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Biology 1/2 > Digestion > Flashcards

Digestion Flashcards

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1
Q

How is cellulose digested?

A

The enzyme cellulase breaks down cellulose which is found in cell walls of plants.

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2
Q

How do herbivores get cellulase?

A

They rely on the bacteria in their gut. It can produce cellulase to ferment their food and release energy within it.

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3
Q

What kind of relationship is there between animals and bacteria?

A

There is a symbiotic relationship as it benefits both the animal and the bacteria.

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4
Q

Why do herbivores chew their food for a long time?

A
  • Cellulase requires a large surface area.

- Mechanical digestion increases the surface area and that is why animals chew for ages.

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5
Q

How can animals accommodate all the bacteria? (Foregut)

A
  • Some have a enlarged stomach or oesophagus.

- These are called Foregut fermenters.

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6
Q

How does an animal accommodate bacteria? (hind-gut)

A
  • Some mammals have modified region of the caecum and colon for fermentation.
  • These are called Hind-gut fermenters
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7
Q

Hind- gut fermenters:

A
  • Animals such as: Horses, rabbits, possums, koalas.
    i) Caecum fermenter: Fermentation occurs in the caecum (found at the junction of the small and large intestine).
    ii) Colon Fermenter: the colon is longer and it has wider diameter than other herbivores.
  • The caecum is where mose absorption takes place.
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8
Q

Fore-Gut Fermenters:

A
  • Animals such as: coes, sheep, giraffes
    i) Ruminants- modified oespohagus (it is a pouch that is formed from part of the oesophagus): cellulose- digesting bacteria is housed here.
    ii) Non-ruminants- modified stomach: eg. kangaroos, wallabies.
  • They have specialised stomachs that house large amounts of bacteria.
  • Their stomachs look like large sacks or a long tube.
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9
Q

What are the advantages of fore-gut fermenters?

A
  • The nutrients can be absorbed along the entire length of the small intestine.
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10
Q

What are the disadvantages of fore-gut fermenters?

A
  • It takes a long time -> Hours/days/constant regurgitation.
  • There is very little nutritional value.
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11
Q

Carnivores

A
  • They feed mainly on herbivores.
  • Carnivores have a shorter digestive system because protein is easier to digest than cellulose.
  • They tend to have a reduced or small caecum.
  • All enzymes are produced in the gut.
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12
Q

Phagocytosis in Kingdom Protoctista

A

the cell membrane engulfs food particles in the fluid around the cell. The food is enclosed in a food vacuole in the cytoplasm, enzymes are secreted into vacuole an food is digested.

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13
Q

Carnivorous plants

A
  • They can trap animal, mostly insects
  • They usually have a sticky substance on the tentacles.
  • Plants have adapted due to poor habitat because they need additional nutrients.
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14
Q

Kingdom Fungi

A
  • They exhibit extra-cellular digestion.
  • They release digestive enzymes onto food which breaks down the complex compounds into simpler molecules which are then absorbed by the fungi.
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15
Q

Digestion

A

the process of breaking food into molecules small enough to pass through membranes into cells.

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16
Q

Digestion occurs in 4 steps:

A
  1. Ingestion of food
  2. Mechanical (or physical) digestion.
  3. Chemical digestion
  4. Absorption
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17
Q
  1. Ingestion of food
A

the taking in of nutrients

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18
Q
  1. Mechanical (or physical) digestion
A
  • Teeth

- Muscular movements of the stomach to increase the surface area of the food for enzymes to act on.

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19
Q
  1. Chemical digestion
A

Enzymes

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20
Q
  1. Absorption
A
  • The taking up of digested molecules into the body’s cells.
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21
Q

What are the 4 types of teeth?

A
  1. Incisors
  2. Canines
  3. Premolars
  4. Molars
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22
Q

Incisors

A
  • They are used to get food into the mouth.
  • They are sharp and cut big pieces of food into smaller pieces.
  • Humans have 8 incisors (4 top, 4 bottom)
23
Q

Canines

A
  • they are pointed teeth used to pierce and tear food.
  • Humans have 4 canines
  • Very large carnivores have them so they can tear through meat tissue.
24
Q

Premolars

A
  • They are responsible for grinding food.

- Humans have 8 premolars.

25
Q

Molars

A
  • They have rigid surfaces to grind food.
  • Herbivores have large molars and premolars as they must grind down a lot of plant material.
  • Humans have 12 molars. (including wisdom teeth).
26
Q

What type of teeth do carnivores have?

A

Carnivores have well developed canines for tearing meat from bones.

27
Q

What kind of teeth do herbivores have?

A

Herbivores have incisors to clip the grass, and molars to grind.

28
Q

What kind of teeth do humans have?

A

Humans have teeth that are appropriate for a varied diet. (incisors, canines, premolars and molars).

