In your Biology textbook Proteins and Enzymes In your Biology textbook Proteins: Pages 57 -65 Enzymes: Pages 143 - 150

DNA transcription mRNA translation Polypeptide(Protein)

Proteins Protein: Extremely complex substances that consist of amino-acid residues joined by peptide bonds, contain the elements carbon, hydrogen, nitrogen, oxygen, usually sulfur, and occasionally other elements (as phosphorus or iron), and include many essential biological compounds (as enzymes, hormones, or antibodies)

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Proteins Four levels of protein structure Primary structure - the basic order of amino acids in the polypeptide protein chain, before any folding or bonding between amino acids has occured. Proteins are usually not functional on the primary level, and all proteins have a primary structure.

Secondary structure - the repeated, regular structure protein chains take due to hydrogen bonding between amino acids. The secondary structure is usually in one of two forms: alpha helix (similar to a DNA chromosome) beta-pleated sheet (similar in form to the corrugations of cardboard).

tertiary structure - complex, three-dimensional protein shape resulting from the folding of the polypeptide due to different types of bonds between the amino acids hydrogen bonds disulphide linkages (between two sulfur containing amino acids) ionic bonds (between the negative and positive molecules of amino acid groups)

Tertiary Protein Structure

Hemoglobin is an example of quartenary structure quaternary structure - one or more peptide chains bonded together This is the functional form of many proteins, but again, just as not all proteins have secondary or tertiary structure, not all proteins have a quaternary structure. Hemoglobin is an example of quartenary structure Hemoglobin

Fibrous vs. Globular Proteins Fibrous proteins are in their secondary structure, which could be in the alpha helix or beta pleated forms made of a repeated sequence of amino acids that can be coiled tightly around in a pattern that makes it a very strong structure Structural proteins

Mostly insoluble in water Two examples are keratin (in hair and skin) and collagen (in tendons, cartilage, and bones)

Globular Proteins are in their tertiary or quaternary structure, which is folded, creating a globular, three-dimensional shape Used mostly for metabolic process Soluble in water Examples include enzymes and hemoglobin

Polar vs. Non-Polar proteins Non-polar amino acids have non-polar (neutrally charged) R chains while polar amino acids have R chains with polar groups (charged either positive or negative)

Proteins with a lot of polar amino acids are hydrophyllic and therefore able to dissolve in water Proteins with many non-polar amino acids are more hydrophobic and are less soluble in water Proteins fold themselves so that the hydrophilic amino acids are on the outside and hydrophobic amino acids are on the inside

protein folding allows hydrophilic molecules and ions to pass in and out of the cells through the channels they form

Six functions/types of proteins: #1 Transport - An example is hemoglobin, which transports oxygen around the body within a blood cell #2 Support and structure – Actin and myosin are examples of muscle proteins but there is protein in skin and bone as well. Collagen, Spider silk #3 Enzymes (catalyzation of cellular reactions)– examples include amylase and trypsin and Rubisco

#4 Hormones (celllular communication) - examples include insulin and estrogen #5 Antibodies (fight disease) – produced by b-cells (type of white blood cell) immunoglobulins #6 Storage – Iron is stored in the liver as part of a complex with the protein ferritin

Proteome The proteome is the entire set of proteins expressed by a genome, cell, tissue or organism at a certain time. More specifically, it is the set of expressed proteins in a given type of cell or organism, at a given time, under defined conditions. Every individual has a unique proteome.

Enzymes Preview Enzyme activity

Enzymes act as a catalyst to increase the rate of biochemical reactions by lowering the activation energy needed to start the chemical reaction.

Enzymes and Active Sites Enzymes: globular proteins that have a very specific 3-dimensional shape help to catalyze chemical reactions without being used up in the reaction themselves Active site: site on the surface of the enzyme to which the substrate binds and where the reaction is catalyzed

How Enzymes Work Enzyme-Substrate Specificity Substrates are the molecules in the reaction that are being changed (the reactants) Active site will fit only one specific substrate “lock and key” model: the substrate is the “key” that fits in the active site “lock” How Enzymes Work

Factors that affect enzymatic activity Temperature Reaction rates catalyzed by enzymes have an upper limit of temperature they are effective at eventually the enzyme starts to loose its shape and is no longer effective (denatured)

pH Enzyme active sites usually contain areas of positive or negative charge. excess H+ (acid) or OH- (base) can interfere with substrate binding OR change the shape of the enzyme (denature) enzymes have an optimal pH

Substrate concentration Increasing substrate concentration will increase the rate of a reaction because the more substrate there is, the more product that can be formed Eventually the reaction rate will stabilize because all of the active sites of all of the enzymes are occupied Adding more substrate after this point will not affect the reaction rate unless more enzyme is added

Affect of Changing Substrate Concentration on Reaction Rate Enzyme Saturation Point Reaction Rate Substrate Concentration

Denaturation: When an enzyme loses its shape, including the shape of the active site. can be permanent (especially if the peptide bonds are broken) but is sometimes only temporary caused by change in pH or temperature

Lactase Humans are born with ability to digest lactose because they produce an enzyme called lactase breaks down the disaccharide lactose into monosaccharides Most people lose the ability to make lactase as they age undigested lactose is consumed by bacteria in intestines, causing symptoms of lactose intolerance Milk products can be treated with lactase before consumption so the lactose is predigested for people who are lactose intolerant

Immobilized Enzymes Enzymes that are attached to an inert, insoluble material such as calcium alginate (form a bead). It also allows enzymes to be held in place throughout the reaction, following which they are easily separated from the products and may be used again - a far more efficient process  Immobilized enzymes are widely used in industry because it allows the reaction to flow continuously and the product will not be contaminated with the enzyme so will not need to be purified.