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Enzymes Lab 7. Enzymes  Enzymes – proteins that are the catalysts used by cells to initiate chemical reactions.  Cells can regulate which reactions.

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Presentation on theme: "Enzymes Lab 7. Enzymes  Enzymes – proteins that are the catalysts used by cells to initiate chemical reactions.  Cells can regulate which reactions."— Presentation transcript:

1 Enzymes Lab 7

2 Enzymes  Enzymes – proteins that are the catalysts used by cells to initiate chemical reactions.  Cells can regulate which reactions occur and how quickly by regulating which enzymes are present.

3 Enzymes  An enzyme works by binding to a specific molecule and stressing the bonds of that molecule to make the reaction more likely.  Shape of the enzyme is key.  An enzyme is specific for a particular reactant.

4 Enzymes  Active site – place on enzyme where reactant fits.  Binding site – place on reactant where it binds to enzyme.

5 Enzymes  An enzyme lowers the activation energy of a particular reaction.  It may encourage the breaking of a particular chemical bond in the reactant. 3 Catalyzed reaction Course of reaction Energy is released. Activation energy Uncatalyzed Catalyzed Product Reactant

6 Enzymes  Or, an enzyme may encourage the formation of a link between 2 reactants holding them near each other.

7 Regulating Enzymes  Enzymes must have a precise shape to work properly.  Cells can control when an enzyme is active by altering its shape.

8 Calories for Energy  Carbohydrates are used for energy.  Fats are used to construct cell membranes & other cell structures, to insulate nervous tissue, and to provide energy. Fat-soluble vitamins that are essential for proper health are also absorbed with fats.  Proteins are used as building materials for cell structures, enzymes, hemoglobin, hormones, and muscle & bone tissue.

9 Digestion  Chemical digestion breaks down larger food particles of polysaccharides, fats, & proteins into smaller subunits: Monosaccharides Fatty acids Amino acids

10 Amylase  In the mouth, food is mixed with saliva. It moistens & lubricates the food. Saliva contains amylase, an enzyme that breaks down starch.

11 Pepsin  Gastric glands have 2 kinds of secretory cells: Parietal cells secrete HCl. Chief cells secrete pepsinogen.  Pepsinogen is a weak protease (protein-digesting enzyme) that only works at very low pH, which is supplied by the HCl.  Activated pepsinogen molecules become pepsin which is a stronger protease.

12 Lipase  Liver – secretes bile which consists of bile pigments and bile salts which are delivered to the duodenum during digestion. Bile salts work like a detergent to disperse fats into tiny droplets in a process called emulsification, resulting in a greater surface area for the enzyme lipase to break fats down into fatty acids.

13 Digestion  Large molecules are broken down into small molecules as digestion is completed. Acid from the stomach gets neutralized. Digestion is completed.  Carbohydrates sugars  Proteins amino acids  Fats fatty acids Small molecules pass through the epithelial layer and are absorbed into the bloodstream.


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