Component 2.4 Adaptations for nutrition Flashcards
Modes of Nutrition
Autotrophic
Photoautotrophic
Chemoautotrophic
Heterotrophic
Saprotrophic / Saprobiontic
Holozoic
Parasitic
Symbiosis / Mutualism
Autotrophic
Synthesis of complex organic chemicals from inorganic substances using an energy source.
Photoautotrophic
Uses light energy to combine inorganic substances into complex organic chemicals.
Chemoautotrophic
Uses chemical energy, from chemicals such as hydrogen sulphide, to combine inorganic substances into complex organic chemicals.
Heterotrophic
Cannot synthesise its own complex organic chemicals; to gain energy, it must digest organic chemicals produced by other organisms and use the products of digestion to synthesise their own organic chemicals.
Saprotrophic / Saprobiontic
Saprotrophic Nutrition – Explained Simply:
Saprotrophs (like fungi and some bacteria) feed on dead or decaying material – this is called saprotrophic nutrition.
They do not eat food like animals do. Instead, they:
Release enzymes onto the material they live on (outside their body).
The enzymes break down large, complex molecules (like proteins, carbohydrates, fats) into smaller, soluble molecules.
These small molecules are then absorbed into the saprotroph’s body.
This gives them the energy and raw materials they need to grow and survive.
Holozoic
Absorption of organic matter followed by internal digestion of the organic chemicals within the organism.
In single celled organisms, organic matter is taken into the cell where intracellular digestion takes place; products of digestion are released and used within the cell and waste / undigested material is released to the outside.
Most multicellular organisms have a digestive system whereby organic matter is ingested and digested extracellularly but still within the organism; products of digestion are then absorbed into cells / transport system and utilised by different parts of the body. Waste / undigested material is released to the outside as faeces during egestion.
Parasitic
Living in or on another host organism, whereby nourishment is obtained from a host organism, usually to the detriment / harm of the host; the host usually derives no benefit.
Ectoparasites live on the outside of a host organism, while endoparasites live inside a host organism, some are intracellular, and others are extracellular.
Symbiosis / Mutualism
Many organisms live in / on other organisms in a relationship that provides benefit to both organisms.
Photoautotrophs
All photoautotrophic organisms carry out photosynthesis
The process uses energy from photons of light and transfers light energy into chemical energy. The process is summarised below:
carbon dioxide + water → glucose + oxygen
Light energy is transferred to carbon containing compounds as chemical energy. By the addition of atoms of other elements, photoautotrophs are able to synthesise all the organic compounds needed for the organism to grow and reproduce.
Chemoautotrophs
Chemoautotrophs can also combine inorganic substances to synthesise organic compounds but use energy from chemicals to enable these reactions to take place. Many of these organisms are members of the Archaebacteria, extremophiles that live in conditions that are uninhabitable by most organisms
Chemoautotrophs
Eg
Pyrolobus extreme thermophile living in temperatures of >100ºC
Methanococcus lives in the stomach of a cow and uses ethanoic acid as an energy source.
Some bacteria are also chemoautotrophs e.g.
Nitrosomonas obtain their energy from ammonia
Methylomonas oxidises methane as a source of energy.
heterotrophic egs
animals, fungi, bacteria, archaea
Heterotrophic organisms need food sources that contain complex organic chemicals as sources of:
- carbon for making their own organic chemicals
- nitrogen for making proteins and nucleic acids
- phosphate for ATP, phospholipids and nucleic acids
- vitamins and minerals for making a wide range of biochemicals
- energy.
heterotrophic organisms that have saprotrophic nutrition
eg
fungi and many bacteria
saprotrophic nutrition of a fungus.
why is this an eg of heterotrophic nutrition
This is an example of heterotrophic nutrition as the fungus is unable to synthesise complex organic chemicals from inorganic chemicals and cannot utilise energy from sources other than organic chemicals.
Parasites are:
organisms that live in (endoparasites) or on (ectoparasites) another organism
they obtain nourishment at the expense of the host
usually cause harm to the host.
Define:
1. Primary host
2. Secondary host
3. Vectors
The PRIMARY host organism is where the adult forms of the parasite develop.
