Adaptations for nutrition Flashcards
What type of nutrition do protoctists (such as the amoeba) use?
Holozoic nutrition
why do protoctists have a large SA:VOL?
they are single celled
How do protoctists obtain nutrients such as oxygen and glucose?
The cell membrane via diffusion, facilitated diffusion and active transport
How do protoctists take in large food molecules and what are they surrounded by to form?
They take in large food molecules such as bacteria and microscopic algae via endocytosis. The food molecules are surrounded by membranes, forming vacuoles.
What do the food vacuoles then do?
-The food vacuoles fuse with lysosomes containing hydrolytic enzymes which digest the contents of the food vacuoles. The products of digestion are then absorbed into the cell cytoplasm.
-Indigestible remains are egested by exocytosis.
What are the stages of digestion?
Ingestion
Digestion
Absorption
Assimilation
Egestion
What are Hydra?
Multicellular freshwater animals
What are hydra the same phylum as?
Jellyfish
What’s a hydra shaped like?
-Cylindrical shape
-Tentacles at the top of the body, which contains stinging cells
what type of digestive system do hydra have?
An undifferentiated digestive system
What is the process of nutrition in hydra?
-Their tentacles move paralysed prey in through the mouth and into the sac-like hollow body cavity where the prey digested
-The products of digestion are absorbed into body cells and indigestible remains are adjusted through the mouth- they therefore have only a single opening in their digestive system
What is a tube gut?
Most animals have a distinct anterior and posterior end, and a digestive system that is a tube with two openings.
Where is food ingested and where is indigestible waste egested? (Animals)
Food is ingested at the mouth and indigestible waste is egested at the anus.
Why must food be digested in humans?
-Food molecules are insoluble and are too large to cross membranes and be absorbed into the bloodstream.
-polymers must be converted to the monomers, so they can be rebuilt (assimilated) in molecules needed by body cells
What are the four main functions of the human gut performs?
-ingestion
-Digestion (mechanical and chemical)
-Absorption
-egestion
What is ingestion?
taking food into the body through the mouth
What is digestion?
the breakdown of large insoluble molecules into soluble molecules that are then small enough to be absorbed into the blood
What is mechanical digestion and what does it do?
cutting and crushing by teeth
-muscle contractions of the gut wall
-increases the surface area over which enzymes can act
What is chemical digestion?
-Breakdown using digestive enzymes. -Bile and stomach acid also contribute to this
What is absorption?
the passage of small soluble molecules and ions through the gut wall into the blood.
What is egestion?
the elmination of indigestible waste e.g. cellulose (dietary fibre).
Where does digestion and absorption occur?
In the gut
what is the gut?
-Long, hollow, muscular tube that allows movement of its contents in one direction only
-each section is specialised and forms particular steps in the process of mechanical and chemical digestion, and absorption
What is food propelled along the gut by?
Peristalsis
what is peristalsis?
-The wave of muscular contractions and relaxations of the gut wall, which propel the contents along the whole length of the gut.
-Circular muscles contract behind the bolus of food and then relax after the wave contraction has passed
what aids peristalsis in the intestines?
Dietary fibre
What is the process of peristalsis?
-contraction of circular muscles behind food
-Contraction of longitudinal muscles ahead of food
-Contraction in circular muscle layer, forces food forward
What are the parts of the digestive system?
-Mouth (Buccal Cavity)
-oesophagus
-Stomach
-Duodenum
-Ileum
-Colon
Rectum
-Anus
What is the function of the mouth?
-Ingestion.
-Mechanical digestion of food due to crushing action of the teeth.
-Chemical digestion of starch by salivary amylase.
what is the function of the oesophagus?
Carriage of food to the stomach by peristalsis.
What is the function of the stomach (in digestion)
-Contraction of stomach muscles to churn up the food - mechanical digestion.
-Secretion of hydrochloric acid.
-Chemical digestion of proteins by enzymes.
what is the function of the duodenum?
