2.3 Adaptations for nutrition Flashcards
1
Q
Define nutrition.
A
Nutrition is the process by which organisms obtain energy to maintain life functions and matter to create and maintain structure.
2
Q
Where is energy and matter obtained?
A
Energy and matter are obtained from nutrients.
3
Q
What are the two types of nutrients?
A
Autotrophic
Heterotrophic
4
Q
What are the two types of autotrophs?
A
Photoautotrophic
Chemoautotrophic
5
Q
What are the types of heterotrophic nutrition?
A
Saprotrophic
Holozoic
Mutualistic
Parasitic
6
Q
What is a trophic response?
A
A growth response in plants
7
Q
What are autotrophs?
A
Autotrophs are called producers
8
Q
Why are autotrophs producers?
A
Because they manufacture complex organic molecules from simple inorganic materials (CO2 and H2O)
i.e. they synthesise their own food and do not need to consume.
9
Q
Give examples of photoautotrophs.
A
green plants, some protoctista, some bacteria
10
Q
How do photoautotrophs make food?
A
They use light as the energy source and carry out photosynthesis.
11
Q
Give examples of chemoautotrophs.
A
prokaryotes
12
Q
How do chemoautotrophs make food?
A
Use energy from chemical reactions (special methods of respiration) to synthesise organic molecules.
13
Q
How efficient are chemoautotrophs?
A
Less efficient than photoautotrophs
14
Q
What are heterotrophs?
A
They are known as consumers.
15
Q
How do heterotrophs obtain nutrition?
A
They consume complex organic materials produced by autotrophs, since they cannot synthesise their own food.
16
Q
List some examples of heterotrophs.
A
All animals, fungi, some protoctista and some types of bacteria.
17
Q
Give some examples of saprotrophs.
A
Saprotrophs include the fungi and some bacteria.
18
Q
How do saprotrophs feed?
A
They feed by secreting digestive enzymes (proteases, amylases, lipases and cellulases), externally digesting food substances and then absorbing the products of digestion into the organism.
19
Q
What is saprotrophic nutrition an example of?
A
Extracellular digestion.
20
Q
Do saprotrophs have a specialised digestive system?
A
No.
21
Q
Why are microscopic saprotrophs important?
A
Microscopic saprotrophs are important decomposers and help to decay leaf litter and recycle important nutrients, e.g. nitrogen.
22
Q
What is holozoic nutrition?
A
The internal digestion of food substances.
Most animals feed holozoically.
They ingest food into their bodies and break it down by the process of digestion in a specialised digestive system. The digested material is then absorbed into the blood and is used or assimilated by body cells. Ingestible remains are egested.
23
Q
List the types of holozoic feeders.
A
Herbivores
Carnivores
Omnivores
Detritivores
24
Q
Herbivore
A
feeds on plants
25
Carnivore
feeds on other animals
26
Omnivores
feeds on both plants and animals
27
Detritivores
feeds on dead and decaying matter (e.g. leaves)
28
How do unicellular organisms feed (e.g. amoeba)?
Amoeba is a single-celled heterotrophic protoctist which has a large surface area to volume ratio.
Food molecules are ingested by diffusion, facilitated diffusion or active transport across the cell membrane. Larger particles are taken in by endocytosis into food vacuoles.
These fuse with lysosomes and their contents are digested intracellularly.
The products of digestion are absorbed into the cytoplasm and wastes are egested by exocytosis.
29
How does a hydra digest food?
In a combination of intracellular and extracellular digestion.
30
Describe how hydra lives and feeds.
They are sessile. They stick to a substance.
It traps its prey with its tentacles, stings its prey, then pulls the prey into its mouth.
31
Hydra are diploblastic, what does this mean?
They have 2 body layers.
32
What do endodermal cells secrete?
What type of digestion is this?
They secrete enzymes.
This type of digestion takes place within the hydra and extracellularly.
33
How do hydra obtain sugars?
1. They digest carbohydrates and absorb sugars
2. They have a symbiotic arrangement with green photosynthetic microorganisms that give them sugars.
34
Describe the gut of an earthworm.
Tube gut with tube gut with two openings, one for ingestion and one for egestion. They also have specialised regions for the digestion of different food stuffs.
They have a distinct anterior and posterior end. Food is ingested at the mouth and indigestible wastes egested at the anus.
35
How does the human gut move food?
Humans have a long muscular tube gut.
It allows movement of food in one direction by the process of peristalsis.
Peristalsis pushes food along the gut
36
How is the bolus pushed down the gut?