SECONDARY hosts are where larval / intermediate forms of the parasite are found.
VECTORS are secondary hosts which actively and directly transfer the parasite from one primary host to another primary host (e.g. Malaria).
endoparasite eg
pork tapeworm (Taenia solium)
beef tapeworm (Taenia saginata)
Lifecycle of tapeworm
- or cysts
Tapeworms have several structural adaptations to enable them to live in the digestive system of an animal.
- The head of the tapeworm is called the scolex. This is embedded in the gut wall and has hooks and suckers to prevent it being dislodged by peristalsis.
- There is no digestive system or mouth as the tapeworm only needs to absorb nutrients that have already been digested.
- The body is flat to increase surface area for absorption of nutrients from the gut contents.
- Each proglottid is covered in a thick cuticle which is resistant to the action of digestive enzymes. They also secrete mucus and enzyme inhibitors to reduce the risk of digestion.
- Respiration is anaerobic as there is no oxygen in the gut lumen.
- Each proglottid is hermaphrodite containing both male and female reproductive organs. Therefore, it does not need to find a mate as it can self-fertilise. Each proglottid can contain about 50,000 eggs, this increases the chance of infecting another host.
Pediculus humanus capitis
headlouse
ecctoparasite
it lives on the head where it clings to hairs using strong claws. Eggs are laid and glued to the base of hairs. When empty they are white, these are called nits. Both adults and larval stages of headlice feed on blood.
Head lice are obligate parasites and can only live in human hair. They have no vectors or secondary hosts and transmission is by direct head-to-head contact when adults, larvae or eggs can be transferred from one host to another.
dodder
parasitic plant
no leaves or roots. Dodder has many suckers which penetrate the xylem (to obtain water and minerals) and the phloem (to obtain sugars and amino acids).
Dodder cannot carry out photosynthesis so is called an obligate parasite: it has to live on a host plant to survive.
mistletoe
semi-parasitic. Its roots penetrate the xylem and phloem of the host plant,
but it also has leaves which can carry out photosynthesis.
Holozoic nutrition
involves the ingestion and then digestion of a food source.
This means that an organism does not have to remain attached to its food source in order to digest the food, it can ingest its food and then digest the food elsewhere. The products of digestion are then absorbed and assimilated and waste is egested.
assimilation
is the process of absorbing nutrients from the environment and making them part of the body’s structure.
Amoeba
a single-celled organism that ingests and digests its food.
holozoic nutrition in Amoeba.
intracellular digestion
food particles are ingested through endocytosis / phagocytosis and undigested food / waste products are expelled through exocytosis.
Multi-cellular holozoic animals
have digestive systems
carry out extracellular digestion (within the organism)
products of digestion are then absorbed, and undigested food egested.
However, they still have to ingest and then digest their food sources.
Hydra
found in freshwater environments
This organism is related to jellyfish (Cnidaria) and has a simple, sac-like gut with only one opening to the external environment.
Digestion is a combination of extracellular and intracellular digestion. Large scale digestion takes place in the digestive sac (called the gastrovascular cavity) to break down food into fragments that can then be absorbed into cells lining the gut.
Digestion in the gut cavity is a combination of mechanical digestion, due to the contraction of the body, and chemical digestion, through the action of extracellular, hydrolytic enzymes.
Fragments of food are absorbed into the cells lining the gut cavity by phagocytosis and large molecules, e.g. proteins, are absorbed by pinocytosis. Intracellular digestion completes the breakdown of food within food vacuoles.
diagram of hydra
extracellular digestion
diagram of hydra
intracellular digestion
Flatworms (platyhelminths)
a single gut cavity for digestion of food
The gastrovascular cavity is highly branched. As a result, food can be digested, and the products of digestion can be absorbed throughout the organism. Therefore, there is no need for a designated transport system to deliver raw materials to the tissues.
flatworms digestive system label
types digestion in tube guts
- mechanical digestion by teeth, muscular action
- chemical digestion by acids
- chemical digestion by enzymes with different optimum pH.
advantages of tube gut
This type of gut increases the efficiency of digestion and also enables an organism to eat and digest a wider range of foods.
epiglottis
closes to prevent food from entering the trachea and lungs
oesophagus
liver
Deamination
Urea is formed in the liver as part of nitrogen excretion.
