PROTEINS Flashcards
What is a protein
Long chain of amino acids
What is a protein
Long chain of amino acids
How does protein provide energy
Excess protein is converted into glucose which is stored in the liver as glycogen - secondary source of energy
What is a protein
Long chain of amino acids
How does protein provide energy
Excess protein is converted into glucose which is stored in the liver as glycogen - secondary source of energy
Functions of protein
Growth and repair
Secondary source of energy
Maintains body producing enzymes/hormones
Sources of protein
Nuts
Pulses
Meat
Eggs
Example of protein deficiency
Kwashiorkor
- common in children after weaning
Symptoms
- bloated abdomen
- muscle wasting
- stunted growth
Treatment
- balanced diet (more vitamins and minerals
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
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
Examples of protein complementation
Beans on toast
Rice and peas
Rice and kidney beans
What are essential amino acids
Amino acids that CANT be made by our bodies - must EAT them
What are non- essential amino acids
CAN be made by our bodies
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)
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
What are HBVs (high biological value proteins)
Proteins that contain all essential amino acids
Examples of HBVs
Animal sources
Meat
Fish
Soya
Dairy
Eggs
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)
What are LBVs (low biological value proteins)
Proteins that don’t contain all essential amino acids
Examples of LBVs
Plant sources
Peas
Beans
Lentils
Nuts
Grains
Rice
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
What is a peptide link
Chemical bond linking two amino acids along a peptide chain
What is a dipeptide link
When two amino acids join together
What is a tripeptide bond
3 amino acids
What is a Polypeptide chain
Long chain of amino acids joined together
More than 3
What is condensation polymerisation
Molecule of water is eliminated during the formation of a peptide link
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
Secondary physical structure of protein
Amino acids linked by various amino acids to give shape - spiral
Hydrocarbon chain different in each amino acid
Tertiary physical structure of protein
Coiled/ folded chain of amino acids coiled/ folded further
More bonds form between the parts of polypeptide chain
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
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
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
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
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
Effect of acids/ alkalis on protein
Fibrous proteins affected
