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Biology of Cells and Organisms (sem 1) > Digestion > Flashcards

Digestion Flashcards

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1
Q

What is the difference between heterotrophs and autotrophs?

A

Heterotrophs - unable to synthesise organic compounds from inorganic molecules, must ingest them e.g animals
Autotrophs - can synthesis organic compounds using inorganic compounds e.g plants using photosynthesis

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2
Q

What are the essential nutrients that an animal needs?

A

Organic compounds:

  • carbohydrates (MAIN energy source used to yield ATP)
  • lipids
  • proteins

Also require:

  • essential amino acids (body doesn’t produce these, we must consume them)
  • essential fatty acids (only two in humans which are N3 and N6)
  • vitamins (humans need 13)
  • minerals
  • water (very important for process of digestion (e.g saliva)
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3
Q

What are vitamins?

A

Organic elements essential for metabolism

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4
Q

What are minerals?

A

Inorganic elements essential for metabolism

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5
Q

What factors influence how much food an animal needs?

A
  • type of food and ability to digest it

- metabolic rate, age and reproductive stage

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6
Q

What does an animal’s metabolic rate vary with?

A

Varies with levels of activity, body mass and environmental conditions.

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7
Q

What plays a BIG role in determining metabolic rate? Explain why.

A
  • size of animal/body mass
  • while bigger animals do need more energy than smaller ones, small animals require more energy PER UNIT OF BODY MASS and/or more energy rich food
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8
Q

What is digestion?

A
  • the breakdown of large molecules such as fats, proteins and carbohydrates into molecules that are small enough to be transported across the gut wall
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9
Q

What are the two types of digestion that exist? Briefly describe them.

A
  • mechanical/physical digestion (physical breakdown of molecules via grinding or chewing)
  • enzymatic/chemical digestion
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10
Q

Why is mechanical digestion necessary for efficient enzymatic/chemical digestion?

A

Grinding and chewing of food into smaller particles results in greater surface area allowing more access for enzymes and therefore better enzymatic digestion.

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11
Q

What is the pathway of mammalian/alimentary digestion?

A
  1. Buccal cavity/mouth
  2. Pharynx
  3. Oesophagus
  4. Stomach
  5. Small intestine
  6. Large intestine (including caecum which is absent in humans)
  7. Anus
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12
Q

What are the different locations enzymes come from in the digestive tract?

A
  • salivary glands
  • stomach
  • liver
  • pancreas
  • small intestine
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13
Q

What does enzymatic digestion involve?is it sequential or non sequential?

A

Breakdown of complex molecules by hydrolytic enzymes, usually secreted into the gut lumen.

It also involves the sequential secretion of digestive enzymes along the length of the gut.

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14
Q

What are the reaction rates of digestive enzymes dependent on?

A

pH and temperature

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15
Q

Are digestive enzymes highly specific or the opposite?

A
  • aren’t as specific as most other enzymes.
  • lower specificity
  • tend to be specific for types of MOLECULES rather than types of bonds
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16
Q

What do the digestive enzymes an animal produces correspond with?

A

They correspond with the food an animal eats. E.g human vegetarians have higher salivary amylase activity (which hydrolyses starch to sugar) than those who eat a lot of meat.

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17
Q

What is the function of the buccal cavity (mouth)?

A
  • physical breakdown of food by mastication (chewing)
  • mixing food with saliva which aids in lubrication, helping food move along digestive tract
  • enzymatic breakdown occurs with amylase digesting starch from food
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18
Q

How can you deduce the type of diet and digestive system from the buccal cavity (mouth)?

A

Teeth within mouth indicates type of diet and digestive system

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19
Q

What does the time available for digestive enzymes to break down food depend on? Describe some examples.

A

It depends on the speed that food moves down the digestive tract.

E.g Cellulose resists hydrolysis and requires a long time for digestion. Other materials such as sucrose and starch are readily hydrolysed.

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20
Q

How can more time be given to allow for longer enzymatic breakdown?

A

Increasing the length of the gut and expanding regions for storage.

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21
Q

Describe the disadvantages of allowing food to remain in the gut for a longer amount of time (longer period of enzymatic breakdown).

A

Disadvantages: no nutritional advantages and yields fewer nutrients than new food would provide.

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22
Q

What animals have high and low mass-specific metabolic rates? Elaborate of the types of foods they eat as a result.