It results from the breakdown of excess amino acids when protein intake exceeds the body’s needs.
Since amino acids cannot be stored, they are broken down in a process called deamination.
Deamination involves the removal of the amino group (-NH₂) and a hydrogen atom, forming ammonia (NH₃).
gall bladder
s
pancreas
appendix
rectum
This is the last part of the large intestine; it is a muscular tube that temporarily stores the faeces before they are eliminated from the body.
colon
The main part of the large intestine; this is where the rest of the water and mineral salts are absorbed. Vitamins produced by microorganisms in the colon are also absorbed into the blood. This leaves a semi-solid mass of undigested food, dead intestinal cells and bacteria (about 50% of the total mass). This forms the faeces.
small intestine
stomach
Chemical: through the action of enzymes and hydrochloric acid
Mechanical: through the action of the muscles in the stomach that contract and relax to mix food with gastric juice and to further breakdown large particles of food into smaller particles with a larger surface area for chemical action.
The end result of digestion in the stomach is a semi-liquid called chyme.
Muscles of the Stomach & Mechanical Digestion – Summary:
The stomach wall contains three layers of smooth muscle:
Longitudinal,
Circular,
Oblique (unique to the stomach).
These muscles contract in different directions, allowing churning and mixing of food with gastric juices.
This physical breakdown of food is called mechanical digestion.
It helps:
Increase the surface area of food,
Mix it thoroughly with enzymes and acid,
Form a semi-liquid mixture called chyme, making chemical digestion more efficient.
buccal cavity (mouth)
a mixture of mechanical and chemical digestion takes place:
**lips, tongue and teeth work together to:
**
capture and receive food
move food about the mouth
cut, grind and chew food into smaller pieces
mix the food with saliva to lubricate food
forms food into a bolus to make swallowing easier.
**salivary glands secrete about 1500 cm3 of saliva each day
**
saliva has a slightly acid pH
it contains the enzyme salivary amylase:
salivary amylase equation
Oesophagus
carries food to the stomach by the process of peristalsis
due to waves of contraction of muscles in the gut wall which push the food forward through the whole gut.
diagram of peristalsis
stomach wall contains:
- zymogenic/chief cells
- oxyntic cells
- goblet/neck cells
zymogenic/chief cells
oxyntic cells
goblet/neck cells
diagram stomach wall
jejunum
part of the duodenum between the duodenum and the ileum
Duodenum
The stomach opens into the first part of the small intestine called the duodenum. This is about 30cm and receives secretions from the accessory organs:
bile from the liver
pancreatic juice from the pancreas.
structure of duodenum
The wall of the small intestine is folded to increase its surface area for the final stages of digestion and absorption.
These folds are called villi.
At the base of the villi there are also intestinal glands called the crypts of Lieberkühn.
The duodenum also has Brunner’s Glands that secrete alkaline fluid (containing sodium hydrogen carbonate) and mucus to neutralise the acid chyme from the stomach.
Crypt of Lieberkuhn
Main Functions:
Secretion of Intestinal Juice:
The crypts contain cells that secrete alkaline intestinal juice (also called succus entericus), which helps neutralise stomach acid and provides an environment for enzymes to work.
Production of Digestive Enzymes:
Some cells produce enzymes (e.g. maltase, peptidases) that are released onto the surface of the villi for final digestion of nutrients.
Cell Renewal:
The crypts contain stem cells that constantly divide to replace damaged or worn-out epithelial cells on the villi.
These new cells migrate upwards to maintain the villus lining.
Ileum
The ileum is nearly 5m long and is where digestion is completed and is the main site of absorption of the products of digestion.
Because of its length, food takes a relatively long time to pass through the ileum, thus increasing the time available for digestion and absorption.
The villi also increase the surface area greatly and have a rich blood supply to remove the products of digestion. Most of the water in our food is absorbed in the ileum.
The diagram shows the upper part of the human digestive system and the connections to the accessory organs.
The diagram shows the upper part of the human digestive system and the connections to the accessory organs.
anus
This is made from sphincter muscles that control when defaecation occurs.
large intestine
The ileum opens into the first part of the large intestine called the caecum. This has no role in the human digestive system. However, in some animals, this is the site of cellulose digestion. The appendix is a blind-ended sac which opens from the caecum. It has no known role in digestion in humans.
