SM

Module #2

Eukaryotic Features

  • A network of internal membranes → the endomembrane system

Includes

  1. Nuclear envelope

    1. defines boundary of the nucleus and contains an inner and outer membrane with nuclear pores

Proteins

Functions of proteins

  1. At as enzymes →

  2. Aid in support

  3. Support → cytoskeleton within the cell or proteins

  4. Defense -) antibodies, complement proteins

Amino Acid Structure

Proteins consist of amino acids that are covalently linked into linear polymers → a.k.a. polypeptides (protein = polypeptide)

Amino Acid Structure

  • central (alpha - a) carbon is covalently linked to four groups

    1. Carboxyl (-COOH)

    2. Amino (-NH2)

    3. Hydrogen (H)

    4. R group (side chain)

      1. Each amino acid has a unique R group

Joining Amino Acids

At physiological pH (7.4) the carboxly group and amino groups are ionized → amino acids have both positive and negative charges

  • A zwitterion

Amino acid are joined by a covalent bond

  • peptide bond

peptide bond!

When peptide bonds, form the carboxyl group releases an oxygen atom, and the nitrogen loses loses two hydrogen atoms to produce a water molecule

20 genetically encoded amino acid monomers (see module 5) → the order provides information carried out by the protein

Sometimes two or more polypeptide chains must combine to form a mature protein

Nucleic Acids

General Info

Nucleic Acids are information molecules → encode genetic info in the sequence of nucleotides

Two types of nucleic acids

  1. Deoxyribonucleic acids → DNA

    • The genetic material in all cellular organisms

    • Contains information used to direct protein synthesis

  2. Ribonucleic acid → RNA

    • Multiple functions → key player in protein synthesis & regulation of gene expression

Nucleotides

DNA and RNA are polymers of nucleotides, which are composed of:

  1. A nitrogen containing base that is one of two types

    • Pyrimidine base that contains a single ring → cytosine (C), thymine (T), and uracil (U)

      • prymidines CUT

    • Purine base that contains a double ring → adenine (A) and guanine (G)

      • Pure As Gold

  2. A 5-carbon (pentose) sugar

    1. In DNA → deoxyribose

    2. in RNA → ribose

  3. One of more phosphate group

Nitrogenous Bases

DNA uses the bases

  • A, T, C, G

RNA uses the bases

  • A, U, C, G

Order of the nitrogenous bases determines the information carried in DNA & RNA molecules

Structure

A nucleoside has just a base and a sugar

Functions

  1. Are the monomers of DNA & RNA

  2. Important signal molecules within cells → example cyclic adenosine monophospate (cyclic AMP or cAMP)

  3. Transfer of energy in metabolism → cleave off terminal phosphate group to release stored energy

  4. Act

Connection Nucleotides

  • Covalent linkage betweenthe phosphate group of one nucleotide to the sugar unit 3’-OH on another → forms a phosphodiester bond

    • Formation releases a water molecule

  • Formation of the bond also establishes directionality/polarity of the strand

  • Beginning of the chain → 5’ end

  • New nucleotides can be added to the → 3’ end

  • Always 5’→ 3’ (IMPORTANT)

DNA

DNA consists of two strands of nucleotides twistde around each other to form a double helix

Sugar-phosphate backbone wraps around the outside → antiparallel arrangement

Complementary bases face inwards with H-bonds forming between bases

Complementary Base Pairing:

A-T

C-G

Purine-Pyrimidine

It is beneficial for one strand to create H-Bonds with their complementary strand because it allows DNA to “unzip” down the middle

  • Hydrogen bonds are weak bonds (individually)

Carbohydrates

Carbohydrates (sugars) are made up of C, H, O atoms

  • Usally in a ration of 1:2:1 (CH2O)

Serve as a major source of energy for metabolism, but also serve as structural molecules → e.g. cellulose in plants

Most come in 5 or 6 carbon sugars

6-Carbon Sugars

All 6-carbon sugars have the same chemical formula: C6H12O6

Differ in configuration → are isomers so they are funtionally differnt from one another

Simple sugars → monosaccharides

  • mono = 1

Cyclic Monosaccharides

In cells, virutally all monosaccaharides are in cyclic form

The cyclic structure forms when one of the linear molecule binds to another

Linking Sugars

The covalent linkage between monosaccharides → glycosidic bond

  • Formation of these bonds results in the release of a water molecule

  • Forms between C1 of one monosaccharide and -OH group on the carbon of a different monosaccharide

Covalently linking two monosaccharides → forms a disaccharide (di = “two”)

  • e.g. sucrose (C12H22O11)

A few monosaccharides joining → forms oligosaccharides (oligo = “dew”)

  • Can be attached to:

    • Proteins forming → glycoproteins

    • Lipids forming → glycolipids

  • More than two monosaccharide monomers

Lipids

Lipids are a chemically diverse group of molecule → it is the only macromolecule that is not a polymer

They are all grouped together because they share the same physical property → hydrophobic

Cells use different lipids in the following ways:

Triacylglycerol

Major component of animal fat and vegetabe oil

Made up ofL

  1. Three fatty acids → a type of lipid made up of a long chain of carbons attached to a carboxyl group (-COOH) at one end

    • Has carbon-carbon double bonds = unsaturated

Steroids

Steroids are composed of many carbon atoms bonded to characteristic four fused rings

Hydrophobic

Cholesterol is a component of animal cell membranes

Phospholipids

A major component of cell membranes

Made up of:

  1. Glycerol backbone attached to a polar phosphate group → hydrophilic

  2. Two fatty acid tails which are nonpolar → hydrophobic

Molecules with both hydrophilic& hydrophobic regions are called amphipathic (KEY)