Carbohydrates Overview

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Questions and Answers

What is the basic building block of carbohydrates?

Polysaccharide

Oligosaccharide

Monosaccharide (correct)

Disaccharide

Which carbohydrate is commonly known as 'table sugar'?

Fructose

Maltose

Sucrose (correct)

Lactose

What type of carbohydrate is starch classified as?

Simple carbohydrate

Monosaccharide

Oligosaccharide

Complex carbohydrate (correct)

Which of the following is NOT a monosaccharide?

Lactose Signup and view all the answers

What are oligosaccharides primarily known for?

Being short carbohydrate chains of 3 to 10 monosaccharides Signup and view all the answers

What is one of the functions of soluble fiber?

Delay glucose absorption Signup and view all the answers

What is the primary role of the endocrine system in relation to blood glucose?

Regulating blood glucose levels Signup and view all the answers

Which type of fiber helps minimize the risk of Type II Diabetes?

Soluble fiber Signup and view all the answers

What can excessive fiber intake potentially lead to?

Intestinal discomfort Signup and view all the answers

Which of the following foods is a source of insoluble fiber?

Carrots Signup and view all the answers

What type of bonds are found in starch and are responsible for linking monosaccharides?

Alpha bonds Signup and view all the answers

Which statement correctly describes glycogen?

It has highly branched chains of glucose units. Signup and view all the answers

What is a characteristic feature of dietary fiber?

It includes non-digestible carbohydrates intrinsic to plants. Signup and view all the answers

In which location in the digestive system is salivary amylase active?

Mouth Signup and view all the answers

Which monosaccharide is absorbed by facilitated diffusion in the small intestine?

Fructose Signup and view all the answers

What is the main product of the digestion of resistant starches and fibers by bacteria in the large intestine?

Short chain fatty acids Signup and view all the answers

Which of the following symptoms is commonly associated with lactose intolerance?

Bloating Signup and view all the answers

How much glucose intake is typically required to spare body protein from being broken down?

50 to 100 grams Signup and view all the answers

Which food option is a good source of dietary calcium for individuals who might avoid milk products?

Canned fish with bones Signup and view all the answers

What is the primary function of carbohydrates in the body?

Providing energy Signup and view all the answers

Which of the following is NOT a consequence of low lactase activity?

Cow's milk allergy Signup and view all the answers

Why is adequate carbohydrate intake important for fat metabolism?

It prevents ketosis Signup and view all the answers

What is a rich source of vitamin D recommended for individuals not consuming dairy?

Fortified margarine Signup and view all the answers

What is the main purpose of using sugar alcohols in food?

To provide energy without causing caries Signup and view all the answers

What daily value of carbohydrates is typically suggested for a 2000 kcal diet?

300 g per day Signup and view all the answers

Which sweetener is known to be 600 times sweeter than table sugar?

Sucralose Signup and view all the answers

Which of the following is a recommended dietary approach to reduce the risk of caries formation?

Limit between meal snacks containing sugars and starches Signup and view all the answers

What is the acceptable intake for dietary fiber for women below age 50?

25 g per day Signup and view all the answers

Which amino acid is a component of aspartame that poses a risk for individuals with PKU?

Phenylalanine Signup and view all the answers

What is the maximum percentage of energy intake that sugar should comprise in a diet?

10% Signup and view all the answers

What distinguishes non-nutritive sweeteners from nutritive sweeteners?

Non-nutritive sweeteners provide negligible energy Signup and view all the answers

Study Notes

Carbohydrates

Important source of energy
Monomer is a monosaccharide
Provides structural support for cells and communication between cells
Made up of carbon, hydrogen, and oxygen (CHO)

