10/7: Nutrients in Food

What are three major macromolecules in food?

• Carbohydrates, lipids, proteins

Carbohydrates

• Bread, sugar, pasta, crackers

Lipids

• Fat, adipose

• Butter, oil

Proteins

• Meat, burgers

Food also contain

• minerals (salt) vitamins 

How is energy stored?

• In chemical bonds

  • Breaking those bonds will release energy (ATP)

  • Can be measured in calories 

Metabolism

• All chemical reactions that occur in your body

Anabolism

• We take smaller molecules and form larger molecules with them

  • For cytoplasmic membrane, cell wall, ribosomes, etc

• Helps the body grow, repair tissues, and store energy

• Ex:

  • Building proteins from amino acids

  • Building glycogen from glucose

  • Storing fat in adipose tissue

Catabolism

• Breaks larger molecules into smaller molecules 

• Release energy that the body can use 

• Ex

  • Breaking down glucose to produce ATP

  • Breaking down stored fat for energy

  • Breaking down proteins into amino acids (nutrients) 

  • Making nucleotides

Catabolism/anabolism example: the liver

Mass Balance Model

• Mass cannot be created or destroyed - only transformed

• So what comes in must go out, only stay inside 

Glucose

• Simple sugar that cells use to produce energy (ATP)

• Travel through the bloodstream to supply energy to cells

• Comes from digesting carbohydrates and can also be made by the liver 

• Glucose from food is absorbed in the intestines

Glycogen

• The storage form of glucose in animals and humans.

• Stored mainly in the liver and skeletal muscles.

• The liver can break down glycogen to help maintain blood glucose; muscles use their stored glycogen for their own energy needs.

Glycogenesis

• The process of converting glucose into glycogen for storage.

• Occurs when glucose is available in sufficient amounts, such as after a meal.

• Stimulated by insulin.

Glycogenolysis

• The process of breaking down glycogen into glucose-related molecules to make energy available.

• In the liver, it helps raise blood glucose levels.

• In muscles, it supplies fuel for muscle activity.

Genesis

• Creating/storing glycogen

Lysis

• Breaking down glycogen

Classification of Carbohydrates

• Classified based on how many sugar units they contain.

• Three types

  • Monosaccharides (simple)

  • Disaccharides (simple)

  • Polysaccharides (complex)

Salivary amylase

• Produced in saliva and is used to break down starches

Enzymes for carbohydrate

• Used to break down complex carbohydrates into simple carbohydrates

Simple Carbohydrates

• Monosaccharides

• Disaccharides

Monosaccharides

• Simplest carbohydrates

• Cannot be broken down into smaller sugars

• In digestion, carbohydrates are broken down into monosaccharides which then be absorbed through small intestine 

• Ex:

  • Glucose

  • Fructose

  • Galactose

Disaccharides: How are they formed?

• Formed when two monosaccharides (sugar) join together by a glycosidic bond

• Formed in a dehydration reaction (loss of water)

• Ex

  • Sucrose (table sugar)

  • Lactose (milk sugar)

    • Glucose + galactose

  • Maltose

Complex Carbohydrates 

• Polysaccharides - many sugar units

  • Long chains of sugar units joined together

Complex Carbohydrates Types

• Starch

• Glycogen

• Cellulose

Starch

• Stores glucose in plants; found in potatoes, rice, and bread.

• Formed in two ways

  • Amylose: The nonbranched (linear) part of starch

    • Straight chain of glucose molecules

  • Amylopectin: The branched part of starch

    • A branched chain of glucose molecules 

    • Branches are easier to break down, so access is faster 

Amylose

• The nonbranched (linear) part of starch

• Straight chain of glucose molecules

Amylopectin

• The branched part of starch

• A branched chain of glucose molecules 

Glycogen

• Stores glucose in animals and humans, mainly in the liver and muscles.

Cellulose

• Makes up plant cell walls

• Humans lack the enzyme to break this down

• Acts as dietary fiber and helps support regular bowel movements (prevents constipation)

Chemical Formula of Carbohydrates

• CH₂O