6.1 Digestion

Question 1

Purpose of Digestion

Answer 1

The main purpose of the digestive system is to break down large molecules into smaller subunits due to the fact:

• Large molecules are typically chemically inert and need to be broken down and reassembled into usable products.
  -Large molecules are typically insoluble and cannot be easily absorbed into cells, whereas smaller sub subunits are in soluble.

Question 2

Digestive System Components

Answer 2

The digestive system is composed of the alimentary canal and a variety of supporting accessory organs

Question 3

Alimentary Canal

Answer 3

Directly Transfers food
- Oesophagus- Food Tract from moth to stomach
- Stomach- Storage tank with low pH (protein digestion)
-Small Intestine - Site of nutrient absorption
- Large intestine - Absorbs water and dissolved minerals

Question 4

Accessory Organs

Answer 4

Supports Digestive processes
- Salivary gland - Moistens food bolus (starch digestion)
-Pancreas - Secretes key enzymes into small intestine
- Liver - Metabolizes absorbed nutrient’s (produce bile)
- Gall Bladder - Stores and secretes bile (emulsifies fats)

Question 5

Digestive Movement: Peristalsis

Answer 5

Peristalsis
- Unidirectional movement of food along alimentary canal
- Caused by contractions of sequential longitudinal muscles

Question 6

Digestive Movement: Segmentation

Answer 6

• Bidirectional mixing of food within the small intestine.
• Caused by contraction of non-sequential circular muscles.

Question 7

Types of Digestion: Mechanical Digestion

Answer 7

The breakdown of food via physical actions
- Chewing (grinding food using teeth)
- Churning (squeezing stomach contents)
-Segmentation (intestinal contrations)

Question 8

Types of digestion: Chemical digestion

Answer 8

The breakdown of food via chemical agents
- Stomach acids (low pH environment)
- Bile (emulsification of fats into droplets
- Enzymes (catalysen hydrolysis reactions)

Question 9

Starch Hydrolysis

Answer 9

Starch is composed of glucose monomers
- Is linear (amylose or branched (amylopectin)

Amylase (salivary or pancreatic) digestion starch
- It digests amylose into maltose disaccharides
-It digests amylopectin into dextrin chains

The Pancreas regulates the upstate of glucose
- Insulin increases glucose uptake by cells
- Glucagon decreases glucose uptake by cells

The liver is responsible for glucose storage.
- Glucose is stored as glycogen (polysaccharide)