Mammalian NutritionMiss Tagore

Food Groups• There are 5 main food groups:

1. Carbohydrates▫ Contain the elements carbon, hydrogen and oxygen

▫ Used as the main source of energy

▫ Can be small, soluble sugars such as glucose and maltose or large insoluble molecules such as starch and cellulose

Carbohydrates•There are three types of carbohydrate

that you need to know about:

▫Monosaccharaides (mono = one)

▫Disaccharides (di = two)

▫Polysaccharides (poly = many)

Monosaccharaides (mono = one)•The simplest form of carbohydrate

•Single structured molecules

Disaccharides (di = two)• Disaccharides are formed from the combination

of two monosaccharaides by a chemical reaction called dehydration synthesis (more on this later).

• Examples of disaccharides are sucrose, maltose and lactose.

Polysaccharides (poly = many)• Polysaccharides are many monosaccharaides linked

together. These are stored form of sugar. • Examples of polysaccharides are starch (synthesized by

plants), glycogen (synthesized by animals) and cellulose (material that makes the plants cell wall).

Food Groups2. Fats

▫ Contain the elements carbon, hydrogen and oxygen

▫ Used as an energy source but contain twice as much energy as carbohydrates

▫ One fat molecule consists of 3 fatty acids and one glycerol

▫ Organic molecules that are waxy or oily

Fats• 3 major roles:

▫Store energy

▫Form biological membranes

▫Chemical messengers (hormones)

• 3 types of lipids:

▫Neutral fats

▫Phospholipids

▫Sterols (steroids)

Neutral Fats• Found on humans in the inner thigh and

torso area.

•Two types: ▫Saturated fats

▫Unsaturated fats

Saturated Fats• All carbon atoms have two

hydrogen atoms attached

• There are no double bonds between carbons

 • The lack of double

bonding makes saturated fats a solid at room temperature

• Examples of saturated fats are lard, butter, animal fats

Unsaturated Fats• Not all carbon atoms have

two hydrogen atoms attached

• The lack of single bonds makes unsaturated fats a liquid at room temperature

• Examples of unsaturated fats are olive oil, corn oil and palm oil.

• All neutral fats are made from a glycerol molecule with 3 fatty acid chains attached to it

Phospholipids• Have the same structure as

neutral fats, except one fatty acid chain has a polar group that contains phosphorus.

• Part of the molecule is attracted to water (hydrophilic = water loving), the other end repels it (hydrophobic = water fearing).

• These properties make a phospholipid perfect for forming cell membranes.

Steroids• Steroids are made of 4

interlocking rings. They are an important part of the body involved in building cells and carrying messages.

• Examples of steroids are cholesterol and sex hormones.

Food Groups3. Protein

▫ Contain the elements carbon, hydrogen, oxygen and nitrogen

▫ Proteins are essential part of our diet as they help to make muscle, hair and many other structural parts of the body

▫ Proteins are made from sub-units called amino acids

▫ There are about 20 different amino acids

Amino Acid Structure• Each amino acid has an amine group (-NH2) and a

carboxyl group (-COOH).

• It is between these groups that amino acids link together to form chains.

• What makes each of the 20 different amino acids different is the ‘R’ group. This region is different, thus making each amino acid different.

Peptide Bonds• Peptide bonds are bonds

formed between amino acids that result from dehydration synthesis.

• Two amino acids bonded together are known as dipeptides (2 amino acids)

• Three amino acids bonded together are known as tripeptides (3 amino acids), Polypeptides are a long chain of amino acids.

• A complete protein contains one or more polypeptide chains.

The Function of Proteins•Carry out

chemical reactions (enzymes)

•Pump molecules into and out of cell

•Make cells move.

Food Groups4. VITAMINS

• Do not give energy and they are needed in very small quantities. • Vitamins are necessary for normal growth, work with enzymes,

and regulate cellular activities.

• Vitamins are complex molecules needed in small amounts and cannot be made in the body.

5. MINERALS

• Some of these elements are called Essential elements because they are required by living things to perform essential functions.

• Minerals are inorganic substances like Ca, Cl, Mg, K, P, Na, Fe, F, I.

What to do now…•Complete task 3 in your booklet.

•Make sure that you review your notes on this section and use them to help you answer the questions.

•Check the answers with your teacher.

•Amend any corrections.

HOW MOLECULES BOND TOGETHER AND BREAK APART• The process of forming large compounds (polymers) by

joining together smaller compounds (monomers) is known as polymerization.

• This process allows living things to form many molecules from the combination of just a few subunits

▫ for example different proteins being formed from only 20 amino acids;

▫ the different types of fats and carbohydrates that are naturally produced.

Polymerization• All polymers are formed by

the process of dehydration synthesis.

• As the name suggests, this involves a loss of water. 

• The OH- group on one monomer combines with the H on another monomer.

Hydrolysis Reaction• Hydrolysis reactions break up a polymer into its

monomers by the addition of water to a bond.

• This reaction is the exact opposite reaction of dehydration synthesis since the –OH group of water goes to one monomer and the other -H group goes the bond on the second monomer.

Food Tests• Starch

• Iodine solution changes from orange to blue/black if starch is present

• Glucose

▫ Benedict’s solution changes from blue to brick red/orange when heated to 80oC (tests for other simple sugars also e.g. Maltose)

▫ Clinistix also tests for the presence of glucose

• Protein

▫ Buriets reagent tests for the presence of protein by changing from blue to lilac only if protein is present

• Fats

▫ Leaves a translucent spot on filter paper if fat is present (think of chips on kitchen roll)

Testing Unknown Food Groups

AIM: to identify three unknown food group using different food tests.

Method1. In groups of three, allocate each person to test a single

powder.

2. Each person should collect: • 3 Boiling tubes• a Large beaker • Test tube rack• Stirring rod• Spatula• Safety goggles!!!

3. Using only your assigned powder, add one spatula full into each boiling tube and half fill the boiling tube with water.

4. Stir the contents with the glass rod to ensure that all the particles have dissolved as much as possible.

5. Test each tube with the three different testing solutions; iodine solution, Benedict's solution and biuret’s reagent.

6. Feed back to the rest of your group which solution gave a positive test with which particular testing solution.