Digestive System UNIT 1

Question 0

Oesophagus

Answer 0

The tube this takes food from the mouth to the stomach using waves of muscle contractions called peristalsis. Mucus is secreted from tissues in the walls, to lubricate the foods passage downwards

Question 1

The polymers in our food are…

Answer 1

Insoluble, they can’t be directly absorbed into the bloodstream and assimilated (made) into new products. The polymers have to be hydrolysed into smaller, more soluble molecules by adding water. This process happens during digestion. Hydrolysis is catalysed by digestive enzymes

Question 2

Stomach

Answer 2

Small sac, has lots of folds, allowing stomach to expand. The entrance and exit of stomach are controlled by sphincter muscles. The stomach walls produce gastric juice which helps break down food. Gastric juice consists of HCl, pepsin and mucus. Pepsin hydrolyses proteins into smaller polypeptide chains, only works in acidic conditions (provided by HCl). peristalsis of the stomach turns food into an acidic fluid called chyme

Question 3

Small intestine

Answer 3

Two main parts- the duodenum and the ileum. Chyme is moved along the small intestine by peristalsis. In the duodenum bile(which is alkaline) and pancreatic juice neutralise the acidity of the chyme and break it down into smaller molecules. In the ileum the small soluble molecules (eg glucose,amino acid) are absorbed through structures called villi that line the gut wall. Molecules are absorbed by diffusion, facilitated diffusion and active transport

Question 4

Large intestine

Answer 4

Absorbs water, salts and minerals. Like other parts of the digestive system it has a folded wall this provides a large surface area for adsorption. Bacteria that decompose some of the undigested nutrients are found in the large intestine

Question 5

Rectum

Answer 5

Faeces are stored in the rectum and then pass through sphincter muscles at the anus during defecation.

Question 6

Which two glands are very important in digestion

Answer 6

The salivary glands and pancreas

Question 7

Info on salivary glands involving digestion

Answer 7

They secrete saliva that consists of mucus, mineral salts and salivary amylase. This salivary amylase breaks down starch into maltose. It also has other roles in digestion, eg it helps to lubricate food, making it easier to swallow

Question 8

Info on the pancreas involving digestion

Answer 8

Releases pancreatic juice into the duodenum through the pancreatic duct. Pancreatic juice contains amylase, trypsin, chymotrypsin and lipase. Also contains sodium hydrogencarbonate which neutralises the acidity of HCl from stomach

Question 9

Digestive enzymes can be divided into 3 classes….

Answer 9

Carbohydrate…….catalyse the hydrolysis of carbohydrates
Proteases………’ ‘Proteins
Lipases…….’ ‘ lipids

Question 10

Define digestion

Answer 10

the act or process in living organisms of breaking down ingested food material into easily absorbed and assimilated substances by the action of enzymes and other agents.