A

High: small animals. Eat foods that are digested easily and pass through the gut rapidly
Low: large animals. Eat foods that are digested less easily and take longer to pass through the gut.

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23
Q

Where is the pharynx and what is its function?

A

It is where the oral and nasal cavities meet (back of mouth). Transports food to the oesophagus.

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24
Q

What is the function of the oesophagus?

A

Transports food (bolus) to stomach via peristalsis (wavelike contraction of muscles).

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25
Q

Describe the mechanical and chemical breakdown processes that occur in the stomach.

A

Mechanical: Muscular walls churn food.

Chemical: enzymes in very acidic environment (ph 1-2) such as pepsin and other processes digest protein and some lipases

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26
Q

What is one of the main functions of the stomach? Why is this function important?

A

Acts as storage vessel for food.

This is important because without this storage vessel, food would have to be constantly eaten.

27
Q

What is the final product of the stomach? Where does this final product enter?

A

Chyme (food reduced to small size).

The pyloric sphincter allows this chyme into the duodenum (part of small intestine).

28
Q

Name the regions of the muscular tube in the small intestine.

A

Opening region: duodenum
Middle region: jejenum
Ending region: ileum

29
Q

Describe what generally occurs in the small intestine.

A
  • mainly enzymatic digestion

- absorption of nutrients into bloodstream (via both diffusion and active transport)

30
Q

What increases the rate of absorption of nutrients into the bloodstream from the small intestine?

A

By increasing the surface area of the small intestine in adding many VILLI (waves in the intestine)

31
Q

What is the caecum of the small intestine? What species typically have it?

A
  • “blind end” of small intestine where cellulose from plants breaks down
  • humans don’t have these
32
Q

Why does the length of the small intestine differ among species? Describe some examples.

A

Because it differs according to diet.

E.g longer caecum if animal’s diet is heavily plant based, many villi to maximise surface area if diet is composed of materials such as meat which take longer to digest

33
Q

What is the function of the membrane intestinal wall and what does it contain?

A

Secretes enzymes and breaks down mainly sugars.

Contains villi which increases surface area and therefore rate of absorption

34
Q

Name the digestive glands that release enzymes into the small intestine and what enzymes they release.

A
  • pancreas releases fluid that contains lots of enzymes which break down protein (pepsin, trypsin), lipids (lipases) and carbohydrates (amylase)
    ((Specific enzymes are in brackets)
  • liver releases bile via gall bladder which contains lipases that emulsify fat
35
Q

What are the main structural components of the large intestine?

A
  • caecum: blind ended pouch at start of large intestine, involved in the digestion of cellulose
  • colon: removal of water, formation of faeces, elimination through anus. Also responsible for reabsorption of fluids to produce dry faeces.
36
Q

Why is it important for the colon to not remove all water?

A

Otherwise we’d dehydrate.

37
Q

What structures of the animal is diet reflected in?

A

Teeth and digestive tract

38
Q

Describe the composition of plants as food.

A
  • mostly composed of carbohydrates
  • very little protein
  • some unsaturated lipids
  • minerals depend on soil
39
Q

Describe the trade-off involved with plants as a food source.

A

Easy to catch but hard to digest and low in nutrition.

40
Q

What is characteristic of a herbivore’s digestive tract?

A

Longer and more complex digestive tracts as plant tissue is hard to digest and therefore takes longer to digest.

41
Q

Describe the composition of animals as a food source.

A
  • mostly protein
  • little carbohydrates
  • some lipids (saturated)
42
Q

What is the trade-off that exists with having animals as a food source?

A

Easy to digest but hard to catch.

43
Q

What is characteristic of a carnivore’s digestive tract?

A

Short and simple digestive tracts as meat is easy to digest.

44
Q

Why don’t carnivores need to eat vegetables/plants to obtain glucose?

A

Carnivores can produce glucose from proteins and other materials. This process is called gluconeogenesis.

45
Q

Describe the characteristics of a carnivore (e.g lion) in terms of diet, teeth and digestive tract.

A
  • needs to catch and kill prey (eats 5-7kg of meat a day)
  • diet is very high in protein
  • teeth are specialised for puncturing and tearing
  • very short and simple digestive tract as meat is easy to digest
46
Q

Describe the characteristics of an omnivore (e.g chimpanzee) in terms of diet, teeth and digestive tract.

