Eduqas AS Biology; Component 3: "Adaptations for Nutrition"

Define nutrition

The process by which organisms obtain energy to maintain life functions and matter to create and maintain structure

What is autotrophic nutrition?

Autotrophic nutrition is when organisms synthesise their own complex organic material from simpler inorganic molecules using energy.

Name and define the two types of autotrophic nutrition.

Photoautotrophic: organisms use energy from sunlight to carry out photosynthesis to make organic molecules from the inorganic molecules CO2 and water

Chemoautotrophic: using energy from chemical reactions to synthesise organic molecules

What type of organisms carry out autotrophic nutrition?

Plants and algae.

Define holozoic nutrition.

Organisms which have specialised disgestive systems in which they ingest food, digest it and egest any indigestible remains

What is heterotrophic nutrition?

Heterotrophic organisms cannot produce their own organic molecules so they consume complex organic molecules from other organisms and then break it down to smaller molecules to assimilate.

Name the four types of organisms which use holozoic nutrition and their diets

CARNIVORES: consume animal material only

HERBIVORES: consume plant material only

OMNIVORES: consume both plant and animal material

DETRITIVORES: consume dead/decaying matter only

What do saprotrophs consume?

dead or decaying organic material

Explain how saprotrophs obtain nutrients.

Extracellular digestion: they secrete enzymes which works on the food outside their body and then absorb the soluble products of digestion by diffusion and active transport

Define parastic nutrition

Parasites are organisms that live in or on another organism (a host) and always cause harm to the host.

What are the two types of parasitic nutrition?

Endoparasite: feed on the host internally

Ectoparasite: feed on the host externally

Give two examples of parasites.

The human headlice

Pork tapeworm

Whats the difference between chemical and mechanical digestion?

Mechanical: cuttibg and crushing the food with teeth and muscle contractions of the gut wall to increase the S.A for the enzymes to act upon

Chemical: secretion of digestive enzymes

Why does food need to be digested?

Food needs to be taken into the body and digested since large food molecules cant cross cell membranes and are insoluble in the bloodstream. Foods are also polymers so they need to be broken down into monomers to be assimulated into required molecules.

How do unicellular obtain nutrients and remove waste?

They obtain some nutrients through their membrane (diffusion, active transport)

They take in large food molecules by endocytosis which are then hydrolysed, and the remains are egested by exocytosis

Describe the structure of a hydra and how it consumes its food.

A multicellular organism which is cylindrical and has tentacles at the top. Undifferentiated digestive system.

Their tentacles move paralysed prey into the mouth for digestion and the indigestible remains are egested through the mouth

Describe the structure of the mammalian gut wall.

Inner lumen- mucosa - sub mucosa- inner circular muscularis- outer longitudinal muscularis- serosa

Whats the function and structure of the serosa?

Tough connective to protect the gut wall.

Reduces friction with other abdominal organs during peristalsis

Whats the function and structure of the submucosa?

Consists of connective tissue containing blood and lymph vessles to remove the absorbed products of digestion

Contains the nerves for peristalsis

Whats the function of the muscularis?

Peristalsis

Inner circular muscles and other longitudinal muscles

What role does the mucosa play?

Lines the gut wall and secrets mucus through the epithelium to lubricate and protect itself

Sometimes releases digestive juices, sometimes absorbs digested food

What role does the mouth have?

Ingestion

Chemical digestion by using the saliva and mechanical digestion of food by using the teeth

What does saliva contain? Describe the role of each component if it has one.

Amylase: hydrolyses starch to maltose

Mucus to lubricate the food (from mucosa)

HCO3^(-) and CO3^(2-) ions to create optimum pH for amylase

What is the role of the epiglottis?

A flap that blocks food entering the windpioe

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.

Name the two sphincters of the stomach.

Cardiac and pyloric

What fluid is released into the stomach and where does it come from?

Gastric juice from glands in the mucosa called gastric pits

What does gastric juice contain? Explain the role of each component and the cells from which they came.

