Adaptations for Nutrition C3 Flashcards
what does it mean for an organism to be single -celled?
they have a large surface area to volume ratio
what example of a protoctist uses holozoic nutrition?
amoeba
what three ways does an amoeba obtain nutrients such as oxygen and glucose through their cell membranes?
diffusion
facilitated transport
active transport
how do amoebas take in food?
they take in large food molecules such as bacteria and microscopic algae via endocytosis
the food molecules are surrounded by membranes, forming vacuoles
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
describe hydra
they are multicellular fresh water animals
they are in the same phylum as jellyfish
they are cylindrical in shape and have tentacles at the top of the body which contain stinging cells
they have an undifferentiated digestive system
label the hydra
tentacle
mouth
hollow body cavity in which digestion occurs
jelly layer
ectoderm
endoderm
how do hydra take in food?
their tentacles move paralysed prey in through the mouth and into the sac-like hollow body cavity where the prey is digested
the products of digestion are absorbed into the body cells and the indigestible remains are egested through the mouth
they therefore have only a single opening in their digestive system
what is a tube gut?
it is found in most animals and has two openings: mouth and anus
what is a sac-like body cavity?
found in hydra and only contains one opening which is the mouth
describe tube gut in animals
most animals have a distinct anterior and posterior end and a digestive system that is a tube with two openings
food is ingested at the mouth and the indigestible waste is egested at the anus
why must food be digested? give two points
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 rebuilt (assimilated) into molecules needed by body cells
what are the four main functions of the human gut?
ingestion
digestion
absorption
egestion
what two types of digestion?
mechanical digestion
chemical digestion
what is the function of ingestion?
taking food into the body through the mouth
what is the function of digestion?
the breakdown of large insoluble molecules into soluble molecules that are then small enough to be absorbed into the blood
what is the function of mechanical digestion?
cutting and crushing by teeth and muscle contractions of the gut wall, increasing the surface area over which enzymes can act
what is the function of chemical digestion?
breakdown using digestive enzymes
bile and stomach acid also involved
what is the function of absorption?
the passage of small soluble molecules and ions through the gut wall into the blood
what is the function of egestion?
the elimination of indigestible waste eg cellulose (dietary fibre)
describe the gut in three points and what two functions of the human gut happen in the gut?
digestion and absorption
a long, hollow, muscular tube
allows movement of its contents in one direction only
each section is specialised and forms particular steps in processes of mechanical and chemical digestion and absorption
what causes the food in the gut to propel along?
peristalsis
what is peristalsis and mention dietary fibres?
wave of muscular contractions and relaxations of gut wall which propel contents along the whole length of the gut
circular muscles contract behind bolus of food, then relax after wave of contraction has passed
dietary fibres aid peristalsis in intestines
give 3 steps of peristalsis
longitudinal on outer layer and circular on inner
step 1 - contraction of circular muscles behind food
step 2 - contraction of longitudinal muscles ahead of food
step 3 - contraction in circular muscle layer forces food forward
label the human digestive system (alimentary canal)
there are 14
salivary glands
mouth
epiglottis
esophagus
stomach
liver
gall bladder
pancreas
small intestine:
duodenum
ileum
large intestine (colon)
rectum
anus
what is the function of the mouth?
ingestion
mechanical digestion of food by crushing action of teeth
chemical digestion of starch by salivary amylase
what is the function of the esophagus?
carriage of food to stomach by peristalsis
what is the function of the stomach?
contraction of stomach muscles to churn up the food aka 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 digested food
what is the function of the colon?
absorption of water
what is the function of the rectum?
storage of feces
what is the function of the anus?
site of egestion
label the structure of the mammalian gut wall
lumen
mucosa
sub-mucosa
muscularis - inner-circular and outer-longitudinal
serosa
describe the layers of the mammalian gut wall
the thickness varies in different regions of the digestive system eg stomach, ileum
describe serosa
it is the outermost layer containing tough connective tissue which protects the gut wall
it helps to reduce friction with other abdominal organs during peristalsis
describe muscularis
composed of two layers - inner circular and outer longitudinal
they make coordinated waves of contraction (peristalsis) pushing the bolus of food along the alimentary canal
describe submucosa
consists of connective tissues containing blood and lymph vessels which remove the absorbed products of digestion
also contains the nerves which coordinate peristalsis
describe mucosa
innermost layer
lines the gut wall
epithelium secretes mucus which lubricates and protects the mucosa
in some regions, it secretes digestive juices and in others it absorbs digested food
what makes the absorption of nutrients by gut epithelial cells possible?
