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[h] iGCSE Biology Notes Human nutrition
[q] What is a healthy diet?
What do you need to eat for a healthy diet?
[a]
- A balanced diet is one which contains all essential nutrients in the correct proportions
- The essential nutrients are carbohydrates, protein, lipids, minerals, nutrients and water
- You also need fibre (roughage)
[q] What is a healthy diet?
What do you need to eat for a healthy diet?
[a] Link the source to the vital nutrient
[q] Why is each nutrient needed?
[a] Draw a table and fill it in!
[q] What is a healthy diet?
What happens if you don’t get these things?
[a]
- What happens if you don’t get enough vitamin C?
- You get scurvy which causes bleeding gums, poor wound recovery and pain, especially in the legs
- What happens if you don’t get enough vitamin D?
- You get rickets which causes weak and brittle bones, bone pain and bone deformation in children
[q] Some key terms!
Make sure you know your digestion from your ingestion!
Ingestion
[a] Ingestion is the intake of substances like food and drink into the body through the mouth
[q] Digestion
[a] Digestion is the break down of large insoluble molecules into smaller water-soluble molecules by mechanical and chemical means
[q] Mechanical digestion
[a] Mechanical digestion is the break down of food into smaller piece without any chemical changes
[q] Chemical digestion
[a] Chemical digestion is where food molecules are digested into smaller molecules (chemical bonds are broken)
[q] Absorption
[a] Absorption is the movement of digested food molecules from the intestines into the blood
[q] Assimilation
[a] Assimilation is where food molecules move from the blood to the body cells and become part of the body cells
[q] Egestion
[a] Egestion is the removal of food that is undigested, as faeces, through the anus
[q] The digestive system and the alimentary canal
What organs make up the digestive system?
[a] Let’s draw it!
HUMAN DIGESTIVE SYSTEM
[q] Why do we have different types of teeth?
What is each tooth type for?
What does each tooth do?
[a] This is all part of mechanical digestion.
[q] Incisors
[a] Incisors are for biting and cutting food
[q] Canines
[a] Canines are for gripping and tearing food
[q] Premolars
[a] Premolars are for tearing and crushing food
[q] Molars
[a] Molars are for crushing and grinding food
[q] What is a tooth made of?
What do the parts of a tooth do?
What does each part do?
[a]
[q] Enamel
[a] Enamel is the hard outer layer
[q] Cement
[a] Cement is a bone like tissue that surrounds the tooth and keeps it in place
[q] The root
[a] The root is embedded in the bone
[q] Dentine
[a] Dentine is a softer material making up most of the tooth
[q] The gum
[a] The gum is a soft tissue that surrounds and protects the tooth and bone
[q] The pulp
[a] The pulp is another soft tissue in the tooth which contains the blood vessels
[q] What is bile for?
Why does the liver secrete bile?
[a]
- It neutralizes the acid from the stomach to create a slightly alkaline pH for the small intestine (for the enzymes)
- It emulsifies fats by increasing the surface area for lipase action
[q] Let’s look at villi!
What is the structure of a villus?
[a]
- Can anyone point to any labels of the villus?
[q] Why is a villus so great at absorption?
How are villi adapted for nutrient absorption?
[a]
- Huge surface area for faster diffusion, osmosis and active transport
- Villus cells have lots of mitochondria for energy for active transport
- Good blood supply so a high concentration gradient is maintained
- Only one cell thick so short diffusion pathway
[q] What is the lacteal for?
Why do villi have lacteals?
[a]
- Amino acids and glucose is absorbed into the blood capillaries, but glycerol and fatty acids (digested fats) are absorbed into the lacteals, which contain lymph fluid.
- All these lacteals join up into larger vessels as part of the lymphatic system and eventually lead back into the blood to be transported to cells.
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