IGCSE Biology - Human Nutrition

Flashcards for vocabulary review of human nutrition topics in IGCSE Biology.

Balanced Diet

Consists of all of the food groups in the correct proportions.

Necessary Food Groups

Carbohydrates, Proteins, Lipids, Vitamins, Minerals, Dietary Fibre, Water

Vitamin C

Forms an essential part of collagen protein, which makes up skin, hair, gums, and bones. Deficiency causes scurvy.

Vitamin D

Helps the body to absorb calcium and so required for strong bones and teeth.

Calcium

Needed for strong teeth and bones and involved in the clotting of blood. Deficiency can lead to osteoporosis later in life.

Iron

Needed to make haemoglobin, the pigment in red blood cells that transports oxygen.

Vitamin D Deficiency

Causes rickets - where bones become soft and deformed because vitamin D is needed for absorption of calcium into the body which is a key component of bones and teeth.

Iron Deficiency

Causes anaemia – where there are not enough red blood cells so tissues do not get enough oxygen delivered to them because iron is a key component of haemoglobin.

Malnutrition

Caused by not eating a balanced diet.

Types of Malnutrition

Starvation, Coronary heart disease, Constipation, Obesity

Kwashiorkor

Caused by a lack of protein in the diet, most common in children under 2. Often caused by poverty as high protein foods tend to be more expensive and scarcer. Children suffering from kwashiorkor are always underweight for their age but they often have a swollen abdomen as their diet may contain a lot of carbohydrate.

Marasmus

The most severe form of PEM, where there is a lack of both protein and energy in the diet. People suffering from this have a much lower body weight than normal and look emaciated.

Ingestion

The taking of substances, e.g. food and drink, into the body through the mouth

Mechanical digestion

The breakdown of food into smaller pieces without chemical change to the food molecules

Chemical digestion

The breakdown of large, insoluble molecules into small, soluble molecules

Absorption

The movement of small food molecules and ions through the wall of the intestine into the blood

Assimilation

The movement of digested food molecules into the cells of the body where they are used, becoming part of the cells

Egestion

The passing out of food that has not been digested or absorbed, as faeces, through the anus

Mouth/Salivary Glands

Where mechanical digestion takes place - teeth chew food to break it into smaller pieces and increase its surface area to volume ratio. Amylase enzymes in saliva start digesting starch into maltose.

Oesophagus

Tube that connects the mouth to the stomach - where the food bolus goes after being swallowed. Wave-like contractions will take place to push the food bolus down without relying on gravity.

Stomach

Food is mechanically digested by churning actions while protease enzymes start to chemically digest proteins. Hydrochloric acid is present to kill bacteria in food and provide the optimum pH for protease enzymes to work.

Small Intestine

First section is called the duodenum and is where the food coming out of the stomach finishes being digested by enzymes produced here and also secreted from the pancreas. Second section is called the ileum and is where absorption of digested food molecules takes place. The ileum is long and lined with villi to increase the surface area over which absorption can take place.

Large Intestine

Water is absorbed from remaining material in the colon to produce faeces. Faeces is stored in the rectum and removed through the anus.

Pancreas

Produces all three types of digestive enzyme amylase protease and lipase. Secretes enzymes in an alkaline fluid into the duodenum for digestion to raise pH of fluid coming out of the stomach.

Liver

Produces bile to emulsify fats (break large droplets into smaller droplets) - an example of mechanical digestion. Amino acids not used to make proteins broken down here (deamination) which produces urea.

Gall Bladder

Stores bile to release into duodenum as required

Diarrhoea

The loss of watery faeces from the anus. Can be effectively treated by oral rehydration therapy.

Vibrio Cholerae Action

Bacteria attach to the wall of the small intestine, produce a toxin, the toxin stimulates the cells lining the intestine to release chloride ions from inside the cells into the lumen of the intestine. These chloride ions accumulate, and water starts to move out of the cells into the intestine by osmosis. Large quantities of water are lost from the body in watery faeces.

Mechanical Digestion

The breakdown of food into smaller pieces without chemical change to the food molecules. It is mainly carried out by the chewing action of the teeth, the churning action of the stomach and the emulsification of fats by bile in the duodenum.

Incisors

Chisel-shaped for biting and cutting

Canines

Pointed for tearing, holding and biting

Premolars and molars

Larger, flat surfaces with ridges at the edges for chewing and grinding up food

Plaque

A sticky film with saliva, which coats teeth and the areas where they attach to gums. Bacteria in this plaque feed on sugar and turn it into acids, which gradually dissolve the enamel coating of the teeth, working its way into the dentine.

Three Main Types of Digestive Enzymes

Amylases, Proteases and Lipases

Carbohydrases

Amylases are produced in the mouth and the pancreas (secreted into the duodenum) and digest starch into smaller sugars.

Proteases

Proteases are a group of enzymes that break down proteins into amino acids in the stomach and small intestine (with the enzymes in the small intestine having been produced in the pancreas).

Lipases

Lipase enzymes are produced in the pancreas and secreted into the duodenum and digest lipids into fatty acids and glycerol.

Hydrochloric Acid Role

Kills bacteria in food and gives an acid pH for enzymes to work in the stomach

Low PH Helpfulness

The low pH kills bacteria in food that we have ingested as it denatures the enzymes in their cells. Hydrochloric acid ensures that conditions in the stomach remain within the optimum range for pepsin to work at its fastest rate.

Bile's Role

It is alkaline to neutralise the hydrochloric acid which comes from the stomach.It breaks down large drops of fat into smaller ones. This is known as emulsification. The larger surface area allows lipase to chemically break down the lipid into glycerol and fatty acids faster.

Absorption

The movement of digested food molecules from the digestive system into the blood (glucose and amino acids) and lymph (fatty acids and glycerol)

Adaptations of the Ileum for Absorption

It is very long and has a highly folded surface with millions of villi (tiny, finger like projections). These adaptations massively increase the surface area of the ileum, allowing absorption to take place faster and more efficiently.

Adaptations in Small Intestine

Microvilli on the surface of the villus further increase surface area for faster absorption of nutrients. Wall of villus is one cell thick meaning that there is only a short distance for absorption to happen by diffusion and active transport. Well supplied with a network of blood capillaries that transport glucose and amino acids away from the small intestine in the blood. Lacteal runs through the centre of the villus to transport fatty acids and glycerol away from the small intestine in the lymph