adaptations for nutrition Flashcards
1
Q
describe the structure of the mammalian gut wall
A
- along its length, the gut wall consists of 4 tissue layers surrounding the lumen of the gut.
- the proportions of the different layers of the gut wall vary, depending on the function of the part of the gut
2
Q
what are the 4 tissue layers that surround the lumen of the gut?
A
- serosa
- muscularis
- submucosa
- mucosa
3
Q
what can you say about the thickness of these layers?
A
the thickness of these layers varies in different regions of the digestive system
e.g stomach, ileum
4
Q
describe the serosa
A
- this is the outermost layer
- contains connective tissue which protects the gut wall
- helps to reduce friction with other abdominal organs during peristalsis
5
Q
describe muscularis
A
- composed of 2 layers : the inner circular muscles and the outer longitudinal muscles
- they make coordinated waves of contraction (peristalsis), pushing the ball (bolus) of food along the alimentary canal
6
Q
describe submucosa
A
- consists of connective tissue containing blood and lymph vessels which remove the absorbed products of digestion
- this layer also contains the nerves which coordinate peristalsis
7
Q
describe mucosa
A
- lines the gut wall and is the inner most layer
- 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
8
Q
what is the function of the mouth?
A
ingestion
- mechanical digestion of food due to crushing action of the teeth
- chemical digestion of starch by salivary amylase
9
Q
what is the function of oesophagus?
A
carriage of food to the stomach by peristalsis
10
Q
what is the function of the stomach?
A
- mechanical digestion by contraction of stomach muscles to churn the food
- secretion of hydrochloric acid
- chemical digestion of proteins by enzymes
11
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
12
Q
what is the function of the ileum?
A
- chemical digestion of carbohydrates, fats and proteins by enzymes
- absorption of digestion food
13
Q
what is the function of the colon?
A
absorption of water
14
Q
what is the function of the rectum?
A
storage of faeces
15
Q
what is the function of the anus?
A
site of egestion
16
Q
define ingestion
A
taking food into the body through the mouth
17
Q
define digestion
A
the breakdown of large insoluble molecules into soluble molecules that are then small enough to be absorbed into the blood.
18
Q
how many types of digestion are there?
describe them.
A
MECHANICAL DIGESTION - cutting and crushing by teeth and muscle contractions of the gut wall, increases the surface area over which enzymes can act
CHEMICAL DIGESTION - breakdown using digestive enzymes, bile and stomach acid also contribute to this
19
Q
define absorption
A
the passage of small soluble molecules and ions through the gut wall into the blood
20
Q
define egestion
A
the elimination of indigestible waste
e.g cellulose (dietary fibre)
21
Q
what 4 main functions does the human gut perform?
A
- ingestion
- digestion
- absorption
- egestion
22
Q
why must food be digested?
A
- food molecules are insoluble and are too large to cross membranes and be absorbed into the bloodstream
- polymers must be converted to their monomers, so they can be assimilated into molecules needed by body cells
23
Q
define peristalsis
A
wave of muscular contractions and relaxations of the gut wall which propel the contents along the whole length of the gut
24
Q
what aids peristalsis in the intestines?
A
dietary fibre
25
describe the steps in peristalsis
1. contraction of circular muscles behind food
2. contraction of longitudinal muscles ahead of food
3. contraction in circular muscle layer forces food forward
26
describe the gut
- long, hollow, muscular tube
- allows movement of its content in one direction only
27
what does saliva contain?
- amylase
starch --> maltose
- bicarbonate ions
these create an optimum pH for amylase
- mucus
this lubricates the food
28
food is mechanically digested in the mouth, explain how
food is mixed with saliva by the tongue and chewed with the teeth
this increases the surface area of food for the enzymes to work on
29
what are the 2 regions of the small intestine?
ileum and duodenum
30
what is the function of the sphincter muscles at the base of the stomach?
releases partially digested food into the duodenum
31
what is the role of bile in the small intestine?
to emulsify lipids
32
where is bile produced and stored?
- produced in the liver
- stored in the gall bladder
33
what are endopeptidases?
they hydrolyse peptide bonds within the protein molecule
e.g pepsin and trypsin
34
what are exopeptidases?
they hydrolyse peptide bonds at the end of shorter polypeptide chains to make amino acids, dipeptides
35
what does the gastric juice contain?