29
Q

Saliva

A
  • saliva is produced in the saliva glands
  • it makes food slippery so it can be swallowed.
  • it dissolves some food so it can be tasted.
  • Saliva contains amylase that breaks down complex carbohydrates into simple sugars.
30
Q

Tongue

A
  • it helps catch and manipulate food
  • it helps food form a bolus.
  • The swallowing reflex allows us to swallow food.
31
Q

Oesophagus

A
  • It takes 5 seconds for food to reach the stomach.
  • it is about 20-23cm long
  • It secretes mucus to help food move the stomach.
  • Food is moved along the oesophagus by the process of Peristalsis.
32
Q

Epiglottis

A
  • A flap of tissue that closes off the entry to the trachea to stop food going down the trachea into the lungs.
33
Q

Why doesn’t food go out of the mouth?

A
  • The entrance of the stomach is the Cardiac Sphincter.

- This is a ring of muscle that contracts and allows food entry to the stomach.

34
Q

Stomach

A
  • Protein digestion starts in the stomach.
  • Protein is broken down into amino acids by protease enzymes.
  • The stomach stores food
  • food stimulates the secretion of gastric juices.
35
Q

Mucus

A
  • It is produced by the stomach wall.

- it coats/protects the stomach against “auto- digestion” by the acid.

36
Q

Enzymes in the stomach.

A
  • proteases are enzymes found in the stomach e.g. pepsin.
  • Pepsin starts protein digestion by making peptides.
  • the muscles in the stomach churn the food around to form a thick liquid called chyme.
37
Q

Food in the stomach

A
  • on average, food stays in the stomach for 1-4 hours.
  • Meals high in fat stay in the stomach the longest.
  • rich in protein stays for less that fatty
  • Carbohydrates stay for the shortest
  • alcohol and some drugs are absorbed in the stomach.
38
Q

Liver

A
  • Largest gland in the body
  • Produces Bile
  • Breaks large molecules into smaller ones
  • stores glucose as glycogen
  • breaks down poisons
39
Q

Bile

A
  • it is secreted into the small intestine

- it is stored in the gall bladder

40
Q

Pancreas

A
  • secretions come from the pancreatic duct

- the pancreatic duct joins to the bile duct and then empties into the duodenum.

41
Q

Pancreatic secretions:

A
  • Pancreatic juices
  • bicarbonate
  • amylases
  • proteases
  • lipases
  • nucleases
  • insulin
42
Q

Small intestine

A 
There are three main parts: 
- The duodenum
- The jejunum
- The ileum
It digests carbohydrates, proteins and the start of fats.
- Food stays for 3-6 hours
43
Q

What secretions does the small intestine rely on?

A
  1. Liver (bile)
  2. Gall bladder (stored bile)
  3. Intestine
  4. Pancreas (enzymes- amylase, proteases, lipases, nucleases and insulin
44
Q

where is amylase secreted?

A

pancreas

45
Q

where are enzymes secreted?

A

small intestine cell walls

46
Q

What % of proteins remains undigested?

A

15%

the rest is moved along the small intestine

47
Q

Jejunum and ileum

A
  • pancreatic juices continue to act on any undigested food.

- The cell walls of the Jujunum and ileum secrete aminopeptidases.

48
Q

Aminopeptidases

A

Peptides -> amino acids

  • proteins are broken down by aminopeptidases (proteases) from the stomach and S.I.
  • Amino acids are now small enough to be absorbed.
49
Q

Where are lipids (fats) broken down?

A

In the small intestine into glycerol and fatty acid by lipase enzymes.

50
Q

Absorption in the small intestine

A
  • the lining of the S.I. has folds. It gives it a greater surface area.
  • therefore, greater absorption rate.
  • the small intestine has villi which also increases the surface area.
  • there is also microvilli that covers the villi.
51
Q

What is absorbed in the small intestine?

A
  • Amino acids
  • glucose and other monosaccharides
  • glycerol and fatty acids
52
Q

What is inside the microvilli?

A
  1. Capillaries: They absorb amino acids and monosaccharides.
  2. Lacteal: They absorb glycerol and fatty acids and enter the blood stream via veins near the neck.
    - Nutrients travel to the liver via Hepatic portal veins. They then go to the heart with pumps them to the rest of the body.
53
Q

Large intestine

A

It consists of two parts:
1. Colon
2. Rectum
- it compacts undigested food such as fibre.
- it absorbs water and some salt back into the body
- there is millions of bacteria in the colon that act on undigested plant matter.
The bacteria have enzymes called cellulase that breaks down cellulose in cell walls.

54
Q

What are faeces composed of?

A
  • food remains
  • water
  • bacteria
  • dead cells from the intestine
    they are generally made up on 2/3 water.

Biology 1/2 (7 decks)

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