Nutrition Flashcards
define autotrophic
– makes complex organic molecules from
simple inorganic ones.
Name the two types of autotrophic organisms.
● Photoautotrophic
● Heterotrophic
What is a photoautotrophic organism?
Use light as a source of energy for synthesis of food.
What is a chemoautotrophic organism?
Oxidise inorganic molecules to provide energy for the synthesis of food
Define heterotrophic.
An organism that cannot produce its own
food. It obtains energy by feeding on
organic compounds produced by other
organisms
What is a saprotroph?
An organism that feeds by extracellular
digestion, e.g. fungi
Describe extracellular digestion by saprotrophs
● Release enzymes which catalyse the
breakdown of dead plant and animal
material into simpler organic matter
● Absorb the products of digestion
What is meant by the term ‘holozoic’?
Describes a heterotrophic organism that
internally digests food substances
What processes does holozoic nutrition involve?
Ingestion, digestion, absorption,
assimilation and egestion
Define ingestion.
The process by which organisms take
food into their bodies.
Define digestion.
The processes by which large, insoluble
molecules are broken down into smaller,
soluble molecules that can be absorbed across cell membranes.
Name the two types of digestion.
● Mechanical digestion
● Chemical digestion
What is mechanical digestion?
● Type of digestion that involves physically
breaking down food material into smaller pieces
● Increases the total surface area for chemical digestion
What is chemical digestion?
A type of digestion that involves breaking
down large, insoluble molecules into
smaller, soluble molecules using enzymes.
What is assimilation?
The synthesis of biological compounds
from absorbed simpler molecules
Define absorption.
The movement of useful substances into
the bloodstream
Define egestion
The removal of undigested waste
material from the body
Describe how unicellular organisms obtain nutrients
● Ingestion via phagocytosis
● Intracellular digestion (using hydrolytic enzymes) breaks down large, insoluble molecules into smaller, soluble molecules
● Products of digestion pass into the cytoplasm by diffusion and active transport
● Undigested material removed by exocytosis
What is a Hydra?
A small, multicellular, freshwater
organism of the phylum Cnidaria.
Describe the structure of Hydra
● Basic, undifferentiated sac-like gut
● Single opening, surrounded by tentacles,
that serves as a mouth and an anus
● Single gut cavity (known as the enteron)
Outline the process of digestion in
Hydra.
● Hydrolytic enzymes secreted into the enteron by the endodermis
● Extracellular digestion partially digests food molecules
● Partially digested food transported, via phagocytosis, into endodermal cells where intracellular digestion takes place
● Undigested material egested from the enteron via the single opening
Describe the shape of the gut in more complex organisms.
Tube-like with two openings, a mouth for
ingestion and anus for egestion.
What type of diet is the human gut adapted to?
An omnivorous diet consisting of plant
and animal material.
State the names of the different layers of
the gut wall
● Epithelium
● Mucosa
● Submucosa
● Muscle layer
● Serosa
What is the epithelium?
A single layer of cells that line the gut
wall.
Describe the structure of the mucosa
layer of the gut wall.
● Mucous membrane lining the gut wall
● Contains glands that secrete digestive
enzymes, mucus, and an acid or alkaline liquid that provides an optimum pH
Describe the structure of the sub-mucosa layer of the gut wall.
● Layer of connective tissue below the mucous membrane
● Contains blood vessels and lymph for the transport of digestion product and glands that secrete an alkaline fluid
Describe the muscle layer of the human gut
A layer of circular and longitudinal
muscles beneath the submucosa
Explain the action of circular and longitudinal
muscles in peristalsis.
The contraction of the circular muscle behind
the bolus of food and the relaxation of the
longitudinal muscle in front forces food down
the gut.
What is the serosa?
The tough, protective layer that
surrounds the gut.
What is the buccal cavity?
The oral cavity through which food
enters the body
Which type(s) of digestion take place in
the buccal cavity?
Mechanical digestion and chemical
digestion of starch.
What is the normal pH range of the
buccal cavity?
pH 6.5 to 7.5
What is the function of the teeth?
Crush and grind food into smaller pieces,
increasing its surface area.
What is the tongue?
A muscular organ in the buccal cavity
that is vital in the chewing and
swallowing of food
Describe the function of salivary glands.