Types of Carbohydrates

Simple Carbohydrates
- Monosaccharides (single sugars)
  - Glucose: Carbohydrate form used by the body, referred to as "blood sugar". Basic sub-unit of other larger carbohydrate molecules. Found in fruits, vegetables, and honey.
  - Fructose: Sweetest of the sugars. Occurs naturally in fruits and honey, "fruit sugar". Combines with glucose to form sucrose.
  - Galactose: Combines with glucose to form lactose "milk sugar".
- Disaccharides (two sugars)
  - Sucrose ("table sugar"): Glucose + Fructose
  - Lactose ("milk sugar"): Glucose + Galactose
  - Maltose ("malt sugar"): Glucose + Glucose
Complex Carbohydrates
- Oligosaccharides
  - Short carbohydrate chains of 3-10 monosaccharides
  - Found in legumes and human milk
  - Examples: Raffinose and Stachyose
- Polysaccharides
  - Long carbohydrate chains of monosaccharides linked by glycosidic bonds
    - Alpha (a) bonds (starch)
    - Beta (b) bonds (found in fiber)
  - Starch: Plant storage form of carbohydrate. Long branched or unbranched chains of glucose.
    - Amylose
    - Amylopectin
  - Glycogen: Highly branched chains of glucose units. Animal storage form of carbohydrate. Located in the liver and muscle. Humans store ~100g in liver; ~400g in muscle. Negligible source of carbohydrates in the diet (meat)
  - Fiber : Non-digestible carbohydrates (chains of monosaccharides) and lignin that are intact and intrinsic in plants. Includes oligosaccharides.

Dietary Fiber

Non-digestible carbohydrates (chains of monosaccharides) and lignin that are intact and intrinsic in plants (includes oligosaccharides)

Functional Fiber

Isolated, non-digestible carbohydrates that have beneficial physiological effects in humans.

Types of Non-starch Polysaccharides

Cellulose
Hemicelluloses
Pectins
Gums & Mucilages
b-glucans
Chitin & chitosan
Lignans

Digestion & Absorption

Mouth
- Chewing
- Salivary amylase
Stomach
- Fibers remain in the stomach longer, delays gastric emptying
Small Intestine
- Pancreas secretes enzyme pancreatic amylase
- Enzymes located on the cell membranes of the intestinal epithelial cells complete digestion
- Only monosaccharides can be absorbed
  - Glucose & galactose absorbed by ACTIVE TRANSPORT
  - Fructose absorbed by FACILITATED DIFFUSION
- All three monosaccharides travel in the portal vein to the liver
- Three fates of glucose at the liver:
  - Energy, storage as glycogen, released to blood
Large Intestine
- Resistant starches and fibers may be digested by bacteria
  - Produces short chain fatty acids
    - Absorbed by the intestine and used for energy (dietary fiber yields about 2 kcal/g)
    - Other health benefits
Lactose Intolerance
- Occurs as a result of insufficient lactase & low lactase activity
- Lactose molecules from milk remain in the intestine undigested
- lactose intolerance ≠ milk allergy
- Undigested lactose digested by bacteria, producing irritating acid and gas
  - Symptoms include bloating, abdominal discomfort, diarrhea
- Individuals who consume little or no milk products may be at risk of developing nutrient deficiencies
- Dairy options: yogurt, aged cheddar, small quantities of milk (~ ½ cup), acidophilus milk, cottage cheese
- Best to consume with other foods and spread intake throughout the day
- Gradual increases in milk intake may cause intestinal bacteria to adapt

Alternatives to Milk

Calcium: Canned fish with bones, bone soup stock, broccoli, cauliflower, calcium fortified beverages, blackstrap molasses
Vitamin D: 15 minutes exposure to sunlight several times per week. Fortified margarine, fortified cereals, fatty fish (herring, tuna, salmon, sardines), fortified soy or rice milk.
Riboflavin: Beef, chicken, liver, clams, mushrooms, broccoli, breads, fortified cereals

Functions of Carbohydrates

Energy
- Glucose fuels the work of most of the body's cells
  - Preferred fuel of nervous tissue (the brain, nerves) and red blood cells (RBC)
- Excess glucose is stored as glycogen in liver and muscle tissue
Sparing Body Protein
- If diet does not provide enough glucose, then other sources of glucose must be found
- If carbohydrate intake < 50-100 g, body protein will be used to make glucose
- An adequate supply of carbohydrate spares body proteins from being broken down to synthesize glucose
Preventing Ketosis (Anti-ketogenic)
- Carbohydrates required for the complete metabolism of fat
- Incomplete fat metabolism produces ketones
- An adequate supply of carbohydrate (> 50-100 g per day) prevents ketosis

Ketosis

A metabolic state or process in order to keep our body working. When it doesn't have enough carbohydrates from food for your cells to burn for energy, it burns fat instead. As part of this process, it makes ketones.

