Digestion.

Question 0

What is autotrophic nutrition?

Answer 0

The ability to use Carbon Dioxide from CO₂ to make complex organic molecules such as glucose. Most autotrophs are plants which carry out photosynthesis. Though there are also a group of bacteria which carry out Chemosynthesis.

Question 1

What are the two main types of Nutririon?

Answer 1

Autotrophic

Heterotrophic

Question 2

What is Chemosynthesis?

Answer 2

This is the use of energy from Chemical reactions to make organic molecules.

Question 3

What is Hetrotrophic Nutrition?

Answer 3

This is the uptake and use of complex organic molecules made by autotrophic living things.

Question 4

What are the two ways of being Heterotrophic?

Answer 4

Saprophytic nutrition

Holozoic nutrition.

Question 5

What is Saprophitic nutrition?

Answer 5

These are fungi and bacteria which decay dead plants and animals by producing extra cellular enzymes and absorb the end products of digestion across the whole surface of the body.

Question 6

What is Holozoic Nutrition?

Answer 6

This is the ingestion and digestion of solid organic material. in order to take in and digest solid food all animals need the following:

A mouth
Teeth to mechanically crush food
A gut (alimentary canal)

Question 7

Outline the structure of the ilium. (Layer sequence is the same for the rest of the gut)

Answer 7

1. ) Epithelium
2. ) Mucosa
3. ) Muscularis mucosa.
4. ) Submucosa
5. ) External muscle coat
6. ) Serosa.

Question 8

What does the epithelium of the gut consist of?

Answer 8

This is a single layer of cells consisting of two cell types, microvilli epithelium and goblet cells.

Question 9

What does the mucosa consist of?

Answer 9

Found directly beneath the epithelium it is folded to produce finger like villi. Between the villi there are crypts of Lieberkühn which are lined with specialized epithelial called cells of paneth which secrete intestinal juice obtaining all of the final enzymes to complete digestion.

Question 10

What is the Muscularis mucosa?

Answer 10

This is a thin layer of muscle separating the mucosa and submucosa.

Question 11

What is the submucosa?

Answer 11

This layer contains lymphatic vessels, arterioles and venuoles.

Question 12

What does the External muscle coat consist of?

Answer 12

This is a thick layer of circular muscle followed by a thin layer of longitudinal muscle.

Question 13

What is the Serosa?

Answer 13

This is a thin layer of tissue which binds the gut to the body wall.

Question 14

What is the sequence of steps involved in human digestion?

Answer 14

1. ) Mouth
2. ) Oesophagus
3. ) Stomach
4. ) Duodenum
5. ) Illium
6. ) Colon
7. ) Rectum.

Question 15

What role does the mouth play in digestion?

Answer 15

The teeth are used to mechanically break down the food to reduce particle size and increase the surface area for enzyme action.

Question 16

Where is saliva produced in the mouth?

Answer 16

In three salivary glands in the mouth.

Question 17

What does saliva consist of?

Answer 17

Saliva contains water, mucus salt and amylase. It has a pH of about 7 Amylase hydrolysis starch to the disaccharide maltose.

Question 18

What role does the Oesophagus have in the human digestive system?

Answer 18

This is a simple muscular tube which transports food from the pharynx to the stomach.

Question 19

Outline the structure of the stomach.

Answer 19

This is a muscular bag the inner wall of which is folded into ridges called rugae. Gastric pits dive deeply into this muscle wall and produce gastric juice.

Question 20

What does gastric juice contain?

Answer 20

Water, mucus, HCl and two enzymes, rennin and pepsin.

Question 21

Hat are the two main functions of the stomach?

Answer 21

To begin protein digestion.

To protect the body from pathogens.

Question 22

In what form is pepsin secreted, and why is it secreted in this form?

Answer 22

Pepsin is secreted as an inactive form called pepsinogen which prevents the cells which make it being digested.

Question 23

How is pepsinogen converted to pepsin?

Answer 23

It is converted by the low pH (2.0) in the stomach.

Question 24

What is the role of pepsin?

Answer 24

Pepsin is an endopeptidase

I.e it breaks down peptide bonds within polypeptide chains to create shorter (about 13 units long) called peptones.

Question 25

Where are other protease enzymes found and what is their role?

Answer 25

These are found in the rest of the gut and are called exopeptases which remove amino acids form the ends of the chain.

Question 26

What is the function of rennin in the stomach?

Answer 26

Rennin causes milk protein called called caecein to clot together. It is produced mainly in young mammals because milk protein is their only protein source.

Question 27

What two fluids enter the duodenum?

Answer 27

Bile

Pancreatic juice.

Question 28

What is bile and what is it’s function?

Answer 28

Bile is a geen alkali fluid containing bile salts and various toxins. It’s main function in digestion is to emulsify fats I.e the salt creates lipid droplets which speeds up lipid digestion by lipase.

Question 29

What is pancreatic juice and what is it’s function?

Answer 29

This is a secretion of the pancreas which contains the enzymes lipase, trypsinogen and pancreatic amylase.

Question 30

What is the main function of the duodenum?

Answer 30

To digest lipids which are converted directly into fatty acids and glycerol. I.e lipid digestion begins and ends in the duodenum. Starch digestion that began in the mouth continues again in the duodenum except that the pH optimum is closer to 9 than 7.

Question 31

Where is protein digestion resumed?

Answer 31

Protein digestion resumes in the Illium when trypsinogen is activated to tripsin.