Monday Notes

Lecture

Found a site w/ good pictures http://www.chemistar.com/Biology/organicmolecules.html

Lipids

General Functions:

  • Provide energy (9 cal/gram compared to carbs & proteints at 4cal/gram)
  • Provide structure (ex. cell membranes)
  • Some are hormones. (ex. estrogen, testosterone)

Contain C, H, O

Sources – Fats, oils, waxes, phospholipids (part of cell membranes), steroids.

Fats  are a subgroup of Triglycerides – a typical triglyceride molecule is found in oils (plants) & fats (animals).

ex.      1 glycerol + 3 fatty acids = 1 triglyceride (ester bond- connects glycerol to fatty acids)

Subgroups of Lipids…

Fats:

Saturated: maximum # of Hydrogen attached to each carbon. (no double bonds between Carbon atoms)

Monounsaturated: has only one double bond in the chain. Therefore, fewer Hydrogens & a kink in the chain. (Oleic Acid)

Polyunsaturated:2 + double bonds in the chain. Also, has less Hydrogen & more kinks in the chain. (Linoleic Acid)

Phospholipids:

1 glycerol + 2 fatty acids + 1 phosphate group + 1 organic functional group = phospholipid

Phosphate groups – Interacts with water; because the phosphate head is polar.

Fatty acid ‘legs’ – Non-polar, do not interact with water and align themselves together to be protected from the water while exposing the phosphate groups to the water.

Steroids:

  • Contain 4 fused rings
  • Include cholesterol  (found in cell membranes of animals)

Proteins

General Functions:

  1. Structural
  2. Involved in cell communications (ex. hormones)
  3. Catalysts for chemical RXNs (enzymes)

Contains C, H, N, O (S)

Protein Monomers: Amino Acids – Single amino acids contains a central carbon, carboxyl group(COOH), amino group (NH2) & side group (R-group).

  • R-group: Glutamine; Serine

Polypeptides (Polymers): 2+ amino acids linked together.

  • Peptide Bonds- Protein covalent bonds
  • DNA provides the instructions to make (LARGE CHAINS) proteins; they are made inside the cell linking one amino acid to another.
  • Each protein has a unique combination of amino acids
  • 20 different types of amino acids formed in living things.

Levels of Protein Structure:

  1. Primary – The specific order of amino acids in a polypeptide chain.
  2. Secondary – Hydrogen bonds form between the carboxyl groups & amino groups. This stage forms β -pleated sheets & α-helices throughout the polypeptides.
  3. Tertiary – Additional bonding occurs involving R-groups to make simpe proteins (one peptide chain) functional.
  4. Quaternary – Additional bonding occurs between more than one polypeptide chain to make functional protein (complex)

Ex. of importance of primary structure:

  • Prion that causes Scrapie (sheep) : Alanine is substituted for valine and #136 resulting in a mis-fold of proteins. 
  • Sickle Cell Disease (humans): Valine gets substituted for glutamate @ # 6  in hemoglobin. Valine does not interact well w/ water causing it to crystalize and form a deformed cell.

Protein Denaturation – The loss of tertiary or quaternary structure, resulting in a loss of function. Causes are high heat, alcohol, some metals and/or acids.

Extra Credit: Smith Lemli Opitz Syndrome – an autosomal recessive metabolic and developmental congenital disorder that causes the inability to correctly produce or synthesize cholesterol due to a low occurrence of the 7-DHC reductase enzyme.

Only a few of the symptoms:

  • Small head size (microcephaly)
  • Mental retardation
  • Learning disabilities and behavioral problems
  • Malformations of the heart, lungs, kidneys, gastrointestinal tract, and genitalia
  • Hypocholesterolemia
  • Paleness
  • Low muscle tone (hypotonia)

 Lab

Gram Stain

Q: Is my bacteria gram positive or gram negative?

A: Use a gram stain… Thanks to Hans Gram in 1884 we have a differential stain technique that distinguishes cells based on content of cell walls

Purple colored cells = gram positive

  • Gram Positive Cells – have thick peptidoglycan (multiple layers) that contains teichoic acid

Pink colored cells = gram negative

  • Gram Negative Cells – Thin peptidoglycan (few layers) with outer membrane that contains lipopolysaccharides (toxic to mammalian cells)

KOH Test

Can be used to identify Gram-Positive vs. Gram-Negative cells. Potassium Hydroxide causes Gram – Negative cells to lyse (busrt), releasing a viscous liquid. (It will be ‘snotty-like’) Gram-positive cells do not lyse when mixed with KOH, so the liquid remains thin/non-viscous.

Acid Fast Stain

Q: Does the unknown bacteria have mycolic acid (was like substance) in its cell walls?

A: Use an acid fast stain.

Note: Mycolic acid is only found in gram positive cells, but not all gram positive cells have mycolic acid.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s