if larger molecules like carbohydrates, fats and proteins are first digested into smaller molecules
different enzymes digest different food molecules and a number of enzymes are usually required to complete digestion
describe the digestion and breakdown of carbohydrates
starch -> (enzyme amylase) maltose -> (enzyme maltase) alpha glucose
lactose is also hydrolysed to glucose + galactose by lactase
sucrose is also hydrolysed to glucose + fructose by sucrase
describe the digestion and breakdown of proteins
polypeptides -> dipeptides -> amino acids
what is the difference between endopeptidases and exopeptidases?
endo: they hydrolyse peptide bonds within the protein molecule eg pepsin and trypsin
exo: they hydrolyse peptide bonds at the end of shorter polypeptide chains to make amino acids/dipeptides
describe the digestion and breakdown of fats
fats are hydrolysed by lipase and the products are fatty acids and glycerol
describe what happens in the buccal cavity
where mechanical digestion happens (in the mouth)
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
what is saliva and what 3 things does it contain?
is a watery secretion
amylase - digests starch into maltose
bicarbonate ions - which creates an optimum pH which is slightly alkaline for amylase
mucus - lubricates the food
what happens to the bolus of food in the stomach?
it is kept there by the contraction of sphincter muscles
the swallowed food can remain in the stomach for several hours
the stomach wall muscles contract rhythmically to churn the food with gastric juice secreted from gastric glands in the mucosa of the stomach wall
what three things does gastric juice contain?
mucus - secreted by goblet cells lining the mucosa, forms a protective lining which protects the stomach wall from digestive enzymes and hydrochloric acid and helps to lubricate food
hydrochloric acid - lowers the pH of the stomach contents to pH 2 to create an optimum environment for enzymes and kills bacteria
pepsin - secreted as inactive pepsinogen., is a peptidase that works optimally in the acidic environment, activation of pepsinogen by HCl forms active pepsin
why are enzymes secreted in an inactive form?
the active form would digest the cells of the stomach/intestine wall (autolysis)
what two regions does the small intestine contain?
duodenum and ileum
how is the partially digested food transported from the stomach to the duodenum?
relaxation of the sphincter muscles at the base of the stomach releases the partially digested food, known as chyme, into the duodenum, a little at a time
describe the duodenum
the first section of the small intestine
receives secretions from the liver and pancreas
food coming from the stomach is lubricated by mucus and the hydrochloric acid is neutralised by alkaline secretions, NaHCO3, from cells in the sub mucosa
where is bile stored and made and how is it passed to the duodenum?
in the liver
stored in the gallbladder
passed through the bile duct into the duodenum
what is the role of bile?
they contain 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
it is alkaline and neutralises the acid in the food coming from the stomach creating an optimum pH environment for enzymes in the small intestine
where is pancreatic juice secreted?
secreted by specialised cells in the pancreas
enters the duodenum through the pancreatic duct
what enzymes does the pancreas secrete?
endopeptidases
trypsinogen
amylase
lipase
what is the function of trypsinogen?
inactive enzyme converted into the endopeptidase trypsin by enterokinase
what does the duodenum secrete?
sodium hydrogen carbonate - NaHCO3 (raises pH to make pancreatic juice more alkaline)
enterokinase
give 4 features of the ileum that make it well adapted for absorption
very long - around 6 metres
lining is folded
surface of the folds contain villi
epithelial cells lining villi have microscopic projections called microvilli
all features help increase surface area
what is another structure in the ileum linked to the lymph vessel?
lacteal
glycerol and fatty acids go to the lymphatic vessel/ lymphatic vessel that absorbs dietary fats
give two specialised cells in the mucosa of the ileum
columnar epithelial cells
goblet cells
what are 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 the blood vessels do in the ileum?
remove products of digestion which diffuse or are actively transported in
label the structure of one villus
goblet cell
epithelial cells - one layer
lacteal
blood vessel
crypt of Lieberkühn
what is the role of the crypt of Lieberkühn?
in the duodenum, these valleys between the villi contain special glands called Brunner’s glands that produce sodium hydrogen carbonate and enterokinase
what are special about the epithelial cells on the tips of the villi in the ileum?
there are enzymes associated with them
what is the role of the cells at the tips of the villi in the ileum to protein digestion?
