Digestion

Question 1

Why do animals eat?

Answer 1

To obtain energy
To maintain cellular metabolism
To allow growth and reproduction

Question 2

What type of trophs are all animals?

Answer 2

Heterotrophs

Question 3

What do animals extract from food?

Answer 3

Proteins
Carbs
Fat
Ions
Trace elements
Water
Vitamins
Essential amino acids

Question 4

What type of teeth do carnivores have?

Answer 4

Enlarged canines for gripping killing and tearing prey

Question 5

What type of teeth do herbivores have?

Answer 5

Incisors and canines to tear plants

Large molars and premolars to grind plant matter

Question 6

What type of teeth do omnivores have?

Answer 6

Multipurpose teeth

Question 7

What are gastroliths?

Answer 7

Stomach stones used to grind food

Question 8

Describe the structure of the human digestive system

Answer 8

Mouth
Stomach
Small intestine
Large intestine 
Rectum

Question 9

What is the mouth for?

Answer 9

Responsible for breaking up large amounts of food and mixing it with saliva

Question 10

What is the stomach for?

Answer 10

Responsible for mechanical mixing of food with stomach acid

Question 11

What is the small intestine for?

Answer 11

Responsible for further mixing and absorption of nutrients and is aided by bile and pancreatic juice

Question 12

What is the large intestine for?

Answer 12

Responsible for absorbing water and forming stool

Question 13

What is the rectum for?

Answer 13

Responsible for storing stool before expulsion

Question 14

What are the salivary glands for?

Answer 14

Secrete liquid and enzymes (salivary amylase) into the oral cavity for chemical digestion

Question 15

How does the stomach digest?

Answer 15

In anticipation as well as the arrival of food, it releases HCl and pepsin
Coordinated contractions of muscle layers lead to mixing of food creating chyme

Question 16

Where does chyme go after the stomach?

Answer 16

Released into small intestine duodenum via the pyloric sphincter

Question 17

How does HCl chemically digest food?

Answer 17

Denatures proteins by breaking electrostatic interactions in the tertiary structure
Also sterilises food

Question 18

Where does the HCl and pepsinogen come from?

Answer 18

Gastric pits are deep folds of the stomach mucosal epithelium

Question 19

How does HCl activate pepsinogen?

Answer 19

Pepsinogen is an inactive precursor enzyme that is activated by HCl into pepsin

Question 20

Describe the mucus-bicarbonate barrier

Answer 20

Bicarbonate neutralises the acid

Mucus is a physical barrier

Question 21

What happens when chyme enters the duodenum?

Answer 21

Digestive enzymes are released from the pancreas and gallbladder and bicarbonate is released to neutralise the acid

Question 22

What is gastrin?

Answer 22

A hormone produced by G cells and is innervated by the postganglionic fibres of the vagus nerve during parasympathetic stimulation

Question 23

What is secretin?

Answer 23

A hormone that is produced by S cells and inhibits the production of gastrin and neutralises the duodenum pH

Question 24

What is cholecystokinin?

Answer 24

A hormone that stimulates the release of bile and pancreatic juice

Question 25

What are the 3 parts of the small intestine?

Answer 25

Duodenum Jejunum Ileum

Question 26

How does absorption happen in the small intestine?

Answer 26

Na+/K+ ATPase generates a chemical gradient for Na+ and this requires energy The gradient is used to cotransport other substrates into the luminal membrane The interstitial membrane contains transporters (uniporters) which releases the substrates

Question 27

How are fats digested?

Answer 27

Fats are emulsified into micelles through bile in the intestinal lumen Pancreatic lipase hydrolyses the micelles into fatty acids and monoglycerides They enter the cell by diffusion Are resynthesised into triglycerides in the endoplasmic reticulum Triglycerides are packaged with cholesterol and phospholipids in protein-coated chylomicrons Chylomicrons are enclosed in vesicles and leave the cell by exocytosis and enter the lymphatic system

Question 28

Where does the absorbed material go?

Answer 28

Transported by the portal vein to the liver for detoxification

Question 29

What happens in the large intestine?

Answer 29

No digestive enzymes but bacterial digestion occurs | Salt and water are absorbed

Question 30

What is aldosterone?

Answer 30

A steroid hormone that stimulates the absorption of Na+ and water

Question 31

What is the appendix for?

Answer 31

A reservoir for beneficial microorganisms

Question 32

Describe fermentation in the cecum in herbivores?

Answer 32

A microbial fermentation chamber called the cecum extends from the large intestine for bacterial digestion

Question 33

What is coprophagy and why is it practiced?

Answer 33

Nutrient absorption in the cecum is inefficient so some eat waste to redigest and get more nutrients