HCl from oxyntic cells: optimum pH for enzymes

Mucus from goblet cells in the mucosa: protective lining to protect the stomafh wall from HCl and digestive enzymes, and for lubrication

Pepsinogen from chief cells at the base of the gastric glands: becomes pepsin due to HCl activation

Define endopeptidase with examples

Hydrolyse peptide bonds within the protein molecule to form smaller polypeptides

Trypsin, pepsin

Define exopeptidase.

Hydrolyse peptide bonds at the end of shorter polypeptide chains to form amino acids

How is food released into the duodenum?

Relaxation of the pyloric sphincter at the base of the stomach releases food/chyme little at a time.

What does pancreatic juice contain?

Endopeptidases, tryspinogen, enterokinase, amylase, lipase, sodium hydrogen carbonate

What juices does the duodenum recieve and from where?

Bile from the liver

Pancreatic juice from islet cells in the pancreas

What is the role of the mucus secreted by the duodenum?

Lubrication

Explain how bile salts work.

They are ampiphatic so they emulsify lipids in the food and break them into smaller globules to increases S.A for lipase action

What are the two roles of the ileum?

Absorption of digested food

Chemical digestion of proteins, fats and carbohydrates

Name the processes involved in holozoic nutrition in order

Ingestion- digestion- absorption into the bloodstream- assimilation- egestion

What type of nutrition do decomposers use?

Saprotrophic

In saprotrophic nutrition in fungi, where are the enzymes secreted from?

The fungal hyphae tips

What type of nutrition do protoctista use?

Holozoic

Define digestion

The breakdown of large insoluble molecules into soluble molecules that are small enough to be absorbed into the blood

What causes the bloating feeling?

When bacteria produce unwanted gas during respiration in the small intestine, using nonhydrolysed sugars

What is the role of the duodenum?

Chemical digestion of carbohydrates,fats and proteins

What is the function of the stomach

Mechanical digestion by churning food due to the contraction of muscles.

Chemical digestion of proteins

What is the function of the oesophagus?

Carriage of the food to the stomach by peristalsis

What does the duodenum secrete to neutralise the acidic food from the stomach? Where does the secretion come from?

Sodium hydrogen carbonate from the base of the brunner's glands in the mucosa

What is the function of enterokinase?

converts trypsinogen into trypsin

What features of the ileum makes it well adapted for absorption?

Folded lining to increase S.A

Very long

Villi on the mucosa surface to increase S.A

Epithelial cells on the villi have microvilli

What type of epithelial cells does the mucosa of the ileum have?

Columnar

How are the epithelial cells of the mucosa adapted for the ileum's function?

Microvilli

Large numbers of mitochondria to produce ATP for active transport

Describe the structures of a villi in the ileum and their roles.

Lined with epithelium thats one cell thick

Goblets cells in the epithelium to release mucus

Lacteal to absorb dietary fats for the lymphatic system

Capillaries to take digested food away

Crypt of Lieberkuhn containing Brunner's glands

From where are the peptidases secreted in the ileum?

Tips of the villi

Where does the final stage of carbohydrate digestion occur in the ileum?

Inside the epithelial cells of the villi i.e. intracellular

What is the large intestine divided into?

Caecum- ascending colon- transverse colon- descending colon

What is the function of the large intestine?

Absorption of water,mineral ions and vitamins produced by symbiotic bacteria in the gut

How are mammals adapted for their diet?

They have a palate that seperates the nasal cavity from the mouth so food can be chewed whilst they breathe

What are the 3 teeth types and their functions?

Incisors: biting and cutting food

Canines: tearing and ripping meat

Molars and premolars: grinding and chewing food

What transport mechanism is used to absorb amino acids and peptides in the ileum?

Active transport into the epithelial cell and facilitated diffusion into the blood

What happens to fatty acids and glycerol after they diffused into the epithelial cells of the ileum?

They diffuse into the lacteal and then are reassembled elsewhere

Why are herbivore teeth adapted for grinding?

Their diet is cellulose based which is hard to digest. Grinding increases S.A. for cellulase action

Describe the structural features of a herbivore's dentition and their functions.

