Topic 6 Food and Digestion

Need for food

Energy (for respiration), growth and repair of tissues, vitamins and minerals to keep the body healthy

Diet

The food eaten in one day

Balanced diet

A diet that contains all of the required nutrients, in suitable proportions, and the right amount of energy

Why a balanced diet is essential

Gives every nutrient in the right proportions so the body has energy, can grow and repair, and stays healthy

Too little of a nutrient

Deficiency disease, e.g. no vitamin C causes scurvy, no vitamin D causes rickets

Too much energy

Obesity, which raises the risk of type 2 diabetes and heart disease

Malnutrition

A diet with the wrong balance of nutrients, too little or too much

Top of the healthy eating pyramid

Cakes and fizzy drinks (eat least)

The 7 food chemicals (PCFMVFW)

Proteins, carbohydrates, fats (lipids), minerals, vitamins, fibre, water

Function of carbohydrates

Source of energy (the main immediate energy source)

Sources of carbohydrates

Bread, rice, pasta, potatoes, cereals

Function of proteins

Growth and repair of tissues

Sources of proteins

Meat, fish, eggs, dairy, beans, nuts

Function of lipids

Energy storage, insulation, protection of organs (also an energy source)

Sources of lipids

Butter, oil, nuts, fatty meat

Function of fibre

Provides bulk (roughage) for the intestine to push food through

Function of vitamins and minerals

Needed in small amounts to maintain health

Function of water

Needed for chemical reactions to take place in cells

Vitamin C

Makes collagen (skin, gums, tissues); lack causes scurvy; found in citrus fruit and green vegetables

Vitamin D

Helps the body absorb calcium for strong bones and teeth; lack causes rickets; found in oily fish, eggs, dairy, sunlight

Calcium

Strong bones and teeth, and blood clotting; found in milk and cheese

Iron

Needed to make haemoglobin, which carries oxygen in red blood cells; found in red meat and spinach

Why "iron carries oxygen" is not precise enough

Iron is needed to make haemoglobin; the haemoglobin carries the oxygen

Why "fat is useless" is wrong

Fat is also an energy source, and gives insulation and protection of organs

Why low vitamin D causes weak bones

Vitamin D is needed to absorb calcium, and calcium is needed for strong bones

Monomer

A small repeating unit that joins in chains to make a large food molecule

Monomers of carbohydrates

Simple sugars, e.g. glucose

Monomers of proteins

Amino acids

Monomers of lipids

Fatty acids and glycerol

Ingestion

The taking of food and drink into the body

Absorption

The movement of nutrients from the alimentary canal into the blood

Assimilation

The uptake and use of nutrients by cells

Egestion

The removal of undigested food from the body as faeces

Digestion vs absorption

Digestion: breakdown of large food molecules into smaller molecules. Absorption: digested molecules move into the blood

Order of the food processes

Ingestion, digestion, absorption, assimilation, egestion