PROTEINS

Characteristics of Proteins  Contain carbon, hydrogen, oxygen, nitrogen, and sulfur  Account for more than 50% of dry weight in most cells  Instrumental in everything the organism does  Basic building block is the amino acid  Vary extensively in structure, each type of protein has a unique 3-D shape/

Proteins (Polypeptides)  Amino acids are the monomers, or building blocks of proteins  20 different kinds of Amino Acids used to make proteins  Amino acids are linked together by Condensation reactions to form peptide bonds.  Proteins are also called polypeptides 3

Formation of a Dipeptide Condensation

Amino Acid + Amino Acid --> Dipeptide Amino Acid + Dipeptide --> Tripeptide A.A. + A.A. + …..+ Tripeptide --> Polypeptide

Amino Acid Amine group acts like a base, tends to be positive. Carboxyl group acts like an acid, tends to be negative. “R” group is variable, from 1 atom to 20. Two amino acids join together to form a dipeptide. Adjacent carboxyl and amino groups bond together.

Amino Acids 20 different Amino Acids 3 different types (according to ‘R’ chain) – Nonpolar – Polar – Electrically Charged (acidic & basic) Do not need to know 20 amino acids, but must recognize polar, nonpolar, and charged

Nonpolar Amino Acids Non-polar R side chains Hydrophobic Found in regions of proteins lined to the hydrophobic area of cell membrane Essential in determining specificity of enzymes 8

Nonpolar Amino Acids

Polar Amino Acids Polar R side chains Hydrophilic properties Found in regions of proteins exposed to water (exterior of cell membrane) Create hydrophilic channels through which polar substances can move Essential in determining specificity of enzymes 10

Polar Amino Acids

Charged Amino Acids Acidic – R side chains are negatively charged – Carboxyl group is dissociated in cellular pH levels Basic – R side chains are positively charged – Amine groups are positively charged at cellular pH levels 12

Charged Amino Acids

2 minute convo  How will the different types of amino acids determine the structure of protein molecules? 14

Proteins (Polypeptides) Four levels of protein structure: A.Primary Structure B.Secondary Structure C.Tertiary Structure D.Quaternary Structure Structure of proteins is closely tied with its function. 15

Primary Structure peptide bonds (straight chains) unique to each protein Amino acids bonded together by peptide bonds (straight chains) unique to each protein 16 aa1aa2aa3aa4aa5aa6 Peptide Bonds Amino Acids (aa)

Primary Structure Unique sequence of amino acids Precise primary structure is determined by inherited genetic information (DNA) Amino Acid sequence at primary structure determines the next three levels of structure and thus, the 3-D shape of a protein 17

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Secondary Structure primary structurecoilspleats hydrogen bonds 3-dimensional folding arrangement of a primary structure into coils and pleats held together by hydrogen bonds. Does not involve the use of R-chains Two examples: Two examples: 19 Alpha Helix Beta Pleated Sheet Hydrogen Bonds

Secondary Structure Created by the formation of hydrogen bonds between the amino and carboxyl groups of amino acids. Contributes to overall structure of protein. Two examples: Two examples: 20 Alpha Helix Beta Pleated Sheet Hydrogen Bonds

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Tertiary Structure Secondary structuresbentfolded more complex 3-D arrangement Secondary structures bent and folded into a more complex 3-D arrangement of linked polypeptides. Involves interaction of side chains (R groups) and amino acid backbone. Bonds: H-bonds, ionic, disulfide bridges (S-S) Bonds: H-bonds, ionic, disulfide bridges (S-S) “subunit”. Call a “subunit”.

23 Alpha Helix Beta Pleated Sheet

3-D structure gives proteins their functional properties, such as active sites on enzymes. 24

Quaternary Structure Composed of 2 or more “subunits” Overall protein structure results from combination of subunits Form in Aqueous environments enzymes (hemoglobin) Example: enzymes (hemoglobin) 25 subunits

2 minute convo Discuss how the different levels of protein structure depend on each other 26

Types of Proteins Globular Fibrous

Protein Type Globular – 3-D in shape – Mostly Soluble – Mostly Functional Proteins Hemoglobin (transport) Insulin (regulate blood sugar) Amylase (digests starch) Fibrous – Polypeptide chains in long narrow shape – Mostly insoluble – Structural of Functional Proteins Collagen (connective tissue) Keratin (hair, nails) Actin (muscle contraction 28

2 minute convo  What are 2 types of proteins and examples of each. 29

The specific function of a protein is a property that arises from the architecture of the molecule. 31

Proteins (Polypeptides) Functions of proteins vary extensively because of the number of amino acids (100s-1000s) and the range of possible amino acids (20) in each spot Functions of proteins vary extensively because of the number of amino acids (100s-1000s) and the range of possible amino acids (20) in each spot Six functions of proteins: Six functions of proteins: 1.Storage:albumin (protein)/Ferritin (Iron) 2.Transport: hemoglobin 3.Regulatory:hormones (insulin) 4.Movement:muscles (actin/myosin) 5.Structural:membranes, hair, nails (keratin) 6.Enzymes:cellular reactions (Amylase) 32

Protein Functions Storage – Ferritin stores iron in a protein capsule Transport – Hemoglobin contains iron that transports oxygen throughout the body Regulatory – Insulin is secreted by pancreas and regulates blood glucose levels 33

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Protein Functions Movement – Actin & Myosin cause muscle contractions and movement Enzymatic – Amylase is a digestive enzyme that breaks down starch Structural – Spider silk in webs and Collagen is in connective tissues in animals Immunoglobulins – Antibodies fight bacteria and viruses 35

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2 minute convo What are 6 different functions of proteins and examples of each? 37

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BILL 18.List four functions of proteins, giving an example of each. (Total 4 marks) 39

BILL Markscheme Name of function and named protein must both be correct for the mark. storage – zeatin (in corn seeds) / casein (in milk); transport – hemoglobin / lipoproteins (in blood); hormones – insulin / growth hormone / TSH / FSH / LH; receptors – hormone receptor / neurotransmitter receptor / receptor in chemoreceptor cell; movement – actin / myosin; defence – antibodies / immunoglobin; enzymes – catalase / RuBP carboxylase; structure – collagen / keratin / tubulin / fibroin; electron carriers – cytochromes; pigments – opsin active transport – sodium pumps / calcium pumps; facilitated diffusion – sodium channels / aquaporins; Mark first four functions only. Allow other named examples. 40