PROTEINS Flashcards Preview

A Level Food Technology > PROTEINS > Flashcards

Flashcards in PROTEINS Deck (35):
1

What is a protein

Long chain of amino acids

2

What is a protein

Long chain of amino acids

3

How does protein provide energy

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

4

What is a protein

Long chain of amino acids

5

How does protein provide energy

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

6

Functions of protein

Growth and repair

Secondary source of energy

Maintains body producing enzymes/hormones

7

Sources of protein

Nuts

Pulses

Meat

Eggs

8

Example of protein deficiency

Kwashiorkor
- common in children after weaning

Symptoms
- bloated abdomen
- muscle wasting
-stunted growth

Treatment
- balanced diet (more vitamins and minerals

9

Effects of excess

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

10

What is protein complementation?

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

11

Examples of protein complementation

Beans on toast

Rice and peas

Rice and kidney beans

12

What are essential amino acids

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

13

What are non- essential amino acids

CAN be made by our bodies

14

Chemical structure of protein

Amino/ Acidic
Alkaline Part
Part

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

R = Variable (changes for each amino acid)

15

What does amphoteric mean?

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

16

What are HBVs (high biological value proteins)

Proteins that contain all essential amino acids

17

Examples of HBVs

Animal sources

Meat

Fish

Soya

Dairy

Eggs

18

Chemical structure of protein

Amino/ Acidic
Alkaline Part
Part

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

R = Variable (changes for each amino acid)

19

What are LBVs (low biological value proteins)

Proteins that don't contain all essential amino acids

20

Examples of LBVs

Plant sources

Peas

Beans

Lentils

Nuts

Grains

Rice

21

Chemical structure of protein

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

22

What is a peptide link

Chemical bond linking two amino acids along a peptide chain

23

What is a dipeptide link

When two amino acids join together

24

What is a tripeptide bond

3 amino acids

26

What is a Polypeptide chain

Long chain of amino acids joined together

More than 3

27

What is condensation polymerisation

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

28

Primary physical structure of protein

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

29

Secondary physical structure of protein

Amino acids linked by various amino acids to give shape - spiral

Hydrocarbon chain different in each amino acid

30

Tertiary physical structure of protein

Coiled/ folded chain of amino acids coiled/ folded further

More bonds form between the parts of polypeptide chain

31

Globular protein - tertiary

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

32

Fibrous protein - tertiary

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

33

Denaturation of protein

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

34

Coagulation in protein

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

35

Effect of heat on protein

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

36

Effect of acids/ alkalis on protein

Fibrous proteins affected