA nucleotides matched to DNA nucleotides
A to U, T to A, G to C, C to G

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Termination
(transcription - protein)

Terminator on DNA tells RNA polymerase to detach

24

Translation
(protein synthesis)

mRNA to protein using tRNA and ribosomes

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Codon

three mRNA nucleotides "translate to one amino acid"

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Start codon

AUG - Methionine
protein synthesis will always start with this

27

Stop codon

UAA, UAG, UGA
will stop synthesis

28

tRNA

1. Single strand of folded RNA
2. Amino acid attached to one end
3. Anticodon is on other end

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Anticodon

match up to amino acid on the other side (will be the opposite "code" of the amino acid)

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Location of Anticodon and codon

Anticodon is on tRNA
Codon is on mRNA

31

Ribosomes are composed of

proteins and rRNA

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Prokaryote ribosomes

30S + 50S = 70S

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Eukaryote ribosomes

40S + 60S = 80S

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Small unit of ribosomes has ____ binding site(s) for ____

one binding site for mRNA

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large subunit for ribosomes has ____binding site(s) for ____

three binding sites for tRNA

36

How does Erythromycin work

binds to the 50S subunit and inhibits protein synthesis

37

Large subunit binding sites

A site = Amino Acid
P site = polypeptide
E site = exit
Sites are arranged in EPA

38

Translation : 3 steps

Initiation
Elongation
Termination

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Initiation
(Translation)

1. ribosome binds to mRNA at ribosome binding site
2. tRNA will bind to starter codon at P site
3. another tRNA will bond to the next codon at the A site and a polypeptide bond will connect the two amino acids

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Elongation
(Translation)

1. Ribosome moves to next codon
2. Ribosome keeps moving along mRNA in 5' to 3' direction and amino acids added one at a time to make a long polypeptide chain

41

Termination
(translation)

1. Stop codon on mRNA that is not recognized by any tRNA
2. components come apart and polypeptide chain is released

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Which type of cell can transcription and translation happen simultaniously

Prokaryotes

44

Comparing Protein Synthesis

Eukaryote
1. mRNA has introns and special endings
2. Monocisronic
3. mRNA must be transcribed and moved from nucleus to cytoplasm before translation can start
PROKARYOTE
1. mRNA is not processed
2. Polycistronic
3. Transcription can work before translation is finished

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Monocistronic

information for only one gene is found on the mRNA
(Eukarote)

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Polycistronic

mRNA can carry information for more than one gene
(Prokaryote)

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Post-translation modification of proteins

-polypeptide chain folded into inal functional structure with CHAPERONE proteins
- SIGNAL SEQUENCES are added to polypeptides that will be transported to another area of the cell

48

Bacteria gene regulation

-Bacteria will take nurients from environment
-Bacteria can synthesize many nutrients

49

Bacteria will take nutrients from environment....

-turn off genes not needed
- to save energy of biosynthesis
- use energy for cell division

50

Bacteria can synthesize many nutrients...

-turn on genes needed
- slow down cell division

51

Alternative sigma factors

- alternative versions of sigma factors can be made to recognize different promoters
-anti-sigma factors can be made by cell to inhibit sigma factors

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sigma factor

part of RNA polymerase that recognizes specific promoters

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Operon

a set of regularoty genes on DNA

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Operon's function

1. Genes for protein(s)
2. Promoter
3. Operator
4. Activator- binging site

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Promoter
(Operon)

where RNA polymerase starts

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Operator
(operon)

sequence after promoter

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Activator- binding site
(operon)

sequence before promoter

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Repressors - Induction

Repressor protein released from the operator when inducer binds to repressor and transcription can start

59

Stop =
(repressors)

Repressor + operator

60

Go =
(repressors)

Repressor + inducer

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Repressors - Repression

Repressor protein must combine with corepressor to bind to operator and stop transcription

62

Activators

Activator protein can bind to activator-binding site only when combined with an inducer
-then allows RNA polymerase to bind

63

Stop
(activators)

Activator protein alone

64

Go
(activators)

Activator protein + inducer

65

Example

lac operon - codes for proeins involved in lactose degredation and transport in E.coli