Secrete amylase, mineral ions and
mucus into the buccal cavity
What is the function of the oesophagus?
Carries food from the buccal cavity to the
stomach by peristalsis.
Describe the processes that take place
in the stomach
Mechanical digestion (mixing and grinding)
and chemical digestion of protein.
What type of glands are found in the
stomach?
gastric glands
function of gastric glands
Secrete endopeptidases, hydrochloric
acid and an alkaline mucus into the
stomach
What is the normal pH of the stomach?
pH 2
function of liver
Secretes bile into the small intestine via
the gallbladder and bile duct.
Describe the composition and function
of bile
● Consists of bile salts and an alkaline fluid
● Neutralises stomach acid, providing an
ideal pH for lipase
State the two main divisions of the small
intestine.
● Duodenum
● Ileum
what is the duodenum
The first section of the small intestine
where proteins and lipids are hydrolysed.
what is the ileum
The second section of the small intestine
that serves as the main site of absorption
of the products of digestion.
What is the normal pH range of the small
intestine?
ph 7 to 8
What is the pancreas and where is it located?
A gland situated behind the stomach.
Describe the role of the pancreas.
It secretes enzymes and an alkaline fluid
into the duodenum via the pancreatic
duct.
What is the large intestine also called?
colon
Describe the function of the colon.
Reabsorbs water and minerals from the
waste material
What is the rectum?
The segment of the large intestine that
stores faeces prior to egestion
Which enzymes are involved in
carbohydrate digestion? Where are they
found?
● Amylase in saliva and pancreatic juice
● Maltase, sucrase, lactase on the
membrane of the epithelial cells of the small
intestine
What are the substrates and products of
the carbohydrases?
● Amylase hydrolyses starch to maltose
● Maltase hydrolyses maltose to alpha-glucose
● Sucrase hydrolyses sucrose to glucose and fructose
● Lactase hydrolyses lactose to glucose and galactose
What is the optimum pH of amylase?
pH8
Which enzymes are involved in protein
digestion? What are their roles?
● Endopeptidases - hydrolyse non-terminal peptide bonds within a protein to form smaller peptides
● Exopeptidases - hydrolyse the terminal peptide bonds of a protein to form dipeptides and amino acids
Give some examples of endopeptidases
trypsin
pepsin
Describe how trypsin is produced.
● Secreted by the pancreas as inactive
trypsinogen
● Enterokinase converts inactive trypsinogen into active trypsin in the duodenum
Name the inactive form of pepsin
pepsinogen
Where is pepsinogen secreted from?
gastric glands
Describe how inactive pepsinogen is converted into its active form, pepsin
Hydrochloric acid converts inactive
pepsinogen into active pepsin.
Where are lipids digested
small intestine
What must happen before lipids can be digested?
They must be emulsified by bile salts
produced by the liver. This breaks down large
fat molecules into smaller, soluble molecules
called micelles, increasing the surface area.
How are lipids digested
Lipases hydrolyse lipids into monoglycerides, fatty acids and glycerol.
Where are lipases found?
pancreatic juices
State the processes by which absorption takes place in the ileum.
● Simple diffusion
● Facilitated diffusion
● Active transport
● Osmosis
Which molecules are absorbed by simple
diffusion in the ileum
Monoglycerides, fatty acids and glycerol.
Why can monoglycerides, fatty acids and
glycerol be absorbed via simple
diffusion?
They are non-polar molecules so can
easily diffuse across the membrane of
the epithelial cells
What happens to monoglycerides, fatty acids and glycerol once they are absorbed into cells?
They are reformed into triglycerides,
absorbed into the lacteals and transported
via the lymphatic system into the blood.
How are amino acids absorbed from the lumen of the gut?
Via active transport into epithelial cells
and then into the bloodstream by
facilitated diffusion.
Which molecules rely on co-transport from the lumen
of the gut into the cytoplasm of the epithelial cells?
glucose and monosaccharides
Explain how sodium ions are involved in
co-transport
Sodium ions (Na+) are actively transported
out of the cell into the lumen, creating a
diffusion gradient. Nutrients are then taken
up into the cells along with Na+ ions.
What are herbivores?
Animals that only eat plants.
