Nutrition in Humans (2.24-2.33B)

the 7 food groups that a balanced diet should include

carbohydrates, proteins, lipids, fibre, minerals, vitamins and water

sources and functions of carbohydrates

sources - wheat, potatoes, bread

function - long term energy store/release

sources and functions of proteins

sources - meat, fish, eggs

function - growth and repair of body tissues

sources and functions of lipids

sources - milk, cheese, yoghurt

function - protection and insulation of vital organs

sources and functions of fibre

sources - chia seeds, chickpeas, wholegrains

function - provides bulk to push food through the intestines

sources and functions of minerals (calcium and iron)

calcium

sources - cheese, milk, yoghurt

function - bone health and teeth

iron

sources - red meat, fish, eggs

function - haemoglobin production to facilitate oxygen transport

sources and functions of vitamins (A, C, D)

Vitamin A

sources - liver, fish, eggs

functions - eye health and cell growth

Vitamin C

sources - oranges, peppers, strawberries

functions - wound healing

Vitamin D

sources - body’s own production through sun exposure

functions - bone health, immune function

energy requirements based on age, activity level and pregnancy

age - amount of energy required increases towards adulthood (for muscle growth and growth) then decreases after

activity level - amount of energy required increases with activity level as more energy is needed to respire

pregnancy - amount of energy required by females during pregnancy will increase as more energy is needed to support the growing foetus

function of mouth in digestion

teeth breaks down food mechanically, food is rolled into bolus

oesophagus

long tube that connects to stomach. Peristalsis occurs here to help push bolus down towards stomach

stomach

food is turned into frothy mixture called chyme. Stomach churns mechanically, enzymes digest chemically and hydrochloric acid maintains optimum pH to increase enzyme activity rate

small intestine

more digestive enzymes and bile added. Coated with thousands of tiny projections called villi, each connected to a network of capillaries. Nutrients are absorbed into the bloodstream.

large intestine

where undigested food goes. Excess water is gradually absorbed as food is pushed along.

rectum/anus

temporarily holds waste, absorbs remaining water. Nerves in rectum sends a message to brain when there are faeces ready to be released.

pancreas

releases digestive enzymes into small intestine

where is bile produced and stored? what is its function?

produced in liver, stored in gallbladder

function: emulsifying (breaking down) lipids, neutralising stomach acid

roles of digestive enzymes - amylase (salivary), starch, maltose and amylase (pancreatic)

amylase (salivary)

substrate - starch; product - maltose; works in mouth

protease

substrate - proteins; product - amino acids; works in stomach

lipase

substrate - lipids; product - fatty acids and glycerol; works in small intestine

amylase (pancreatic)

substrate - starch; product - maltose; works in small intestine

adaptations of small intestine

very long (over 6m) - surface area increases rate of diffusion

villi - increases surface area to volume ratio

wall is only one cell thick - minimises diffusion distance and increases rate of absorption

partially permeable - only allows food molecules into bloodstream