Circular muscles contract pushing the bolus down. (longitudinal muscles relax)
Longitudinal muscles contract shortening the pathway for the bolus (circular muscles relax)
37
Why must food be digested?
because molecules are too big and insoluble for absorption into the blood. They are polymers which need to be broken down into monomers.
38
What are the 4 steps for processing of food by the gut?
Ingestion
Digestion
Absorption
Egestion
39
What is ingestion?
The taking in of food at the mouth/buccal cavity
40
What is digestion?
The breakdown of large insoluble food molecules into simple soluble molecules that may be absorbed into the blood.
41
What are the two types of digestion?
Mechanical
Chemical
42
What happens during mechanical digestion?
Crushing of teeth and contraction of muscles of gut wall to increase surface area over which enzymes act.
43
What happens during chemical digestion?
digestive enzymes work on large surface area. Bile and stomach acid also contribute.
44
What happens during absorption?
This is the passage of digested food - molecules and ions - through the gut wall into the blood.
45
What happens during egestion?
This is the elimination from the body of food that cannot be digested as faeces, e.g. cellulose of plant cell walls.
46
What is assimilation?
use of products of digestion.
47
List the layers of the lumen of the gut wall.
From the outside to the lumen:
Serosa
External muscle
Submucosa
Mucosa
48
Describe the structure of the serosa.
Made up of tough connective tissue
49
State the function of the serosa.
Protects the wall of the gut.
It is smooth, so reduces friction as gut moves on gut in peristalsis
50
Describe the structure of the external wall of the gut.
longitudinal on the outside.
circular on the inside
51
State the function of the external wall of the gut.
for peristalsis
52
Describe the structure of the submucosa
connective tissue
53
State the function of the submucosa
contains lots of blood and lymph vessels to remove products of digestion from the gut. nerves to coordinate peristalsis
54
Describe the structure of the mucosa (with epithelium)
connective tissue with an inner epithelium.
55
State the function of the mucosa.
secretes mucus to lubricate the passage of food through the gut, also, mucus protects the epithelium,
May release digestive enzymes (depending on location) or absorb products of digestion.
56
List the types of digestive enzymes.
1. Carbohydrases
2. Proteases, peptidases
3. Lipase
57
What do carbohydrases do?
Carbohydrases break down polysaccharides into disaccharides and then into monosaccharides.
58
What does amylase hydrolyse?
Starch into maltose
59
What does maltase hydrolyse?
Maltose to alpha glucose
60
What enzyme breaks down sucrose?
Sucrase
61
What enzyme breaks down lactose?
Lactase
62
How are proteins digested?
Proteins are hydrolysed into polypeptides, then dipeptides and finally amino acids
63
Give two examples of proteases.
Endopeptidases
Exopeptidases.
64
What do endopeptidases do?
They hydrolyse non-terminal peptide bonds
(bonds within the polypeptide chain)
65
What do exopeptidases do?
They hydrolyse terminal peptide bonds
(peptide bonds towards the end)
66
Why do endopeptidases and exopeptidases work together?
Both enzymes together means that endopeptidases can create more ends for exopeptidases to hydrolyse.
67
How are lipids broken down?
Lipids are hydrolysed into fatty acids and glycerol
68
What do lipases hydrolyse lipids into?
fatty acids and glycerol.
69
What do the secretions of the glands contain?
These secretions may contain enzymes for digestion, mucus for lubrication and protection and are alkali/acidic to provide optimum conditions for enzyme action.
70
List the type of glands in the gut.
1. Large glands fount outside the gut with secretions passing through ducts into the gut cavity
2. Glands in the form of cells in the submucosa
3. Glands in the form of cells in the mucosa
71
Give examples of large glands outside the gut.
1. Salivary glands which secrete saliva into the mouth
2. Liver which secretes bile into the duodenum.
3. Pancreas which secretes pancreatic juice into the duodenum.
72
Give examples of glands in the submucosa.
1. Glands which secrete mucus into the duodenum.
73
Give examples of glands in the mucosa.
1. Gastric glands in the stomach wall which secrete gastric juice into the stomach (containing enzymes and HCl)
2. Glands found at the base of the villi in the small intestine which secrete enzymes into the small intestine.
74
Where is bile made in?
In the liver
75
Where is bile stored?
In the gall bladder
76
State the pH of the mouth/buccal cavity
7.5
77
What happens in the mouth?
Mechanical digestion of food occurs here.
