Digestive system

Question 1

What is ingestion?

Answer 1

Swallowing.

Question 2

What is digestion?

Answer 2

Breaking food down into smaller soluble molecules.

Question 3

What is absorption?

Answer 3

When soluble molecules are taken into the blood stream or lymphatic system.

Question 4

What is peristalsis?

Answer 4

The involuntary contraction and relaxation of smooth muscles to push food through the digestive tract.

This is controlled by the autonomic nervous system.

Question 5

What is egestion?

Answer 5

Discharging undigested waste from the body.

Question 6

How do glands know when to secrete enzymes, bile or acid?

Answer 6

• The food is seen, tasted or smelt.
• Signals are then sent to the brain via the sensory neurons.
• The brain processes the signals and the send them to the digestive glands to release their products.

Question 7

What do the salivary glands produce?

Answer 7

Saliva which contains amylase, which begins the digestion of starch into maltose.

Question 8

Where are the different digestive glands?

Answer 8

• Salivary glands
• Stomach
• Pancreas
• Gal bladder
• Small intestine

Question 9

What enzymes does the stomach produce?

Answer 9

Acid which activates the enzymes pepsin and lipase.

Question 10

What enzymes does the pancreas produce and activate?

Answer 10

It secretes trypsin and activates lipase and amylase.

Question 11

What does the gall bladder produce?

Answer 11

Bile.

Question 12

What enzymes does the small intestine produce and activate?

Answer 12

Amylase, maltase and lipase.

It activates trypsin.

Question 13

What is startch?

Answer 13

Insoluble polysaccharides found in plants.

Question 14

What is maltose?

Answer 14

A disaccharide.

Question 15

What is glucose?

Answer 15

A monosaccharide sugar.

Question 16

What is glucose stored in your body as?

Answer 16

Glycogen.

Question 17

How is starch turned into glucose?

Answer 17

• (Amylase) (Maltase)
  Starch ————> Maltose ————> Glucose

Question 18

Why does glycogen need to be turned back into glucose to be used?

Answer 18

It is a polysaccharide and is therefore too large of a molecule to diffuse through cells, so it is broken down to glucose to be used for energy.

Question 19

How is glucose converted into glycogen?

Answer 19

By insulin.

Question 20

How is glycogen converted into glucose?

Answer 20

By glucagon.

Question 21

What are polysaccharides?

Answer 21

Long term storage molecules of energy.

Question 22

What does amylase do?

Answer 22

• (Amylase)
  Starch ———-> Maltose

Question 23

What does maltase do?

Answer 23

• (Maltase)
  Maltose ———> Glucose

Question 24

What does lipase do?

Answer 24

• (Lipase)
  Lipids ———> Fatty acids + Glycerol

Question 25

What are the two types of protease?

Answer 25

Trypsin and pepsin.

Question 26

What does trypsin do?

Answer 26

- (Trypsin) Proteins -----------> Amino acids

Question 27

What does pepsin do?

Answer 27

- (Pepsin) Proteins -----------> Smaller peptides + Amino acids

Question 28

Explain the process of digestion.

Answer 28

- (MOUTH) Your salivary glands produce mucin and amylase which lubricates and starts the break down of carbohydrates. Your teeth help grind the food up and as the food is lubricated by the saliva the tongue manipulates the food into a bolus, which is then swallowed. - (PHARYNX) The pharynx muscles contract and relax when swallowing to push down the food into the oesophagus. - (OESOPHAGUS) Peristalsis takes place in the oesophagus to push the bolus down into the stomach. - (STOMACH) The stomach churns up the food with stomach enzymes pepsin and lipase, produced by glands in the gastric pits. This churns as the muscles relax and contract. - (SMALL INTESTINE) The chyme leaves the stomach, into the small intestine. Bile from the gall bladder and enzymes from the pancreas feed into the duodenum via ducts to neutralise the chyme and continue digestion. Absorption then takes place in the jejunum and ileum. This occurs through the lining of the small intestine, which has villi, which have micro villi - giving the small intestine a large SA for absorbing nutrients. The small intestines are also vascular, so nutrients are taken by the capillaries and transported throughout the body. - (LARGE INTESTINE) The large intestine reabsorbs water from the undigested waste and passes it into the rectum. - (RECTUM) Impulses are sent to the brain to voluntarily decide to open the external sphincter muscle, to release waste from the anus.

