Chem 2C

Proteins

  • Most Abundant organic molecules in the body

  • Composed primarily of carbon, oxygen, hydrogen, and Nitrogen

  • Worker molecules of body:

  • organize and facilitate all Metabolic processes

  • Catalyze chemical reactions

  • used for cell Structures and structural body tissues

  • regulate growth

  • Transport ions and molecules into and out of cells

  • Defend body against invaders

Amino Acids

  • Building blocks of proteins

  • 20 different amino acids 

  • Sequence of amino acids makes each protein unique

  • Defines the protein’s Function

  • Basic structure:

  • central Carbon atom attached to a hydrogen atom

  • Amino group (NH2)

  • Carboxyl group (COOH)

  • side chain = R group

  • Defines each amino acid

  • Amino acids are categorized into four groups based on the “R” group characteristics. 

  • The “R” group can be:

1. neutral and Nonpolar 

2. neutral and Polar 

3. Basic 

4. Acidic

  • Specific combination of amino acids is determined by the cell’s DNA

Peptide - two or more amino acids are linked together

  • dipeptide

  • tripeptide

  • polypeptide

  • protein

  • Formed by Dehydration synthesis

  • Peptide bond

Protein Composition

  • Simple proteins contain only amino acids

  • Conjugated proteins contain amino acids and other organic or inorganic components

  • Prosthetic groups

  • Lipids, carbohydrates, metal ions, phosphate groups

Structure of Proteins

  • Shape of protein molecule directly determines its function

  • Structure often described on four levels

  • Primary structure

  • Sequence and number of _Amino_ Acids that link together to form the peptide chain

Secondary structure

  • Natural Bends of parts of the peptide chain

  • Most common shapes

  • alpha Helix

  • beta-pleated Sheet

  • Held by Hydrogen bonds

Tertiary structure

  • Overall shape of a single molecule

  • Held by:

  • Hydrophobic regions inside

  • Hydrogen bonds 

  • Salt bridges

  • Between acidic and basic amino acids

  • Disulfide bonds

Disulfide bridge (bond):

  • Covalent bond between S of two CYSTEINES

  • Holds single peptide chain in a loop or two peptides together

Peptides with Disulfide Bridges

  • Vasopressin - Antidiuretic hormone - decreases urine formation

  • Oxytocin - causes Uterine contractions

Quaternary structure

  • Two or more protein chains join to form a Macromolecule

Protein Size

  • Proteins:

  • Extremely Large natural polymers

  • Too large to pass through cell Membranes

  • Contained inside the cells where they were formed

  • Can leak out if cell is Damaged by disease or trauma

  • Protein in urine can indicate damaged kidneys

Protein Denaturation

  • Denaturation – protein unfolds, loses its characteristic shape and loses function

  • Can occur because of Hyperthermia

  • Elevated body temp

  • Hydrogen bonds holding protein in tertiary structure Break

  • Some proteins denature at 40°C

  • Death can occur at 41.7°C if maintained for 30 minutes

Protein Function

  • Catalytic proteins - Enzymes

  • Structural proteins - form structural materials other than the inorganic components of the skeleton

  • Storage proteins - store small molecules or ions

  • Ovalbumin – stored form of amino acids used by embryos in bird eggs

  • Casein – storage protein in milk

  • nourishes animals

  • Protective proteins 

  • Antibodies - protect the body from invasion by viruses, bacteria, and other foreign substances

  • Blood Clotting

  • Carried out by thrombin and fibrinogen

  • Regulatory proteins - responsible for hormone regulation of body processes

  • Growth hormone

  • Gastrin

  • Stimulates stomach to secrete acid

  • Glucagon

  • Stimulates Glycogen metabolism in liver

  • Insulin

  • Regulates glucose metabolism

  • Nerve impulse Transmission proteins -receptors of small molecules that pass between gaps separating nerve cells

  • Rhodopsin – in rod cells of the Retina

  • Acetylcholine receptor – impulse transmission in Nerve cells

  • Movement proteins -muscle

  • Actin and Myosin

  • Transport proteins - bind and transport numerous small molecules and ions through the body

