Carbohydrates

• Macromolecule


  A very large molecule, such as Carbohydrates, protein, Lipids and Nucleic acids
• Macromolecules


  • They are composed of thousands of covalently bonded atoms
  • Many macromolecules are polymers of smaller molecules called monomers
• Carbohydrates


  The sugars, starches and fibers found in fruits, grains, vegetables and milk products
• Carbohydrates are one of the basic food groups that are important to a healthy diet
• Macronutrients


  They are one of the three main ways the body obtains energy, or calories
• Carbohydrates are the body's main source of energy
• Carbohydrates contain carbon, hydrogen and oxygen
• Macronutrients


  • Carbohydrates
  • Protein
  • Fats
• Macronutrients


  • They are essential for proper body functioning, and the body requires large amounts of them
  • They must be obtained through diet because the body cannot produce macronutrients on its own
• Functions of carbohydrates


  • Provide fuel for the central nervous system and energy for working muscles
  • Prevent protein from being used as an energy source
  • Enable fat metabolism
• Carbohydrates and brain function

  • They are an influence on "mood, memory, etc., as well as a quick energy source"
  • The RDA of carbohydrates is based on the amount of carbs the brain needs to function
• Simple carbohydrates


  • They contain just one or two sugars, such as fructose and galactose
  • They are digested and absorbed more quickly and easily than complex carbs
• Disaccharides


  Carbs with two sugars, such as sucrose, lactose and maltose
• Simple carbs in processed foods

  • They are made with processed and refined sugars and do not have vitamins, minerals or fiber
  • They are called "empty calories" and can lead to weight gain
• Complex carbohydrates (polysaccharides)


  • They have three or more sugars
  • They are often referred to as starchy foods and include beans, peas, lentils, peanuts, potatoes, corn, parsnips, whole-grain breads and cereals
• Simple carbs vs complex carbs


  • Simple carbs cause bursts of energy much more quickly than complex carbs because of the quicker rate at which they are digested and absorbed
  • Simple carbs can lead to spikes in blood sugar levels and sugar highs, while complex carbs provide more sustained energy
• Carbohydrate metabolism


  1. Carbs break down into smaller units of sugar, such as glucose and fructose

  2. The small intestine absorbs these smaller units, which then enter the bloodstream and travel to the liver

  3. The liver converts all of these sugars into glucose, which is carried through the bloodstream accompanied by insulin and converted into energy for basic body functioning and physical activity

  4. If the glucose is not immediately needed for energy, the body can store up to 2,000 calories of it in the liver and skeletal muscles in the form of glycogen

  5. Once glycogen stores are full, carbs are stored as fat

  6. If there is insufficient carbohydrate intake or stores, the body will consume protein for fuel
• Fiber


  • Fibers promote healthy bowel movements and decrease the risk of chronic diseases such as coronary heart disease and diabetes
  • Fibers are not absorbed in the small intestine and are not converted to glucose
  • Instead, they pass into the large intestine relatively intact, where they are converted to hydrogen and carbon dioxide and fatty acids
• The Institute of Medicine recommends that people consume 14 grams of fiber for every 1,000 calories
• Sources of fiber include fruits, grains and vegetables, especially legumes
• Carbohydrate structure and classification


  • Carbohydrates can be represented by the stoichiometric formula (CH2O)n, where n is the number of carbons in the molecule
  • Carbohydrates are classified into three subtypes: monosaccharides, disaccharides, and polysaccharides
• Monosaccharides


  • They are simple sugars, the most common of which is glucose
  • In monosaccharides, the number of carbons usually ranges from three to seven
  • Most monosaccharide names end with the suffix –ose
  • If the sugar has an aldehyde group, it is known as an aldose, and if it has a ketone group, it is known as a ketose
  • Depending on the number of carbons in the sugar, they also may be known as trioses, pentoses, and or hexoses
• Monosaccharide structure


  • Monosaccharides can exist as a linear chain or as ring-shaped molecules
  • In aqueous solutions they are usually found in ring forms
  • Glucose in a ring form can have two different arrangements of the hydroxyl group (−OH) around the anomeric carbon, alpha (α) or beta (β)
• Disaccharides


  • They form when two monosaccharides undergo a dehydration reaction
  • The covalent bond formed between the monosaccharides is known as a glycosidic bond
  • Glycosidic bonds can be of the alpha or the beta type
• Polysaccharides


  • A long chain of monosaccharides linked by glycosidic bonds
  • The chain may be branched or unbranched, and it may contain different types of monosaccharides
  • Examples include starch, glycogen, cellulose, and chitin
• Starch


  • It is the stored form of sugars in plants and is made up of a mixture of amylose and amylopectin (both polymers of glucose)
  • Plants synthesize glucose, and the excess glucose is stored as starch in different plant parts
  • The starch in the seeds provides food for the embryo as it germinates and can also act as a source of food for humans and animals
  • The starch that is consumed by humans is broken down by enzymes, such as salivary amylases, into smaller molecules, such as maltose and glucose
• Disaccharide


  Sugar formed by a dehydration reaction between two glucose molecules
• Sucrose


  The most common disaccharide, composed of the monomers glucose and fructose
• Polysaccharide


  A long chain of monosaccharides linked by glycosidic bonds
• Polysaccharides


  • Starch
  • Glycogen
  • Cellulose
  • Chitin
• Starch


  • The stored form of sugars in plants, made up of a mixture of amylose and amylopectin (both polymers of glucose)
  • Plants synthesize glucose and excess is stored as starch
  • Starch provides food for plant embryos and can be a source of food for humans and animals
  • Starch is broken down by enzymes like salivary amylases into smaller molecules like maltose and glucose
• Glycogen


  • The storage form of glucose in humans and other vertebrates, a highly branched molecule usually stored in liver and muscle cells
  • Glycogen is broken down to release glucose when blood glucose levels decrease (glycogenolysis)
• Cellulose


  • The most abundant natural biopolymer, a major component of plant cell walls providing structural support
  • Cellulose is made up of glucose monomers linked by β 1-4 glycosidic bonds
• Protein


  The building blocks of life, a highly complex substance present in all living organisms
• Proteins


  • Every cell in the human body contains protein
  • Proteins are needed to repair cells and make new ones
  • Proteins are important for growth and development in children, teens, and pregnant women
  • Proteins are of great nutritional value and are directly involved in the chemical processes essential for life
  • Proteins are species-specific and organ-specific
• Amino acids


  The basic structure of proteins, classified into essential, nonessential, and conditional amino acids
• Peptide bond


  The bond linking amino acids, formed when the carboxyl group of one amino acid bonds with the amino group of another, releasing water
• Amino acid structure


  • Each amino acid has a central α carbon with a hydrogen, α-carboxyl group, α-amine group, and an R-group (side chain)
  • Proline is a minor exception with the R-group attached to the α-amine
• Protein structure types


  • Primary
  • Secondary
  • Tertiary
  • Quaternary
• Protein functions


  • Structural components (e.g. keratin, collagen)
  • Genetic information expression
  • Transport (e.g. hemoglobin)
  • Homeostatic control (e.g. plasma proteins)
  • Blood clotting
  • Immune defense (antibodies)
  • Hereditary transmission
  • Storage (e.g. ovalbumin, glutelin)
  • Muscle contraction (e.g. actin, myosin)