Microbiology #B1

Definition of a Polymer

• Made up of repeating, similar parts

• Built by cells

Examples of a Polymer

• Polysaccharides

• Nucleic Acids

• Proteins

Definition of a Monomer

A single part of the chain/polymer

Examples of a Monomer

• Monosaccharides (sugars)

• Nucleotides

• Amino Acids

Why are fats not considered polymers?

They are not constructed from long chains of repeating, identical monomer units.

What macromolecules are good for energy storage?

Sugars and fats

What are sugar polymers made of?

Glucose/Monosaccharides

Two Glucose

Maltose/Disaccharide

More than two glucose

Glycogen/Polysaccharide

Why are sugar polymers good for storage?

• Compact, easier to store

• Relatively easy to break down and catabolize

Why are sugar polymers good for structure?

• Cell Wall: Peptidoglycan, Cellulose, Chitin

• Lipopolysaccharides, Glycocalyx

What are fatty acids made of?

• Triglycerides

• C/H, no oxygen

• Hydrophobic

Why are fatty acids good for storage?

• More dense than starch

What is a con for using fatty acids for storage?

They take longer to get energy out, so most bacteria don’t bother using fats for storage.

Why are fatty acids food for structure?

Useful for making up cell membranes

Central Dogma of Biology

DNA → RNA → Protein

Role of DNA in the city analogy

City hall library with plans

Role of RNA in the city analogy

Copies of the master instructions, are sent out into the city to accomplish NOW, are only half-good machines

Role of proteins in the city analogy

The workers/machines that perform the plans

Types of Nucleotides

• Adenine 

• Thymine

• Cytosine

• Guanine

What type of bond do nucleotides have?

Hydrogen

Rules of base pairing

• Adenine to Thymine

• Cytosine to Guanine

“Deoxyribose” in DNA

Sugar

What type of helix is DNA?

Double helix

What is the process in which DNA is built?

DNA replication

What is the backbone of the DNA helix made of?

Sugars and phosphates

What part of the backbone are base pairs attached to?

Deoxyribose sugar

What are DNA polymers built by? // What enzyme executes DNA replication?

DNA polymerase

What is semi-conservative replication?

When DNA splits into two strands, creating two new strands composed of one original and one complementary strand.

How many times does DNA replication occur per cell division?

Once, copying the entire chromosome

Difference between Prokaryotic and Eukaryotic origin of replication

Prokaryotic: One origin of replication on round chromosome

Eukaryotic: Many origins of replication across linear chromosomes

What is an origin of replication?

Specific DNA sequences where the process of DNA duplication begins

Difference between base pairs of DNA/RNA

RNA has uracil (U) instead of thymine (T)

What is ribose in RNA?

Sugar

What process created RNA?

Transcription

What enzyme executes transcription?

RNA polymerase

What are the three parts of a protein?

Amino group, side group, carboxyl group

Proteins are polymers of?

Amino acids

What are the involved structures in the Central Dogma of Biology?

DNA Polymerase, RNA Polymerase, Ribosomes

What is “Gene Expression"“?

How genetics are translated through the process of the Central Dogma of Biology.

What happens in translation?

Ribosomes translate RNA to synthesize proteins

How many different amino acid “letters” are there?

20

What is a codon?

Strings of nucleotides that indicate specific amino acids

How many different types of codons are there?

64

What is the “Genetic Code”?

The set of rules by which information is encoded in genetic material is translated into proteins by living cells

Codon for “Start”

“AUG”

Codons for “STOP”

“UAA”, “UGA”, “UAG”

Which direction do ribosomes run?

5’3’

Why are bacteria much faster at replicating?

They can transcribe and translate at the same time

What is a mutation?

A change to the base sequence of DNA

Why might a genetic mutation occur?

Spontaneously or caused by mutagens (radiation/chemicals)

What are the effects of a genetic mutation?

It depends on how important the gene is AND how different the change is.

What is a substitution?

• Change to one base

• Can lead to Silent Mutation and Nonsense Mutation

Silent Mutation

• Caused by substitution

• When there is a base change, but no amino acid change

• Therefore, no change in protein function

Nonsense Mutation

• Caused by substitution

• Amino acid is changed to a STOP codon

What is an insertion/deletion?

• Add or subtract one or more bases

• Can lead to Frameshift Mutation or In-Frame Deletion

Frameshift Mutation

Mutation affects the downstream of amino acids

In-Frame Deletion

Amino acid gone, downstream unaffected

What happens if you have too many mutations?

You can’t pass hereditary information down well enough

What happens if you have too little mutations?

Your offspring can’t adapt to the environment well enough

What is a “Mutation Rate”?

How often mutations occur

What is a “mutagen”?

• Any chemical/physical treatment that increases mutation rate

• Ex. Ionizing radiation, UV light, chemical mutagens

• Chemical mutagens also affect risk of developing carcinogens

The Ames’ Test

• Determines if chemical is a mutagen

• Positive result: Chemical is a mutagen in bacteria, cannot conclude if is carcinogen

• Negative result: Cannot conclude it isn’t a carcinogen

• Uses rat liver enzymes to mimic human body

What is a reversion mutation?

A genetic change that restores a gene’s function after an initial forward mutation

What is “Vertical Gene Transfer”?

The transfer of genes to offspring

What is “Horizontal Gene Transfer”?

• Only for bacteria

• Transfer genes to other members of the population

• Involves a donor and recipient cell

• Part OR all of DNA is transferred

• Most of the time, DNA becomes permanent part of the recipient

Who discovered the concept of transformation?

Frederick Griffith with virulent and avirulent Streptococcus pneumoniae in attempt to make a vaccine

How does transformation work?

Cells die, DNA bleeds into environment, alive cells take up naked DNA

Competent bacteria

• Only few are naturally competent: Bacillus, Neisseria, Streptococcus

• However, almost all bacteria can be MADE competent

What does conjugation require?

• Needs direct contact

• Donor (F+) carries a plasmid F factor (fertility factor) that allows conjugation with a recipient (F-)

• F factor carries genes to build pilus and perform conjugation

What happens in conjugation?

• Bacteria makes copy of plasmid

• Sends to recipient through sex pilus

• Best occurs between members of same species, can sometimes occur between different

What is transduction?

• Bacteriophage: Virus that infects bacteria, protein shell delivers piece of DNA

• Replicate genome inside bacteria, chop up bacterial DNA to be safe

• Sometimes accidentally take up bacteria’s DNA and transfer to other bacteria

• Generally requires the donor to be dead (killed by virus)

• Can be from distance, no exposed DNA in environment

What are plasmids?

• Non essential, round genes

• No longer than 5-10,000 base pairs long

• Have own origin of replication

• Cause different bacterial strains to act differently

Dissimilation Plasmids

• Carry genes for dealing with unusual metabolic needs

• Ex. Petroleum can be used for deep waters

Virulence factors in Plasmids

• Can carry genes with toxins or defense mechanisms

Resistance Factors (R factors)

• Can carry genes that confer resistance to antibiotics

Resistance transfer factors (RTF)

• Includes conjugation and resistance genes