Section 6.4 Proteins
Objectives Distinguish among proteins, carbohydrates, lipids and nucleic acids. (SPI 3210.1.3) List the functions of proteins. Describe the structure of amino acids and proteins. Describe factors that influence protein shape. Identify positive tests for carbohydrates, lipids and proteins (SPI 3210.1.4)
Proteins Functions Monomers Polymers 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)
20 amino acids in proteins Protein Composition Polymers Amino Acid Monomers 20 amino acids in proteins
Amino Acids R C H C NH2 O OH acid group amino group
Two or more amino acids bonded together. 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.
Shape determines function. Protein Structure Shape determines function.
Levels of Protein Structure Primary The sequence of amino acids.
Levels of Protein Structure Secondary Helix
Levels of Protein Structure Secondary Pleated Sheet
Levels of Protein Structure Tertiary Secondary structures are folded.
Levels of Protein Structure Quarternary Results when two or more polypeptides combine. (Hemoglobin, most enzymes)
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
Pink – peptides (short chains) Test for Proteins Reagent - Biuret Positive Violet proteins Pink – peptides (short chains)
Enzymes Extremely Important Type of Proteins
What role do enzymes play in organisms? Essential Questions What is an enzyme? What role do enzymes play in organisms?
Objectives Identify how enzymes control chemical reactions in the body (SPI 3210.1.5) Explain how enzymes affect activation energy. Describe how an enzyme’s shape is important to its function.
Key Terms Activation energy Catalyst Substrate 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? 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.