Digestion

Question 1

What is ingestion?

Answer 1

The take in of food from buckle cavity (mouth)

Question 2

What is digestion?

Answer 2

The break down of food (mechanically or chemically) from large molecules into smaller molecules

Question 3

What is absorption?

Answer 3

• Nutrients move from small intestine into the bloodstream

- Products of digestion are absorbed into your bloodstream

Question 4

What is assimilation?

Answer 4

• Using nutrients for metabolic reactions, when digested molecules have been absorbed into the cells of the body by diffusion and assimilated
• They are moved into body cells, the digested molecules then become part of the cells
• E.G. When amino acids (form digested proteins) are assimilated they are used by cells to make cellular proteins
• They are used for energy and to build up into chemicals needed by the cells

Question 5

What is egestion?

Answer 5

• The removal on undigested food in the form of faeces
• Water, undigested food, enzymes, dead cells, bile pigments and mucus move though the large intestine. Water is removed. The remaining material is passed out of the anus as faeces

Question 6

What is excretion?

Answer 6

The removal of harmful chemicals produced by you metabolism

Question 7

What happens to large insoluble molecules in the breakdown?

Answer 7

Large insoluble molecules are broken down mechanically and chemically into small soluble molecules which can be absorbed into the blood

Question 8

What happens in your mouth?

Answer 8

1. Chemical digestion takes place as the amylase in the salivary glands turn the starch into maltose
2. Mastication also occurs which is when your teeth break down food mechanically

Question 9

What happens in your oesophagus? How and why does food move through the gut by peristalsis?

Answer 9

1. Food moves down via peristalsis which is a series of involuntary muscle contractions that move the bolus of food down the digestive tract
2. There is muscular tissue all the way down the alimentary canal, its job is to squeeze boluses through your gut, otherwise it would get clogged up with bits of old food
3. This squeezing action, which is waves of circular muscle contractions is called peristalsis

Question 10

What happens in your stomach?

Answer 10

-Food is temporarily stored here
Gastric Juices are secreted:
1. Hydrochloric acid kills the bacteria and creates an optimum pH (pH 2) for protease
2. Pepsin is a protease enzyme breaks down the proteins into amino acids
-Mechanical Digestion also occurs:
3. Muscles in the wall of the stomach contract to churn up food, while it is being chemically digested
-Mucus is secreted by stomach cells to protect the lining from the hydrochloric acid

Question 11

What is the sphincter?

Answer 11

The sphincter muscle is a ring on muscle that holds semi-digested food in the stomach and when it relaxes it releases food into the first part of the small intestine, the duodenum

Question 12

Describe the pancreas

Answer 12

• The pancreas is attached to the duct that goes to the small intestine
• It secrets amylase, protease, and lipase into the small intestine

Question 13

Describe the gallbladder

Answer 13

• Attached to the bile duct

- Stores bile

Question 14

Describe bile, what is its function?

Answer 14

• Biter, greenish, yellow alkaline liquid
• It neutralises the acidic stomach food, so that the enzymes can work in the small intestine
• Emulsifies fats: breaks lipids from large to small droplets so that there is a bigger surface area of lipids for the lipase enzyme to work on, which makes its digestion occur faster (more efficient for lipase enzyme)

Question 15

Describe the liver

Answer 15

• Produces bile
• Removes toxins
• Where RBCs go when they have done their job, and the iron in RBCs rust and make faeces brown so if you have anaemia your faeces might be pale

Question 16

Describe the small intestine, how is it adapted for its function?

Answer 16

1. Chemical digestion, 90% of absorption and major organ of digestion
   Duodenum (most digestion)
   Jejunum (absorption of nutrients and water)
   - The ileum absorbs the digested food
2. LSF, which means that it can quickly and efficiently absorb the soluble products of digestion into the blood
3. Very long (over 6m), so there is time to break down and absorb all the food before it reaches the end
4. Folds in lining
5. Millions of villi each only about 1-2mm long, provides a massive area in contact with the digested food
6. Each villus also has microvilli which increase the surface area for absorption even more

Question 17

How are the villi adapted for their function?

Answer 17

-They are one cell thick (single permeable layer of surface cells)
-Rich blood supply
-Microvilli
These help to make absorption glucose and amino acids quick and efficient

Question 18

Describe the large intestine

Answer 18

-Colon absorbs most of remaining water content

Question 19

Where is amylase found and what does it do?

Answer 19

-Found: salivary glands, pancreas and small intestine
-Job: breaks starch down into glucose
(Maltase converts maltose into glucose)

Question 20

Where is lipase found and what does it do?

Answer 20

• Found: pancreas and small intestine

- Job: breaks lipids down into fatty acids and glycerol

Question 21

Where is protease found and what does it do?

Answer 21

• Found: stomach, pancreas and small intestine

- Job: breaks proteins down into amino acids

Question 22

What do digestive enzymes do?

Answer 22

Digestive enzymes break down big molecules into smaller ones