- mucus
- hydrochloric acid
- pepsin
36
describe the mucus in the gastric juice
- secreted by goblet cells which line the mucosa
- forms a protective lining which protects the stomach wall from digestive enzymes and hydrochloric acid
- helps to lubricate the food
37
describe the hydrochloric acid in the gastric juice
it lowers the pH of the stomach contents to pH2 to create an optimum environment for enzymes and kills bacteria
38
describe pepsin in the gastric juice
- secreted as inactive pepsinogen
- this is a peptidase that works optimally in the acidic environment of the stomach
- activation of pepsinogen by hydrochloric acid forms active pepsin
39
why are enzymes secreted in an inactive form?
as the active form would digest cells of the stomach (autolysis)
40
what is the function of the duodenum?
digestion of carbohydrates, fats and proteins
41
describe the duodenum
it is the first section of the small intestine
- recieves secretions from the liver and pancreas
- the food coming from the stomach is lubricated by mucus and the hydrochloric acid is neutralised by alkaline secretion (NAHCO3) from cells in the submucosa
42
BILE
what is bile?
what does bile contain?
what is the function of bile?
BILE
- made in the liver
- stored in the gall bladder
- passed through the bile duct into the duodenum
- contains bile salts which are hydrophilic and hydrophobic
- they emulsify lipids present in the partially digested food and breaking up large globules into smaller droplets, increasing surface area for lipase action
- bile is alkaline, and so neutralises the acid in the food coming from the stomach creating an optimum pH environment for the enzymes in the small intestine
43
what is pancreatic juice?
- secreted by specialised cells in the pancreas
- it enters the duodenum through the pancreatic duct
44
what are the duodenal secretions?
what are their functions?
sodium hydrogen carbonate:
raises the pH to make pancreatic juice more alkaline
enterokinase:
an enzyme that converts trypsinogen to trypsin
45
what are the pancreatic secretions?
what are their functions?
endopeptidases:
hydrolyses protein to 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
46
what is the function of the ileum?
absorption
47
how is the ileum adapted for absorption?
- it is very long
- its lining is folded
- on the surface of the folds are villi
- the epithelial cells lining the villi has microscopic projections called microvilli
these helps to INCREASE SURFACE AREA
48
what are the 2 specialised cells in the mucosa of the ileum?
1. columnar epithelial cells
2. goblet cells
49
what are the 2 main adaptations of the columnar epithelial cells?
- microvilli providing a large surface area for absorption of the products of digestion
- large numbers of mitochondria to produce ATP energy for active transport
50
what is the function of the goblet cell?
secretes mucus
- lubricates and protects the lining of the intestine
51
describe the structure of a villus
- columnar epithelial cells
- goblet cell
- lacteal
- blood capillary
- crypt of luberhuk
52
what is the lacteal?
lymphatic capillary which absorbs dietary fats
glycerol & fatty acids
53
what is the function of the capillary in the villus?
products of digestion diffuse or actively transport into blood capillary
amino acids & glucose
54
describe how proteins are digested in the ileum
- endopeptidases and exopeptidases are secreted by cells at the tips of the villi into the gut lumen and continue the digestion of polypeptides
- dipeptides are hydrolysed to amino acids by enzymes on the cell membranes of epithelial cells
polypeptides --> dipeptides --> amino acids
55
describe how are carbohydrates are digested in the ileum
carbohydrases (e.g maltase) on epithelial cell membranes hydrolyse disaccharides into monosaccharides (e.g alpha glucose)
- the monosaccharides can then be absorbed into the epithelial cells
maltose ---> alpha glucose
sucrose ---> fructose + glucose
lactose ---> galactose + glucose
56
In Crohn's disease villi in the small intestine are destroyed.
Suggest how this could lead to diarrhoea.
- more solute in the lumen so a lower water potential
- more water moves from epithelial cells into lumen
- leading to diarrhoea
57
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 glucose concentration in the cell, which creates a concentration gradient for glucose
- glucose moves into blood by facilitated diffusion
58
what are the uses of the products of digestion?
