Biochemistry Lecture 33 Carbohydrates
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Alpha-Amylase, found in the mouth, begins the digestion of carbohydrates
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Indicates our necessity to make ATP
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Plants can take Sunlight + Carbon Dioxide + Water --> Carbohydrates
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ATP is the most central carbon compound in all living systems
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Central to ATP is the Carbohydrate!
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Alpha-D-Glucose (a monosaccharide)
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Arrangement of OH groups in the Alpha or Beta position is the result of
the direction the carbonyl carbon attacked from. In solution, there's a
50/50 mix of Alpha and Beta. They constantly switch back and forth between
linear and cyclic forms.
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Glucose Metabolism
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Glucose is the major carbohydrate that enters metabolism as described below:
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Glycolysis --> Citric Acid Cycle + O2 --> Electron
Transport Chain
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Sucrose (a Disaccharide)
(Fructose Below)
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Sucrose is easily cleaved by Sucrase, an enzyme to give free up
Glucose.
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It also begins the process of converting Fructose to Glucose
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Sucrose --> Glucose + Fructose (where Fructose --> Glucose)
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This process catalyzed by Sucrose is called the Inversion of Sucrose
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There are 2 other kinds of Disaccharides that produce Glucose
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Maltose and Lactose
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Produces Glucose via the enzyme Alpha Amylase
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Maltose consists of two glucose monomers connected by an Alpha 1,4 bond
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see pages 206 and 207 in the text for references to Maltose
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Lactose
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Lactose produces Glucose via the action of the enzyme Beta Amylase
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Glucose and Galactose monomers connected by Beta 1,4 Bond
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Alpha and Beta Amylase are 2 separate and distinct enzymes
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Humans are defected for Beta Amylase
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Cow stomachs contain bacteria that secrete Beta Amylase
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All herbivores have bacteria that can cleave the Beta 1,4 bond
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See pages 203 through 207 for more details
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Disaccharides can form Polysaccharides
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Glycogen (storage polysaccharide of animal
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Cellulose (primary structural component of plant cell walls)
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Differences Between Glycogen and Cellulose (or Starch)
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1. Alpha 1,4 Bond vs Beta 1,4 Bond
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2. Starch has more crosslinks or Alpha 1,6 bonds
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Plants are rigid because of these extra crosslinks. We cannot digest them,
but plants do also contain regular free sugars that we can digest.