PROTEINS

Question 1

What is a protein

Answer 1

Long chain of amino acids

Question 2

What is a protein

Answer 2

Long chain of amino acids

Question 3

How does protein provide energy

Answer 3

Excess protein is converted into glucose which is stored in the liver as glycogen - secondary source of energy

Question 4

What is a protein

Answer 4

Long chain of amino acids

Question 5

How does protein provide energy

Answer 5

Excess protein is converted into glucose which is stored in the liver as glycogen - secondary source of energy

Question 6

Functions of protein

Answer 6

Growth and repair

Secondary source of energy

Maintains body producing enzymes/hormones

Question 7

Sources of protein

Answer 7

Nuts

Pulses

Meat

Eggs

Question 8

Example of protein deficiency

Answer 8

Kwashiorkor
- common in children after weaning

Symptoms

• bloated abdomen
• muscle wasting
• stunted growth

Treatment
- balanced diet (more vitamins and minerals

Question 9

Effects of excess

Answer 9

Excess calories from protein stored as tissue leads to overweight

Strain on organs (kidneys/ liver/ bowel)

Protein foods often high in saturated fat leads to CHD

Question 10

What is protein complementation?

Answer 10

The mixture of LBV proteins as they are incomplete proteins

Two ensure that all essential amino acids are received, two incomplete sources compensate each other’s inadequate supply

Question 11

Examples of protein complementation

Answer 11

Beans on toast

Rice and peas

Rice and kidney beans

Question 12

What are essential amino acids

Answer 12

Amino acids that CANT be made by our bodies - must EAT them

Question 13

What are non- essential amino acids

Answer 13

CAN be made by our bodies

Question 14

Chemical structure of protein

Answer 14

Amino/ Acidic
Alkaline Part
Part

H             H          O 
|               |           ||
N      -     C    -     C  -  OH 
|               |            
H             R 

R = Variable (changes for each amino acid)

Question 15

What does amphoteric mean?

Answer 15

Amino acids are amphoteric because they contain at least one alkaline group and one acidic group displaying acidic and base properties

Question 16

What are HBVs (high biological value proteins)

Answer 16

Proteins that contain all essential amino acids

Question 17

Examples of HBVs

Animal sources

Answer 17

Meat

Fish

Soya

Dairy

Eggs

Question 18

Chemical structure of protein

Answer 18

Amino/ Acidic
Alkaline Part
Part

H             H          O 
|               |           ||
N      -     C    -     C  -  OH 
|               |            
H             R 

R = Variable (changes for each amino acid)

Question 19

What are LBVs (low biological value proteins)

Answer 19

Proteins that don’t contain all essential amino acids

Question 20

Examples of LBVs

Plant sources

Answer 20

Peas

Beans

Lentils

Nuts

Grains

Rice

Question 21

Chemical structure of protein

Answer 21

Proteins are large molecules built up of long chains of amino acids

Only 20 of 80 found in foods
8 of 20 are essential

Each amino acid contains at least one acidic group and one amino (alkaline) group

Question 22

What is a peptide link

Answer 22

Chemical bond linking two amino acids along a peptide chain

Question 23

What is a dipeptide link

Answer 23

When two amino acids join together

Question 24

What is a tripeptide bond

Answer 24

3 amino acids

Question 26

What is a Polypeptide chain

Answer 26

Long chain of amino acids joined together More than 3

Question 27

What is condensation polymerisation

Answer 27

Molecule of water is eliminated during the formation of a peptide link

Question 28

Primary physical structure of protein

Answer 28

Sequence of amino acids in protein chain Amino acid and carboxyl group take part in condensation reaction to form a peptide bond Peptide bonds strong and can only be broken a strong acid/ enzyme

Question 29

Secondary physical structure of protein

Answer 29

Amino acids linked by various amino acids to give shape - spiral Hydrocarbon chain different in each amino acid

Question 30

Tertiary physical structure of protein

Answer 30

Coiled/ folded chain of amino acids coiled/ folded further More bonds form between the parts of polypeptide chain

Question 31

Globular protein - tertiary

Answer 31

Rounded in shape but not necessarily spherical Amino acid chain folded/ molecule kept in shape by cross linkage within amino acid chain Easy for water molecules to penetrate empty spaces within protein molecules Example - ovalbumin in eggs

Question 32

Fibrous protein - tertiary

Answer 32

Organised arrangement/ molecules closely packed together Cross links between between adjacent amino acids Difficult for water molecules to penetrates the structure Not soluble in water Examples - gluten found in wheat Not affected by heat Elastic - straight fibrous protein Inelastic - coiled in a spiral fibrous protein

Question 33

Denaturation of protein

Answer 33

Physical structure of protein is altered in irreversible way Protein become less soluble/ more viscous Process which proteins/ nucleic acids lose tertiary/ secondary structure by external stress

Question 34

Coagulation in protein

Answer 34

Irreversible Involves denaturation of protein - from soluble to insoluble Eggs are heated the egg white proteins coagulate at 60 degrees and whites become opaque forming a gel Yolk proteins coagulate at 66 degrees and yolk thickens Become less soluble and more viscous Unfolded to form clumps when bonding - setting/ hardening

Question 35

Effect of heat on protein

Answer 35

Only globular proteins Heat causes secondary structure of proteins to denature Molecule unfolds and changes shape Sequence of amino acids stays the same Denaturation breaks the cross linkages maintain the shape of molecule - irreversible Insoluble/ more viscous Form clumps when bonding

Question 36

Effect of acids/ alkalis on protein

Answer 36

Fibrous proteins affected