FATTY ACIDS and GLYCEROL
- energy storage and protection of vital organs, thermal insulation under the skin
- synthesis of cell membrane, phospholipids, steroid hormones
GLUCOSE
- required for aerobic respiration
- excess is stored as glycogen
AMINO ACIDS
- protein synthesis (e.g muscles, enzymes)
- excess is deaminated in the liver
59
what is the large intestine composed of?
caecum
appendix
colon
rectum
60
what substances are absorbed in the large intestine?
- water
- mineral ions
- vitamins produced by symbiotic bacteria in the gut, like vitamin K and folic acid
61
what is the function of caecum?
absorption starts here
62
what is nutrition?
the process by which organisms obtain energy to maintain life functions, and matter to create and maintain structure.
63
what are the two ways of nutrition?
- autotrophic nutrition
- heterotrophic nutrition
64
what is autotrophic nutrition?
autotrophic organisms synthesise their own complex organic molecules from simpler molecules using either light or chemical energy
65
what are the 2 types of autotrophic organisms?
1. photoautotrophic
2. chemoautotrophic
66
what are photoautotrophic organisms?
use energy from sunlight to carry out photosynthesis to make organic molecules (glucose) from inorganic molecules (carbon dioxide and water)
e.g green plants, algae, bacteria
67
what are chemoautotrophic organisms?
use energy from chemical reactions to synthesise organic molecules
e.g bacteria respiring in deep sea hydrothermal vents
68
what is heterotrophic nutrition?
heterotrophic organisms cannot produce their own organic molecules and so consume complex organic molecules from other organisms.
they then break this material down into smaller, soluble molecules which they can break down and assimilate.
- these include animals, fungi, some protoctista and some bacteria
69
how many types of heterotrophic nutrition are there?
what are they?
1. holzoic nutrition
2. saprotrophic nutrition
3. parasitic nutrition
70
summarise holzoic nutrition
- these organisms ingest food, digest it, and egest any indigestible remains
these involve:
- carnivores
- herbivores
- omnivores
- detritivores
71
what is meant by:
- carnviores
- herbivores
- omnivores
- detritivores
- carnivores = only eat other animals
- herbivores = only eat plant material
- omnivores = eat both plant and animal material
- detritivores = feed on dead and decaying matter
72
what are the steps in holozoic nutrition?
1. ingestion
2. digestion
3. absorption into bloodstream
4. assimilitation
5. egestion
73
which organisms carry out saprotrophic nutrition?
all fungi and some bacteria
74
define saprotrophs
organisms that feed on dead or decaying organic material
75
what do saprotrophs carry out, and how is this done?
EXTRACELLULAR DIGESTION
- enzymes are secreted onto the food material outside of their body (e.g amylase, protease, cellulase)
- they then absorb the soluble products of digestion into their cells by diffusion or active transport
76
define decomposers
give an example
decomposers are microscopic saprotrophs that play an important role in decaying leaf litter and recycling nutrients such as nitrogen
example : fungi
77
define parasites
organisms that live on or in another organisms (the host), and obtain nourishment at the expense of the host
- parasites cause harm and often death to the host
78
name some examples of parasites
- pork tapeworm
- fungus potato blight
- human head-lice
79
define:
- endoparasite
- ectoparasite
endoparasite = lives IN the host
ectoparasite = live ON the host
80
what are animals parasitised by?
what are plants parasitised by?
what are bacteria parasitised by?
ANIMALS:
bacteria, fungi, virus, nemotodes, insects, Protocista, tapeworms, mites
PLANTS :
bacteroa, fungi, virus, nemotodes, insects
BACTERIA : viruses called bacteriophages
81
what is the pork tapeworm?
it is an example of a specialised parasite which has undergone considerable evolutionary changes in order to survive in the host,
- it has no competition and cannot be preyed upon
82
what are the features of the pork tapeworm?
- the tapeworm is ribbon like and can be upto 10 metres long
- it has a scolex (head) made up of muscle which are suckers and hooks
- its body is a linear series of sections
- it has two hosts : the primary host is human and the secondary host is pig
- 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
83
what is the difference between heterotrophic and autotrophic nutrition?
heterotrophic - consumption of organic molecules from other organisms
autotrophic - use of inorganic molecules to synthesise organic molecules
84
give a defining feature of hydra nutrition
- stinging tentacles paralyse prey
- ingestion and egestion through the same hole
85
Name a protease in humans. State where it is produced and where it is activated.