A
  • eats fruit and plants but also hunts for meat
  • not as efficient at digesting particular foods but can digest a greater variety of food
  • teeth specialised for biting chewing and grinding
  • digestive tract similar to carnivore
47
Q

Describe the characteristics of a herbivore (e.g elephant) in terms of diet, teeth and digestive tract.

A
  • eats 200-300kg per day of plant matter
  • requires up to 110 litres of water per day
  • teeth for prying branches (tusks) and grinding
  • can digest cellulose with help from bacteria
  • long digestive tract
48
Q

Where is cellulose present in plants and what is it composed of?

A
  • located in plant cell walls

- composed of long chains of glucose molecules

49
Q

What is interesting about cellulose in relation to vertebrates?

A

No vertebrate has the enzyme cellulase

50
Q

How do herbivores compensate for the absence of the cellulase enzyme in their digestive system? Where is this component found?

A

They use symbiotic bacteria or protists that contain cellulase in order to hydrolyse (digest) cellulose.

Symbiotic bacteria or protists are found in either the foregut, and bacteria are only located in the hindgut

51
Q

Describe how foregut fermentation works.

A
  • foregut contains trillions of protists and bacteria
  • microbes use glucose (which is bad for animal in symbiotic relationship) from cellulose digestion, but release short chain fatty acids that are released by the animal
  • microbes themselves are a source of protein and are digested further along the digestive tract
52
Q

Is foregut fermentation fast or slow?

A

Slow as it takes longer to digest cellulose.

53
Q

List examples of animals that are foregut fermenters.

A

Sheep, cattle, macropods, hippopotamus (large animals), hoatzin (only bird that is a foregut fermenter)

54
Q

What are ruminant animals? What type of fermentation do they undergo? List examples of these animals.

A
  • have 4 stomachs and chew and regurgitate food
  • sheep cattle etc
  • undergo foregut fermentation
55
Q

Describe a typical stomach of a foregut fermenter.

A

Very large in order to house bacteria and protists.

56
Q

Describe how hindgut fermentation works.

A
  • similar to foregut fermentation but only bacteria are involved and fermentation occurs in the hindgut (large caecum and proximal colon)
  • microbes washed out of hindgut CANNOT be digested, therefore high quality protein is unfortunately lost.
  • BUT easily digested nutrients are absorbed into the animal first (not lost to microbes)
57
Q

List examples of animals that are hindgut fermenters.

A

Horse, koala, wombat, pig, rabbit, ringtail possum (uses caecotrophy as well)

58
Q

Describe the stomach, caecum and proximal colon of a hindgut fermenter.

A

Small stomach, very large caecum and proximal colon

59
Q

Describe what caecotrophy is and examples of animals that undergo it.

A
  • caecotrophy occurs in hindgut fermenters and it is when the animal ingests special faecal pellets that contain more proteins and B-vitamins than normal faeces.
  • lots of microbial protein in faeces
  • redirects protein rich faeces for maximum nutrition
  • can’t afford to lose protein when diet is poor quality
  • occurs in common ringtail possum, rabbits and small rodents
60
Q

Describe what is interesting about pandas diet, teeth and digestive tract.

A
  • large teeth and small digestive tract, panda also has carnivorous ancestry
  • but pandas are herbivores!! They eat 10-15kg of bamboo a day and eat for 10-16 hrs a day
  • effective mastication
  • only digests about 20% of diet
  • rapid elimination of digested food (under 12 hrs)
61
Q

How are vitamins obtained and why are they important to eat?

A
  • only obtained from food
  • needed in trace amounts for normal functioning
  • can’t be stored, therefore must eat regularly
62
Q

Describe diseases caused by lack of vitamins.

A

Rickets: vitamin D deficiency, causes soft bones. Affects Ca2+ uptake

Scurvy: vitamin C deficiency, causes bleeding, skin spots, loss of teeth. Disrupts collagen synthesis

Hypervitaminosis A: vitamin A excess from ingesting carnivore liver, varied symptoms. Affects metabolism of other vitamins, increased bone turnover

63
Q

Describe a disease caused by mineral deficiency.

A

Goitre: iodine deficiency, swelling of thyroid/neck. Prevent by dietary intake of iodine e.g iodised salt.

Biology of Cells and Organisms (sem 1) (17 decks)

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