Microbiology: Molecules of Life

What is a carbohydrate?

Composed of individual sugar subunits called monosaccarides

Polar Molecule

Functions of Carbohydrates

• Energy Source

• Energy storage

• Source of precursor metabolites

• Cellular structures

What is a Disaccharide?

• Two monosoccharides linked together

• Lactose: glucose and galactose

What is condensation synthesis?

Removing a water molecule to link two monosaccharides

What is a biological polymer?

• Polymer = polysaccharaide

• Chain of individual subunits linked by glycosidic bonds

What is a lipid and its function?

• Any non-polar molecule is insoluble in water

• Energy storage and a membrane component

• Polar head and non-polar tail = amphipathic

What is a saturated fatty acid?

made from single covalent bonds

What is an unsaturated fatty acid?

• has one double bond (mono)

• C and H share electrons equally = less electronegative

What is a phospholipid?

• Phosphate containing a polar head group (hydrophilic) with a triglyceride

• Non-polar tail group (hydrophobic)

• No O2

Why are the phospholipids in a bilayer oriented with the fatty acid side chains in the interior?

The hydrophilic head is polar and interacts with water because of the more oxygens

The hydrophobic tail has no oxygens which makes it non-polar and it does not react well with water

What is a protien?

• Composed of subunits called amino acids (20 different ones)

• Has to have the right amino acid sequence and structure

• 50% of dry weight of cells and a huge variety of proteins in cells

Functions of Proteins?

• Catalyzing reactions

• Structure

• Movement

• Acquisition of nutrients

• Gene regulation

• Transport across membranes

Structure of a Protein

Amino group: Positively charged at a neutral pH

Central carbon with a hydrogen attached

Side chain: “R” gives aminos specific properties

Carboxyl group: negatively charged at a neutral pH

What is protein synthesis?

Carboxy terminus of one amino acid is joined with amino terminus of another forming a peptide bond.

Amino + Amino ——→ remove h2o (dehydration synthesis) = dipeptides, tripeptides, and poly peptides

Between what groups does a peptide bond form?

A peptide bond forms between the carboxyl group (-COOH) of one amino acid and the amino group (-NH2) of another amino acid.

What is the primary structure of a protein?

Linear sequence of AA in peptide

Secondary structure of a protien

Structural arrangements along a polypeptide chain

• alpha helix or a beta pleated sheet due to weak bonds

Can a single polypeptide have more than one type of secondary structure?

• As a single polypeptide chain grows and folds, different segments form different shapes.

• One region of the exact same chain might coil into an alpha helix.

• Another region further down the very same chain might fold into a beta sheet.

Tertiary structure of a protein

3-D structure, how the polypeptide folds

• One polypeptide

Quaternary structure of a protein

Structure of a protein composed of several polypeptides

Protein denaturation

• protein loses its function

• heat, pH, salt can disrupt hydrogen bonds

• Reverses each structure but cannot renature.

What is DNA and its function

Deoxyribonucleic acid: double stranded in living organisms (double helix)

Composed of deoxyribonucleotides and stores genetic information

What is RNA and its function?

Ribonucleic acid: usually single stranded in living organisms

Composed of ribonucleotides and has many functions

• mRNA, tRNA, rRNA (primary), siRNA, miRNA (gene reg.)

Nucleotide structure

• Sugar (DNA/RNA)

• 1-3 phosphates

• Nitrogenous base

Sugars in a nucleotide

ribose (OH group on carbon 2)

deoxyribose (H group on carbon 2)

Where are the phosphate groups located on the sugars?

carbon 5

Bases in DNA

Adenine, Thymine, Guanine, Cytosine

Bases in RNA

Adenine, Uracil, Guanine, Cytosine

What are Purines?

Double ring

• Adenine and Guanine

What are Pyrimidines?

Single ring

• Thymine, Uracil, Cytosine

What does Dehydration synthesis do?

adds a nucleotide triphosphate on the 3’ end of a nucleic acid polymer

How are nucleotides within a polymer joined together

Covalent bonds called phosphodiester bonds

What groups are used in the formation of a Phosphodiester bond?

• 3'-hydroxyl group (-OH): Located on the ribose or deoxyribose of one nucleotide.

• 5'-phosphate group (-PO4}): Attached to the 5' carbon of the pentose sugar on the adjacent incoming nucleotide

What is meant by the 5’ end of a nucleic acid polymer?

The termination point of a nucleic acid strand that finishes with a phosphate group attached to the 5’ carbon of the sugar molecule.

What is meant by the 3’ end of a nucleic acid polymer?

The termination point of a nucleic acid strand that finishes with a hydroxyl group attached to the 3’ carbon of the sugar molecule.

What is the structure of a double stranded DNA molecule?

Double helix

What bases undergo complementary pairing?

Guanine and Cytosine

Adenine and Thymine

How many hydrogen bonds are associated with each base pair?

Guanine and Cytosine: 3 H bonds

Adenine and Thymine: 2 H bonds

What is the orientation of the strands of DNA in a double stranded molecule?

Antiparallel

• Left strand: 5’-3’

  • top to bottom

• Complementary strand: 5’-3’

  • bottom to top