Proteins

Proteins Proteins are polymers made of monomers called amino acids All proteins are made of 20 different amino acids linked in different orders Proteins are used to build cells, act as hormones & enzymes, and do much of the work in a cell

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Structure of Amino Acids group Carboxyl group Amino acids have a central carbon with 4 things boded to it: R group Amino group –NH2 Carboxyl group -COOH Side groups Hydrogen -H Variable group -R Serine-hydrophillic Leucine -hydrophobic

20 Amino Acid Monomers-these are the R groups

Linking Amino Acids Cells link amino acids together to make proteins Carboxyl Cells link amino acids together to make proteins Amino R Group The process is called dehydration synthesis Dehydration Synthesis Peptide bonds form to hold the amino acids together Peptide Bond

Proteins (Polypeptides) Four levels of protein structure: A. Primary Structure B. Secondary Structure C. Tertiary Structure D. Quaternary Structure

Protein Structures or CONFORMATIONS Hydrogen bond Pleated sheet Polypeptide (single subunit) Amino acid (a) Primary structure Hydrogen bond Alpha helix (b) Secondary structure (c) Tertiary structure (d) Quaternary structure

Primary Structure Amino acids bonded together by peptide bonds (straight chains) aa1 aa2 aa3 aa4 aa5 aa6 Peptide Bonds Amino Acids (aa)

Primary Protein Structure The primary structure is the specific sequence of amino acids in a protein Called polypeptide Amino Acid

Protein Structures Secondary protein structures occur when protein chains coil or fold When protein chains called polypeptides join together, the tertiary structure forms because R groups interact with each other In the watery environment of a cell, proteins become globular in their quaternary structure

Secondary Structure 3-dimensional folding arrangement of a primary structure into coils and pleats held together by hydrogen bonds. Two examples: Alpha Helix Beta Pleated Sheet Hydrogen Bonds

Tertiary Structure Secondary structures bent and folded into a more complex 3-D arrangement of linked polypeptides Bonds: H-bonds, ionic, disulfide bridges (S-S) Call a “subunit”. Alpha Helix Beta Pleated Sheet

Quaternary Structure Composed of 2 or more “subunits” Globular in shape Form in Aqueous environments Example: enzymes (hemoglobin) subunits

Changing Amino Acid Sequence Substitution of one amino acid for another in hemoglobin causes sickle-cell disease 7. . . 146 2 1 3 6 4 5 (a) Normal red blood cell Normal hemoglobin 2 7. . . 146 1 3 6 4 5 (b) Sickled red blood cell Sickle-cell hemoglobin

Other Important Proteins Blood sugar level is controlled by a protein called insulin Insulin causes the liver to uptake and store excess sugar as Glycogen The cell membrane also contains proteins Receptor proteins help cells recognize other cells

Cell membrane with proteins & phospholipids INSULIN Cell membrane with proteins & phospholipids

Nucleic Acids

Nucleic acids Nucleic acids are composed of long chains of nucleotides linked by dehydration synthesis. Function: Dictate amino acid sequences/how proteins are made Source of all genetic information Two types: a. Deoxyribonucleic acid (DNA) b. Ribonucleic acid (RNA)

Nucleotide-monomer/building block of nucleic acid O=P-O Phosphate Group s N Nitrogenous base (A, G, C, or T) CH2 O C1 C4 C3 C2 5 Sugar (deoxyribose)

Another look at a Nucleotide – Nucleic acid monomer

Nucleic Acids Nucleic acids are polymers of nucleotides Nucleotide Nitrogenous base (A,G,C, or T) Nucleic acids are polymers of nucleotides Phosphate group Thymine (T) Sugar (deoxyribose) Phosphate Base Sugar Nucleotide

Nucleic acids Nucleotides include: phosphate group pentose sugar (5-carbon) nitrogen bases: adenine (A) thymine (T) DNA only uracil (U) RNA only cytosine (C) guanine (G)

Bases Each DNA nucleotide has one of the following bases: Adenine (A) Thymine (T) Cytosine (C) Adenine (A) Guanine (G) Thymine (T) Cytosine (C) Adenine (A) Guanine (G)

DNA Two strands of DNA join together to form a double helix Base pair

DNA - double helix P O 1 2 3 4 5 P O 1 2 3 4 5 G C T A

RNA – Ribonucleic Acid Ribose sugar has an extra –OH or hydroxyl group Nitrogenous base (A,G,C, or U) Uracil Phosphate group It has the base uracil (U) instead of thymine (T) Sugar (ribose)

ATP – Cellular Energy ATP is used by cells for energy Adenosine triphosphate Made of a nucleotide with 3 phosphate groups

The Chemistry of Life Organic Compounds Lab

Indicator A substance used to show the presence of another substance Color change = positive test (the substance is present)

Distilled Water Use it as a control – to make sure the indicators are working. No color change with water = indicators are working

Lipid Test Sudan III stain – red is a positive test Brown paper bag – Lipids leave translucent spots (grease spots)

Carbohydrate Test Starch – Iodine- blue/black is a positive test Sugar – Benedict’s solution – **MUST BE HEATED!!!!* blue/green changes to orange/yellow = positive test

Protein Test Biuret reagent - varying shades of purple = positive test