Teeth chew food and the tongue moves food around the mouth. Both increases the surface area of the food for enzyme action.
Chemical digestion also occurs.
The salivary glands release saliva.
78
What is the saliva made up of?
The saliva is a watery solution of:
1. amylase - which starts the digestion of starch to maltose
2. HCO3 and CO32- so the pH is slightly alkaline, optimum for amylase
3. mucus to lubricate food as the bolus passes along oesophagus
79
Does the oesophagus have a role in digestion?
No. it just joins the mouth to the stomach
80
How long is the oesophagus?
about 20cm long
81
What is the epiglottis?
What is its role?
A cartilage flap that reflexively covers the trachea during swallowing.
82
State the pH of the stomach.
pH 2
83
What happens in the stomach?
Mechanical digestion occurs here.
Stomach is a muscular bag that churns the food for 3-4 hours.
Chemical digestion also occurs.
Gastric juice is secreted by glands in gastric pits in the mucosa of the stomach.
84
State the role of goblet cells.
To produce mucus which protects the epithelium from acid and enzymes.
85
State the role of parietal/oxyntic cells.
produces hydrochloric acid, which:
- provides the optimum pH for enzyme action
- activates the enzyme produced in the stomach
- kills any microbes on food.
86
State the role of chief/ zymogen cells.
produces pepsinogen, which is activated by HCl to produce pepsin, an enzyme
87
What is the difference between an endocrine and exocrine gland?
The endocrine gland makes hormones. It is a ductless gland, where hormones are directly released into blood e.g. ovary
The exocrine gland makes other secretions e.g. enzymes. Exocrine glands have a duct.
88
State the pH of the duodenum.
pH8.5
89
What is the duodenum?
The first 25 cm of the small intestine.
90
From where does the duodenum receive secretions from?
1. Brunner's glands
2. the liver
3. the pancreas
91
Where are the Brunner's glands?
at the base of the Crypts of Lieberkuhn
92
What do the Brunner's glands release?
alkaline secretions to neutralise the chyme from the stomach
93
Does bile contain enzymes?
No. It contains bile salts.
94
How does bile break down lipids?
Bile salts are amphipathic, i.e. molecules have hydrophillic and hydrophobic parts.
They emulsify lipids by decreasing their surface tension and breaking up large globules into smaller globules.
This increases the surface area for lipase action.
95
State another function of bile.
Bile is also alkaline and neutralises the acidic food entering the duodenum from the stomach.
It provides an optimum pH for enzymes working in the duodenum
96
What does the pancreas secrete?
pancreatic juices from islet cells in the exocrine pancreas.
It flows down the pancreatic duct to the duodenum.
97
What does the pancreatic juice contain?
What is its role?
It contains sodium hydrogen carbonate that neutralises the acid from the stomach and provides optimum conditions for enzyme action.
98
List the enzymes in the pancreatic juices.
1. Endopeptidases, e.g. inactive trypsinogen (activated by enterokinase)
2. Amylase
3. Lipase
99
State the function of enterokinase.
Enterokinase from the mucosa activates trypsinogen to trypsin, which is the active endopeptidase enzyme.
100
State the function of amylase.
hydrolyses starch into maltose
101
State the function of lipases.
hydrolyses lipids into fatty acids and glycerol
102
Why are proteases such as trypsin and pepsin secreted as inactive precursor pepsinogen and trypsinogen?
so that they don't hydrolyse the cells that make them.
103
Describe what happens in the ileum.
1. Endopeptidases and exopeptidases are secreted from the epithelial cells and break down polypeptides. Enzymes on the epithelial cell's membranes break down dipeptides to amino acids.
2. Disaccharides are absorbed into the epithelial cells and carbohydrases in their cell membranes digest them into monosaccharides. Intracellular digestion.
104
State the pH of the ileum.
pH 8.5
105
How is the ileum well adapted for absorption?
Has a large surface area:
- it is very long and folded.
- has finger-like projections called villi.
- epithelium has microvilli
Maintenance of steep concentration gradient:
- after a meal, the lumen has a high concentration of products of digestion.
- capillaries and lacteals rapidly remove the products of digestion
- diffusion distance is short - a single layer of epithelial cells between the lumen and capillaries.
- many mitochondria in epithelial cells.
106
Where do the lacteals take their products of digestion?
The lacteals empty into lymph system that empties into the vein in your neck.
107
Where do the capillaries in the villi take their products of digestion?
hepatic portal vein transports products of digestion to the liver.
glucose is converted to glycogen
excess amino acids are deaminated to form urea.
