Home Ec - Protein

Protein

Elemental Composition:

• Carbon (C)
• Hyrdrogen (H)
• Oxygen (O)
• Nitrogen (N)

 And sometimes:

• Sulpher (S)
• Phosphorous (P)
• Iron (fe)

Chemical Composition:
                                       
                           H                                                         H = hydrogen
                            |                                                          NH2 = Amino Group
                            |                                                          C = Carbon
         NH2------ C -------COOH                                  COOH = Carboxyl group 
                            |                                                          R = variable eg is H in Glycine
                            |
                           R


Essential amino acids are the amino acids that cannot be synthesised (made) by the bosy and must be obtained from food.
                    Eg. Threonine, Methionine, Lysine, Valine

Non-essential amino acids are the amino acids that can be synthesised by the body.
                    Eg. Serine, Alanine

Formation of a peptide link:

 

·        The H from the amino group of amino acid number 1 joins with the OH from the Carboxyl group of the second amino acid

·     This makes H₂O

·     Results in formation of peptide link and a water molecule

·     Condensation reaction

The reverse of this is Hydrolysis

Where water is added back into the protein to break the bonds

Eg digestion of food

Structures:

Three Types:      1. Primary structure

                             2. Secondary Structure

                             3. Tertiary structure

Primary Structure

·        The Number and order of amino acids on a polypeptide/protein chain.

Eg Insulin is mad up of 50 amino acids arranged in a definite            order

Secondary Structure

·        The further folding of the primary structure to give a definite shape

·        The folding is caused by links or bridges:

o   Di-sulphide link

o   Hydrogen bond

Di-sulphide link

·        Amino acid cysteine contains sulphur

·        Two Cysteine units on the same chain, or chains side by side, join and a di-sulphide link is formed

Hydrogen bond

·        Hydrogen from one amino acid joins with oxygen from another amino acid. Eg collagen 

Tertiary structure

·        The further folding of the secondary structure to give a 3-D shape.

·        Can be fibrous or globular

Fibrous – straight, curved or zigzag

E.g. elastin in meat

Globular – spherical in shape

E.g. ovalbumin in egg white

Classification of proteins:

1.   Simple Proteins -       From animals and plants

Contains only protein

2.   Conjugated Protein -          Contains a protein and a non-protein

3.   Derived Protein -        made by chemical or  enzymic action

From another protein

E.g. Caesinogen in milk to caesin

Sources of protein

Animal                                             Plant

Meat                                                 Pulse veg – peas, beans, lentils

Fish                                                  Nuts

Milk                                                 Cereals

Eggs                                                 Seeds

Cheese                                                          

                                                                                     Pulse veg – a veg that

                                                                                      grows in a pod

Home Economics - Factors that affect food choice

Factors that affect food choice:

·        Culture – different countries/religions have their own eating patterns

o   E.g. Italian food, Jews don’t eat pig meat.

·        Availability – Different foods more available at different times of the year.

o   E.g. brussel sprouts at Christmas,

o   Canned and frozen foods makes more foods available all year round.

·        Nutritional Awareness – today people more health conscious. Read food labels, choosing healthier options. Television and subjects like Home Ec. and SPHE, make people more aware of nutrition.

·        Sensory Aspects – Our senses of sight, smell, taste, touch, have major impact. Expectations of flavour, colour, texture temperature appearance. Colour and design of packaging, instant appeal, food should look fresh wholesome and attractive.

·        A person’s eating habits – busy lifestyles, increase in fast food and convince foods. Type and hours of work influence meal times and food choices.

·        Marketing and advertising – advertising aims to increase awareness of a product, TV, radio, magazines. Marketing influences food choice with supermarket layouts, promotions and tastings.

·        Cost – your Budget influences choices. Lower socio-economic group will have fewer luxuries. Higher income more money spent eating out and travelling abroad which influences food choices

·        Health status – special dietary needs eg high cholesterol – low fat products, coelaics – gluten free products

CAN SAM Cook Healthy

It is highly unlikely you would be expected to write all of these in an exam, however, I would still recommend trying to know them as they may be incorporated into other answers or they may give you some of them and expect you to give other ones.