Question 29

What adaptions does the small intestine have in order to facilitated absorption?

Answer 29

- Rich blood supply (The constant movement of blood means there will be a constant favourable concentration gradient for nutrients, which will be absorbed). - Villi & Micro Villi (These project into the lumen, increasing the SA). - Epithelial cells have many mitochondria to provide ATP for active transport.

Question 30

Explain the process of absorption in the small intestine.

Answer 30

- The sodium-potassium pump co-transports sodium and potassium between the epithelial cell and the blood. - Sodium then diffuses down its gradient through the sodium-glucose pump. It brings glucose with it via symport. - Glucose has now been taken into the cell. - The glucose then moves by facilitated diffusion into the blood. - The potassium is then pumped back out via the potassium pump. - Everything is now back as it was, and this process repeats.

Question 31

Why is the potassium pump so important within the epithelial cell?

Answer 31

Without the K pump there would be a build up of K in the epithelial cell, causing it to swell and therefore destroying the cell.

Question 32

What does the gastrointestinal tract (GI) consist of?

Answer 32

• Oesophagus • Stomach • Small intestine • Large intestine

Question 33

What do the walls of the GI tract consist of?

Answer 33

It has 4 layers. • Mucosa: The innermost layer surrounding the lumen. Which is the open space within the tube of the GI tract. The structure of mucosa varies in the different parts of the GI tract, according to the function of each part. • Submucosa: Consists of a dense layer of connective tissue with blood vessels, lymphatic vessels and nerves. • Muscularis: The ‘muscle layer’ has an inner oblique layer, a middle circular layer and an outer longitudinal layer. • Serosa: This forms the outer layer and consists of several layers of connective tissue.

Question 34

What is physical digestion?

Answer 34

This is when food is broken down into smaller pieces to increase the efficiency of chemical digestion.

Question 35

What is the process of physical digestion?

Answer 35

• Chewing the food which begins the mechanical breakdown and mixes the food with saliva. The saliva helps lubricate the chewed food and contains the enzyme salivary amylase. • It continues in the stomach where contraction of smooth muscle in the stomach wall causes a churning action, mixing the food with digestive enzymes and acid.

Question 36

What is chemical digestion?

Answer 36

This involves digestive enzymes that catalyse (speed up) the hydrolysis reactions that break down the large molecules in food (proteins, lipids and starch) into smaller and simpler molecules.

Question 37

What is the role of the pancreas in chemical digestion?

Answer 37

The pancreas is a major source of digestive enzymes. Pancreatic fluid is made by the pancreas and released into the duodenum via the pancreatic duct.

Question 38

What does pancreatic amylase do?

Answer 38

Completes the digestion of starch into maltose.

Question 39

What does sucrase do?

Answer 39

Converts sucrose into glucose and fructose.

Question 40

What does lactase do?

Answer 40

Converts lactose into glucose and galactose.

Question 41

What are the two other main components of chemical digestion?

Answer 41

• Hydrochloric acid: secreted by glands in the stomach wall, helping to sterilise food and provide acidic conditions required by stomach proteases such as pepsin. • Bile: this is produced in the liver, stored in the gall bladder and released into the duodenum via the bile duct and pancreatic duct. Bile acts as a surfactant and helps to break up large fat globules into smaller droplets as that lipases can work more effectively.

Question 42

What is the estimated total number of cells in the body?

Answer 42

3.0 x 10(13)

Question 43

What is the estimated number of bacterial cells in the body?

Answer 43

3.8 x 10(13)

Question 44

Where does most of the bacteria in our body reside?

Answer 44

In the colon, making up the microbiome.

Question 45

What does the gut bacteria (in the colon) help with in humans?

Answer 45

It aids the digestion of complex carbohydrates which aren’t broken down by the enzyme amylase.