108
How is glucose assimilated?
Taken in the hepatic portal vein to the liver and then round the body to cells.
Some is used for respiration to release energy.
Some is stored as glycogen in skeletal muscles and liver.
Excess is stored as fat
109
How is protein assimilated?
Taken in the hepatic portal vein to the liver and then round the body to cells.
They are used for protein synthesis.
Excess cannot be stored so the liver deaminates them and converts the -NH2 group to urea which is carried in the blood and removed by the kidney.
The remains of the amino acids are converted into carbohydrate for storage as fat.
110
How are lipids assimilated?
Lipids are used to make membranes and hormones.
Excess is stored.
111
What is passed into the colon?
Undigested food, mucus, bacteria and dead cells.
112
What happens in the colon?
The colon has fewer villi than the ileum, but is the major site of water absorption together with mineral ions.
Vitamin K and folic acid are both secreted by mutualistic microorganisms living in the colon.
On reaching the rectum, the gut contents are in a semi-solid condition.
Cellulose fibre is required to provide bulk and stimulate peristalsis.
The undigested material is egested as faeces, a process called defecation.
113
Why are mammals able to breathe while they eat?
Because they have a palate that separates the air path from the mouth so allows the retention of food in the mouth.
114
Describe the gut of a carnivore
They eat only animals so their diet is mainly protein and lipid.
This is easy to digest so their small intestine is short relative to body length.
The large intestine is straight with a smooth lining.
115
Describe the gut of a herbivore.
They eat only plant matter, which is difficult to digestive.
Small intestine long relative to body length, allowing time for digestion and absorption.
Large intestine is pouched and can stretch to accomodate the large volume of faeces produced with a cellulose rich diet.
It is also long with villi to absorb water.
Herbivores do not produce their own cellulase enzymes so:
Non ruminants: have cellulase-secreting bacteria living in their caecum
Ruminants have bacteria living in the specialised 'stomach' (4 chambers)
116
Describe the gut of an omnivore.
They eat both plants and animals.
Their gut is intermediate in length
117
Why are teeth used in mechanical digestion?
To increase surface area of food for enzyme action.
118
List the 4 types of teeth humans have.
1. Incisors
2. Canines
3. Premolars
4. Molars
119
State the function of incisors.
Used for biting and tearing food.
120
State the function of canines.
Used for gripping prey
121
State the function of molars and premolars
grinding and shearing meat
122
Why are human teeth not particularly specialised?
Because humans are omnivores.
123
Tell me about the dentition in herbivores.
1. Small flat-topped incisors on the lower jaw only that cut against a horny pad.
2. Small canines similar to the incisors.
3. A large gap or diastema that allows movement of tongue to move grass cutting front to grind back.
4. Large, ridged premolars and molars that interlock like a W filling into an M.
5. Lower jaw loosely articulated and moves in a horizontal plane in a circular motion to grind grass
6. Grinding surfaces become worn down exposing sharp edged enamel ridges
7. Teeth have open roots and grow continuously so they are continually replacing worn out surfaces.
8. Herbivore's jaw muscles do not have to be strong as their food does not struggle. Its skull is therefore smooth without sites for strong muscle attachment
124
Tell me about the dentition in carnivores.
1. Sharp incisors for gripping and tearing meat from bone.
2. Large, curved, backward-pointing canines for seizing prey, killing, holding onto prey, ripping
3. No diastema
4. Pointed premolars and molars for cutting and crushing
5. Specialised pair of carnassial cheek teeth (last upper premolar and first lower molar) that slide past each other like the blades of gardening shears for cutting through bone
6. Lower jaw moves in a vertical plane with very strong muscles to grip struggling prey.
Jaw muscles attached to protrusions on skull
Jaw opens very wide to capture and kill the prey
7. Teeth stop growing because no roots.
125
Define mutualistic.
A type of symbiosis, when two species live together in the long term
126
How do the ruminant and microorganisms benefit from each other?
Ruminant gets access to cellulase, meaning that the cellulose in the gut can be broken down into glucose.
The microorganisms get a habitat and a constant supply of food. they get warmth
127
Tell me about the stomach of ruminants.
Ruminants have a four chambered stomach.
The first three are modified oesophagus and the fourth a true stomach
128
List the four chambers of the stomach in a ruminant.
Rumen
Reticulum
Omasum
Abomasum (true stomach)
129
Describe how food is digested in a cow.