Receives pancreatic juice from the pancreas and bile from the gall bladder.
Chemical digestion of carbohydrates, fats and proteins by enzymes.
what is the function of the ileum?
-Chemical digestion of carbohydrates, fats and proteins by enzymes
-Absorption of digestive food
what is the function of the colon?
Absorption of water
What is the function of the rectum?
Storage of faeces
What is the function of the anus?
Site egestion
What happens to the thickness of the layers in the mammalian gut walls in different regions of the digestive system?
The thickness of these layers vary
What are the tissue layers that the mammalian gut wall consists of?
-Serosa
-Muscularis
-Submucosa
-Mucosa
what is the serosa?
-outermost layer
-contains connective tissue which protects the gut wall
-helps to reduce friction (reduce heat and slowing down of food) with other abdominal organs during peristalsis
what are the muscularis composed of and what di they do
-composed of two 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.
What is the submucosa?
-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.
what is the mucosa?
-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.
What are carbohydrates hydrolysed by?
-Starch to maltose via amylase
-Maltose to alpha glucose by maltase
-Lactose to glucose and galactose by lactase
-Sucrose to glucose and fructose sucrase
why should larger molecules be digested into smaller?
so they can be absorbed by gut epithelial cells
What do endopeptidases do?
hydrolyse peptide bonds within the molecule- e.g. pepsin and trypsin
what do exopeptidases do?
Hydrolyse peptide bonds at the end of the shorter polypeptide chains to make amino acids/dipeptides
What are proteins broken down to?
Dipeptides to amino acids
What are fat hydrolysed by and what are the products?
lipase and the products of fatty acids and glycerol
what happens at in the buccal cavity?
-mechanical digestion occurs here
-Food is mixed with saliva by the tongue and chewed with the teeth
what does food being chewed with teeth mean? (buccal cavity)
This increases a surface area for the food enzymes to work on
what is saliva?
A watery secretion containing:
-amylase (turns starch to maltose)
-Bicarbonate ions which create an optimum pH (slightly alkaline) for amylase
-Mucus which lubricates the food
what does the oesophagus do in the digestive system?
It has no role in digestive, but connects the buccal cavity to the stomach
What does the stomach do in digestion?
-bolus of food enters the stomach and is kept there by the contraction of sphincter muscles.
- swallowed food can remain inside the stomach for several hours. -stomach wall muscles contract rhythmically to churn the food with gastric juice secreted from gastric glands in the mucosa of the stomach wall.
What does gastric juice contain?
-mucus
-hcl
-pepsin
what does mucus do in the stomach? (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, and helps to lubricate the food.
what does Hydrochloric acid do in the stomach? (gastric juice)
It lowers the pH of the stomach contents to pH2 to create an optimum environment for enzymes and kills bacteria.
What does pepsin do in the stomach? (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 (HCI) forms active pepsin.
Why are enzymes secreted in an inactive form?
as the active form would digestive cells of the stomach wall (auto lysis)
what does the small intestine consist of?
-to regions the duodenum and ileum
what does the relaxation of the sphincter muscles at the base of the stomach do?
-releases the partially digested food (chyme) into the duodenum a little at a time
What is the duodenum?
-the first section of the small intestine and receives secretions from the liver and pancreas.
-food coming from stomach is lubricated by mucus and the hydrochloric acid is neutralised by alkaline secretions (NaCO,) from cells in the sub mucosa
where is bile made stored and passed through to get to the duodenum?
made in the liver, stored in the gall bladder and passed through the bile duct into the duodenum.
What does bile contain and what do they do?
bile salts which are hydrophilic and hydrophobic.
-They emulsify lipids present in the partially digested food and breaking up large globules into smaller droplets, thus increasing the surface area for lipase action.
What is bile and what does it do?
-alkaline and neutralises the acid in the food coming from the stomach creating an optimum pH environment for the enzymes in the small intestine.
What is pancreatic juice secreted by?