The undigested food and remaining water and minerals first pass into the colon.
The diagram shows the large intestine of the human digestive system.
liver and bile
produces bile by breaking down haemoglobin
Bile is stored in the gall bladder and is secreted into the duodenum through the bile duct.
The liver receives nearly all the products of digestion from the small intestine, carried there by the
hepatic portal vein
The liver has many functions including:
excess glucose is stored as glycogen
amino groups are removed from amino acids (de-amination) and converted into urea
many vitamins are also stored in the liver.
The pancreas has two main secretory functions.
ENDOCRINE: it secretes the hormones insulin and glucagon for control of blood glucose levels. Blood carries secretions to site of action
EXOCRINE: it secretes pancreatic juice, a mixture of:
enzymes
enzyme precursors
sodium hydrogen carbonate.
These secretions are carried by the pancreatic duct to their site of action in the duodenum.
wall of the alimentary canal
Serosa
a layer of connective tissue carrying blood vessels, lymphatic vessels and nerves.
Longitudinal and circular muscle layers
responsible for peristalsis.
Submucosa
generally carries the main arterioles and venules. It may also contain glands.
Muscularis mucosa
a thin layer of muscle involved in moving the inner wall of the gut.
Mucosa
covered by a layer of epithelial cells; some of these produce mucus and others are responsible for the final stages of digestion and absorption of nutrients.
how these tissue layers differ in the stomach, the small intestine, and the large intestine.
diagram
how these tissue layers differ in the stomach, the small intestine, and the large intestine.
The duodenum and ileum are adapted to increasing the efficiency of digestion and absorption by:
having folds in the wall to increase surface area
the inner surface is further folded to form millions of structures called villi
the surface of the epithelial cells covering the villi is further folded to form many microvilli.
A. Autotrophs (make their own food)
1. Autotrophic – general term for making complex organics from inorganic substances. 2. Photoautotrophic – use light as energy. 3. Chemoautotrophic – use chemicals (like hydrogen sulphide) as energy.
Mnemonic: “Auto = Alone”, and remember Photo = Light, Chemo = Chemicals
B. Heterotrophs (eat others)
4. Heterotrophic – can’t make own food, must consume it.
C. Ways heterotrophs feed
5. Saprotrophic/Saprobiontic – external digestion (enzymes secreted out). 6. Holozoic – internal digestion (take food in first).
Mnemonic:
• Sapro = Spill enzymes • Holo = Hold it in (eat first, then digest inside)
D. Special cases
7. Parasitic – live in/on a host, harm it. • Ecto = outside • Endo = inside 8. Symbiosis/Mutualism – both organisms benefit.
what do the 3 diagrams show
One estimate of the surface area of the small intestine is over
7 000 m2
Each villus is further adapted to increasing the efficiency of digestion and absorption as shown in the drawing below.
As the diagram below shows the villus has the following adaptations:
- rich capillary network to absorb and remove products of digestion and maintain a concentration gradient
- lacteals to absorb the products of fat digestion and maintain a concentration gradient
- they are thin to reduce diffusion distance
- microvilli increase surface area
- epithelial cells contain large numbers of mitochondria to provide the ATP for active transport.
columnar epithelium
capillary network
lacteal
muscularis mucosa
crypt of Lieberkuhn
Contains
Goblet cells
Panettone cells
Enterocytes (epithelial cells type of)
new epithelial cells
Paneth cells
Bottom of crypt of Lieberkuhn
Secretes enzymes eg
1. Antimicrobial enzymes: • Lysozyme – breaks down bacterial cell walls. • Defensins – small proteins that insert into microbial membranes and kill bacteria. • Phospholipase A2 – degrades bacterial membranes.
Microvilli
Gobelt cell
Digestion involves a combination of mechanical and chemical digestion.
Mechanical digestion is by the teeth and muscle contraction to break large pieces of food into smaller pieces. This increases the surface area for the action of enzyme.
