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Unit 1: Nutritional Science. Carbohydrates. Carbohydrates. When you hear the word carbohydrate, what types of food come to your mind? Is it an apple or a banana? How about bread, pasta, or rice? Or perhaps it's the sugary treats you ate as a child.
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Unit 1: Nutritional Science Carbohydrates
Carbohydrates • When you hear the word carbohydrate, what types of food come to your mind? • Is it an apple or a banana? How about bread, pasta, or rice? Or perhaps it's the sugary treats you ate as a child. • The fact that you can immediately associate food with the word carbohydrate is a testament to how important this nutrient is for your cells and for your body.
Carbohydrates: Structure • All carbohydrates are composed of carbon, hydrogen, and oxygen in a 1:2:1 ratio. • The basic unit is called a monosaccharide and includes glucose, fructose, and galactose.
Carbohydrates: Structure • Monosaccharides are classified by the number of carbon atoms they contain. The table below describes the different types of monosaccharides in terms of the number of carbon atoms they contain.
Carbohydrates: Structure • Monosaccharide molecules contain a hydroxyl functional group and either a ketone or an aldehyde, depending on the location of the carbonyl group.
Carbohydrates: Structure • The hexose carbohydrates include glucose, galactose, and fructose. These carbohydrates are the most useful for cells. Hexose molecules all have the same chemical formula (C6H12O6) but their physical arrangement differs. These molecules are isomers. Look at the diagrams below and note the difference.
Disaccharides • Disaccharides are made up of two monosaccharides linked together in a condensation reaction. The types of monosaccharides that link together will determine the type of disaccharide that forms. Sucrose is formed when fructose and glucose unite. Maltose is the result of two glucose molecules joining together.Draw a disaccharide:
Disaccharides • When disaccharides are consumed, cells in the body work to break them apart into their individual components. These reactions are crucial for cell survival because cells can only use glucose for cellular respiration. Cellular respiration is the process that provides the body with energy in the form of ATP.
Disaccharides Use a diagram to show how a disaccharide can be broken apart What is the name of this reaction?
Polysaccharides • Polysaccharides are composed of hundreds of monosaccharides linked together. While monosaccharides represent simple sugars, polysaccharides represent complex sugars. • Polysaccharides can exist as long chains or as a long chain with branches. The shape and linkage determines the physical properties of each polysaccharide. • Some biologically important polysaccharides include cellulose and starch which are found only in plants and glycogen which is found in animals. Starch and glycogen are storage molecules and cellulose provides structural support for plants.
Starch • During the process of photosynthesis, plants produce extra glucose so that it can be stored and used later. The excess glucose molecules are joined together by enzymes to form starch. • Starch is a main staple for human consumption and is found in such things as potatoes, rice, and wheat. Starch is the combination of two polysaccharides, amylose and amylopectin.
Cellulose • Cellulose is also found in plants and is formed by excess glucose molecules. However, cellulose provides structural support rather than nourishment for the plant. • The orientation of the glucose molecules within cellulose creates strong, tough fibers. This strengthens the cell wall of plants and it also provides industrial products such as lumber, paper, and clothing.
Building Blocks Alpha Glucose Beta Glucose *Alpha Glucose is used to create starch
Did you know? • Both starch and cellulose are composed of glucose molecules but humans are only able to use the energy from starch. Humans lack the enzyme needed to break apart the glucose bonds in cellulose and therefore are unable to attain nutrients from cellulose. Cows, rabbits, and some other animals contain intestinal bacteria that produce enzymes that are capable of breaking the linkages in cellulose and therefore are able to use cellulose as a source of energy. • Cellulose does provide an important benefit to humans. The undigested cellulose moves through the digestive system and scratches the walls of the large intestine. This stimulates the intestinal walls to release mucus which lubricates feces and aides in the elimination of wastes.
Glycogen • Glycogen is a polysaccharide that is only found in animal cells and is generated when there is an excess of glucose is in your blood. Glycogen is stored in the liver and in muscle cells and it provides long term energy storage. • Having an energy reserve is essential for athletes competing in strenuous activities like swimming, running, and cycling. Many athletes train their bodies to stockpile glycogen so that the energy reserve is well stocked for use during competitions.