  • Serum albumin – transports _fatty_ acids between adipose tissue and other tissues

  • Hemoglobin – carries oxygen from lungs to other body tissues

Types of Proteins

  • Proteins can be classified as:

Fibrous Protein:

  • Used for adding Strength to tissues or cells

  • long, stringy shape

  • water-insoluble

Fibrous Protein Examples

  • Collagen – main protein in connective tissues

  • Fibrin – connective tissue in blood clots

  • Keratin – main protein in hair, hooves, feathers, horns, and outer layer of skin

Globular Protein

  • Highly Chemically active molecule

  • convoluted, changeable shape

  • Water-soluble

  • Examples:

  • hemoglobin, antibodies, protein-based hormones, and enzymes 


REVIEW

  1. What element is found in all proteins that is not found in carbohydrates? Ans is Nitrogen

  2. What is the building block for proteins? Ans is Amino acids

  3. What holds the tertiary structure of a protein together? Ans is Disulfide bonds, Salt bridges between acidic and basic amino acids, Hydrogen bonds, And the Hydrophobic regions inside

  4. Collagen is an example of what type of protein and what is it’s function? Ans is Fibrous shape, and it’s function is structural as it adds strength.

  5. Hemoglobin is an example of what type of protein? Ans is Globular in shape, and its function is that it is a transport (and if you want to be specific it carries oxygen from lungs to other tissues.)

Enzymes

  • Proteins that act as catalysts to Speed up chemical reactions

  • Enzymes are Specific to the reaction they catalyze

  • lock and key properties

  • Substrates = substances enzymes act upon

  • enzyme fits its substrate exactly

  • enzyme is Unaltered at end of reaction

  • Enzymatic reactions are often in a series of reactions

  • Products of one reaction act as substrate for next reaction

Nucleic Acids

  • Composed of carbon, hydrogen, oxygen, nitrogen, and Phosphorus

  • Examples: Able to use the abbreviation on tests :) for all these three

  1. DNA (deoxyribonucleic acid) 

  2. RNA (Ribonucleic acid) 

  3. ATP (adenosine triphosphate)

Nucleotides

  • Molecular building blocks of nucleic acids

  • Five different types with same basic structure:

  • nitrogen base

  • a five-carbon sugar

  • Deocyribose in DNA

  • Ribose in RNA

  • a Phosphate group



  • Found in DNA:

  • Adenine

  • Guanine

  • Cytosine

  • Thymine

  • Found in RNA:

  • Adenine

  • Guanine

  • Cytosine

  • Uracil

DNA

  • Function: stores Genetic information in its sequence

  • DNA structure: _Double_ Helix

  • Alternating sugar and phosphate groups form the sides

    • Sugar_-___Phosphate__ backbone

  • Phosphate of one nucleotide links to sugar of adjacent nucleotide

  • Two strands of nucleotides twisted around in a double helix

  • Strands are connected by Hydrogen bonds between nitrogen bases

  • Adenine can bond only with Thymine

  • Guanine can bond only with Cytosine

  • Base pairing occurs when the two polynucleotide chains are lined up in opposite directions

RNA

  • Consists of only One strand of nucleotides

  • Three types:

  • Ribosomal RNA (rRNA) – large component of ribosomes, the site of protein synthesis

  • Messenger RNA (mRNA) - carries information for polypeptide synthesis from nucleus to ribosomes 

  • Transfer RNA (tRNA) - carries specific amino acids to the ribosome for synthesis of polypeptides

Adenosine Triphosphate (ATP)

  • Energy currency of cells

  • Composed of:

  • Adenine

  • Ribose

  • Three phosphate groups

  • Energy is stored in the phosphate high-energy Bonds of the ATP molecule

  • Energy is Released when phosphate groups are removed

Review

  1. What is the function of an enzyme? Ans is they are catalysts that speed up chemical reactions

  2. What three parts compose a nucleotide? Ans is Nitrogen base, A phosphate group, and a five-carbon sugar