Chapter 19.docx - 1 Chapter 19 notes Chapter 19 Biochemistry Biochemistry The study of the chemical substances and processes that occur in plants

Chapter 19.docx - 1 Chapter 19 notes Chapter 19...

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1 Chapter 19 notes Chapter 19 Biochemistry Biochemistry The study of the chemical substances and processes that occur in plants, animals, and microorganisms is biochemistry. The Cell and its Main Chemical Components The cell is the smallest structural unit of living organisms. The main chemical components of the cell can be divided into four classes: carbohydrates, lipids, proteins, and nucleic acids. Carbohydrates Carbohydrates are the primary molecules used for short-term energy storage in living organisms. Carbohydrates are comprised of carbon and water. Structurally the carbohydrates are aldehydes and ketones that contain multiple –OH groups. Glucose, with the formula C 6 H 12 O 6 , is an aldehyde with –OH groups on most of the carbon atoms. The presents of so many –OH groups make glucose soluble in water and in blood. This is fortunate because glucose is the fuel source for cells. Glucose is soluble in both the blood stream and the aqueous interior of the cell. Monosaccharides Glucose (yes, it’s called blood sugar) is a great example of a monosaccharide , a carbohydrate that cannot be broken down into simpler carbohydrates. Monosaccharides are all simple sugars that have an unbranched chain of three to six carbon atoms, with one carbon in a carbonyl group and the rest attached to hydroxyl groups. In an aldose , the carbonyl group is on the first carbon as an aldehyde (-CHO); a ketose contains the carbonyl group on the second carbon atom as a ketone (C= O).
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2 Chapter 19 notes A monosaccharide with three carbon atoms is a triose , one with four carbons is a tetrose , a pentose has five carbons, and a hexose contains six carbon atoms. Thus, an aldohexose is a five carbon monosaccharide that is an aldehyde; a ketopentose is a five carbon monosaccharide that is a ketone. Examples: Cyclic Structures of Monosaccharides The monosaccharides have been shown as open chains; however, these molecules normally exist as cyclic structures (rings). For example, in glucose, a ring of six atoms forms when the –OH group on carbon 5 (C5) reacts with the carbonyl group (C=O) on carbon 1 (C1).
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3 Chapter 19 notes Position of the carbonyl group affects the size of the ring. Look at fructose; a ketohexose found in fruits and vegetables (fruit sugar) and galactose; an aldohexose found commonly within the brain and nervous system of most animals (brain sugar). Disaccharides A disaccharide is composed of two monosaccharides linked together. The two monosaccharides can react, eliminating water to form a carbon-oxygen-carbon bond called a glycosidic linkage that connects the two rings. See the following example:
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4 Chapter 19 notes Polysaccharides A polysaccharide is a polymer of many monosaccharides joined together. Monosaccharides and disaccharides are known as simple sugars and simple carbohydrates .
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