104 lines
5.4 KiB
Markdown
104 lines
5.4 KiB
Markdown
- Carbohydrates are a class of nutrients that is a major source of energy for the body
|
|
- Can also server as a glue that holds cells together
|
|
- Classified as simple or complex
|
|
- Plants are rich sources of carbohydrates
|
|
There are 3 categories of carbs.
|
|
|
|
# Sugars
|
|
- A **monosaccharide** is a simple sugar that is the basic molecule of carbohydrates:
|
|
- Glucose: Primary fuel for muscles, nerves, and other cells, the most common.
|
|
- Fructose: In **fruits**, honey, and certain vegetables
|
|
- Galactose: Component of lactose
|
|
- A **disaccharide** is a simple sugar comprised of two monosaccharides.
|
|
- Maltose: Disaccharide composed of two glucose molecules "malt sugar"
|
|
- Sucrose: Disaccharide composed of a glucose and fructose molecule "table sugar"
|
|
- Lactose: Disaccharide composed of a glucose and a galactose molecule "milk sugar"
|
|
|
|
- High fructose corn syrup is a syrup obtained from the processing of corn
|
|
- No conclusive evidence that the use of HFCS causes poor health and disease
|
|
- Excessive calories from beverages sweetened with HFCS contributes to increased risk for diabetes and heart disease
|
|
- Nutritive sweeteners are substances that sweeten and contribute energy to foods
|
|
- Each gram of mono or disaccharide supplies 4 kcal
|
|
- Added sugars are sugars added to foods during processing or prep
|
|
- The main source of added sugars in the American diet is sugar sweetened beverages.
|
|
- Alternative sweeteners are substances that sweeten foods while providing few or no calories
|
|
- Sugar alcohols are alternative sweeteners use to replace sucrose in some some sugar free foods:
|
|
- Sorbitol, xylitol, mannitol
|
|
- Not fully absorbed by the intestinal tract
|
|
- Supply 2kcal/g
|
|
- Can cause diarrhea when consumed
|
|
- Non-nutritive sweeteners are a group of synthetic compounds that are intensely sweet tasting compared to sugar
|
|
- Examples include Aspertame, Saccharin, Acesulfame-K, Neotame, and Sucralose
|
|
|
|
- Glycogen = storage form of glucose
|
|
- A highly branched storage polysaccharide in animals
|
|
- Muscles and liver are major storage sites
|
|
# Starches
|
|
Complex carbs have 3 or more monosaccharides bonded together
|
|
- Starch is a storage polysaccharide in plants.
|
|
- Composed of amylose and amylopectin
|
|
- Rich sources include:
|
|
- Bread and cereal products made from wheat, rice, barley, and oats
|
|
|
|
# Fiber
|
|
- Plants also use complex carbohydrates to make supportive and protective structures
|
|
- Dietary fiber is non-digestible plant material
|
|
- Most types are polysaccharides
|
|
- Soluble fiber
|
|
- Forms of dietary fiber that dissolve or swell in water. includes pectins, gums, mucilages, and some hemicelluloses
|
|
- Delays stomach emptying, slows glucose absorption and lowers blood cholesterol
|
|
- Insoluble fiber
|
|
- Forms of dietary fiber that generally do not dissolve in water: Includes cellulose, hemicelluloses, and lignin
|
|
- Helps with bowel movements and fecal bulk
|
|
# Consumption
|
|
- In developing nations, diets supply 70% or more of energy from unprocessed carbs
|
|
- In industrialized nations, people tend to eat more highly refined starches and added sugars
|
|
- Americans consume about 30% of energy from added sugars (600 kcal/day)
|
|
- Regular soft drinks and energy drinks are major sources of added sugars in Americans' diets
|
|
- According to the dietary guidelines, people should limit their added sugar to
|
|
|
|
# Digestion
|
|
- Salivary amylase is an enzyme secreted by salivary glands that begins work in the mouth, stops working soon after food enters the stomach
|
|
- The small intestine is the main site for carbohydrate digestion and absorption
|
|
- Pancreatic amylase
|
|
- Enzyme secreted by the pancreas that breaks down starch into maltose molecules
|
|
- Maltase
|
|
- Enzyme that splits maltose molecules
|
|
- Sucrase
|
|
- Enzyme that splits sucrose molecules
|
|
- Lactase
|
|
- Enzyme that splits lactose molecules
|
|
- Only monosaccharides are absorbed
|
|
1. Dietary carbohydrates from stomach are delivered to small intestine
|
|
2. Glucose and other monosaccharides are transported to liver
|
|
3. Blood levels of glucose maintained for brain and other body cells
|
|
4. Glucose transported to muscle
|
|
- Fructose and galactose are converted to **glucose** in the liver.
|
|
- Absorption of monosaccharides mainly occurs in the small intestine
|
|
- Galactose and glucose are absorbed by active transport
|
|
- Fructose is absorbed by facilitated diffusion
|
|
- Monosaccharides enter the capillary network
|
|
- Transported to the lever by the hepatic portal vein
|
|
- Simple sugars are:
|
|
- Made into glycogen or fat by the liver
|
|
- Released into bloodstream for energy use
|
|
- Fiber is not digested
|
|
- Eventually enters large intestine
|
|
- Bacteria ferment soluble fiber (producing gas)
|
|
- Used for energy
|
|
- Insoluble fiber contributes to softer fees
|
|
- Any fiber Present in food would delay rate at which chyme enters from the stomach
|
|
- Promotes satiety
|
|
- Refined grain products are generally low in fiber
|
|
# Glucose
|
|
- Insulin is the hormone secreted from the beta cells of the pancreas that helps regulate blood glucose levels by helping glucose enter cells
|
|
- Released when blood glucose levels are **HIGH**
|
|
- Glucagon is a hormone secreted from the alpha cells of the pancreas that helps regulate blood glucose levels
|
|
- Released when blood glucose levels are **LOW**
|
|
- Glyconeogenisis: Creates glucose
|
|
- Glycogenolysis: Glycogen stores are broken down
|
|
|
|
- Cells need glucose to properly metabolize fat
|
|
- When not enough glucose is available, ketone bodies form
|
|
- Chemicals formed from the incomplete breakdown of fat
|
|
- Ketosis is a condition in which ketone bodies accumulate in blood; can result in loss of.... |