Exam 2 - Nutrition Flashcards
Carbohydrates
- consumed in diet as sugar, starch, and fiber
- plants are main source
- glucose is a universal energy source for cells, and especially preferred by red blood cells and neurons
Monosaccharides
- have generic formula C6H12O6
Disacchardies
two monosaccharides linked by covalent bonds
Polysaccharides
many glucose molecules linked together
Glucose
- most abundant monosaccharides
- linked together with other sugars in our diets
- blood sugar
Disaccharide are:
- maltose, sucrose, and lactose
- 2 monosaccharides linked together in a condensation reaction
- humans have low levels of enzymes capable of hydrolyzing beta bonds
Fructose
found in fruits, vegetables, honey, and high-fructose corn syrup
C-O-C alpha bonds form
maltose and sucrose
C-O-C beta bond forms
lactose
maltose
- glucose-glucose
- found in seeds and alcoholic beverages
sucrose
- glucose-fructose
- table sugar
- sugarcane, sugar beets, maple tree sap
lactose
- glucose-galactose
- milk and milk products
Oligosaccharides
- 3 to 10 sugar units
- raffinose and stachyose
Raffinose and stachyose
- plant sources such as broccoli and beans
- contain beta bonds that humans can’t break
- metabolized by bacteria in large intestine, which produce gas
Polysaccharides
- complex carbohydrates with more than ten sugar units
- starch: amylose, amylopectin
- glycogen
- fiber: indigestible polysaccharides
Starch
amylose and amylopectin
amylose
unbranched chain of glucose molecules linked by 1-4 alpha bonds
Amylopectin
- more branches, more sites for enzyme action
- faster increase in blood glucose levels
- branches are formed by 1-6 alpha bonds
Dietary Fiber
- a family of carbohydrates that are linked by beta bonds
- cannot be broken by human enzymes
- bacteria convert some components of fiber into fatty acids which can be used by cells of large intestine
Soluble fibers
- dissolve in water
- found inside and around plant cells
- pectins, gums, mucilages, and some hemicelluloses
- oat bran, fruits, legumes, and psyllium
- inside part of fruits and veggies
Insoluble fibers
- do not dissolve in water
- form strucutral parts of the plant cell
- cellulose, hemicellulose, ligins
- seeds and whole grains
Carbohydrates in foods
starch: much of carbohydrates in our diets, from plant based foods: legumes, tubers, grains
fibers: found in many of the same foods as starch, but processing often decreases fiber content
Net carbs or impact carbs
- calculated by people on low carbohydrate diets and occasionally advertised on low-carb food products
- Not FDA regulated
- Subtract fiber and sugar alcohol from total carbohydrates, since these have less effect on blood glucose
Which form of fiber is associated with decreased blood cholesterol levels?
Soluble