Canines: none

Molars: interlocking

Open roots: the teeth continue to grow as grinding wears them down

Horizontal jaw movement: produces circular grinding motion

Diastema: gap between the cheek teeth and front teeth so the tongue can move grass to the large cheek teeth surfaces

Incisors and horny bad: the animal pulls the grass tight across the upper horny pad so the lower incisors can cut it

Describe the structural features of a carnivore and their functions

Large curved canines: sieze and hold onto prey

Powerful jaw muscles: grip prey

Molars: crushing food

Small sharp incisors: grip and tear flesh from bones

Carnassials: sharp teeth that slide past each other like blades to crush bone

Vertical jaw movement: jaw can open widely without dislocation when the prey is struggling

What is the dentition of an omnivore like?

An intermediate between herbivore and carnivore

What are ruminant animals?

Animals which mainly eat grass and forage but they dont have the enzyme cellulase. They have a four part stomach and rely on mutualistic microorganisms which secrete celullase in their gut.

Explain digestion in a ruminant herbivore

1. Grass is chewed and swallowed with saliva

2. Grass passes into the ruman and is mixed with bacteria which secret cellulase to form B glucose from cellulose

3. The fermented grass passes into the reticulum chamber and is formed into cud. Cud is regurgitated several times for further chewing to increase S.A for cellulose action

4. The cud passes to the omasum where water is absorbed back into the blood

5. The cud goes to the abomasum where the bacteria are killed and digested to gain protein

6. Other products go to the small intestine for absorption

Name the places of digestion the food goes through in ruminant herbivores, in order.

Mouth- rumen- reticulum- mouth- reticulum- omasum- abomasum- small intestine- large intestine- rectum

Why are the bacteria kept seperate in the rumen?

So theyre not in contact with the extreme pH and enzymes in digestive juices

What happens to the B glucose formed in ruminant herbivores after digestion?

B glucose is fermented under anaerobic conditions to form organic acids which are absorbed into the blood, providing energy. Methane gas and CO2 are waste products and are released.

Give an example of a nonruminant herbivore

Rabbit

How are nonruminant herbivores adapted for cellulose digestion?

Larger small intestines due to a larger caecum; this accomodates the cellulose digesting bacteria

What happens in nonruminant herbivores instead of regurgitation?

Refection: the rabbit ingests faecal pellets so the material passes through the gut twice and increases the efficiency of digestion

How does refection result in an in increased efficiency of digestion?

The caecum is after the small intestive where absorption occurs so egested material could contain cellulose which still needs to be digested.

Compare the gut of a carnivore to that of a herbivore.

The carnivorous gut is relatively short since protein is easily digested compared to cellulose. Herbivore large intestine is pouched, not straight, to accomodate the larger volume of faeces from plants

What organisms parasitise bacteria?

Viruses called bacteriophages

How do humans become infected by tapeworms?

The larval form is found in the secondary host: the pig. The pig becomes infected when it feeds on drainage channels contaminated with human faeces containing eggs. Humans become infected by eating contaminated undercooked pork and are the primary host

Give some features of the pork tapeworm

Ribbon like

Can be upto 10m long

The body is a linear series of sections called proglottids

Its scolex is made up of muscle which has suckers and hooks

How is the tapeworm adapted to overcome the constant motion of the gut?

Suckers and hooks on the scolex attach to the gut wall

How is the tapeworm adapted for the exposure to the extreme pH, digestive enzymes and the immune reponse of the host?

A thick cuticle and the production of the inhibitory substances on its surface (anti enzymes)

If the host dies, what happens to the tapeworm?

It dies also without causing discomfort

What do lice feed on?

Blood

Why can lice only survive on their host?

They are unable to fly, their legs are poorly adapted to jumping and walking.

How are tapeworms adapted to the lack of unavailability of a mate within their hosts and the difficulty of eggs reaching a new host?

Hermaphrodites: can self fertilisee

Large numbers of eggs with tough shells are produced so they can survive being eating.

How does the tapeworm gain nutrients from its host?

It has a large S.A to vol ratio since its long thin and flat.

It stays in the small intestine so its surrounded by digested food which can diffuse in over its whole surface