Exam 2: Chapter 5, Carbohydrates Flashcards
How are carbohydrates classified?
Be able to identify monosaccharides
Not broken down further during digestion.
- Glucose (most abundant)
- Fructose (found in fruits, vegetables, honey, and high fructose corn syrup)
- Galactose (found most abundantly as a part of lactose, a milk sugar)
- Sugar alcohols (monosaccharide derivatives, these include sorbitol, mannitol, xylitol)
- Pentoses (ribose and deoxyribose, part of our genetic material)
Define and identify disaccharides
Definition: carbohydrates containing 2 monosaccharides that are linked by a condensation reaction
- Maltose: Glucose + Glucose; joined by an alpha bond
- Sucrose (i.e. table sugar): Glucose + Fructose; joined by an alpha bond
- Lactose (primary sugar found in milk): Galactose + Glucose; joined by a beta bond
- Contain 3-10 sugar units
- Raffinose and Stachyose (found in onions, cabbage, etc.)
- Indigestible; pass undigested to large intestine where bacterial fermentation occurs – this produces gas
Oligosaccharides
- Contain many glucose molecules
- Some polysaccharides are digestible like starch and some are indigestible like fiber
- Digestibility is determined by whether the glucose units are linked by alpha or beta bonds
Polysaccharides: Starch, Glycogen, and Fiber
How is fiber classified?
-
Total Fiber=Dietary Fiber + Functional Fiber
- Dietary Fiber is the fiber that occurs naturally in foods
- Functional Fiber is the fiber that is added to food to provide health benefits
-
Soluble Fibers- they dissolve easily in water
- Examples: Pectin, gum, mucilages and some hemicelluloses
-
Insoluble Fibers-do not dissolve easily in water
- Examples: Cellulose, hemicelluloses and lignin
What is starch and what types of starch exist?
Storage form of glucose in plants.
- Amylose: linear straight chain, contains 1 type of alpha bond (called 1-4 bond)
- Amylopectin: highly branched-chain structure, contains two alpha bonds (1-4 and 1-6)
What is glycogen and where is it primarily stored?
The storage form of carbohydrate in humans and other animals, it is highly branched, similar to amylopectin.
- Liver glycogen (90g): can be converted into blood glucose to supply the body with energy
- Muscle glycogen (300g): glucose for muscle use, especially during high-intensity exercise
What is the function of nutritive sweeteners in food?
Metabolized to yield energy and provide sweetness to foods.
- Mono and disaccharides (i.e. lactose, sucrose, maltose)
- High fructose corn syrup
- Sugar alcohols (i.e. sorbitol, mannitol, xylitol)
What is the AMDR for carbohydrates?
45%-65% of total energy needs
What is the RDA for carbohydrates?
130 grams/day of digestible carbohydrate
What is the adequate intake (AI) for fiber?
- 14g/1000kcal is adequate intake
- 25g/d - women under 50 (21g/d after 51)
- 38g/d - men under 50 (30g/d after 51)
Functions of digestible carbohydrates in the body
- Provide energy: 4 kcal/g
- Spare protein
- Body does not utilize gluconeogenesis
- Prevents ketosis
- Incomplete breakdown of fatty acids
Functions of indigestible carbohydrates in our body
- Promote bowel health
- Constipation and hemorrhoids
- Diverticulosis and diverticulitis
- Reduce obesity risk
- Fullness and satiety
- Enhance blood glucose control
- Soluble fibers
- Reduce cholesterol absorption
- Soluble fibers
Trace the path of digestion of carbohydrates: seven organs involved, in order
- Mouth
- Stomach
- Pancreas
- Small Intestine
- Liver
- Large Intestine
- Rectum and Anus
What occurs during each step in the path of digestion?
- Mouth
- Stomach
- Pancreas
- Small Intestine
- Liver
- Large Intestine
- Rectum and Anus
- Mouth: Salivary amylase begins digestion
- Stomach: Salivary amylase is deactivated by acidity of stomach, no further digestion
- Pancreas: pancreatic amylase and dextrinase secreted to small intestine to break polysaccharides from starch into monosaccharides
- Small Intestine: enzymes break down disaccharides, fiber not broken down
- Liver: absorbed monosaccharides are transported to liver by portan vein
- Large Intestine: some soluble fiber is metabolized into acids and gases by bacteria
- Rectum and Anus: insoluble fiber excreted in feces
How are carbohydrates absorbed?
Most absorption occurs in the small intestine.
- Active transport: Glucose and Galactose →Active transport requires a carrier protein + energy (ATP)
- Facilitated diffusion: Fructose→ Requires a carrier protein to move a molecule down a concentration gradient (i.e. from high to low)
How is glucose stored?
In muscle and liver glycogen.
Excess glucose is converted to fat by the liver and stored as adipose tissue.
What is the normal concentration of blood glucose and what is it regulated by?
Normal concentration: 70-100mg/dL
Regulated by the liver
What role does insulin play in regulation of blood glucose?
- Insulin (pancreas)
- Hormone that facilitates transfer of glucose from blood into cells
- Lowers blood glucose
What hormones raise blood sugar?
- Glucagon
- Cortisol
- Epinephrine
- Norepinephrine
- Growth Hormone
What is glycemic index?
- Ratio of the blood glucose response to a given food, compared with a standard
- Influenced by many factors
- Based on a 50g carbohydrate serving
What is glycemic load?
- Amount of carbohydrate in consumed food multiplied by GI and divided by 100
- Better reflects a food’s effect on blood glucose than GI alone
Diabetes mellitus
the leading cause of blindness in the United States and accounts for 44% of all new cases of kidney failure.
- Type 1 Diabetes: Insulin is no longer made in the body.
- Type 2 Diabetes: Insulin is present, but the cells do not respond.
Gestational diabetes
occurs in women during pregnancy. There may be an increased risk of developing type 2 diabetes later in life.
Decription and Treatment of Type 1 Diabetes Mellitus
- Insulin producing cells in pancreas are destroyed (autoimmune disease)
- Insulin therapy required for life
- Diet must be coordinated with insulin
- Exchange system, carbohydrate counting
- Increased risk for cardiovascular disease, blindness and kidney disease
Description and Treatment of Type 2 Diabetes Mellitus
- Progressive disease
- Characterized by insulin resistance
- Insulin production may be low, normal, or high
- Most common type of diabetes (90% of cases)
- Treatment:
- Diet
- Physical activity
- Medications
What happens in Type I and Type II Diabetes?
