Function : Main structural component of membranes, where they arrange in bilayers.
Phospholipids in Water
Lipids that serve as coatings for plant parts and as animal coverings.
Structure : Four carbon rings with no fatty acid tails
Component of animal cell membranes (Ex: Cholesterol)
Modified to form sex hormones
What are Proteins?
Chains of amino acid monomers connected by peptide bonds
Have a 3 dimensional globular shape
Examples of Protein Functions
Binding of antibodies (proteins) to foreign substances
Membrane transport proteins that move substances across cell membranes
Hemoglobin carries oxygen, iron, and other substances through the body.
actin and myosin fibers that interact in muscle tissue.
Hormones such as insulin regulate sugar levels in blood.
Monomers of polypeptides
Molecules with carboxyl and amino groups
Differ in their properties due to differing side chains, called R groups
20 different amino acids exist The sequence of amino acids and the interactions of the different amino acids determine a proteins shape
Peptide bonds connect amino acids to form polypeptide chains
One or more polypeptide chains make up a protein
Proteins are very complex! Their specific structure determines their function. HEMOGLOBIN: Transport of gases and iron in blood ACTIN: Filament involved in muscle contraction
Four Levels of Protein Structure
Is the unique sequence of amino acids in a polypeptide
Figure 5.20 – Amino acid subunits + H 3 N Amino end o Carboxyl end o c Gly Pro Thr Gly Thr Gly Glu Seu Lys Cys Pro Leu Met Val Lys Val Leu Asp Ala Val Arg Gly Ser Pro Ala Gly lle Ser Pro Phe His Glu His Ala Glu Val Val Phe Thr Ala Asn Asp Ser Gly Pro Arg Arg Tyr Thr lle Ala Ala Leu Leu Ser Pro Tyr Ser Tyr Ser Thr Thr Ala Val Val Thr Asn Pro Lys Glu Thr Lys Ser Tyr Trp Lys Ala Leu Glu Lle Asp
Is the folding or coiling of the polypeptide into a repeating configuration resulting from hydrogen bonding of amino with carboxyl groups
Includes the α helix and the β pleated sheet
O C α helix β pleated sheet Amino acid subunits N C H C O C N H C O H R C N H C O H C R N H H R C O R C H N H C O H N C O R C H N H H C R C O C O C N H H R C C O N H H C R C O N H R C H C O N H H C R C O N H R C H C O N H H C R C O N H H C R N H O O C N C R C H O C H R N H O C R C H N H O C H C R N H C C N R H O C H C R N H O C R C H H C R N H C O C N H R C H C O N H C H H Figure 5.20
Is the overall three-dimensional shape of a polypeptide
Results from interactions between amino acids and R groups
CH 2 CH O H O C HO CH 2 CH 2 NH 3 + C - O CH 2 O CH 2 S S CH 2 CH CH 3 CH 3 H 3 C H 3 C Hydrophobic interactions and van der Waals interactions Polypeptide backbone Hydrogen bond Ionic bond CH 2 Disulfide bridge
Is the overall protein structure that results from the aggregation of two or more polypeptide subunits
Are protein molecules that assist in the proper folding of other proteins
Hollow cylinder Cap Chaperonin (fully assembled) Steps of Chaperonin Action: An unfolded poly- peptide enters the cylinder from one end. The cap attaches, causing the cylinder to change shape in such a way that it creates a hydrophilic environment for the folding of the polypeptide. The cap comes off, and the properly folded protein is released. Correctly folded protein Polypeptide 2 1 3 Figure 5.23
Sickle Cell Disease: A simple change in Primary Structure
Are a type of protein that acts as a catalyst, speeding up chemical reactions up to 10 billion times faster than they would spontaneously occur.
Environmental Factors That Determine Protein Conformation
Change in environment may lead to denaturation of protein (pH, temperature, salinity, etc.)
Denatured protein is biologically inactive
Can renature if primary structure is not lost
D. Nucleic Acids : The stuff of Genes
Nucleic acids store and transmit hereditary information
Are the units of inheritance
Program the amino acid sequence of polypeptides
Are made of nucleic acids
Two Kinds of Nucleic Acids
DNA ( Deoxyribonucleic acid)
can self replicate
makes up genes which code for proteins is passed from one generation to another
RNA ( Ribonucleic acid)
functions in actual synthesis of proteins coded for by DNA
is made from the DNA template molecule
1. Nucleotide Monomer Structure
Both DNA and RNA are composed of nucleotide monomers.
Nucleotide = 5 carbon sugar, phosphate, and nitrogenous base
Deoxyribose in DNA Ribose in RNA
2. Building the Polymer
Phosphate group of one nucleotide forms strong covalent bond with the #3 carbon of the sugar of the other nucleotide.
2 polynucleotide chains wound into the double helix