Adaptations for Nutrition Flashcards
1
Q
What type of nutrition do amoeba use?
A
Holozoic
2
Q
How do amoeba obtain nutrients such as oxygen and glucose?
A
Through their cell membrane via:
- diffusion
- facilitated diffusion
- active transport
3
Q
How do amoeba take in large food molecules such as bacteria and microscopic algae?
A
Endocytosis
4
Q
The food vacuoles in amoeba fuse with ________ containing _________ ____________ which _______ the contents of the food molecules. The products of digestion are then absorbed into the ____ _____________
A
Lysosomes, hydrolytic enzymes, digest, cell cytoplasm
5
Q
In amoeba, indigestible remains are egested by ______________
A
Exocytosis
6
Q
Describe digestion and nutrition in hydra
A
- Their tentacles move paralysed prey in through the mouth into the hollow sac like body cavity where the prey is digested
- The products of digestion are absorbed into body cells
- The indigestible remains are egested through the mouth
- They only have a single opening in their digestive system
7
Q
Describe a tube gut
A
Food is ingested at the mouth and indigestible waste is egested at the anus
8
Q
Name the 4 functions of the human gut
A
- Ingestion
- Digestion (mechanical and chemical)
- Absorption
- Egestion
9
Q
Define ingestion
A
Taking food into the body through the mouth
10
Q
Define digestion
A
The breakdown of large insoluble molecules into soluble molecules that are then small enough to be absorbed into the blood
11
Q
Define mechanical digestion
A
Cutting and crushing by teeth and muscle contractions of the gut wall, increasing the surface area over which enzymes can act
12
Q
Define chemical digestion
A
Breakdown using digestive enzymes. Bile and stomach acid also contribute to this
13
Q
Define absorption
A
The passage of small soluble molecules and ions through the gut wall into the blood
14
Q
Define egestion
A
The elimination of indigestible waste
15
Q
Define peristalsis
A
The wave of muscular contractions and relaxations of the gut wall which propel the contents along the whole length of the gut
16
Q
What is the function of the mouth?
A
Ingestion. Mechanical digestion of food due to crushing action of teeth. Chemical digestion of starch by salivary amylase
17
Q
What is the function of the oesophagus?
A
Carriage of food to the stomach by peristalsis
18
Q
What is the function of the stomach?
A
Contraction of stomach muscles to churn up food (mechanical digestion). Secretion of hydrochloric acid. Chemical digestion of proteins by enzymes.
19
Q
What is the function of the duodenum?
A
Receives pancreatic juice from the pancreas and bile from the gall bladder. Chemical digestion of carbohydrates, fats and proteins by enzymes
20
Q
What is the function of the ileum?
A
Chemical digestion of carbohydrates, fats and proteins by enzymes. absorption of digested food.
21
Q
What is the function of the colon?
A
Absorption of water
22
Q
What is the function of the rectum?
A
Storage of faeces
23
Q
What is the function of the anus?
A
Site of egestion
24
Q
What is the function of the serosa?
A
Contains tough connective tissue which protects the gut wall. It helps to reduce friction with other abdominal organs during peristalsis
25
What is the function of the muscularis (inner circular muscles and outer longitudinal muscles)?
They make co-ordinated waves of contraction (peristalsis), pushing the ball of food along the alimentary canal
26
What is the function of the sub-mucosa?
Consists of connective tissue containing blood and lymph vessels which remove the absorbed products of digestion. This layer also contains nerves which coordinate peristalsis
27
What is the function of the mucosa?
The epithelium secretes mucus which lubricates and protects the mucosa. In some regions of the gut it secretes digestive juices and in others it absorbs digested food
28
What do endopeptidases do?
Hydrolyse peptide bonds within the protein molecule eg pepsin and trypsin
29
What do exopeptidases do?
Hydrolyse peptide bods at the end of shorter polypeptide chains to make amino acids/dipeptides
30
What reaction does amylase catalyse?
Starch --> maltose
31
What is secreted in the mouth to create the optimum pH for amylase?
Bicarbonate ions (slightly alkaline)
32
What does gastric juice contain?
