Digestion (6.1)

Question 1

Define the alimentary canal

Answer 1

The organs through which food actually passes (eg. oesophagus, stomach, small/large intestine)

Question 2

Define the accessory organs

Answer 2

The organs that aid in digestion but do not transfer food (eg. salivary glands, pancreas, liver, gall bladder)

Question 3

What two groups of organs comprise the human digestive system?

Answer 3

The alimentary canal and the accessory organs.

Question 4

Define mechanical digestion

Answer 4

Where food is physically broken down into smaller fragments by chewing (mouth), peristalsis (oesophagus, stomach and small intestine) and segmentation (the intestines).

Question 5

Describe peristalsis

Answer 5

Occurs in the oesophagus, stomach and small intestine.
Continuous segments of longitudinal smooth muscle rhythmically contracting and relaxing, pushing food along the alimentary canal.

Question 6

Describe segmentation

Answer 6

Occurs in the intestines.
The contraction and relaxation of non-adjacent segments of circular smooth muscle.

Question 7

Define chemical digestion

Answer 7

Where food is broken down by the action of chemical agents (enzymes, acids and bile).

Question 8

Describe how stomach acids aid with chemical digestion

Answer 8

The stomach contains gastric glands which release digestive acids that create a low pH (acidic) environment. This denatures proteins/other macromolecules, aiding in digestion as it changes their shape, increasing their surface area for absorption and making it easier to transport.

Question 9

Describe how bile aids with chemical digestion

Answer 9

The liver produces bile which is stored in the gall bladder and released into the intestines. Bile contains bile salts which break down fats into smaller pieces (emulsification).

Question 10

Describe how enzymes aid with chemical digestion

Answer 10

Digestive enzymes are secreted predominantly by the pancreas but can also be released by the stomach and salivary gland. Enzymes allow for digestive processes to occur at speeds necessary for survival.

Question 11

What is absorption?

Answer 11

The process of taking nutrients from the digestive system into the blood.

Question 12

What are the features of villi?

Answer 12

High SA - microvilli
Surrounded by a dense capillary network (rich blood supply)
Single layer epithelium (minimal diffusion distance)

Question 13

What are the methods of absorption?

Answer 13

1) Simple diffusion (hydrophobic nutrients eg. lipids)
2) Facilitated diffusion (hydrophilic nutrients eg. fructose)
3) Active transport (eg. glucose/amino acids)
4) Osmosis (water/ions)

The main method of transport is endocytosis. This uses vesicles to pass fluid through the membrane.

Question 14

Salivary glands

Answer 14

Releases saliva to moisten food. It also contains enzymes to initiate starch breakdown (salivary amylase).
(Accessory organ)

Question 15

Oesophagus

Answer 15

Connects the mouth to the stomach. Food is mixed with saliva and moved in a bolus via peristalsis.
(Alimentary canal)

Question 16

Liver

Answer 16

Used for detoxification. Stores vitamins. Produces and secretes bile which helps in the absorption/emulsification of fats.
(Accessory organ)

Question 17

Gall bladder

Answer 17

Stores the bile produced by the liver. Releases it into the small intestine.
(Accessory organ)

Question 18

Stomach

Answer 18

Stores food (between 3-10 hours). Begins protein digestion.
(Alimentary canal)

Question 19

Pancreas

Answer 19

Produces enzymes which are released into the small intestine. Secretes hormones (insulin/glucagon) to regulate the concentration of blood sugar.
(Accessory organ)

Question 20

Small intestine

Answer 20

A long folded tube where nutrients are absorbed. Composed of three regions: duodenum, jejunum and ileum. Lined with smooth muscle for peristalsis and segmentation.
(Alimentary canal)

Question 21

Large intestine

Answer 21

The final section of the Alimentary canal. Water and dissolved minerals are absorbed here. Faeces pass through to the rectum.

Question 22

How is starch digested in the small intestine?
(Amylose - linear chains, amylopectin - branched chains)

Answer 22

The digestion of starch is initiated by salivary amylase in the mouth and then continued by pancreatic amylase in the small intestine. Amylase breaks down amylose into maltose and amylopectin into dextrin. Maltose and dextrin are digested by the maltase enzyme which is fixed to the epithelial lining of the small intestine. The hydrolysis of maltose and dextrin produces glucose monomers.

Glucose can be hydrolysed to produce ATP or stored as glycogen.

Question 23

Define surfactants

Answer 23

Substances that allow oil and water to mix/emulsify.

Question 24

What is assimilation?

Answer 24

The process of carrying absorbed nutrients to various cells to produce energy.

Question 25

What enzyme does the salivary glands produce?

Answer 25

Salivary amylase for digestion of starch (starch -> maltose)

Question 26

What enzymes do the stomach produce?

Answer 26

The stomach contains gastric glands which produce stomach acids that aid in chemical digestion. The stomach also produces proteases (protein -> polypeptides).

Question 27

What enzymes do the pancreas produce?

Answer 27

Pancreatic amylase (starch -> maltose)
Lipase (triglycerides -> fatty acids)
Endopeptidase (peptides -> amino acids)
Nuclease (DNA/RNA -> nucleosides)