An egg and a bowl of pulse both give you protein, yet their nutrient value is not the same. Ghee and mustard oil look nothing alike, yet both are lipids. This note looks at what protein and lipid are made of, where we get them and what they do in the body.
1. What protein is made of
A protein is built from carbon, hydrogen, oxygen and nitrogen, and sometimes sulphur too. After digestion, protein is converted into amino acids. Amino acids are the units that proteins are built from. So far 20 types of amino acid have been found in the human body.
By source, protein comes in two kinds. Animal protein comes from animals: fish, meat, egg, milk, cheese. Plant protein comes from plants: pulse, bean, seeds, pea, nuts.
2. Why animal protein is worth more
Nine out of the 20 amino acids are essential. The body can synthesise the other amino acids. Turn the two cards to check yourself.
count themtap to turn over
Essential amino acids
QuestionHow many of the 20 are essential?
AnswerNine.
QuestionWhere do the other amino acids come from?
AnswerThe body can synthesise them itself.
The essential amino acids are more available in animal protein, so the nutrient value of animal protein is much higher than that of plant protein.
Among plant foods, pulse, soybean, pea and maize have higher nutrient value. The other plant foods have no essential amino acid, so they have less nutrient value.
Protein is also what the body is built of. Bone, muscle, hair, bird feather, nail and animal horns are all made of protein. About 50% of the dry weight of an animal cell is protein.
3. Lipid: fat and oil
Lipids are composed of fatty acids and glycerol. There are 20 types of fatty acid in food, and the quality of a lipid depends on its fatty acids.
A lipid that is solid at normal temperature and pressure is called a fat. It has saturated fatty acids, for example the fat of fish and meat. A lipid that is liquid under the same conditions is called an oil. It has unsaturated fatty acids, for example soybean oil and mustard oil. Tap all four.
spot themtap a chip
Fat or oil?
A fat. Solid at normal temperature and pressure, saturated fatty acids.
A fat. Solid and saturated, like the fat of fish.
An oil. Liquid at normal temperature and pressure, unsaturated fatty acids.
An oil. Liquid and unsaturated, like soybean oil.
One question splits them: solid or liquid at normal temperature and pressure? Solid is fat, liquid is oil.
Animal lipid comes from meat with fat, butter, ghee, cheese and the yolk of eggs. Plant lipid comes from mustard, soybean, sesame, linseed, maize, coconut, sunflower and palm oil; cashew, pistachio and peanut are also sources. Now sort the sources of protein and lipid together.
sort themchip, then bin
Animal or plant?
Pick up a chip, then drop it in a bin. Ask: does it come from an animal or a plant?
Right. Next one.
Not yet. Does this food come from an animal or from a plant?
All in place. Cheese is an animal source of both protein and lipid.
4. What lipid does, and too little or too much
Among all food components, lipid produces the highest amount of heat and energy. It is also essential for the growth and nutrition of the body.
Lipid prevents the misuse of heat and works as a source of food storage for the future. It keeps the skin smooth, soft and healthy and protects it from skin disease. It also helps to absorb the vitamins A, D, E and K. The grid below has five roles; tap the cells in the lipid column.
gridtap a cell
Five roles of lipid
role
lipid
carbohydrate
highest energy
✓
no
smooth skin
✓
no
A, D, E, K absorption
✓
no
future storage
✓
no
prevents heat loss
✓
no
Highest energy: lipid. Lipid produces the highest heat and energy among all food components.
Smooth skin: lipid. Lipid keeps the skin smooth, soft and healthy and protects it from skin disease.
Vitamin absorption: lipid. Lipid helps to absorb the vitamins A, D, E and K.
Future storage: lipid. Lipid works as a source of food storage for the future.
Prevents heat loss: lipid. Lipid prevents the misuse of heat.
Too little lipid makes the skin dry and rough and damages its natural beauty. A long shortage breaks down stored protein and the body loses weight. Too much does harm as well: excess lipid disturbs blood circulation, and a fatty body is more prone to different diseases.
Too little lipid and too much both do harm. Drag the mark left and right and watch the skin, the weight and the blood vessel change.
drag and seeGo to both ends
The lipid dial
A model of what the book says, not a measurement.
5. Check yourself
The first question is about protein.
check yourselfpick one answer
Question 1
What is the unit of protein formation?
Carbolic acid is not the unit of protein.
Right. Amino acids are the units of protein formation.
Hydrochloric acid is not a protein unit.
Formic acid is not a protein unit. The right answer is: Amino acid.
In the next one, match the role of lipid.
check yourselfpick one answer
Question 2
What are fats that are liquid at normal temperature and pressure called?
Fats are solid at normal temperature. The right answer is: Oils.
Right. Lipids liquid at normal temperature and pressure are called oils (unsaturated).
Glycerol is one component of fat. The right answer is: Oils.
Proteins are not fats. The right answer is: Oils.
The last question is about a lack of lipid.
check yourselfpick one answer
Question 3
Which one produces the highest heat and energy?
Right. Cheese is a source of animal fat, and fat gives the most heat and energy.
Red amaranth is a vitamin source. The right answer is: Cheese.
Mango is mainly a carbohydrate and vitamin A source.
Pulse is protein and gives less energy than fat.
The whole note on seven cards.
cut from the notetap to turn over
Seven cards
QuestionHow many of the 20 amino acids are essential?
AnswerNine; the body can synthesise the others.
QuestionWhy is animal protein of higher nutrient value than plant protein?
AnswerAnimal protein has more of the essential amino acids.
QuestionWhat are fats that are solid and fats that are liquid at normal temperature called?