Biology - Human Nutrition

Diet - 7 food groups

Carbohydrates, lipids, protein, fibre, vitamins, minerals, water

Carbohydrates

Sugars (glucose) are used in respiration to release energy. Starch is made of many glucose molecules joined together - so starch is also a source of energy.

How much energy the body requires varies with:

age, level of activity, sex and pregnancy

Proteins

Made of many amino acids joined together. They are needed for growth and repair and to make enzymes

Lipids

Made of 2 types of molecule: glycerol and fatty acids. A source of energy and are also used for insulation and protection and they are important in making cell membranes

Iron

Make haemoglobin, sourced from red meat and pluses, deficiency disease is anaemia

Calcium

Make strong teeth and bones, sourced from dairy products, deficiency disease is ricketts

Vitamin A

Used in immune system and eyesight; sourced from vegetables, deficiency is poor eyesight and low light levels

Vitamin C

Used in production of conega and neurotransmitters; sourced from citrus fruits; deficiency is scurry

Vitamin D

Used in building bone, sourced from fish; deficiency is Ricketts and Osteoporosis

Water

Essential solvent for chemical reactions in the body. Blood plasma = mostly water; many substances are dissolved in the blood plasma to be transported around the body. Water is important in temperature regulation in the body; the evaporation of sweat helps lower the temperature of blood

Fibre

Plant material that can’t be digested. (cellulose). assists in the movement of food through the intestine by peristalisis

Energy from food

Measure the energy conten of a food by burning a sample of food under a boiling tube of water and measuring the temperature change. 4.2 joules of energy increases the temperature of 1g of water by 1°C. energy release / g = (mass of water (g) x temperature rise (°C) x 4.2) / mass of food sample (g)

Parts of digestive system

Mouth, salivary glands, oesophagus, stomach, pancreas, small intestine, appendix, liver, gall bladder, large intestine, rectum, anus

Peristalsis

This moves food down the oesophagus and through the alimentary chord. As the food is swallowed, a small sphere called a bolus is formed. Smooth muscle in the walls of the oesophagus contract to push the bolus down. This contraction continues in a wave all along the oesophagus. It also occurs in the small and large intestine

Ingestion

Eating; how food enters your digestive system

Digestion

Break down of large insoluble molecules into small soluble molecules (by enzymes)

Absorption

Movement of small soluble molecules into the blood streams from the small intestine

Assimilation

Conversion of small soluble molecules into molecules that can be used by the body

Egestion

Removal of undigested food through the anus

Excretion

Removal of waste (toxic or excess metabolites)

Physical digestion

The process of breaking down food into smaller pieces without changing its chemical structure, typically through mechanical means such as chewing or grinding.

Chemical digestion

When large insoluble molecules are broken down into small, soluble molecules by the action of digestive enzymes. This occurs in the mouth, stomach and small intestine

Salivary Amylase

Made in mouth. Site of action = mouth. Turns starch → maltose

Pepsin

Made in stomach. Site of action = stomach. Turns proteins → polypeptides

Pancreatic Amylase

Made in pancreas. Site of action = small intestine. Turns maltose → glucose

Protease (trypsin and peptidose)

Made in pancreas. Site of action = small intestine. Turns proteins → amino acids

Lipase

Made in pancreas. Site of action = small intestine. Turns lipids → fatty acids and glycerol

Role of bile

Produced by liver. Stored in gull bladder. Job 1: emulsifies the fats by turning large fat droplets into many smaller fat droplets to increase their surface area to increase rate of reaction. Job 2: Neutralises the chyme when it leaves the stomach

Chyme

The mush that leaves the stumach

Small intesitne

Has two parts: the duodenum and the ileum. By the time food reaches the ileum, digestion is complete and the small molcules must be absorbed into the blood to be transported around the body. This happens by diffusion and active transport

Adaptions of small intestine

• Wall of ileum is covered in villi which in turn have microvilli and this provides a large surface area

• The wall of the ileum is 1 cell thick which gives a short diffusion distance

• There is a large network of capillaries to keep blood flowing givin a steep concentration gradient

Waste material

Consists of mainly fibre, water, minerals, vitamins and dead red blood cells (+ other dead cells)

Large intestine

1. Undigested material arrives at large intestine from small intestine

2. Water is absorbed into the blood

3. The end result is solid waste (faeces)

4. Faeces is stored in the rectum

5. Faeces is egested through the anus