Edexcel iGCSE Biology-2.25 functions of carbohydrate, protein, lipid- Study Notes- New Syllabus

Components of a Balanced Diet – Sources & Functions

📝 Introduction

• Our body needs different nutrients every day to stay healthy and work properly.
• Each nutrient has a specific function, so no single food can provide everything our body needs.
• Eating a variety of foods helps us get all the nutrients in the right amounts.

A balanced diet should include:

• Carbohydrates
• Proteins
• Lipids (fats and oils)
• Vitamins (A, C and D)
• Minerals (Calcium and Iron)
• Water
• Dietary fibre

🍞 Carbohydrates

Main Function

• Carbohydrates are the main source of energy for the body.
• They are broken down into glucose during digestion.
• Glucose is used in respiration to release energy.
• Any extra glucose is stored as glycogen in the liver and muscles.
• If glycogen stores become full, the remaining glucose is converted into fat.

Sources

• Rice
• Bread
• Chapati
• Pasta
• Potatoes
• Cereals
• Corn
• Sugar
• Fruits

Why are they important?

• Provide energy for daily activities.
• Supply energy to the brain and muscles.
• Help proteins perform their main job instead of being used for energy.

🍗 Proteins

Main Function

• Proteins are needed for growth and repair of body tissues.
• They help replace worn-out or damaged cells.
• Proteins are also used to make:
  • Enzymes
  • Hormones
  • Antibodies
• During long periods without enough carbohydrates or fats, proteins can also be used as an energy source.

Sources

• Meat
• Fish
• Eggs
• Milk
• Cheese
• Beans
• Lentils
• Soybeans
• Nuts

Why are they important?

• Build muscles and body tissues.
• Support normal growth.
• Help wounds heal faster.
• Protect the body against infections through antibodies.

🥑 Lipids (Fats and Oils)

Main Function

• Lipids are the body’s long-term energy store.
• They release more energy than carbohydrates when broken down.
• Fat is stored under the skin and around organs.

Sources

• Butter
• Vegetable oils
• Cheese
• Nuts
• Seeds
• Avocados
• Oily fish

Why are they important?

• Store energy for future use.
• Keep the body warm by reducing heat loss.
• Protect delicate organs from injury.
• Form part of cell membranes.
• Help absorb fat-soluble vitamins (A, D, E and K).

🥕 Vitamin A

Main Function

• Vitamin A helps keep the eyes healthy.
• It is especially important for seeing in dim light.
• It also helps maintain healthy skin and body tissues.
• Supports the immune system in fighting infections.

Sources

• Carrots
• Sweet potatoes
• Spinach
• Liver
• Milk
• Cheese
• Eggs

Why is it important?

• Maintains normal vision.
• Keeps skin healthy.
• Supports healthy growth.
• Helps the body resist infections.

🍊 Vitamin C

Main Function

• Vitamin C is needed to make collagen, an important protein found in skin, gums, blood vessels and connective tissues.
• It helps damaged tissues repair quickly.

Sources

• Oranges
• Lemons
• Strawberries
• Tomatoes
• Bell peppers
• Broccoli
• Kiwi fruit

Why is it important?

• Helps wounds heal.
• Keeps gums healthy.
• Maintains healthy skin.
• Strengthens connective tissues.
• Helps support the immune system.

☀️ Vitamin D

Main Function

• Vitamin D helps the body absorb calcium from food.
• It is essential for building strong bones and teeth.

Sources

• Sunlight (made in the skin)
• Oily fish
• Egg yolk
• Fortified milk
• Butter

Why is it important?

• Helps calcium enter the blood.
• Keeps bones hard and strong.
• Supports healthy teeth.
• Helps normal bone growth in children.

🦴 Calcium

Main Function

• Calcium is the main mineral needed for healthy bones and teeth.
• It also helps muscles and nerves work normally.

Sources

• Milk
• Cheese
• Yogurt
• Green leafy vegetables
• Sardines

Why is it important?

• Builds strong bones.
• Keeps teeth healthy.
• Helps muscles contract.
• Helps blood clot after an injury.
• Supports normal nerve function.

🩸 Iron

Main Function

• Iron is needed to make haemoglobin, the red pigment inside red blood cells.
• Haemoglobin carries oxygen from the lungs to all body cells.

Sources

• Red meat
• Liver
• Spinach
• Beans
• Lentils
• Fortified cereals

Why is it important?

• Helps transport oxygen around the body.
• Supports respiration by delivering oxygen to cells.
• Helps reduce tiredness by maintaining healthy red blood cells.

💧 Water

Main Function

• Water is one of the most important substances in the body.
• Every cell depends on water to function properly.

Sources

• Drinking water
• Milk
• Fruit juices
• Fruits
• Vegetables

Why is it important?

• Acts as a solvent for many substances.
• Transports nutrients and waste in the blood.
• Helps chemical reactions happen inside cells.
• Regulates body temperature through sweating.
• Prevents dehydration.
• Keeps cells hydrated.

🌾 Dietary Fibre (Roughage)

Main Function

• Dietary fibre is made mainly from cellulose found in plant cell walls.
• Humans cannot digest fibre, but it is still essential for a healthy digestive system.

Sources

• Wholegrain bread
• Brown rice
• Oats
• Fruits
• Vegetables
• Beans
• Cereals

Why is it important?

• Adds bulk to food.
• Helps food move through the intestines.
• Supports regular bowel movements.
• Prevents constipation.
• Maintains good digestive health.

🌟 Why Does the Body Need All These Nutrients Together?

A healthy diet should include all nutrients because each one has a different role.

• Carbohydrates provide energy.
• Proteins build and repair the body.
• Lipids store energy and protect organs.
• Vitamins keep body processes working normally.
• Minerals support healthy bones, blood and muscles.
• Water keeps every cell functioning.
• Dietary fibre keeps the digestive system healthy.

📊 Summary Table

⚡ Quick Recap
Carbohydrates → Main source of energy.
Proteins → Growth, repair, enzymes and antibodies.
Lipids → Store energy, insulate the body and protect organs.
Vitamin A → Healthy vision, skin and immunity.
Vitamin C → Collagen production and wound healing.
Vitamin D → Helps absorb calcium for strong bones.
Calcium → Healthy bones, teeth, muscles and blood clotting.
Iron → Makes haemoglobin to carry oxygen.
Water → Transport, chemical reactions and temperature control.
Dietary Fibre → Keeps the digestive system healthy and prevents constipation.