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
what is the role of the cells at the tips of the villi in the ileum to carbohydrate digestion?
carbohydrase’s like maltase on epithelial cell membranes hydrolyse disaccharides into monosaccharides like alpha glucose
the monosaccharides can then be absorbed into the epithelial cells
In Crohn’s disease villi in the small intestine are destroyed. How can this lead to diarrhoea?
Less enzymes on the membranes because endopeptidase and exopeptidase are located on the tip of the villi, meaning that digestion is reduced so less absorption of products eg amino acids and glucose
More solute in the lumen lowering water potential
Less water absorption so water moves from epithelial cells into lumen = diarrhoea
How are fatty acids and glycerol transported from the lumen to the epithelial cells? And from the epithelial cells to the lacteal?
Lumen and epithelial: micelles break down and feed a pod of dissolved fatty acids and monoglycerides and enter cell by diffusion
A tryglyceride is reassembled in the endoplasmic reticulum
Epithelial to lacteal: diffusion into lacteal then carried via lymphatic system to the blood
How are glucose and galactose transported from the lumen to epithelial cells and from epithelial cells to capillaries?
Lumen to epithelial cells: co-transport with Na+
Epithelial to capillary: facilitated diffusion into capillary
How is Na+ transported from the lumen to epithelial cells and from epithelial cells to capillaries?
Lumen to epithelial: co-transport with glucose and amino acids
Epithelial to capillary: active transport into capillary
How are amino acids transported from the lumen to epithelial cells and from epithelial cells to capillaries?
Lumen to epithelial: tri and di peptides are hydrolysed on the tips of the villi and then active transport
Epithelial to capillary: facilitated diffusion into capillary
How is water transported from the lumen to epithelial cells and from epithelial cells to capillaries?
Lumen to epithelial: osmosis
Epithelial to capillary: osmosis into capillary
How are substances absorbed in the blood transported to the liver?
Via the hepatic portal vein
How can active transport of Na+ from the epithelial cells into the blood help with the passage of glucose from the lumen into the blood?
There is a lower conc. of Na+ in epithelial cells which have gone to the blood, creating a conc. gradient for Na+
Na+ moves down its conc. gradient into epithelial cell from the lumen by co-transport with glucose
This increases glucose concentration in cell which creates a concentration gradient for glucose
Glucose moves into the blood by facilitated diffusion
Give different uses of products of digestion
Stored as fat for insulation
Energy for cellular respiration, glucose used for aerobic respiration, excess glucose stored as glycogen in the liver
Fatty acids and glycerol used for energy storage, protection of vital organs, thermal insulation, synthesis of cell membranes, steroid hormones
Amino acids used for protein synthesis eg for muscles and enzymes, excess proteins are de animated in the liver
Describe the large intestine
The large intestine is divided into the caecum, the appendix, the colon and the rectum
By the time it reaches the rectum, indigestible food, cells, bacteria and undigested cellulose have become faeces which will be egested
Give three substances absorbed in the large intestine
Water
Mineral ions
Vitamins produced by symbiotic bacteria in the gut like vitamin K and folic acid
Label the large intestine
Transverse colon
Ascending colon
Descending colon
Sigmoid colon
Caecum
Appendix
Rectum
Define nutrition
The process by which organisms obtain energy to maintain life functions and matter to create and maintain structure
Give two types of nutrition
Autotrophic and heterotrophic
What do autotrophic organisms do?
They synthesise their own complex organic molecules from simpler molecules using either light or chemical energy
Give two types of autotrophic nutrition
Photo autotrophic
Chemoautotrophic
What do photoautotrophic organism do?
They are green plants, algae and some bacteria
They use energy from sunlight to carry out photosynthesis to make organic molecules like glucose from inorganic molecules like carbon dioxide and water
What do chemoautotrophic organisms do?
They use energy from chemical reactions to synthesise organic molecules
Eg bacteria respiring in deep sea hydrothermal vents
What do heterotrophic organisms do?
They are consumers and cannot produce their own organic molecules and so obtain complex organic molecules from other organisms
Then they break this material down into smaller soluble molecules which they absorb and assimilate
Eg animals, fungi, some protoctista and some bacteria
What is the equation of hydrothermal energy and chemosynthesis?
CO2 + H2O + H2S + O2 -> *Carb (CH2O) + H2SO4
What are three types of heterotrophic nutrition?
