Protein Structure and Function I

Proteins Come in All Shapes and Sizes

30 to __ amino acids long. __ or fibrous. Form filaments, __, rings and spheres

10,000 : Globular : sheets

Proteins are assembled from a combination of __ amino acids. Amino acids are joined by __ peptide bonds, which are formed through dehydration reactions. Proteins can therefore be referred to as __

20 : covalent : polypeptides

Proteins have a __ backbone. All amino acids have a common base with a __ terminus (COOH) and an __ terminus (NH2). Amino acids differ by their side chains, or ‘__’

polypeptide : carboxyl : amino : R groups

Notice that each peptide chain also has an __ and __ terminus. Three types of non-covalent bonds help from the 3-D shape of proteins: __ bonds, __ attraction (based on __), and Van der Waals

amino : carboxyl : Hydrogen : Electrostatic : charge

The side chains of the amino acids (__ groups) participate in these bonds. Although each are weak, many of these bonds together are relatively strong

R

__ (polar) and __(non-polar) amino acids also determine the structure of the protein

Hydrophilic : hydrophobic

Proteins in polar environments (e.g. __) tend to have __ side groups on the exterior of the protein (with non-polar group amino acids in the interior). Proteins in non-polar environments (e.g.__) tend to have __ groups on the exterior of the protein (with polar amino acids in the interior)

cytoplasm : polar : lipid bilayer : non-polar

Proteins fold into specific 3-D shapes based on their __ sequences. Based on their amino acid sequence, proteins tend to form 3-D structures where the __ energy is minimized (i.e. the most energetically stable configuration)

amino acid : free

Minor changes to protein shape are possible, depending on the two factors (both are key to a protein’s functions): The protein’s __ or the __ that the protein interacts with

environment : molecule(s)

Catalyze __ bond breakage or formation

-ATP-synthase: Synthesizes adenosine triphosphate (ATP) from adenosine diphosphate (ADP)

covalent

Provides __ support to cells and tissue

-Collagen: This protein is the main component of connective tissue and the most abundant protein in mammals

mechanical

Generates __ in cells and tissues

-Myosin: Large superfamily of motor proteins that move along actin filaments

movement

__ small molecules or ions

-Hemoglobin: Iron-containing oxygen-transport protein in the red blood cells of vertebrae

Carries

__ small molecules (amino acids) or ions

-Casein: Source of amino acids for growing organisms found in high amounts in cow milk

Stores

Transmits __ from cell to cell

-Insulin: Hormone that regulates energy and glucose metabolism in the body

signals

Regulates __ by binding to DNA

-NF-kB: protein complex that controls the transcription of DNA in animal cells and plays role in regulating the response to infection

genes

__ and transmits signals

-Rhodopsin: Responsible for the first events in the perception of light

Detects