Digestion Flashcards
(54 cards)
1
Q
How is cellulose digested?
A
The enzyme cellulase breaks down cellulose which is found in cell walls of plants.
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.
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.
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.
5
Q
How can animals accommodate all the bacteria? (Foregut)
A
- Some have a enlarged stomach or oesophagus.
- These are called Foregut fermenters.
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
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.
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.
9
Q
What are the advantages of fore-gut fermenters?
A
- The nutrients can be absorbed along the entire length of the small intestine.
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.
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.
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.
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.
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.
15
Q
Digestion
A
the process of breaking food into molecules small enough to pass through membranes into cells.
16
Q
Digestion occurs in 4 steps:
A
- Ingestion of food
- Mechanical (or physical) digestion.
- Chemical digestion
- Absorption
17
Q
- Ingestion of food
A
the taking in of nutrients
18
Q
- Mechanical (or physical) digestion
A
- Teeth
- Muscular movements of the stomach to increase the surface area of the food for enzymes to act on.
19
Q
- Chemical digestion
A
Enzymes
20
Q
- Absorption
A
- The taking up of digested molecules into the body’s cells.
21
Q
What are the 4 types of teeth?
A
- Incisors
- Canines
- Premolars
- Molars
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
Molars
- 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
What type of teeth do carnivores have?
Carnivores have well developed canines for tearing meat from bones.
27
What kind of teeth do herbivores have?
Herbivores have incisors to clip the grass, and molars to grind.
28
What kind of teeth do humans have?
Humans have teeth that are appropriate for a varied diet. (incisors, canines, premolars and molars).
29
Saliva
- 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
Tongue
- it helps catch and manipulate food
- it helps food form a bolus.
- The swallowing reflex allows us to swallow food.
31
Oesophagus
- 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
Epiglottis
- A flap of tissue that closes off the entry to the trachea to stop food going down the trachea into the lungs.
33
Why doesn't food go out of the mouth?
- 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
Stomach
- 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
Mucus
- It is produced by the stomach wall.
| - it coats/protects the stomach against "auto- digestion" by the acid.
36
Enzymes in the stomach.
- 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
Food in the stomach
- 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
Liver
- Largest gland in the body
- Produces Bile
- Breaks large molecules into smaller ones
- stores glucose as glycogen
- breaks down poisons
39
Bile
- it is secreted into the small intestine
| - it is stored in the gall bladder
40
Pancreas
- secretions come from the pancreatic duct
| - the pancreatic duct joins to the bile duct and then empties into the duodenum.
41
Pancreatic secretions:
- Pancreatic juices
- bicarbonate
- amylases
- proteases
- lipases
- nucleases
- insulin
42
Small intestine
```
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
What secretions does the small intestine rely on?
1. Liver (bile)
2. Gall bladder (stored bile)
3. Intestine
4. Pancreas (enzymes- amylase, proteases, lipases, nucleases and insulin
44
where is amylase secreted?
pancreas
45
where are enzymes secreted?
small intestine cell walls
46
What % of proteins remains undigested?
15%
| the rest is moved along the small intestine
47
Jejunum and ileum
- pancreatic juices continue to act on any undigested food.
| - The cell walls of the Jujunum and ileum secrete aminopeptidases.
48
Aminopeptidases
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
Where are lipids (fats) broken down?
In the small intestine into glycerol and fatty acid by lipase enzymes.
50
Absorption in the small intestine
- 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
What is absorbed in the small intestine?
- Amino acids
- glucose and other monosaccharides
- glycerol and fatty acids
52
What is inside the microvilli?
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
Large intestine
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
What are faeces composed of?
- food remains
- water
- bacteria
- dead cells from the intestine
they are generally made up on 2/3 water.