Specialised cells in the pancreas
How does pancreatic juice enter the duodenum?
Through the pancreatic duct.
What enzymes are involved in pancreatic secreation?
-Endopeptidase
-Trypsinogen
-Pancreatic Amylase
-Lipase
what is the function of endopeptidase?
-Hydrolyses protein to shorter polypeptides
what is the function of trypsinogen?
-inactive enzyme converted into the endopeptidase trypsin by enterokinase
what is the function of pancreatic amylase?
chemically digests any remaining starch and glycerol
What is involved in duodenal secretion?
-NaHCO3
-Enterokinase
what is the function of NaHCO3 in duodenal secretion?
Raises the pH to make pancreatic juice more alkaline
what is the function of enterokinase?
an enzyme that converts trypsinogen to trypsin
how is the ileum well adapted for absorption?
-It is very long (around 6 metres)
-Its lining is folded
-On the surface of the folds are villi
-The epithelial cells lining the villi have microscopic projections called microvilli.
These features help to increase the surface area.
What are the specialised cells in the mucosa of the ileum?
-Columnar epithelial cells
-Goblet cells
what are the two main adaptations of 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.
What do goblet cells secrete and what does this do?
secrete mucus, which lubricates and protects the lining of the intestine.
what enzymes are associated with epithelial cells at the tips of the villi? (in the ileum)
-Endopeptidases (proteins)
-Exopeptidases
-Carbohydrases (carbohydrates)
what do endopeptidases and exopeptidase do in the ileum?
-secreted by the 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
what do carbohydrases do 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.
In Crohn’s disease villi in the small intestine are destroyed, how could this lead to diarrhoea?
-Less microvilli or shorter villi
- reduced surface area
- less enzymes on the membranes cia!
-reduced digestion, or less absorption of products of digestion (e.g. amino acids or glucose)
-most solute in the lumen, so lower water potential
- less water absorption water moves from epithelial cells into lumen=diarrhoea
what molecules are absorbed in the ileum?
-fatty acids, glycerol
-Glucose and galactose
-Na+
-Amino acids
-Water
What is the transport mechanism for the molecules absorbed in the ileum from the lumen into the epithelial cell?
-Fatty Acids, glycerol- diffusion, and then reassembled into triglycerides
-Glucose and Galactose- co transport with Na+
-Na+- co-transport with glucose
-Amino Acids- Active transport
-Water- Osmosis
What is the transport mechanism for the molecules absorbed in the ileum from the epithelial cell nto the capillary/lacteal?
-Fatty acids, glycerol-diffusion into lacteal then carried via lymphatic system to the blood
-Glucose and Galactose- facilitated diffusion into capillary
-Na+- facilitated diffusion into capillary
-Amino Acids- facilitated diffusion into capillary
-Water-osmosis into capillary
What are substances absorbed into the blood transported to the liver by?
The hepatic portal vein
how does the active transport of sodium ions from the epithelial cells into the blood help with the passage of glucose from the lumen into the blood? (ileum)
-lower conc of Na+ in epithelial cells, which creates conc grad for Na+
-Na+ and glucose enter epithelial cell from lumen by co-transport
-increases glucose concentration in cell which creates a con grad for glucose
-Glucose moves into the blood by facilitated diffusion
what are the uses of the products of digestion?
-Glucose- required for aerobic respiration- excess stored as glycogen
-lipids- energy storage, protection of vital organs, thermal insulation under the skin
-Amino acids- used for protein synthesis, excess is deaminated in the liver
What is the large intestine divided into?
-caecum
-appendix
-colon
-rectum
what happens by the time indigestible food, cells, bacteria and undigested cellulose reaches the rectum?
they have become faeces, which will be egested
What substances absorbed in the large intestine?
-water
-Mineral ions
-Vitamins produced by symbiotic bacteria in the gut, like vitamin K and folic acid
What is nutrition?
