Nutrition

Question 1

Define autotroph

Answer 1

Organisms that use simple inorganic molecules to create complex organic molecules

Question 2

Define heterotroph

Answer 2

Organisms that consume complex organic food material

Question 3

GIve the three types of heterotroph and their definitions

Answer 3

Holozoic feeders follow the process of ingestion, digestion, absorption, assimilation and egestion. Parasites live in or on a host organism and cause it harm. Saprophytes feed by extracellular digestion

Question 4

Why do we have a tube gut?

Answer 4

Because we have a varied diet each part is specialised to digest/absorb different molecules

Question 5

From the outside in, what are the layers that make up the gut wall?

Answer 5

Serosa, longitudinal muscle layer, circular muscle layer, submucosa and mucosa

Question 6

What digestion occurs in the mouth?

Answer 6

Chemical digestion of starch by amylase, mechanical digestion by chewing

Question 7

How is food moved down the oesophagus?

Answer 7

Peristalsis- circular muscles contract and longitudinal muscles relax to push the food bolus along

Question 8

What digestion occurs in the stomach?

Answer 8

Chemical digestion of proteins by the enzyme pepsin to shorter chains. Mechanical digestion by churning

Question 9

Which cells produce pepsinogen in the stomach?

Answer 9

Chief cells (/zymogen cells)

Question 10

Which cells produce HCl in the stomach?

Answer 10

Oxyntic cells (/parietal cells)

Question 11

What are the purposes of HCl in the stomach?

Answer 11

To activate pepsinogen to pepsin, to kill bacteria and to give the optimum pH for pepsin enzyme

Question 12

Why is pepsinogen released in inactive form in the stomach and how is it activated?

Answer 12

Otherwise it would cause autolysis (digest the cells making it). It is activated by HCl

Question 13

What are endo and exopeptidases?

Answer 13

Endopeptidases hydrolyse peptide bonds in the middle of a polypeptide chain, exopeptidases at the terminal ends

Question 14

Which enzymes are produced by the pancreas?

Answer 14

Trypsin (endopeptidase), exopeptidases, lipase, amylase

Question 15

What is the function of bile and where is it produced/stored

Answer 15

Emulsifies lipids to increase surface area for lipase. Made in liver, stored in gall bladder

Question 16

Why is trypsinogen released in inactive form and how is it activated?

Answer 16

Otherwise it would cause autolysis (digest the cells making it). It is activated by enterokinase, also from the pancreas

Question 17

Which enzymes are fixed within the cell membrane of the epithelial cells in the duodenum and ileum to digest dimers intracellularly?

Answer 17

Lactase, sucrase, maltase and dipeptidase

Question 18

How are glucose and amino acids absorbed in the ileum?

Answer 18

Co transport with sodium ions

Question 19

How are lipids absorbed in the ileum?

Answer 19

Triglycerides have been broken down into fatty acids and glycerol, which can diffuse through the phospholipid bilayer

Question 20

What happens to glucose after it is absorbed in the ileum?

Answer 20

They enter capillaries by facilitated diffusion then transported via hepatic portal vein to the liver. Used for protein synthesis or deaminated

Question 21

What happens to amino acids after they are absorbed in the ileum?

Answer 21

They enter capillaries by facilitated diffusion then transported via hepatic portal vein to the liver. Used for respiration or stored as glycogen

Question 22

What happens to lipids after they are absorbed in the ileum?

Answer 22

Reassembled into triglycerides at SER. These then pass into the lacteal and are carried via the lymphatic system to the blood at the thoracic duct

Question 23

Why do we need to eat fibre?

Answer 23

Cellulose fibre is required to provide bulk to faeces and stimulate peristalsis.

Question 24

What is the function of the colon?

Answer 24

Absorbs the remaining water, together with vitamins

Question 25

Give the function of incisors, molars and diastema in herbivores

Answer 25

Sharp incisors snip off vegetation against horny pad, molars are ridged for grinding, diastema allows tongue to manipulate food

Question 26

Give the function of incisors, canines, carnassials and molars in carnivores

Answer 26

Sharp incisors strip meat from bone, canines grip/kill prey, carnassials are like scissors for slicing flesh/crushing bones, molars for cutting

Question 27

Why are herbivore guts longer than carnivore guts?

Answer 27

Protein and fat are easier to digest than cellulose, so need less time and enzyme action. Plant matter has less nutrients so herbivores must eat more

Question 28

List the four chambers of a ruminant gut

Answer 28

Rumen, reticulum, omasum, abomasum

Question 29

How are headlice adapted to be ectoparasites?

Answer 29

They have claws which hold onto the hairs and lays eggs which are glued to the base of hairs

Question 30

How has a tapeworm adapted to living in a human gut?

Answer 30

Thick cuticle, produces anti-enzymes, scolex has hooks and suckers to attach to the gut wall, reduced gut, produces large number of eggs