Describe the adaptations of herbivores to
a high cellulose diet.
● Long gut
● Loose articulation of the lower jaw
● Horny pad on the upper jaw
● Specialised dentition for grinding tough plant material
Describe how the dentition of a herbivore is adapted to its diet.
● Small, flat incisors on lower jaw for cutting grass against upper horny pad
● Diastema between incisors and premolars - separates fresh grass from the cud and enables manipulation of food by the tongue
● Premolars and molars have a large surface area and sharply ridged biting
surfaces for grinding plant material
What are ruminants?
Mammals that digest plant material slowly in a specialised four-chambered stomach and
regurgitate it to chew it again, enabling the
efficient breakdown of fibre.
Name the four chambers of the ruminant
stomach.
● Rumen
● Reticulum
● Omasum
● Abomasum
Describe the rumen.
The first stomach of a ruminant. It
contains mutualistic bacteria that are
able to hydrolyse cellulose into glucose
What is a carnivore?
An animal that preys on and eats other
animals.
Describe the adaptations of carnivores to
a high protein diet
● Short gut
● Powerful jaw muscles
● Specialised dentition for cutting and tearing meat
Describe how the dentition of a carnivore
is adapted to its diet.
● Sharp incisors to remove flesh from bone
● Large, pointed canines required to grip and kill prey
● Sharp carnassials (modified premolars and molars) to slice and shear meat
● Molars with sharp, flattened edges to crush bone
Describe how the dentition of a carnivore
is adapted to its diet.
● Sharp incisors to remove flesh from bone
● Large, pointed canines required to grip and kill prey
● Sharp carnassials (modified premolars and molars) to slice and shear meat
● Molars with sharp, flattened edges to crush bone
What is a parasite?
An organism that lives on or in a host
and takes nourishment at the expense of
the other organism
Name the two types of parasite
ecoparasites
endoparasites
What are ecoparasites? Give an
example.
Parasites that live on the host e.g. Head
louse
What are endoparasites? Give an example
Parasites that live in the host e.g. Pork
tapeworm
How does the head louse feed and
transfer from one host to another?
● Feeds by sucking blood from the host’s scalp
● Transfers between hosts by direct contact
Where does the pork tapeworm live?
● Primary host - adult tapeworm lives in
the human gut
● Secondary host - larval form can develop
in pigs
How can humans and pigs become infected by the pork tapeworm?
● Humans become infected by consuming undercooked pork (containing larval forms of the tapeworm)
● Pigs may become infected by ingesting
contaminated faeces
How does the pork tapeworm feed?
Absorbs pre-digested nutrients in the gut
through its cuticle
How is the pork tapeworm adapted to
living in the gut?
● Thick cuticle
● Secretes anti-enzymes that prevent its digestion by host enzymes
● Scolex has suckers and hooks for attachment to gut wall
● Long, thin body proves large surface-area-to-volume ratio for
absorption
what are on tapeworms heads
hooks
suckers
what do hooks and suckers do
they attach head to the intestinal wall and cannot be removed by passage of gut contents
why does a tapeworm have a very simplified digestive system
tapeworms absorb digested products of hosts as it has a large surface area to volume ration
no need to digest its own food
how does tapeworms cause weight loss
tapeworms absorb nutrients from the gut contents which causes malnutrition
block gut lumen
larval forms - form cysts in vital organs
hydra
– single food source
gut = Undifferentiated, sac-like gut with a single opening
earthworms
varied food
A tube gut with different openings for ingestion and egestion and specialised regions for the digestion of different foods
Human
Omnivorous diet
Specialised regions of the gut
The wall of the guy contains
Serosa
Longitudinal muscle
Circular muscle
Sun mucosa
Mucosa
Epithelium
What does the wall of a gut contain
Serosa
Longitudinal muscle
Circular muscle
Sub muscosa
Mucosa
Epithelium
What is Serosa
Tough outer layer coat of connective tissue
muscle (longitudinal and circular)
Longitudinal- contracts to shorten the gut and circular muscle contracts to reduce diameter
These waves of contractions are called peristalsis that force food along the gut
What does peristalsis do
Forces food along the gut
Sub mucosa
Contains blood and lymph vessels to remove digested food products
Mucosa
Inner layer that secretes mucus for lubrication
In some areas it secretes digestive juices
In other it absorbs products
Epithelium
Layer of cells in contact with food
Type of protease
Endopeptidases
Endopeptidases = hydrolyse peptide bonds between specific amino acids in the middle of the polypeptide chain to form shorter polypeptide chains
Exopeptidases
Hydrolyse peptide bonds on the ends of peptides, from the free amino end or the free carboxyl end
What happens in mouth
Chemical digestion
Starch and glycogen into maltose
Done by AMYLASE
Gall bladder
Stores bile before delivering it to duodenum via bile duct
Liver
Produces bile
Bile emulsifies lipids to increase the surface area available for lipase to digest them
* also neutralises stomach acid to create slightly alkaline pH in the duodenum for pancreatic enzymes
Duodenum
Further digestion on epithelial cells of villi
Sucrose digested by sucrase into glucose and fructose
Maltose digested by maltase into alphas glucose
Lactose digested by lactase into glucose and galactose
ileum
Amino acids are actively transported into the epithelial cells of the villi
Facilitated diffusion then occurs into the capillaries in the villi
Fatty acids and glycerol diffuse into epithelial cells
Where are fatty acids and glycerol carried to ?