TRYPSIN:
produced - pancrease
activated - duodenum
PEPSIN:
produced - gastric pits / chief cells
activated - stomach
86
give 2 substances that are secreted by the duodenum only
1. enterokinase
2. sodium hydrogen carbonate
87
how do dipeptides get from the lumen of the intestine into the bloodstream
hydrolysed on tips of villi by exopeptidases
then active transport
88
give a defining feature of herbivorous teeth
- incisors
- diasterna
- no canines
- horizontal jaw movement
89
give a defining feature of carnivorous teeth
vertical jaw movement
large curved canines
90
how do lipids get from the lumen of the intestine into the lacteal?
hydrolysed by lipase into fatty acids and glycerol
then diffusion
then reassembled in epithelial cells
91
Mammals do not produce cellulase. Explain how they are still able to gain nutrition from cellulose.
- symbiotic / mutualistic cellulose
- producing/digesting bacteria
- in rumen or caecum
- chewing cud / eating faeces
92
explain the difference in the digestive systems of herbivores and carnivores
The digestive system of herbivores is adapted to break down plant material, which is difficult to digest, while the digestive system of carnivores is adapted to break down protein and fat.
Herbivores have a longer digestive tract with multiple stomach chambers and rely on microbial fermentation to break down plant material, while carnivores have a shorter digestive tract and rely on strong stomach acids to break down meat.
93
how do herbivores obtain the necessary nutrients and energy from their diet?
by breaking down the cellulose and other complex carbohydrates found in plants, which are rich in energy but difficult to digest.
they do this through microbial fermentation in their gut,
which breaks down the complex carbohydrates into simpler compounds that can be absorbed into the bloodstream.
94
What adaptations do herbivores have to help them break down plant cell walls?
Herbivores have adaptations such as large cecums, multiple stomach chambers, and symbiotic microorganisms that help them break
down plant cell walls. for example.
the cecum is a pouch-like structure found in the digestive tract of many herbivorous animals that
nouses a large population or microorganisms that can break down cellulose
95
Explain why carnivores have a shorter digestive tract compared to herbivores.
Carnivores have a shorter digestive tract compared to herbivores because meat is easier to digest and requires less time to break down. This allows them to pass food through their digestive system more quickly, which reduces the risk of bacterial infections
96
how does the shape of the teeth of herbivores and carnivores reflect their diet?
The shape of the teeth of herbivores and carnivores reflects their diet. Herbivores have flat, broad molars for grinding and chewing tough plant material, while carnivores have sharp, pointed teeth for tearing meat.
97
What is the role of symbiotic microorganisms in the digestive systems of herbivores?
Symbiotic microorganisms play a critical role in the digestive systems of herbivores. They help break down cellulose and other complex
carbonvarates round in plant material into simpler compounas that can be absorbed into the bloodstream.
98
How do herbivores and carnivores obtain water from their diets?
Herbivores obtain water from their diet through the moisture content of the plants they eat.
Carnivores obtain water primarily from the metabolic breakdown or protein and fat in their diet.
99
Explain how the body and metabolic rate of carnivores and herbivores are related to their diet.
Body size and metabolic rate are related to an animal's diet.
Herbivores tend to have a larger body size and lower metabolic rate than carnivores because their diet is less nutrient-dense and requires more time to algest
100
name some problems faced by the tapeworm and outline the adaptations that the tapeworm has evolved to overcome this
1. gut is in constant motion - has suckers and hooks for attachment to the gut wall
2. extremes of pH along gut, exposure to digestive enzymes and the hosts immune response - has a thick cuticle and the production of inhibitory substances on its surface to prevent digestion by the hosts enzymes
3. host death - if the host dies so does the tapeworm (adult tapeworms cause little discomfort to the host)
101
explain how reproduction is a problem in tapeworms and how they are evolved to overcome this
- the tapeworm is both male and female reproductive organs and so can self-fertilise (hermaphrodite)
- large numbers of eggs are produced
- eggs have resistant shells and can survive until eaten by another host
102
outline the adaptations that the tapeworm has evolved to overcome the problem of having no digestive system
the tapeworm is long ans thin so has a large surface area to volume ratio
it lives in the small intestine and is surrounded by the hosts digested food which can be absorbed over the entire body surface of the tapeworm by diffusion
103
describe adaptations of the human head louse
- the human head louse has claws to hold onto the hairs of a human
- the adult lays eggs which are glued to the base of the hairs. they feed by sucking blood from the scalp of their host.