Fiber

Beneficial for weight control by contributing to satiety & delay gastric emptying
Soluble fibers lower blood cholesterol to help reduce risk of cardiovascular disease
Minimizes risk of and helps control Type II Diabetes
Insoluble fibers help promote intestinal health by enlarging stool size and easing passage of stool

Soluble Fiber

Examples: gums, pectins, mucilages, some hemicelluloses
Functions:
- Delay gastric emptying
- Slow transit through the digestive system
- Delay glucose absorption
- Bind to bile, help decrease cholesterol
Food sources: fruits

Insoluble Fiber

Examples: cellulose, hemicellulose
Functions:
- Speed transit through the digestive tract
- Delay glucose absorption
- Increase fecal weight and soften stool to ease passage
- Reduces risk of hemorrhoids, diverticulitis and appendicitis
Food sources: cereal grains, legumes, vegetables, nuts

Excessive fiber

May lead to:
- Displacement of other foods in the diet
- Intestinal discomfort
- Interference with the absorption of other nutrients

Regulation of Blood Glucose

Optimal functioning of the body is dependant on keeping levels of glucose within certain parameters.
Elevated blood glucose = Hyperglycemia
Low blood glucose = Hypoglycemia
The ENDOCRINE SYSTEM is primarily responsible for regulating blood glucose.
The two main hormones are INSULIN and GLUCAGON.

Reducing risk of caries formation

Eat sugary foods with meals
Limit between meal snacks containing sugars and starches
Brush and floss teeth regularly
If brush and flossing not possible, rinse teeth with water or chew sugar-free gum

Nutritive & Artificial Sweeteners

Nutritive Sweeteners: Impart sweetness and provide energy. Includes natural sweeteners, refined sweeteners, and sugar alcohols.
Refined Sweeteners: Composed of simple sugars extracted from other foods.
Non-Nutritive (Artificial) Sweeteners: Impart sweetness but provide a negligible amount of energy.

Sugar Alcohols

Examples: sorbitol, mannitol, xylitol
Considered sugar replacers: Use similar amount as sugar and provide about 2 kcal per gram.
Only found in commercial foods (common in chewing gum)
Bacteria that produce cavity causing acid don't metabolize sugar alcohols

Artificial Sweeteners

Aspartame: 200x sweeter than sugar, yields 4 kcal per gram. Made of two amino acids:
- Aspartic acid
- Phenylalanine
Individuals with PKU (genetic disorder) cannot convert phenylalanine to tyrosine effectively. Increase's in blood phenylalanine concentration can be toxic.
Saccharin: One study found that excess may cause bladder cancer in rats, but longitudinal human studies show no support for saccharin causing bladder cancer.
Acesulfame K: Cannot be digested by the body thus provides no energy. Not affected by heat so can be used in cooking. 200x sweeter than table sugar.
Sucralose: Made from sugar but does not contribute to energy because it is not digested. Approved by the FDA in U.S. in 1998, used in Canada since 1992. Sold under trade name Splenda. 600x times sweeter than table sugar.

How much carbohydrate do I need?

AMDR (Adults): 45-65% of total average energy intake
RDA for Carbohydrates (Adults): 130 g per day
Daily Value (2000 kcal diet): 300 g per day
AI for Fiber (Adults):
- Men: 38 g per day
- Women: 25 g per day
Sugar: Max 10% of energy intake
Note: After age 50, recommendations decrease to 30 and 21 g per day for men and women respectively.

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Description

This quiz covers the vital role of carbohydrates in providing energy and structural support for cells. It explores the different types of carbohydrates including simple and complex sugars, detailing their structures and functions. Test your knowledge on monosaccharides, disaccharides, and more!