Holozoic nutrition
Saprotrophic nutrition
Parasitic nutrition
What organisms use holozoic nutrition?
Mostly animals but also some protoctists such as amoeba
These organisms ingest food, digest it and wheat any indigestible remains
There are 4 types of holozoic organisms. Name them and describe them
1- carnivores: only other animals
2- herbivores: only eat plant material
3- omnivores: eat both plant and animal material
4- detritivores: feed on dead and decaying matter
What organisms use saprotrophic nutrition?
All fungi and dead bacteria
They feed on dead or decaying organic material and carry out extracellular digestion
How does extracellular digestion work?
Enzymes are secreted onto the food material outside of their body eg amylases and cellulases
Then they absorb the soluble products of digestion into their cells by diffusion or active transport
what are decomposers?
they are microscopic saprotrophs that play an important role in decaying leaf litter and recycling nutrients such as nitrogen, eg of decomposers: fungi like Rhizopus
define parasitic nutrition
parasites are organisms that live on or in another organism, called the host, and obtain nourishment at the expense of the host
parasites cause harm and often death eg the pork tapeworm (Taenia solium), fungus potato blight and human head lice
what is the difference between endoparasite and ectoparasite?
endo: lives in the host
ecto: lives on the host
what are plants, animals and bacteria parasitised by?
plants and animals: bacteria, fungi, viruses, nematodes and insects
animals only: Protoctista, tapeworms and mites
bacteria: viruses called bacteriophages
most organisms are parasitised for at least part of their lives
describe the pork tapeworm - taenia solium
a gut endoparasite
it is an example of a specialised parasite that has undergone considerable evolutionary changes in order to survive in the host
has no competition and can’t be preyed upon
give 6 features of the pork tapeworm
the tapeworm is ribbon-like and can be up to 10 metres long
it has a scolex (head) made up of muscle on which are suckers and hooks
its body is a linear series of sections
it has two hosts: the primary host is a human and the secondary host is a pig
the larval form in fond in pigs, the pig becomes infected if it feeds on drainage channels contaminated by human faces containing eggs
humans become infected by eating contaminated undercooked pork
what are five problems that is faced by the tapeworm?
gut is in constant motion from peristalsis and stomach-churning
extremes of pH along the gut, exposure to digestive enzymes and the host’s immune system
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 system
what adaptation has the tapeworm evolved to overcome the problem of the gut being in constant motion?
suckers and hooks for attachment to the gut wall
what adaptation has the tapeworm evolved to overcome the problem of the extremes of pH?
a thick cuticle and the production of inhibitory substances (anti-enzymes) on its surface to prevent digestion by the hosts’ enzymes
what adaptation has the tapeworm evolved to overcome the problem of reproduction?
it has both female and male 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 adaptation has the tapeworm evolved to overcome the problem of the host dying?
if host dies, so does the tapeworm - adult tapeworms cause little discomfort to the host
what adaptation has the tapeworm evolved to overcome the problem of it having no digestive system?
tapeworm is long and thin, and has a flat, ribbon-like shape, so has a large surface area to volume ratio
it lives in the small intestine and is surrounded by hosts’ digested food which can be absorbed over the entire body surface by diffusion
describe lice
there are many species of lice which are specialised to be found on a particular part of a host body
humans can be infected by body, head and pubic lice
describe how head lice work
it 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
give the life cycle of head lice
lice egg (nit) is laid onto the hair shaft
after 6-7 days young louse hatches
first moult 2 days after hatching
second moult 5 days after hatching
third moult 10 days after hatching - now an adult louse
male and slightly larger female begin to reproduce
female lays first eggs 2 days after mating
she lays 4-8 eggs for the next 16 days and then dies
describe human dentition and mention why teeth and chewing are important
teeth important in the mechanical digestion of food
chewing is important to make it easier to swallow and increases surface area for enzyme action
human teeth are relatively unspecialised as we are omnivores
give four different types of teeth and their different functions that are part of human dentition
incisors - biting and cutting food
canines - tearing and ripping meat
molars and pre molars - grinding and chewing food
what is the flappy bit called above the throat?
uvula
what are herbivore teeth adapted for?
herbivore diet is cellulose-based
cellulose is difficult to digest
herbivore teeth adapted for grinding to increase surface area for bacterial cellulase enzyme action
what are 5 structural features of herbivore teeth?