Carried by lacteal to the lymphatic system to be reassembled
Oesophagus
Peristaltic waves of muscle contraction push the bolus of food down to the stomach
* mucus lubricates this way
Stomach
Gastric glands in the mucosa produce gastric juice
Oxyntic cells produce hudrochloric acid that kills bacteria and lowers ph to 2
Chief cells or peptic cells produce pepsinogen- inactive percursor of the Endopeptidases enzyme pepsin
Activated by hcl
Goblet cells produce mucus to protect stomach lining
Pancreas
Produces enzymes that are transported to the duodenum via the pancreatic duct
Carbohydrase - pancreatic amylase
Protease
Trysinogen activated by Endopeptidase trypsin by enterokinase in the d
A villus
The villi increase the surface area in the small intestine for absorption of digested food in blood
What does villus contain
Columnar epithelium
Lacteal
Capillary
What does a carnivore mouth contain
Canines
Incisors
Premolars and molars
Carnassial teeth
What are canines
Long and pointed to pierce flesh and seize and kill prey
Incisors
On upper and lower jaws grip and tear flesh
Premolars and molars
Have sharp cusps that cut and crush
Jaw has strong muscles and moves in a vertical plane opening wide and strongly clamping down to hold prey
Herbivore teeth
Premolars and molars
Diastema
Incisors
Herbivores
Premolars and molars
Cheek teeth
Fit together in W and M shape
Jaw moved horizontal plane so these interlocking teeth grind food
Teeth have open unrestricted roots and so grow throughout life
Diastema
Space where tongue can push food to the grinding cheek teeth
Incisors - herbivores
Occur on lower jaw
Cut vegatation against a horny pad on the upper jaw
** Canines are absent
Gut of carnivores
Relatively short gut
Usually large stomach for digestion of mostly protein diet
Small caecum
Gut of herbivores
Non ruminants
Very long gut for difficult process of cellulose digestion
Large caecum containing bacteria that produce cellulase for cellulose digestion
What are parasites
Live on or in a host organism
Obtaining their nutrition from the host and harming the host
Ectoparasite
Lives on surface of another organism
Endoparasite
Lives inside another organism
Examples of ectoparasite
Head louse feed by sucking blood from scalp of the host
Claws to hold onto hairs
Lays eggs which are glued to the base of hairs
Transfer between hosts is by direct contact as it cannot jump only crawl
Example of endoparasite
Adult pork tapeworm
Lives in guts of humans
Primary host- larval form develops in pigs
Secondary host- infection of humans occur when the person eats pork w live larval forms (tapeworm cysts)
Adaptation of gut
Thick cuticle produces anti enzymes
Scolex to attach to the gut wall
To increase chance of infecting secondary host it produces large number of eggs that pass out of poo
4 chambers of cow stomach
Omasum
Abomasum
Reticulum
Rumen
Omasum
Water absorption occurs here
Abomasum
Protein digestion occurs here
Reticulum
Cud is regurgitated from here and the rumen back into the mouth to be re chewed