Nutrition is the process by which organisms obtain energy to maintain life functions and matter to create and maintain structure.
What are the different types of nutrition?
-autotrophic (photo and chemo)
-Heterotrophic
What is autotrophic nutrition?
Autotrophic organisms synthesise their own complex organic molecules from simpler molecules using either light or chemical energy.
What do photographic organisms do?
(e.g. green plants, algae and some bacteria)- use energy from sunlight to carry out photosynthesis to make organic molecules (glucose) from the inorganic molecules carbon dioxide and water.
What do chemoautotrophic organisms do and give an example
use energy from chemical reactions to synthesise organic molecules.
E.g. bacteria respiring in deep sea hydrothermal vents.
what do heterotrophic organisms do?
-(consumers) cannot produce 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.
What do heterotrophs include?
include animals, fungi, some protoctista and some bacteria.
What are the types of heterotrophic nutrition?
-Holozoic nutrition
-Saprotrophic nutrition (cannot ingest)
what has Holozoic nutrition and what do they do?
Mostly animals and some protoctists, such as amoeba- these organisms, ingest food, digest it and egest any indigestible remains
What are the organisms that have holozoic nutrition?
-Carnivores- only eat other animals
-Herbivores- only eat plant material
-Omnivores- eat both plant an animal material
-Detritivores - feed on dead and decaying matter
what has saprotrophic nutrition?
-All fungi and some bacteria
what do saprotrophs feed on?
-Dead or decaying organic material
what type of digestion do saprotrophs carry out?
extracelluar digestion:
-Enzymes are secreted onto the food material outside of their body (e.g. amylases, proteases and cellulases)
-They then absorb the soluble products of digestion into their cells by diffusion or active transport
What are decomposers?
-microscopic saprotrophs that play an important part in decaying leaf litter and recycling nutrients shush as nitrogen
e.g. fungi such as Rhizopus
What is parasitic nutrition?
-parasites are organisms that live on or in another organism called the host and obtain nourishment at the expense of the host
-Parasites, therefore cause harm and often cause death
e.g. pork tapeworm, human head lice
what is an Endoparasite?
Lives inside the host
What is an ectoparasite?
Lives on the host
what are plants and animals parasitised by?
-bacteria, fungi, viruses, nemotodes, and insects
-animals are also parasitise by protoctista (amoeba), tapeworms and mites
What can bacteria be parasitised by?
viruses called bacteriophages
What is the pork tapeworm an example of?
-specialised parasite which has undergone considerable evolutionary changes in order to survive in the host
-It has no competition and cannot be prayed upon
What are the features of the tapeworm Taneia Solium?
•is ribbon like and can be up to 10 metres long.
•has a scolex (head) made up of muscle on which are suckers and hooks.
• body is a linear series of sections.
•has two hosts: the primary host is human and the secondary host is the 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.
what are the problems faced by the tapeworm?
-Gut is in constant motion (peristalsis / stomach churning)
-Extremes of pH along the gut, exposure to digestive enzymes and the host’s immune response
•Reproduction
- Unlikely to find a mate in host
- High offspring mortality
- Difficult for eggs to reach a new host
-Host death
-Tapeworm has no digestive
What adaption has a tapeworm evolved to overcome peristalsis?
-Suckers and hooks for attachment to the gut wall
What adaptions has the tapeworm evolved to overcome the problem of extremes of pH along the gut, exposure to digestive enzymes and the host’s immune response?
thick cuticle and the production of inhibitory substances (anti-enzymes) on its surface to prevent digestion by the hosts enzymes.
What adaptations has the tapeworm evolved to overcome the problem of reproduction?
-has 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.
what adaptations has the tapeworm involved to overcome the problem host death?
if host dies, so does the tapeworm - adult tapeworms cause little discomfort to the host.
what adaptations has a tapeworm evolved to overcome the problem of having no digestive system?
-long and thin (flat, ribbon like shape) so has a large surface area to volume ratio.
-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
What do human head louse do?