Chemical digestion involves many different enzymes which carry out specific functions to digest a wide range of different biochemicals. Each enzyme has its own optimum temperature (around the body temperature of the organism) and pH.
different pH in gut
provides optimum pH for enzymes
salivary and pancreatic amylase
starch (main polysaccharide in human diet) —> maltose
Digestion of maltose and other disaccharides, e.g. sucrose and lactose, into monosaccharides takes place:
on the surface of the epithelial cells covering the villi.
Where are the enzymes located which digest maltose and other disaccharides
embedded in the cell membrane
monosaccharides are absorbed
Digestion of protein chain
involves breaking long polypeptide chains into amino acids and dipeptides that can be absorbed into the blood.
pepsinogen –> pepsin
Pepsinogen is also secreted in the stomach. It is activated by hydrochloric acid to form the endopeptidase enzyme, pepsin. Pepsin has an optimal pH of about 2.0.
Endopeptidase enzymes hydrolyse peptide bonds between amino acids in the middle of a polypeptide chain (non-terminal peptide bonds).
trypsinogen –> trypsin
In the duodenum the precursor trypsinogen (secreted by the pancreas) is activated by the enzyme enterokinase to form the enzyme trypsin.
Trypsin is also an endopeptidase and has an optimal pH of about 8.0.
exopeptidase
The pancreas and intestinal glands secrete exopeptidase enzymes which break peptide bonds between amino acids at the ends of peptide / polypeptide chains (terminal peptide bonds).
Exopeptidases digest peptides into amino acids and dipeptides.
The final digestion of dipeptides into amino acids
occurs in the ileum
where enzymes are embedded in the epithelial cell membranes.
Endopeptidases break peptide bonds within proteins
while exopeptidases remove amino acids from the ends.
Their combined action speeds up protein digestion.
Digestion by an endopeptidase before digestion by an exopeptidase
increases the rate of digestion of proteins.
eg of polypeptide digested first by an endopeptidase and then with an exopeptidase
Lipids are digested by enzymes called
lipases
Bile effect of lipids
why
Bile emulsifies lipids by breaking large globules of fat into small droplets.
This increases surface area for the action of lipases. Emulsification also allows very small droplets of fat to be absorbed directly into the blood stream.
Absorption takes place mainly
in the ileum by the villi.
Absorption
- Glucose and amino acids are absorbed mainly by active transport, diffusion and co-transport into capillaries.
- They are then carried in the hepatic portal vein to the liver.
- Some disaccharides and dipeptides are absorbed into the epithelial cells where they are digested intracellularly; the monosaccharides and amino acids then pass into the capillaries.
- Glucose is absorbed from the blood by cells, for energy release in respiration. Some is converted to glycogen in the liver and muscles and any excess is stored in fat cells.
- Amino acids are absorbed for protein synthesis; excess cannot be stored so are deaminated whereby the removed amino groups are converted to urea, and the remainder are converted to carbohydrate and stored.
- Fatty acids and glycerol are absorbed separately into the epithelial cells. Most are reassembled into triglycerides.
- Most triglycerides, fatty acids and glycerol pass into the lacteal, then through the lymphatic system to the blood stream opening at the thoracic duct. Some short-chain fatty acids diffuse directly into the blood in the capillaries.
- Lipids are used to produce cell membranes and hormones, and excess is stored as fat.
- Most water is absorbed into the bloodstream in the ileum; the remainder of the water, together with mineral salts along with vitamins secreted by microorganisms in the colon, are absorbed from the colon.
The diagram below summarises the digestion and absorption of the products of digestion.
Carbohydrates - Purple
The diagram below summarises the digestion and absorption of the products of digestion.
Proteins - Green
The diagram below summarises the digestion and absorption of the products of digestion.
Lipids - Red
Herbivores Diet
plant-based diet which is difficult to digest due to the high cellulose content.
Carnivores Diet
eat mainly animal tissues which are rich in protein and fat and easier to digest.
Omnivores Diet
eat a mixed diet and need to be able to digest a wide range of foods.
3 main types of teeth
function
- incisors are involved in biting and tearing flesh
- canines for gripping prey
- molars and premolars are adapted for grinding plant tissue (herbivores and omnivores) or shearing flesh from bones (carnivores).