- Mucus
- Hydrochloric acid
- Pepsin (secreted as inactive pepsinogen)
33
What is the function of mucus in the stomach?
- Secreted by goblet cells
- It forms a protective lining which protects the stomach wall from digestive enzymes and HCl
- Also helps to lubricate food
34
How is pepsinogen activated?
Hydrochloric acid
35
Why are enzymes in the stomach secreted in an inactive form?
Active form would digest the cells of the stomach wall
36
What are the functions of bile salts?
- They emulsify lipids, breaking up large globules into smaller droplets, increasing the surface area for lipase action
- Bile is alkaline and neutralises the acid in the food coming from the stomach creating an optimum pH for enzymes in the small intestine
37
What are the 4 pancreatic secretions and their functions?
**Endopeptidases** hydrolyse proteins into shorter polypeptides
**Trypsinogen** inactive enzyme converted into the endopeptidase trypsin by enterokinase
**Pancreatic amylase** chemically digests any remaining starch to maltose
**Lipase** hydrolyses lipids into fatty acids and glycerol
38
What are the 2 duodenal secretions and their functions?
**Sodium hydrogen carbonate** raises the pH to make pancreatic juice more alkaline
**Enterokinase** an enzyme that converts trypsinogen to trypsin
39
What adaptations of the ileum make it appropriate for absorption?
- It is very long
- Its lining is folded
- On the surface of the folds are villi
- The epithelial cells lining the villi have microscopic projections called microvilli
40
What are the 2 types of specialised cells in the mucosa of the ileum
1. **Columnar epithelial cells** have microvilli (large SA) and many mitochondria to produce ATP for active transport
2. **Goblet cells** secrete mucus which lubricates and protects the lining of the intestine
41
What is the function of the lacteal?
Absorbs glycerol and fatty acids
42
In Crohn's disease, villi in the small intestine are destroyed. Suggest how this could lead to diarrhoea
- Shorter villi
- Reduced surface area
- So less enzymes on the membrane
- Less absorption of products of digestion
- More solute in the lumen lowers the water potential
- More water moves from the epithelial cells into the lumen
43
How are fatty acids and glycerol absorbed in the ileum?
Diffusion from the lumen into the epithelial cell then reassembled into triglycerides. Diffusion into lacteal then carried via lymphatic system to the blood
44
How are glucose and galactose absorbed in the ileum?
Co-transport with Na+ ions from lumen to epithelial cell. Facilitated diffusion into capillary.
45
How is Na+ absorbed in the ileum?
Co-transport with glucose from lumen into the epithelial cell. Facilitated diffusion into capillary.
46
How are amino acids absorbed in the ileum?
Active transport from lumen into epithelial cell. Facilitated diffusion into capillary.
47
How is water absorbed in the ileum?
Osmosis from lumen into epithelial cell. Osmosis into capillary
48
How will substances absorbed into blood be transported to the liver?
Via the hepatic portal vein
49
Explain how active transport of Na+ from the epithelial cells into the blood helps with the passage of glucose from the lumen into the blood
- lower concentration of Na+ in epithelial cells, which creates a concentration gradient for Na+
- Na+ and glucose enter epithelial cell from lumen by co-transport
- increases the glucose concentration in cell, which creates a concentration gradient for glucose
- glucose moves into blood by facilitated diffusion
50
What 3 substances are absorbed in the large intestine?
1. water
2. mineral ions
3. vitamins produced by symbiotic bacteria in gut eg vitamin K and folic acid
51
Define autotrophic nutrition
Organisms synthesis their own complex organic molecules from simpler molecules using either light or chemical energy. Can be photoautotrophic or chemoautotrophic
52
Define photoautotrophic organisms
Use energy from sunlight to carry out photosynthesis to maker organic molecules (glucose) from inorganic molecules (carbon dioxide and water) eg green plants, algae
53
Define chemoautotrophic organisms
Use energy from chemical reactions to synthesise organic molecules eg bacteria respiring in deep sea hydrothermal vents
54
Define heterotrophic nutrition
Organisms cannot produce their own organic molecules so obtain complex organic molecules from other organisms. They then break this material down into smaller, soluble molecules which they then absorb and assimilate
55
Name the 2 types of heterotrophic nutrition
1. Holozoic nutrition
2. Saprotrophic nutrition
56
Define holozoic nutrition
These organisms ingest food, digest it and egest any indigestible remains.
