Biology - Food

Nutrition

One of the characteristics of living organisms where nutrients provide materials and energy for metabolism and continuity.

Why is food necessary? (Reason 1)

It serves as an energy source.

Why is food necessary? (Reason 2)

It provides raw materials for growth and repair.

Six most common elements in food

Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, and Sulfur.

Five elements present in dissolved salts

Sodium, Chlorine, Magnesium, Calcium, and Potassium.

Three trace elements needed in small amounts

Iron, Copper, and Zinc.

Biomolecule

Chemicals found inside a living organism made of 14 elements in different ratios.

Elements in carbohydrates

Carbon, Hydrogen, and Oxygen.

Ratio of Hydrogen to Oxygen in carbohydrates

2:1.

General formula for carbohydrates

Cx(H2O)y.

Monosaccharides

The smallest unit of carbohydrates, sweet and soluble, such as Glucose or Fructose.

Glucose formula

C6H12O6.

Disaccharides

Carbohydrates composed of two monosaccharides joined together, sweet and soluble, such as Maltose, Sucrose, or Lactose.

Polysaccharides

Carbohydrates composed of many sugar units joined together and are insoluble, such as Starch, Cellulose, or Glycogen.

Starch

The form in which food is stored by plants.

Cellulose

Located in plant cell walls; it provides fiber in diets and is difficult to digest due to cross

Glycogen

The form in which glucose is stored in animals, specifically in the liver and muscle.

Metabolic role of carbohydrates

Glucose is broken down in respiration to release energy.

Structural role of carbohydrates

Cellulose is a primary component of plant cell walls.

Dietary sources of carbohydrates

Bread, pasta, and fruit.

Elements in lipids

Carbon, Hydrogen, and Oxygen, with no fixed ratio.

Fats vs. Oils

Fats are solid at room temperature while oils are liquid.

Triglyceride

The basic unit of a lipid consisting of one glycerol and three fatty acids.

Phospholipid

A lipid unit where one fatty acid is replaced by a phosphate, consisting of one glycerol, two fatty acids, and a phosphate.

Metabolic role of lipids

They are used to provide energy.

Structural role of lipids (Membranes)

Phospholipids are a major component of cell membranes.

Structural role of lipids (Protection)

Fats provide insulation and protection for internal organs like the kidneys.

Dietary sources of lipids

Olive oil, butter, cream, and nuts.

Elements in proteins

Carbon, Hydrogen, Oxygen, and Nitrogen.

Elements sometimes present in proteins

Sulfur and Phosphorus.

Amino acid

The subunit or basic unit of a protein; there are 20 common types.

Peptide bond

The bond used to join amino acids together.

Globular proteins

Folded proteins such as enzymes and hormones.

Fibrous proteins

Proteins with little folding that provide strength, such as Keratin (hair), Myosin (muscle), and Collagen (skin).

Metabolic role of proteins (Enzymes)

They act as biological catalysts in chemical reactions.

Metabolic role of proteins (Immunity)

Antibodies are produced in response to antigens.

Metabolic role of proteins (Messengers)

Hormones act as chemical messengers.

Structural role of proteins

Myosin provides strength in muscle and Keratin provides strength in hair.

Dietary sources of protein

Eggs, meat, fish, nuts, milk, and lentils.

Water soluble vitamin

Vitamin C.

Sources of Vitamin C

Oranges, lemons, and broccoli.

Metabolic role of Vitamin C

Formation of connective tissue (skin and blood vessels) and helping wounds heal.

Vitamin C deficiency

Scurvy, characterized by bleeding under the skin and loose teeth.

Fat soluble vitamin

Vitamin D.

Sources of Vitamin D

Liver, fish oils, egg yolk, and made by the skin in sunlight.

Metabolic role of Vitamin D

Uptake of calcium from the intestine for the maintenance of healthy teeth and bones.

Vitamin D deficiency

Rickets (in children) or Osteomalacia, characterized by weak, deformed bones.

Role of Magnesium in plants

Necessary for the formation of chlorophyll.

Role of Calcium in plants

Necessary for the formation of cell walls.

Role of Iron in animals

Necessary for the formation of haemoglobin.

Role of Calcium in animals

Necessary for the formation of strong bones.

Percentage of water in cell mass

70% to 95%.

Importance of water as a solvent

Provides a medium for chemical reactions and allows soluble substances to diffuse.

Metabolic importance of water

Participates in chemical reactions like photosynthesis.

Physical properties of water

It is a good absorber of energy, meaning it is slow to heat up and cool down.

Metabolism

All the chemical reactions taking place in an organism.

Anabolism

Reactions where smaller molecules are built into larger ones using enzymes and energy is absorbed (e.g., Photosynthesis, Protein Synthesis).

Catabolism

Reactions where large molecules are broken down into simpler forms using enzymes and energy is released (e.g., Respiration, Digestion).

Test for Starch

Add a few drops of iodine to the food sample.

Positive result for Starch

Reddish

Test for Reducing Sugar

Dissolve food in water, add Benedict’s solution, and heat in a water bath for 5 minutes.

Positive result for Reducing Sugar

Royal Blue Benedict's turns Brick Red.

Test for Protein

Dissolve food in water and add Biuret solution (sodium hydroxide and copper sulfate).

Positive result for Protein

Blue Biuret solution turns Purple.

Test for Fat

Rub a food sample on brown paper and leave to dry.

Positive result for Fat

A translucent spot remains on the paper when held to the light.

Control in food tests

Repeating the experiment using water instead of the food sample.