-has claws to hold onto the hair of a human
-Adult lays eggs which are glued to the base of the hairs
-They feed by sucking blood from the scalp of the host
Why are teeth important?
for the mechanical digestion of food
Why is chewing important?
It makes it easier to swallow and also increases the surface area for enzyme action
Why are human teeth relatively unspecialised?
Humans are omnivores
What are the four different types of teeth and what are their functions?
Incisors- Biting and cutting food
-Canines- Tearing and ripping meat
Molars and pre molars- grinding and chewing food
what is a herbivore diet base on?
Cellulose based (which is difficult to digest)
What are herbivore teeth adapted for?
grinding to increase surface area for bacterial cellulase enzyme action
what are the structural features of herbivore dentition?
-Horny pad
-Incisors
-Diastema
-Pre-molars and molars
-Loose jaw articulation
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.
What is the function of the incisors?
Slice through the plant material.
What’s the function of the diastema?
Gap between cheek and front teeth. The tongue moves cut grass to the large grinding surfaces of the cheek teeth.
what is the function of the pre-molars and molars?
Interlocking like an M fitting into a W for grinding food.
what is the function of loose jaw articulation?
The lower jaw moves from side to side, and produces a circular grinding action
What are the teeth carnivore mammals have adapted for?
catching and killing prey, cutting or crushing bones and for tearing meat
what are the structural features of carnivore dentition?
-Small, sharp incisors- to grip + tear flesh and bone
-Large curved canines- to seize and hold on to prey
-Pre-molar/molars- cutting and crushing food
-Carnassials- slide past each other and crush bone
-Vertical jaw movement- so jaw can open widely and cannot be dislocated when prey is struggling in its grip
What are carnivore diets high in?
Lipid (fats) and protein
what are ruminants?
-animals such as cows, goats and sheep which eat grass and forage
What does the food that ruminants eat contain?
A lot of cellulose
why are ruminants unable to digest cellulose?
They do not produce the enzyme cellulase
What type of stomach do ruminants have?
A four chambered stomach
What do ruminants rely on to digest cellulose?
-mutualistic bacteria which live in their gut and secrete the cellular enzymes
What does mutualistic bacteria live?
on one of the stomach chambers called the rumen
why is the caecum enlarged in rabbits?
to accommodate cellulose digesting bacteria
why is regurgitation not possible in a rabbit?
As the bacteria are towards the end of the gut
What occurs instead of regurgitation?
-refection (coprophagy) occurs, where the rabbit ingests faecal pellets so that the material passes through the gut twice to increase efficiency of digestion
How does reflection increase the efficiency of digestion?
More time spent on cellulose digestion
Why is the carnivore gut relatively short compared to the length of its body?
Because they have a diet high in protein and protein is easily digested
Why is the gut of a herbivore longer compared to the length of its body?
they eat a diet high in cellulose and cellulose is much harder to digest
why do carnivores have shorter gut length?
diet rich and protein- easy to digest
why do omnivores have an intermediate gut length?
eat protein and cellulose
why do herbivores have a longer gut length?
-they have a diet rich in cellulose- hard to digest- longer=more time
why might herbivores have a longer large intestine?
More water in plant material to be absorbed
what are the similarities between photoautotrophic nutrition and chemoautotrophic nutrition? (autotrophic nutrition)
-both producers
-both synthesise their own complex organic molecules
what are the differences between photoautotrophic and chemoautotrophic nutrition?
-photo- synthesise simple organic molecules using light in photosynthesis
-chemo- synthesise organic molecules using energy from chemical reactions
what are the similarities between phototrophic nutrition and detritivores?
-both are consumers
-both feed off dead and decaying matter
what are the differences between saprotrophic nutrition and detritivores?
-Saprotophic- use extracellular digestion by secreting enzymes onto dead and decaying material and absorbing the soluble products
-Detritivores- ingest dead and decaying matter and breakdown material using specialised internal digestive system