1. Ingestion
2. Digestion
3. Absorption into the bloodstream
4. Assimilation
5. Egestion
57
Define saprotrophic nutrition
Saprotrophs feed on dead or decaying organic material. They carry out extracellular digestion:
- enzymes are secreted onto the food material outside of their body
- they then absorb the soluble products of digestion into their cells by diffusion or active transport
58
Define parasitic nutrition
Parasites are organisms that live on or in another organism, called the host, and obtain nourishment at the expense of the host. They cause harm and often death
59
What is the difference between endoparasites and ectoparasites?
Endoparasites live in the host, whereas ectoparasites live on the host
60
How does a human become infected with tapeworm?
The larval form is found in pigs. The pig becomes infected if it feeds on drainage channels contaminated by human faeces containing eggs. Humans become infected by eating contaminated undercooked pork.
61
How has the tapeworm adapted to fix the problem of the gut being in constant motion?
Suckers and hooks for attachment to gut wall
62
How has the tapeworm adapted to fix the problem of extreme pH along the gut, exposure to digestive enzymes and the host's immune response?
A thick cuticle and the production of inhibitory substances on its surface to prevent digestion by the host's enzymes
63
How has the tapeworm adapted to fix the problem of reproduction (unlikely to find a mate in host, high offspring mortality, difficult for eggs to reach new host)
- Tapeworm has both male and female reproductive organs so can self fertilise
- Large numbers of eggs are produced
- Eggs have resistant shells and can survive until eaten by another host
64
How has the tapeworm adapted to fix the problem of host death?
If the host dies, so does the tapeworm - adult tapeworms cause little discomfort to the host
65
How has the tapeworm adapted to fix the problem of having no digestive system?
The tapeworm is long and thin so has a large SA:V. it lives in the small intestine and is surrounded by the host's digested food which can be absorbed over the entire body surface of the tapeworm by diffusion
66
What is the function of incisors?
Biting and cutting
67
What is the function of canines?
Tearing and ripping meat
68
What is the function of molars and premolars?
Grinding and chewing
69
What are 6 structural features of herbivore dentition?
- incisors and horny pad
- canines
- diastema
- interlocking molars
- loose articulation of lower jaw
- open roots
70
Name and describe 6 structural features of carnivore dentition
- **small sharp incisors** to grip and tear flesh from bone
- **large curved canines** to seize and hold onto prey
- **premolars/molars** for cutting and crushing food
- **carnassials** slide past each other like blades and crush bone
- **vertical jaw movements** so jaw can open widely and cannot be dislocated when prey is struggling in its grip
- **powerful jaw muscles** to grip prey
71
Describe cellulose digestion in cows
1. Grass is chewed, mixed with saliva and swallowed
2. This grass passes into the rumen and it is churned and mixed with bacteria that secrete cellulase to digest cellulose to beta glucose. The beta glucose is absorbed into the blood, providing energy for the animal.
3. Any undigested grass passes to the reticulum chamber and is formed into cud. The cud is regurgitated into the mouth for further chewing which increases the surface area of the grass to allow for more cellulose digestion to take place.
4. The cud then passes to the omasum where water is absorbed into the blood.
5. In the abomasum, bacteria are killed and digested. They provide an important source of protein.
72
What are non-ruminant herbivore adaptations for nutrition eg rabbit
In the rabbit the caecum is enlarged to accommodate cellulose digesting bacteria
As the bacteria are towards the end of the gut, regurgitation is not possible. Instead, refection occurs, where rabbits ingest faecal pellets so that the material passes through the gut twice to increase the efficiency of digestion
73
Compare carnivore and herbivore guts
The carnivore gut is relatively short compared to the length of its body because they have a diet high in protein and protein is easily digested. The gut of a herbivore is longer compared to the length of its body as they eat a diet high in cellulose which is much harder to digest
