Nutrition

Question 1

1. Distinguish between the terms autotrophic and heterotrophic.

Answer 1

Autotrophic:
- Synthesises its complex organic molecules from simpler molecules (inorganic) using light or chemical energy.

Heterotrophic:
- Cannot synthesise complex organic molecules, obtains them from consuming other organisms.

Question 2

2. What does holozoic nutrition mean?

Answer 2

The mode of nutrition which involves digesting internally.

Question 3

3. What does photoautotrophic mean?

Answer 3

Synthesises complex organic compounds from inorganic ones during the process of photosynthesis using light energy.

Question 4

4. What are organisms that makes organic compounds from inorganic ones using chemical energy called?

Answer 4

Chemoautotrophs (all prokaryotes)

Question 5

5. How does a saprophytic organism obtain nutrients?

Answer 5

Saprophytic organisms secrete digestive enzymes externally and absorb the digested substance.

Question 6

6. Define the term parasite.

Answer 6

An organism which obtains nutrition at the expense of the host it lives in or on.

Question 7

7. What five processes occur in holozoic nutrition?

Answer 7

5 stages of holozoic nutrition:
Ingestion
Digestion
Absorption
Assimilation
Egestion

Question 8

8. Distinguish between the terms egestion and excretion.

Answer 8

Egestion is getting rid of undigested food as faeces through the anus. Excretion is the removal of toxic materials, waste products of metabolism and excess substances from organisms.

Question 9

9. Describe how an Amoeba obtains nutrients.

Answer 9

They absorb nutrients directly through their cell membrane by diffusion.

Holozoic nutrition
The amoeba engulfs large food particles by endocytosis and fluid by pinocytosis in a vacuole, a lysosome fuses with it and digestive enzymes are secreted into it.
The digested material is absorbed into the cytoplasm, and the undigested waste is egested by exocytosis.

Question 10

10. Describe the gut of a Hydra.

Answer 10

Single body opening.
Tentacles paralyse prey and pull them into their hollow body cavity through the mouth.
Protease and lipase enzymes are secreted to digest the food extracellularly, and the products are absorbed before the indigestible remains are egested back out of the mouth.

Question 11

1. Draw a labelled diagram to show the layers in the wall of a human gut.

Answer 11

OUT

Serosa
- Tough connective tissue protects the gut and reduces friction with other organs.
Longitudinal muscles
Circular muscles
- Muscles contract in coordinated fashion to push food along
Submucosa
- Connective tissue contains blood and lymph vessels to take away absorbed products of digestion. Nerves are also present to coordinate muscular contractions.
Mucosa
- Innermost layer lining of the gut, bar the epithelium. Secretes alkali mucus to lubricate and protect from enzymes and HCl. Depending on the region, it secretes enzymes and absorbs digested food and nutrients.
Epithelium
Lumen

IN

Question 12

2. What is the main function of the buccal cavity teeth and tongue?

Answer 12

Mechanical digestion of the food and the tongue rolls the food into a bolus to be pushed to the back of the throat to the oesophagus.

Question 13

3. Which enzyme is present in saliva and what reaction does it catalyse?

Answer 13

Salivary Amylase Starch into disaccharides

Question 14

4. Describe the muscle action that transfers a bolus of food from the buccal cavity to the stomach.

Answer 14

Peristalsis
Smooth muscles contract and relax in a wave-like motion to push the bolus of food down.

Question 15

5. The stomach has 3 layers of muscle circular longitudinal and oblique; how does this structural feature relate to one of the functions of the stomach.

Answer 15

The muscles are for churning in the stomach.
Oblique is an extra layer of muscle for this function

Question 16

6. State three functions of hydrochloric acid in the stomach.

Answer 16

• Kill bacteria
• Optimum pH for pepsin
• Activates pepsinogen into pepsin

Question 17

7. Explain why pepsin is released from the cells that make it in the form of pepsinogen.

Answer 17

If it was released in its active form of pepsin it would digest the cells that produce it.

Question 18

8. Describe the reaction that pepsin catalyses.

Answer 18

The hydrolysis of peptide bonds. Endopeptidase that digests proteins into polypeptides.

Question 19

9. Describe the ways in which acidic chyme is neutralised in the duodenum.

Answer 19

Sodium hydrogen carbonate ions in Pancreatic juice
Bile salts in Bile
Alkali mucus (Hydrogen carbonate ions) in intestinal juice

Question 20

10. Where is bile manufactured and stored?

Answer 20

Produced in the Liver and Stored in the Gall bladder

Question 21

11. What is the function of bile in fat digestion?

Answer 21

Emulsifies large lipid globules into smaller globules to increase surface area for lipase to act on.

