B3 Organisation and the digestive system

B3.1 Tissues and organs

Similar specialised cells (with similar structure and function) form a tissue. Muscular tissue contracts to bring about movement, glandular tissue contains secretory cells producing and releasing substances, and epithelial tissue covers the outside of the body and internal organs.

Organs are collections of tissues. The stomach has muscular tissue to churn down the food and digestive juices together, glandular tissue to produce digestive juices breaking down food, and epithelial tissue covers the inside and outside of the organ.

The pancreas make hormones to control blood sugar and some enzymes digesting food.

Organ systems are groups of organs working together to perform specific functions, and form organisms, having adaptations to make them effective.

B3.2 The human digestive system

The food you eat is made up of large insoluble molecules which the body can't use, so they are digested to make up smaller, soluble molecules.

The digestive system squeezes food through the oesophagus; starts at the mouth and ends at the anus. Glands make and release digestive juices containing enzymes to break down food.

The small intestine is where soluble food molecules are absorbed into the body which are transported around the body. The small intestine has a very large surface area due to villi, a good blood supply, and short diffusion distance, increasing diffusion and active transport.

The muscular walls squeeze the undigested food into the large intestine, where water is absorbed from the undigested food into the blood and forming faeces stored and passing out the body through the rectum and anus.

The liver produces bile, digesting lipids.

B3.3 Chemistry of food

Carbohydrates, lipids, and proteins are the main compounds making up the structure of the cell and important in the diet.

Carbohydrates provide us with fuel making reactions of life possible. They contain carbon, hydrogen, and oxygen and made up of sugars. Some carbohydrates only have one sugar unit or two sugar units joined together. These are simple sugars. Complex carbohydrates are made up of long chains of simple sugar units bonded together. Carbohydrates are broken down into glucose needed for cell respiration. Cellulose a carbohydrate supports plants.

Lipids are fats and oils. They're all insoluble in water and the most efficient energy store of the body. They are made up of three molecules of fatty acids joined to a molecule of glycerol which is always the same but the fatty acids vary.

Proteins build up cells and tissues and enzymes. They are made of carbon, hydrogen, oxygen, and nitrogen.They are made up of long chains of small units called amino acids.They are folded, coilded, and twisted to make specific 3D shapes enabling other molecules to fit into the protein. The bonds holding the proteins are sensitive to temperature and pH and if it's broken the shape of the protein is lost and won't function; it is denatured. Proteins act as enzymes, antibodies, hormones, and structural components of tissues.

Required practical: Identify the main food groups.

Carbohydrates: iodine test for starch - yellow-red iodine solution

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B3 Organisation and the digestive system

B3.1 Tissues and organs

Similar specialised cells (with similar structure and function) form a tissue. Muscular tissue contracts to bring about movement, glandular tissue contains secretory cells producing and releasing substances, and epithelial tissue covers the outside of the body and internal organs.

Organs are collections of tissues. The stomach has muscular tissue to churn down the food and digestive juices together, glandular tissue to produce digestive juices breaking down food, and epithelial tissue covers the inside and outside of the organ.

The pancreas make hormones to control blood sugar and some enzymes digesting food.

Organ systems are groups of organs working together to perform specific functions, and form organisms, having adaptations to make them effective.

B3.2 The human digestive system

The food you eat is made up of large insoluble molecules which the body can't use, so they are digested to make up smaller, soluble molecules.

The digestive system squeezes food through the oesophagus; starts at the mouth and ends at the anus. Glands make and release digestive juices containing enzymes to break down food.

The small intestine is where soluble food molecules are absorbed into the body which are transported around the body. The small intestine has a very large surface area due to villi, a good blood supply, and short diffusion distance, increasing diffusion and active transport.

The muscular walls squeeze the undigested food into the large intestine, where water is absorbed from the undigested food into the blood and forming faeces stored and passing out the body through the rectum and anus.

The liver produces bile, digesting lipids.

B3.3 Chemistry of food

Carbohydrates, lipids, and proteins are the main compounds making up the structure of the cell and important in the diet.

Carbohydrates provide us with fuel making reactions of life possible. They contain carbon, hydrogen, and oxygen and made up of sugars. Some carbohydrates only have one sugar unit or two sugar units joined together. These are simple sugars. Complex carbohydrates are made up of long chains of simple sugar units bonded together. Carbohydrates are broken down into glucose needed for cell respiration. Cellulose a carbohydrate supports plants.

Lipids are fats and oils. They're all insoluble in water and the most efficient energy store of the body. They are made up of three molecules of fatty acids joined to a molecule of glycerol which is always the same but the fatty acids vary.

Proteins build up cells and tissues and enzymes. They are made of carbon, hydrogen, oxygen, and nitrogen.They are made up of long chains of small units called amino acids.They are folded, coilded, and twisted to make specific 3D shapes enabling other molecules to fit into the protein. The bonds holding the proteins are sensitive to temperature and pH and if it's broken the shape of the protein is lost and won't function; it is denatured. Proteins act as enzymes, antibodies, hormones, and structural components of tissues.

Required practical: Identify the main food groups.

Carbohydrates: iodine test for starch - yellow-red iodine solution

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