Herbivores - Molars and Premolars
The molars and premolars are highly ridged to provide a large grinding surface for mechanical digestion of grass and other plant material.
Herbivores - Why is plant material tricky to digest?
Plant material contains a large proportion of cellulose and other fibres (ligning, waxy cuticle) that protect cell contents and make plant material relatively harder and less nutritious than flesh from animals.
biting force of herbivores
There is no need for a large biting force, but the masseter muscle is large as plant material requires a large amount of grinding.
Herbivores teeth adaptations
The teeth are adapted to grind tough plant tissues to release nutrients.
Herbivores - Diastema
There are no incisors on the upper jaw and the presence of the diastema between the modified canine and the first premolar means that sheep can use their tongue to divide the buccal cavity into two. Sheep can, therefore, carry on chewing food with their molars and premolars while continuing to eat with their incisors at the front of the mouth.
Carnivores - Adaptations
In carnivores, the incisors and canines (in particular) are adapted for biting and gripping prey.
Carnivores - Molars and Pre molars
The premolars and molars are called carnassial teeth. They have single ridges and slide past each other, acting like scissors to shear flesh from bones.
carnivores jaw
Most carnivores do not chew their food before swallowing but need to hold on to their prey when hunting and exert a great deal of force when eating, for example, cracking bones
Carnivores have a jaw hinge in line with the teeth for powerful closure. A large sagittal crest anchors the temporalis muscle, which provides strong vertical biting force. The masseter is less developed, and jaw movement is mainly vertical for slicing meat.
summarise the differences between stomachs in insectivore, nonruminant herbivore, ruminant herbivore, carnivore
DIAGRAM
summarise the differences between stomachs in insectivore, nonruminant herbivore, ruminant herbivore, carnivore
TABLE
Insectivore
Insects made largely of chitin and protein: easily digestible material, short gut as products of digestion easily absorbed.
Non-ruminant herbivore
Plant material with a high fibre / cellulose content: difficult to digest; bacteria / archaea present in caecum which can digest cellulose and produce protein.
Bacterial digestion occurs after the ileum, so products of bacterial digestion are not absorbed.
Some, e.g. rabbits, will eat their faeces as they can then absorb the extra nutrients.
Others, e.g. horses, do not eat faeces and therefore have less effective digestion and absorption.
rabbits
caecotrophs
Non-ruminant herbivore
Ruminant herbivore
The base of the oesophagus is expanded and differentiated into three chambers (these are usually referred to as part of the stomach, but this is incorrect!).
These chambers contain bacteria and archaea that can digest cellulose and produce fatty acids, proteins and vitamins that can then be utilised by the animals.
Protein digestion begins in the abomasum (true stomach). Absorption occurs after the site of bacterial digestion, so digestion is more efficient.
Most ruminants regurgitate their food following bacterial digestion in the rumen; this is then chewed a second time to further breakdown the tough fibres and release more nutrients.
Carnivore
Meat is made mostly of protein and fat: easily digestible and easily absorbed, no need for long digestive system.
The stomach is relatively larger to enable increased digestion of protein.
4 chambers of stomach
Rumen
Reticulum
Omasum
Abomasum
pathway of food via stomachs
when the animal first swallows the food it enters the reticulum.
Large objects, e.g. stones, collect here
liquids pass into the omasum and solids pass into the rumen.
Solids pass between the rumen and reticulum and are regurgitated (dotted line) and chewed again (this may happen up to 10 times).
In the rumen, bacteria, archaea and protoctista begin to digest the cellulose cell walls which releases cell contents.
The contents of the rumen eventually pass into the omasum where water and minerals are absorbed before the contents pass into the true stomach, the abomasum. This is where bacterial and remaining dietary protein begins to be digested.
microbes function
in the rumen
The microbes produce small fatty acids and B vitamins which provide additional nutrition to the animal. Microbes use protein released from the cells for their own growth.
In young ruminants that feed on milk
food passes from the base of the oesophagus directly to the abomasum; milk is high in protein and only the abomasum is needed to digest protein. There is no milk intake in adults – their diet is high in cellulose and low in protein. In adults, the rumen becomes the largest part of the stomach as most of the food that needs to be digested is cellulose.
