Section 6.4 Proteins

Objectives Distinguish among proteins, carbohydrates, lipids and nucleic acids. (SPI ) Distinguish among proteins, carbohydrates, lipids and nucleic acids. (SPI ) List the functions of proteins. List the functions of proteins. Describe the structure of amino acids and proteins. Describe the structure of amino acids and proteins. Describe factors that influence protein shape. Describe factors that influence protein shape. Identify positive tests for carbohydrates, lipids and proteins (SPI ) Identify positive tests for carbohydrates, lipids and proteins (SPI )

Proteins Functions Form cell structures Chemical messengers Enzymes Body defense Regulation Movement & support Monomers amino acids Polymers Polypeptides Proteins

Protein “Prime importance” Found in: Cells (2/3 of dry cell weight ) Tissues All body fluids except urine and bile Not stored for future use (like carbohydrates and lipids)

 Proteins  Major components of: Skin, nails, claws, hair, wool, feathers, hooves, muscles, tendons and cartilage.

 Proteins  Essential Chemicals  Support (keratin/collagen)  Enzymes (specific catalysts)  Transport (channel proteins/hemoglobin)  Defense (antibodies)  Hormones (regulatory - insulin)  Motion (actin/myosin)  Motion (actin/myosin)

Protein Composition Polymers Amino Acid Monomers 20 amino acids in proteins

Amino Acids R C H C NH 2 O OH acid group amino group

Peptide Two or more amino acids bonded together. AA X

Peptide Bond Covalent bond forms between amino acids during dehydration synthesis reaction.

Polypeptides Chains of many amino acids joined by peptide bonds. Proteins may contain more than one polypeptide chain.

Protein Structure Shape determines function. Shape determines function.

Levels of Protein Structure Primary The sequence of amino acids.

 Helix Levels of Protein Structure Secondary

 Pleated Sheet Levels of Protein Structure Secondary

Secondary structures are folded. Levels of Protein Structure Tertiary

Results when two or more polypeptides combine. (Hemoglobin, most enzymes) Levels of Protein Structure Quarternary

Denaturation Of Proteins Loss of normal shape – a physical change. Once a protein loses it normal shape, it cannot perform its usual function.

How Proteins Can Be Denatured Temperature Cooking an egg Albumin congeals Addition of hydrogen or hydroxide ions (large pH changes) Adding acid to milk Causes curdling Vigorous Shaking Making whipped cream Organic Solvents Salts of heavy metals (mercury, silver & lead) Detergents Ultraviolet Radiation

Test for Proteins Reagent - Biuret Positive Violet proteins Pink – peptides (short chains)

Enzymes Extremely Important Type of Proteins

Essential Questions What is an enzyme? What role do enzymes play in organisms?

Objectives Identify how enzymes control chemical reactions in the body (SPI ) Identify how enzymes control chemical reactions in the body (SPI ) Explain how enzymes affect activation energy. Explain how enzymes affect activation energy. Describe how an enzyme’s shape is important to its function. Describe how an enzyme’s shape is important to its function.

Key Terms Activation energy Activation energy Catalyst Catalyst Substrate Substrate Active site Active site

Reactions in Cells are Orderly

What must happen for a chemical reaction to begin?

Chemical bonds must weaken!

What will weaken chemical bonds!

Input energy!

What is this energy called?

Activation Energy

What form of energy is most readily available?

Heat

Why is heat a poor choice for cells?

Can lead to cell death.

What works better?

Use a catalyst.

In biological systems, what are these catalysts called?

Enzymes

How do they work?

They lower activation energy!

Energy of Activation

Activation Energy

Enzyme-Substrate Complexes

Important Enzyme Terms

Enzyme-Substrate Complexes

Degradation Reaction (Hydrolysis for example)

Some enzymes change shape.

What environmental conditions affect enzyme activity? Why? Hint: Remember that enzymes are proteins!

Factors Affecting Enzyme-Catalyzed Reaction Rates Substrate Concentration Enzyme Concentration Temperature (optimum) pH (optimum)

Temperature and Enzyme-Catalyzed Reaction Rates

pH and Enzyme-Catalyzed Reaction Rates

Review How do enzymes affect activation energy? How do enzymes affect activation energy? Describe how an enzyme’s shape is important to its function. Describe how an enzyme’s shape is important to its function.

Review List the functions of proteins. Describe the structure of amino acids and proteins. Describe factors that influence protein shape.