incisors and dental pad
canines
diastema
molars
horizontal jaw movement
what is the function of incisors and dental pad?
the animals wraps its tongue around the grass and pulls it tight across the horny pad on the upper jaw
what is the function of canines in herbivores?
slice through plant material
what is the function of the diastema?
gap between cheek and front teeth
tongue moves cut grass to the large grinding surfaces of the cheek teeth
what is the function of molars in herbivores?
grinding forms sharp enamel ridges on molars which increases grinding efficiency
interlocking like an M fitting into a W for grinding food
what is the function of the horizontal jaw movement?
the lower jaw moves from side to side and produces a circular grinding action
what is the function of open roots in herbivores?
allows teeth to keep growing without restriction for grinding
what are carnivorous teeth adapted for?
catching and killing prey, cutting or crushing bones and for tearing meat
give 6 structural features of the dentition of a carnivore
small sharp incisors
large curved and pointed canines
premolars and molars
carnassials
vertical jaw movement
powerful jaw muscles
what is the function of powerful jaw muscles in carnivores?
well developed to grip prey firmly and crush bone
what is the function of small sharp incisors?
to grip and tear flesh from bone
what is the function of large curved and pointed canines?
to seize and hold on to prey
what is the function of molars and pre-molars in carnivores?
cutting and crushing food
what is the function of carnassials?
they slide past each other like blades and crush bone
what is the function of the vertical jaw movement?
so the jaw can open widely and cannot be dislocated when prey is struggling in its grip
describe ruminants. state what animals, what food, what stomach…
are animals such as cows, goats and sheep
mainly eat grass and forage
this contains a lot of cellulose which they are unable to digest as they do not produce the enzyme cellulase
they have a four-chambered stomach
what do ruminants rely on? where do they live and what do they do?
mutualistic bacteria which live in their gut and secrete the cellulase enzymes
which chamber does the ruminant bacteria live in and why?
rumen
food can be kept for longer for the bacteria to hydrate the cellulose
it isolates the bacteria from the digestive juices so they aren’t exposed to extreme levels of pH
how does the bacteria convert the cellulose to energy for the animal?
bacterial enzyme breaks bond between glucose molecules
glucose used by bacteria for energy
by-products of glucose fermentation get released and glucose absorbed across rumen membrane
provides energy
name the 4 stomach chambers present in ruminants
rumen
omasum
reticulum
abomasum
explain and describe the process of cellulose digestion
A - grass is chewed, mixed with saliva and swallowed
B - swallowed grass passes into rumen and is churned and mixed with bacteria that secrete cellulase to digest cellulose to beta-glucose
beta-glucose is absorbed into the blood, providing energy
bacteria produce waste products carbon dioxide and methane gas which are released from animal
C - any undigested grass passes to reticulum chamber and is formed into cud
cud is regurgitated into mouth for further chewing
process may be repeated several times and increases surface area of grass to allow more cellulose digestion to take place
D - the cud then passes into the omasum for temporary storage, where excess water is absorbed into the blood
E - in the abomasum or ‘true stomach’, bacteria are killed and digested
bacteria provide an important source of protein for the animal
how does a rabbit, which is a non-ruminant herbivore, digest its food?
the caecum is enlarged in a rabbit to accommodate cellulose-digesting bacteria
bacteria are towards the end of the gut so regurgitation not possible
instead, refection (coprophagy) occurs -the rabbit ingests faecal pellets so that material passes through the gut twice to increase efficiency of digestion, allowing more time for cellulose digestion
rabbits know which poo to eat when it smells the sweetness of it and tastes it a bit to check if it’s sweet
compare the gut of a carnivore to that of a herbivore
carnivore gut is relatively short compared to length of its body because they have a diet high in protein and protein is easily digested
herbivore gut is longer compared to length of its body as they have a diet high in cellulose and cellulose is much harder to digest and takes more time
why may some animals have a longer large intestine?
so that more water in the food material is absorbed
what are the similarities between chemotrophs and phototrophs, who are both autotrophs?
both are producers
both synthesise their own complex organic molecules using a form of energy
what are the similarities between saprotrophs and detritivores?
both consumers
both feed off dead and decaying matter
whats the difference between saprotrophs and detritivores?
saprotrophs use extracellular digestion by secreting enzymes onto dead, decaying material and absorbing the soluble products
detritivores ingest and breakdown dead, decaying material using a specialised internal digestive system
