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Carbohydrates Chapter 15.

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Presentation on theme: "Carbohydrates Chapter 15."— Presentation transcript:

1 Carbohydrates Chapter 15

2 What Are Carbohydrates?
Carbohydrate = an organic compound that is the body’s main source of energy. Made up of two main elements carbon and hydrogen Carbohydrates are found mainly in foods from plant sources, such as fruits, vegetables, grain products, dry beans and peas Carbohydrates consist of simple and complex carbohydrates Simple carbohydrates consist of one or two sugars in very small molecules Complex carbohydrates, which are starches and fiber, are very large molecules

3 How Carbohydrates Form
Carbohydrates are produced by green plants. Using the sun’s energy, plants convert carbon dioxide and water into glucose and oxygen. The carbon dioxide comes from the air, and water is taken up by a plant’s roots, known as photosynthesis. The green pigment for photosynthesis to occur is called chlorophyll. Glucose = basic sugar molecule from which all other carbohydrates are built A plant can convert glucose molecules into other sugars, starches, and fiber. It usually starts by changing glucose into other sugars, these become starches. Green peas from a young plant taste sweeter, than peas from an older one because they are high in simple carbohydrates, or sugar. Peas from an older plant contain a higher level of starch

4 Simple Carbohydrates: Sugars
Simple carbohydrates or sugars, are a natural part of many food. Ex. Pineapple and oranges have a sweet taste Foods with naturally occurring sugars often contain other nutrients too. Sugars can also be extracted from plants and used to sweeten food. The basic sugar molecule is a six-sided ring made of 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms. Hydroxyl group = combination of hydrogen and oxygen, containing one atom of each element. Saccharide = is simply a sugar or a substance made from sugar. (sugars have the following 2 basic molecular structure) Monosaccharide (single sugars) – including glucose, the “building block” of all other sugars – (fructose, galactose – natural sugars found in food) Disaccharides (sugars made up of 2 monosaccharide's bonded together) – include sucrose which is made up of glucose and fructose, lactose – found in milk composed of glucose and galactose, maltose occurs in cereals and sprouting grains

5 Properties of Sugar - Sweetness
Sugars differ in amount of sweetness Fructose is generally found sweetest. Sucrose, glucose, galactose, maltose, and lactose follow in decreasing order of sweetness Honey is an example of a very sweet sugar – when bees make honey, they collect nectar from flowers that contain fructose, glucose and sucrose. An enzyme in their body converts most of the sucrose into fructose and glucose – this makes honey a highly concentrated solution of two of the sweetest sugars. Hot and cold also affects the sweetness of sugar ex. Fructose is generally sweeter in cold foods

6 Properties of Sugar - Caramelization
Caramelization = the browning reaction that can occur with any kind of sugar As sugar is heated, some of the water leaves its molecules in the form of hydrogen and oxygen. The new molecules have a higher concentration of carbon, creating the distinctive caramel color Sucrose, galactose, and glucose all caramelize at 170°C. Fructose on the other hand, caramelizes at 110°C

7 Properties of Sugar – Solubility (ability to dissolve)
Sugars are highly soluble in water Fructose most soluble in water followed by: Sucrose Glucose Glalactose Maltose Lactose Water temperature affects solubility of sugar 25°C the solubility of sucrose is 211g per 100g of water However if you want to dissolve larger quantities of sugar, you need to increase the waters temperature Supersaturated = the solution contains more dissolved solute than it would normally hold at that temperature. ( meaning add sugar to hot water, than cooling the water down, without stirring results in sugar water)

8 Properties of Sugar - Crystallization
Water evaporates, increasing the concentration of sugar in the solvent. When sugar reaches a certain concentration, crystallization occurs Crystallization from a supersaturated solution begins when particles enter the solution (anything even dust) The size of the crystals depends on how many particles are present and how quickly the crystals grow around them

9 Complex Carbohydrates: Starch and Fiber
When people talk about starch and fiber in the diet, they’re speaking of complex carbohydrates Both are found in dry beans, peas and lentils, potatoes, corn, rice pasta and breads. Simple carbohydrates have one or two monosaccharides per molecule Complex carbohydrates, glucose forms compounds called polysaccharides. Polysaccharides is an example of a polymer Polymer = large molecule formed when small molecules of the same kind chain together

10 Structure of Starches Starches are literally plant food, starches are stored in granular form, largely in the seeds and roots A single molecule of starch can include anywhere from 400 to several hundred thousand alpha-D-glucose (form of glucose) Starch molecules can have two structures: Amylose = molecules are linear; they're long and narrow like a line Amylopectin = have multiple branches, like the veins in a leaf

11 Structure of Fiber/Carbohydrates in the Body
The main plant fiber found in food is cellulose, a polymer made of a form of glucose called betaD-glucose Other basic structures of edible fiber include hemicellulose, pectins, and algal polysaccharides

12 Carbohydrates in the Body
55-65% of your daily calories should come from carbohydrates, mostly complex (300g) Glucose is the main carbohydrate found in blood

13 Hydrolysis of Sugars Hydrolysis = splitting of a compound into smaller parts by the addition of water This reaction breaks down carbohydrates until they yield the sugars from which they are formed Hydrolysis of sugars results from the action of enzymes, certain proteins that control chemical activities

14 Blood Glucose Levels The pancreas monitors the flow of glucose to the cells. During digestion, the pancreas secretes the hormone insulin Hormone = a chemical messenger that affects a specific organ or tissue and brings forth a specific response Insulin also helps keep glucose in the blood at a normal level If blood glucose is too high, insulin triggers the liver and muscle cells to remove glucose from the blood and store it as glycogen.


16 Questions How is the term “carbohydrate” related to the nutrient’s composition? How are carbohydrates involved in transferring solar energy to people? Compare monosaccharides and disaccharides, using examples to illustrate. In developing a new recipe, why might you use fructose instead of sucrose? How would a chemist describe a complex carbohydrate? What would happen if carbohydrates in your body were not hydrolyzed.

17 Questions Continued Describe the process that ensures your body a steady flow of glucose. Compare the complications of Type 1 and Type 2 diabetes. What is nutritionally significant about fiber? Suppose you forgot to calibrate your thermometer before making candy. It registers 10°C less than the actual temperature of the syrup. What may result? How do amylose and amylopectin affect thickening? Why do food scientists modify starches for food production?

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