1. Food is chewed in the mouth and mixed with saliva to form cud. It is swallowed.
2. Food passes into the rumen, where anaerobic microbes release cellulase, digesting cellulose into glucose. This is then fermented into organic acids that are absorbed into the blood and provide energy for the cow. The wastes are CO2 and CH4 which are belched out.
3. The fermented grass passes to the reticulum and is formed into balls (cud) for regurgitation into the mouth for further chewing. This may occur several times.
4. The cud is then swallowed into the omasum. Here water and organic acids made from fermented glucose are absorbed.
5. The cud passes to the abomasum, which functions as a 'true' stomach. Here protein is digested. The digested food is then passed on as a liquid chyme to the duodenum.
130
Explain coprophagy in rabbits.
1. Eat grass, hay and nuggets. and they are digested.
2. The caecotrophs are digested in the stomach
3. In the caecum, digestible fibre is fermented by bacteria, which is then gathered together and passed as caecotrophs.
4. Indigestible fibre helps to keep the system moving.
5. Caecotrophs (soft droppings) are expelled and re-eaten at night (step 2 onwards occurs). Waste is excreted as a hard pellet.
131
What is a parasite?
an organism that lives in or on another organism of a different species called a host.
It gains nourishment at the expense of the host and so harms the host
132
Give some examples of parasites of plants
mistletoe
133
Give some examples of parasites of animals
headlice, tapeworm (gut), athlete's foot
134
What is an ectoparasite?
Lives on its host e.g. headlouse
135
What is an endoparasite?
Lives in the host e.g. gut tapeworm
136
What is the primary host of the gut tapeworm?
The adult tapeworm is a ribbon-like worm and can be up to 10m long.
It attaches itself to the small intestine in the human as its primary host.
Here it has little competition and cannot be predated.
137
What is the secondary host of the tapeworm?
Its secondary host is the pig.
Here it forms a larval from called the bladder worm in voluntary muscle.
138
What are some challenges the tapeworm faces?
1. It passes through extreme pHs as it travels to the duodenum
2. The immune system of the host
3. If the host dies, so does the tapeworm
4. It is surrounded by mucus and digestive juices
5. The food around it is in constant motion and the gut wall in peristalsis
6. Very little oxygen in the duodenum.
139
How is the tapeworm adapted to living in the duodenum wall?
Has suckers and a double row of curved hooks for attachment to the duodenum wall
140
How is the tapeworm protected from the host's immune system?
Has a thick cuticle which protects it from the host's immune system.
141
How is the tapeworm protected from digested juices?
Production of anti-enzyme (inhibitors) on its surface to prevent its digestion by the host's enzymes.
142
How does the tapeworm respire?
Anaerobically
143
Does the tapeworm have a digestive system?
No digestive system but a large SA:Vol and digested food is absorbed over its entire surface
Degeneration of unnecessary organ systems in a stable environment. SImple excretory and nervous systems.
144
How does the tapeworm reproduce?
Each segment/proglottid contains male and female reproductive organs (hermaphrodite).
Fertilisation can be achieved with only a single tapeworm in the gut.
Vast numbers of eggs are produced (each mature segment having 40,000 eggs). Mature segments pass out of the body with faeces. The large number of eggs increases the likelihood of them being eaten by a secondary host.
145
How are the eggs transported to the secondary host?
The eggs have a resistant shell that can survive until eaten by a secondary host.
The embryos hatch from the eggs and move through the intestine wall into the pig's muscles.
They remain dormant until the under cooked meat of the pig is eaten by a human.
146
How can we prevent being infected by a pork tapeworm?
1. Don't eat undercooked pork
2. Inspect meat at abattoir
3. Have good sanitation (provide toilets)
147
Do the adult tapeworm in the human gut cause harm to human?
if it is a large infestation in a poorly nourished person
148
How can the lifecycle go wrong and cause damage and possible death to a human?
eggs eaten by a human and a bladder worm lodges in human muscle
(heart or brain)
149
List the adaptations of lice that enable them to stick to hairs?
Lice are wingless insects unable to jump or walk.
It has claws to hold onto hairs and lays eggs which are glued to the base of hairs.
Once removed from their host the lice die.
Transfer between hosts is by direct contact.
150
Give me the lifecycle stages of headlice.
Stage 1 - nits or empty eggs seen on hair/clothing
Stage 2 - egg hatches into a nymph after 1-2 weeks. They look like adults but are smaller (incomplete metamorphosis) and feed on blood by biting in the scalp.
Stage 3 - adults appear after a further 10 days. They also feed on blood from the scalp