104
what is the function of :
- incisors
- canines
- molars and premolars
incisors - biting and cutting
canines - tearing and ripping meat
molars and premolars - grinding and chewing
105
why are teeth important?
they play a vital role in the mechanical digestion of food
106
why is chewing important?
it makes it easier to swallow and also increases the surface area for enzyme action
107
describe the diet of a herbivore
- a herbivore doer is cellulose based
- cellulose is difficult to digest
- herbivore teeth are adapted for grinding to increase surface area for bacterial cellulase enzyme action
108
outline the features which make herbivores adapted for grinding to increase surface area for bacterial cellulase enzyme action
horny pad
incisors
diasterna
premolars and molars
loose jaw articulation
109
what is the function of the horny pad?
the animal wraps its tongue around the grass and pulls it tight across the horny pad on the upper jaw
110
what is the function of the incisors?
slice through the plant material
111
what is the function of the diasterna?
gap between cheek and front teeth
- the tongue moves cut grass to the large grinding surfaces of the cheek teeth
112
what is the function of the premolars and molars?
interlocking like an M fitting into a W for grinding teeth
113
what is the function of loose jaw articulation?
the lower jaw moves from side to side and produces a circular grinding action
114
what are carnivorous mammals adapted for?
catching and killing prey, cutting or crushing bones and for tearing meat
115
what structural features of dentition do carnivores have for their diet?
- small sharp incisors
- large curved canines
- premolars and molars
- carnassials
- vertical jaw movement
116
what is the function of the small sharp incisors in carnivores?
to grip and tear flesh from bone
117
what is the function of large curved canines in carnivores?
to seize and hold onto prey
118
what is the function of molars and premolars in carnivores?
cutting and crushing food
119
what is the function of carnassials in carnivores?
slide past each other like blades and crush bone
120
what is the function of vertical jaw movement in carnivores?
so jaw can open widely and cannot be dislocated when prey is struggling in its grip
121
what are ruminants?
describe their diet.
animals such as cows, goats and sheep which mainly eat grass and forage
- their food contains a lot of cellulose which they are unable to digest as they do not produce the enzyme cellulase
122
what do ruminants rely on and why?
they rely on mutualistic bacteria which live in their gut and secrete the cellulase enzymes
123
where does the bacteria in ruminants live?
bacteria lives in one of the stomach chambers called the rumen
124
describe the process of cellulose digestion in ruminants
1. grass is chewed, mixed with saliva and swallowed
2. the grass is passed into the rumen and it is churned and mixed with bacteria that secrete cellulase to digest cellulose to beta glucose.
3. the beta glucose is absorbed into the blood, providing energy for the animal.
4. any undigested grass passes to the reticulum chamber and is formed into cud. The cud is regurgitated into the mouth for further chewing.
5. the cud then passes into the omasum
4. in the abomasum, bacteria are kiled and digested. they provide an important source of protein for the animal
125
compare the gut of a carnivore and a herbivore
- carnivore gut is short because they have a diet high in protein which is easily digested
- herbivore gut is long because they eat a diet high in cellulose and cellulose is much harder to digest
126
describe non-ruminant herbivore adaptations, using rabbits as an example
- in rabbits, the caecum is enlarged to accommodate cellulose digesting bacteria
- as bacteria are towards the end of the gut, regurgitation is mot possible.
instead, reflection occurs.
127
what is refrection?
it is where the rabbits ingest faecal pellets so that the material passes through the tut twice to increase efficiency of digestion
128
what are the two types of herbivores?
ruminant and non-ruminant
129
why is the cud reguritated in the mouth?
increases the surface area for further cellulose digestion to take place
130
what does the bacteria produce alongside beta glucose?
produces waste products such as carbon dioxide and methane, which are released from the animal
