Protein Structure, Digestion,

Human hemoglobin has four subunits, tretramer.

Protein kinase is also a tetramer.

• Lipoproteins
• Glycoproteins: IgG
• Phosphoproteins
• Hemoproteins: Hemoglobin
• Flavoproteins: Flavin nucleotides
• Metalloproteins: Iron, Ca, Copper

• -First must go through enterocytes (cells that line the small intestine) at the brush border, which line the small intestine lumen.
• - Need to be coupled with Sodium, NA to enter into the cell, with the help of a "carrier", "transporter".
• -The carrier is called a symport because it transports the AA simultanously with the NA.
• - Sodium potassium pump is necessary to pump the "excess" sodium back OUT of the cell.

Dipeptides and tripeptides must be co-transported with a "proton" (hydrogen)

Once in the cytosol of the cell, they are catabolized into amino acids.

The excess H protons are transported out with a Sodium, Hydrogen antiport.

Some of the amino acids that were broken down from the di and tripeptides need to be co-transported out with sodium through a facilitated carrier.

There is a Sodium/Potassium pump on the enterocyte's basolateral membrane to bring potassium in and sodium out.

• Globular - water soluble
• - spherical
• - Complex interactions between secondary and tertiary structural elements

• 1) Enzymes (kinase), biological catalyst
• 2) Hormones (insulin), regulate biological processes
• 3)Transport (albumin), carry molecules in plasma
• 4) Storage (ferratin) store and protect

Fibrous proteins are animal structural materials and water insoluble.

Unique structures obtained by combining special amino acids into regular, secondary structural elements.

• 1) Collagens
• 2) Keratins
• 3) Elastins

Collagen is the MOST ABUNDANT protein in the body.

Forms connective tissue: bones, tendons, ligaments, cartilage.

Keratin makes up protective tissue, such as skin, hair, nails.

Elastin can be found in:

• - Aorta
• - Large arteries
• - Ligamentum flavum

• Triple helix, about 1000 amino acids long
• Most abundant protein
• Glycine makes 1/3 of collagen
• Very strong hydrogen bonding between polypeptide chains because of small size of glycine, increases hydrogen bond strength

Type 1: Has tensile strength

• - Skin
• - Bone
• - Ligaments
• - Tendons

Type II: Resists compression

• - Cartilage
• - Intervertebral disk

Blood vessel walls

Found in the basement membrane of cells.

Collagen is formed by fibroblasts and secreted into the extracellular matrix

• Glycine-Proline- a) hydroxyproline
• b) hydroxylysine

( a and b are Derived Amino Acids ONLY found in collagen)

• Prolyl hydroxylase
• Lyso hydroxylase

(hydroxylase is enzyme that helps to form the bond between the OH group and proline)

Need ascorbate acid, Vitamin C, to hydroxylate prolyl

• Scurvy: deficiency of ascorbic acid, vitamin C
• Tensile strength of collagen fibers can't connect, "cross link" as well due to lack of hydrogen bonding

• -Sore spongy gums
• - Loose teeth
• - Fragile blood vessels
• - Bruises
• - Anemia