Chapter 4 The Carbohydrates: Sugar, Starch, Glycogen, And Fiber

1
Chapter 4The Carbohydrates Sugar, Starch,
Glycogen, And Fiber
2

• Chapter Summary
• The simple carbohydrates include the
  monosaccharides (glucose, fructose, and
  galactose) and the disaccharides (sucrose,
  lactose, and maltose).
• The complex carbohydrates include the
  polysaccharides (glycogen, starch and fibers).
• This chapter discusses the digestion and
  absorption and health effects of sugar, starch
  and fiber.
• Alternative sweeteners are also discussed.
  Safety aspects and advantages and disadvantages
  of sugar and other sweeteners are presented.

3

• Carbohydrates
• The building block for carbohydrates are carbon,
  hydrogen and oxygen (CHO)
• Carbohydrates include both sugars and their
  polymers
• Polymer (macro molecules made from the same
  simple units repeated many times and joined
  together by covalent bond)
• Monosaccharides or simple sugar
• Examples are Glucose, Fructose and Galactose
• The molecular formulas are multiple of CH2O
• Glucose (C6H12O6) is very important in the
  chemistry of life

4

• (2 sugars Disaccharide ) They contain two
  monosaccharides joined together by a glycosidic
  linkage
• A covalent bond forms between two monosaccharides
  by a dehydration reaction
• C6H12O6 C6H12O6 C12H22O11
• 2 Glucose H2O Maltose
• Sugar can also be identified by the size of the
  carbon skeleton
• Six carbon sugars are called Hexoses
• Five carbon sugars are called Pentoses
• Three carbon sugars are called Trioses

5

• Importance of sugars
• Monosaccharides, particularly glucose, are major
  nutrients for cells
• During cell respiration cells extract energy
  stored in glucose molecules
• The carbon skeleton in sugar molecule serve as
  raw material for synthesis of other type of small
  organic molecules, such as amino acids and fatty
  acids
• Unused sugar molecules are usually stored as
  disaccharides or polysaccharides

6

• Polysaccharides (many sugars 10 plus
  monosaccharides)
• These are macro molecules, polymers of
  monosaccharides joined together by glycosidic
  linkage.
• High molecular weight ex. Starch, glycogen,
  cellulose, hemicelluloses, inulin and lignin
• Chitin
• Structural polysaccharide used by arthropods
  (insects, spider, crustaceans and related
  animals) to build their exoskeletons

7

• Three polysaccharides important in an organism
• Starch
• Storage form of glucose in plant.
• Example amylose and amylopectin
• Also nutritive for human beings
• Glycogen
• Storage form of glucose in animals, including
  human beings
• Branched chains are stored in liver and muscle
  cells

8

• Little fiber is digested by the enzymes in the
  human digestive tract. Much of the fiber passes
  through the digestive tract unchanged.
• Cellulose
• Found mostly in plant cell walls
• Gives the plants their structure
• Not digestible by many animals
• Through photosynthesis, plants combine carbon
  dioxide, water and the suns energy to form
  glucose.
• Carbohydrates are made of carbon, hydrogen, and
  oxygen held together by energy-containing bonds

9

• Sugars
• Glucose is the most important monosaccharide in
  the human body. Most other monosaccharides and
  disaccharides become glucose in the body.
• The Need For Carbohydrates
• If I Want to Lose Weight, Should I Avoid
  Carbohydrates?
• Complex carbohydrate is the preferred energy
  source for the body.
• How Does Fiber in Food Affect My Health, and How
  Much Do I Need to Stay Healthy?
• Fibers aid in maintaining the health of the
  digestive tract and help to prevent or control
  certain diseases. Most people probably need
  between 20 and 40 grams of fiber each day.

10

• Can My Diet Have Too Much Fiber?
• Fiber needs are best met with whole foods.
  Purified fiber in large doses can have
  undesirable effects
• From Carbohydrates To Glucose
• Digestion and Absorption of Carbohydrate
• With respect to starch and sugars, the main task
  of the various body systems is to convert them to
  glucose to fuel the cells work. Fibers help
  regulate digestion and contribute a little energy

11

• Why Do Some People Have Trouble Digesting Milk?
• Lactose intolerance is a common condition in
  which the body fails to produce sufficient
  amounts of the enzyme needed to digest the sugar
  of milk. Uncomfortable symptoms result and can
  lead to milk avoidance. Lactose-intolerant people
  and those allergic to milk need milk alternatives
  that contain calcium.
• Splitting Glucose for Energy
• Without glucose the body is forced to alter its
  uses of protein and fat. The body breaks down its
  own muscles and other protein tissues to make
  glucose and convert its fats into ketone bodies,
  incurring ketosis

12

• Storing Glucose as Glycogen
• Glycogen is the bodys form of stored glucose.
  The liver stores glycogen for use by the whole
  body. Muscles have their own private glycogen
  stock for their exclusive use. The hormone
  glucagon acts to liberate stored glucose from
  liver glycogen.
• Returning Glucose to the Blood
• Blood glucose regulation depends mainly on the
  hormones insulin and glucagon. Certain
  carbohydrate foods produce a greater rise and
  fall in blood glucose than other do. Most people
  have no problem regulating blood glucose
  especially when they consume regular mixed meals.

13

• Converting Glucose to Fat
• The liver converts extra energy compounds to fat,
  a more permanent and unlimited energy-storage
  compound than glycogen
• Diabetes And Hypoglycemia
• What is Diabetes?
• Diabetes is an example of the bodys abnormal
  handling of glucose. Inadequate or ineffective
  insulin leaves blood glucose high and cells
  undersupplied with glucose energy.

14

• If I Feel Dizzy Between Meals, Do I Have
  Hypoglycemia?
• Postprandial hypoglycemia is a rare condition in
  which blood glucose falls too low. It can be a
  warning of organ damage or disease