Question 22

12. Which enzymes does the pancreas produce and what reactions do they catalyse?

Answer 22

Pancreatic juice:
- Amylase hydrolyses remaining starch or glycogen into maltose.
- Lipase hydrolyses lipids to fatty acids and glycerol
- Trypsinogen (Inactive endopeptidase) activates chymotrypsinogen
- Chymotrypsinogen (inactive endopeptidase) Active form catalyses the hydrolysis of casein.
- Carboxypeptidase (an exopeptidase which hydrolyses terminal carboxyl end peptides)

Question 23

13. Draw a labelled diagram of a villus from the small intestine.

Answer 23

Capillary network
Lacteal

Question 24

14. Which products of digestion are absorbed into capillaries?

Answer 24

Amino acids
Glucose
Water absorbed by osmosis
Water-soluble vitamins

Question 25

15. What leaves the gut via a lacteal?

Answer 25

Fatty acids and glycerol enter epithelial cells via diffusion, where they recombine as triglycerides Fat-soluble vitamins

Question 26

16. What is absorbed in the colon?

Answer 26

Inorganic ions, Vitamins and a little water

Question 27

17. Distinguish between the terms endopeptidase and exopeptidase.

Answer 27

Endopeptidases hydrolyse non-terminal peptide bonds Exopeptidases hydrolyse terminal peptide bonds

Question 28

18. What activates trypsinogen and what does trypsinogen active?

Answer 28

Enterokinase activates trypsinogen into Trypsin Trypsin activates Chymotrypsinogen into Chymotrypsin (catalyses the hydrolysis of the milk protein casein- coagulates)

Question 29

19. Precisely where are dipeptides and disaccharides digested into their monomers.

Answer 29

The ileum by embedded enzymes on the apical membranes with their active sites facing outwards.

Question 30

20. Describe the absorption of glucose including the role of secondary active transport.

Answer 30

Sodium-glucose cotransport 1) Glucose and sodium are deposited into the cell via symport carrier proteins. High to low 2) To maintain Na+ gradient, Na+ is actively transported out cell into the Blood to keep it low so that S-G are continually deposited in from the extracellular fluid. 3) Passive transport of Glucose and Sodium into the cell, Glucose conc is higher inside the cell than it is in the constantly flowing blood. Thus, Glucose is facilitated and diffuses into the blood.

Question 31

1. What is the key difference between the diets of carnivores and herbivores.

Answer 31

Herbivores have high cellulose diets whereas carnivores do not and mostly eat diets of protein and lipids.

Question 32

2. Which has the longer gut herbivore or carnivore?

Answer 32

herbivore

Question 33

3. Which area of a non-ruminant herbivore contains mutualistic bacteria.

Answer 33

Non-ruminant herbivores have mutualistic bacteria in their enlarged caecum and appendix.

Question 34

4. What is the role of the mutualistic bacteria?

Answer 34

Secretes cellulase to digest cellulose in herbivores

Question 35

5. How many chambers are there in a ruminant stomach?

Answer 35

4 chambers: Rumen Reticulum Omasum Abomasum

Question 36

6. What is “chewing the cud” in ruminants?

Answer 36

They regurgitate cud from the rumen (a mixture of grass and saliva) after it has been digested into glucose and fermented. They regurgitate reformed cud from the reticulum and rechew it several times before passing it into the omasum.

Question 37

7. Which chamber of the ruminant stomach does protein digestion take place in?

Answer 37

Abomasum "true stomach"

Question 38

8. Which chamber of the ruminant stomach contains mutualistic bacteria?

Answer 38

Rumen

Question 39

9. Describe the features of herbivore dentition.

Answer 39

Horny pad on top instead of top incisors for chiselled lower jaw incisors to cut plant material against. Canines are indistinguishable from incisors Diastema is the gap to allows the tongue space to manipulate plant material to the molars to be ground down. Premolars and Molars have an interlocking W M shape for chewing and grinding plant material.

Question 40

10. Describe the features of carnivore dentition.

Answer 40

Incisors for cutting meat Large canines for gripping and piercing prey Premolars and Molars to crush bones Large carnassial teeth to shear meat off bones and crush bones

Question 41

1. Distinguish between the terms endoparasite and ectoparasite.

Answer 41

Endoparasites live inside hosts eg Tapworms Ectoparasites lives on hosts eg Headlice

Question 42

2. What is the common name for Pediculus?

Answer 42

Headlice

Question 43

3. How does Pediculus feed?

Answer 43

Obtains nutrition from the blood of the host

Question 44

4. Why does Pediculus have claws?

Answer 44

To latch onto the hosts' hair

Question 45

5. Where does Pediculus lay eggs?

Answer 45

Glued at the base of hairs

Question 46

6. How is Pediculus transmitted from host to host?

Answer 46

Direct contact

Question 47

7. Which type of parasite is Taenia solium?

Answer 47

Endoparasite

Question 48

8. What organism is the primary host of Taenia solium?

Answer 48

Humans

Question 49

9. What organism is the secondary host of Taenia solium?

Answer 49

Pigs

Question 50

10. How does infection of the primary host happen?

Answer 50

Eating infected pork meat that has not been cooked thoroughly

Question 51

11. How is a tapeworm adapted to not be dislodged by peristalsis?

Answer 51

Hooks and suckers on its scolex to hook onto the gut wall.

Question 52

12. How is the cuticle of a tapeworm adapted to resist gut secretions like enzymes?

Answer 52

Thick waxy cuticle protects it from digestive enzymes

Question 53

13. Why does a tapeworm lack a mouth?

Answer 53

It absorbs digested food/nutrients from the host directly through its body surface.

Question 54

14. What is the significance of a tapeworm producing a large number of eggs that are egested with faeces?

Answer 54

It increases the likelihood of transmission to another secondary host (pig) to consume and be infected by.