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Summary AQA level 3 extended certificate - Applied science - Unit 4 - Human Biology revision notes £4.49
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Summary AQA level 3 extended certificate - Applied science - Unit 4 - Human Biology revision notes

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This document gives summary notes for unit 4 Human Biology. Let me know if you have any questions.

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  • June 27, 2023
  • 14
  • 2022/2023
  • Summary

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Applied science – The human body

Digestive system




Figure 1 - human digestive system



Mouth- where the food enters the digestive system, contains salivary glands
Salivary glands- produces amylase and saliva which break down starch.
Oesophagus- tube which transports food from mouth to stomach, it causes peristalsis
allowing food to move down into stomach.
Liver- produces bile which neutralizes stomach pH and emulsifies fats.
Gall bladder- where bile is stored and then released.
Stomach- protease enzyme pepsin is produced here, as well as HCl which maintains the
stomachs acidic conditions as well as killing bacteria.
Pancreas- produces amylase, protease, and lipase, which are then released into the
small intestine
Small intestine- produces protease, amylase, and lipase to complete the digestion
process.
Large intestine- where excess water and nutrients are absorbed from foods.

, Figure 2 – Descriptive table about Amylase, Maltose, Endopeptidase, Exopeptidase, Dipeptidase and Lipase enzymes

Types of digestion

Mechanical- physical breakup of food molecules into smaller molecules, allowing
enzymes to act.
Chemical- breakdown of complex molecules into simple molecules.

Hydrolysis and condensation reactions

Hydrolysis- insertion of water molecule which breaks bonds e.g. peptide, glycosidic
Condensation- elimination of water molecules, causing joining of components.

Absorption in the small intestine

Adaptations to max absorption

1. Good blood supply which maintains the concentration gradient.
2. Epithelium is one cell thick so there is a short diffusion pathway.
3. Epithelium cells have microvilli on their surface, which allows a greater surface area.
4. Lacteals run into each villus, these absorb glycerol and fatty acids.

Absorption of glucose and protein in ileum

Glucose and protein are absorbed in the ileum by co-transportation.
1. Na+ ions are actively transported out of epithelial cell into blood, which lowers
Na+ concentration in the epithelial cell.
2. Na+ enters a cell from gut down concentration gradient via a carrier, this
generates energy which allows the same carrier to actively transport glucose into
cell.
3. Low concentration of glucose in cell rises, therefore glucose can move into blood
down concentration gradient via facilitated diffusion.
4. Na+ also moves into blood, but it is not co-transported with glucose in this way.

Amino acids are also absorbed in the same way as glucose but use different carriers.

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