Protein

Question 1

Protein in cheese

Answer 1

Caseinogen

Question 2

Protein in milk

Answer 2

Lactalbumin, caseinogen

Question 3

Protein in eggs

Answer 3

Ovalbumin, livetin, vitellin, albumin

Question 4

Protein in fish

Answer 4

Myosin, collagen, actin

Question 5

Protein in meat fibres

Answer 5

Myosin, actin, globulin

Question 6

Protein in meat connective tissue

Answer 6

Collagen, elastin

Question 7

Protein in wheat

Answer 7

Gluten

Question 8

Protein in soya beans

Answer 8

Glycinin

Question 9

Protein in rice

Answer 9

Oryzenin

Question 10

Protein in corn/maize

Answer 10

Zein

Question 11

Structural function of protein

Answer 11

Growth and repair of body cells. Deficiency can result in retarded growth and delayed healing

Question 12

Physiological function of protein

Answer 12

Making hormones, enzymes, antibodies, blood proteins and nucleoprotein. Deficiency can result in malfunction of body organs and prone to infection

Question 13

Nutritive function of protein

Answer 13

Provides essential amino acids to the body. Excess is used for heat and energy. Deficiency can result in kwashiorkor, marasmus and a lack of energy

Question 14

Two classifications of protein

Answer 14

Simple, conjugated

Question 15

Conjugated protein

Answer 15

A protein molecule and non-protein molecule joined together

Question 16

Two examples of conjugated proteins

Answer 16

Lipoproteins eg lecithin (egg), phosphoproteins eg caseinogen (milk)

Question 17

Two subgroups of simple animal proteins

Answer 17

Fibrous, globular

Question 18

Two subgroups of simple plant proteins

Answer 18

Glutenins, prolamines

Question 19

Example of simple fibrous and globular animal proteins

Answer 19

Fibrous - elastin (meat connective tissue)
Globular - ovalbumin (egg whites)

Question 20

Example of simple glutenin and prolamine plant proteins

Answer 20

Glutenins - glutenin (wheat)
Prolamines - zein (maize)

Question 21

6 properties of protein

Answer 21

Denaturation, solubility, Maillard reaction, elasticity, foam formation, gel formation

Question 22

denaturation

Answer 22

Change in the nature of the protein. Protein chain unfolds causing a permanent change to the structure. Caused by heat, chemicals, agitation

Question 23

Heat denaturation

Answer 23

Most proteins coagulate when heated eg egg white at 60°, egg yolk at 68°

Question 24

Chemical denaturation

Answer 24

Acids, alkali, alcohol and enzymes cause protein structure to change. Eg lemon juice in milk causes milk protein caseinogen to curdle

Question 25

Agitation denaturation

Answer 25

Involves whipping or whisking the protein. Causes protein chains to unfold and partial coagulation

Question 26

Solubility (property of protein)

Answer 26

Proteins are generally insoluble in water. Two exceptions are - egg white in cold water, connective tissue (converts to gelatine) in hot water

Question 27

Maillard reaction (property of protein)

Answer 27

Also known as non-enzymic browning. Occurs when food is roasted, baked or grilled. Amino acid + carbohydrates + dry heat = brown colour

Question 28

Elasticity (property of protein)

Answer 28

Certain proteins have an elastic property eg gluten in flour enabling bread to rise during cooking

Question 29

Foam formation (property of protein)

Answer 29

Eggs whites are whisked causing air bubbles to form as protein chains unravel, whisking produces heat which slightly sets egg whites (this foam will collapse after a while unless subjected to heat). Baking causes permanent coagulation of the protein, trapping air bubbles

Question 30

Gel formation (property of protein)

Answer 30

Collagen, when heated, forms gelatine. Gelatin can absorb large amounts of water. On cooling this becomes solid and a gel is formed. A gel is a semi-solid viscous solution. All gels have a 3 dimensional network whereby water becomes trapped

Question 31

Effects of heat on protein

Answer 31

Coagulation, colour change (myoglobin in meat changed red to brown), Maillards reaction (dry heat), tenderizing (moist heat)(collagen in meat changes to gelatine and fibres fall apart), becomes digestible

Question 32

Protein deamination

Answer 32

Left over amino acids are brought to the liver. The NH2 group is broken off, changed to ammonia, then to urea, and then excreted. The rest of the molecule is converted to glucose and used for releasing energy

Question 33

RDA of protein

Answer 33

1g per kg of body weight

Question 34

Energy value of protein

Answer 34

1g of protein gives 4kcal of 17kj

Question 35

What happens to proteins in the stomach

Answer 35

Proteins are churned. Gastric juice contains enzymes rennin and pepsin Rennin changed caseinogen to casein Pepsin changes proteins to peptones

Question 36

What happens to proteins in the pancreas

Answer 36

Pancreatic juice contains enzyme trypsin Trypsin changes protones to peptides

Question 37

What happens to proteins in small intestine

Answer 37

Intestinal juice contains enzyme peptidase Peptidase changes peptides to amino acids