C3: Adaptations for nutrition

Question 1

Define autotroph

Answer 1

An organism that synthesises its own complex orgnic molecules using either light or chemical energy

Question 2

Define Heterotroph

Answer 2

An organism that obtains complext organic molecules from other organisms

Question 3

Describe the two different autotrophic organisms

Answer 3

Photoautotroph - use light as the energy source and perform photosynthesis. this is called holophytic nutrition

Chemoautotroph - use energy from chemical reactions all orokaryotic and this is not sufficient so not dominant.

Question 4

Desscribe three different types of heterotrophic nutrition

Answer 4

Saprophytic- Organisms that derive their energy from the extracellular digestion of dead or decaying material by secreting enzymes. They absorb the soluble products of digestion across their cell membrane by diffusion and active transport.

Holozoic – internal digestion of food. Involves ingestion, absorption,
assimilation and egestion.

Parasitic - endoparasites live in the organism ectoparasites live on it. They obtain nutrients from the living host which harms the host.

Question 5

Describe the process of digestion in an unicellular organism like amoeba

Answer 5

They have a large SA and obtain all nutrients by diffusion, facilitative diffusion and/or active transport
They take in larger molecules by endocytosis.

The food are in vesicles which combine with lysosomes which break down the food molecules.

The waste products of this digestion are egested by exocytosis

Question 6

Describe each layer of the human gut

Answer 6

Serosa - Tough outer coat of connective tissue.

Muscle - Longitudinal muscle contracts to shorten the gut and circular muscle contracts to reduce diameter. These waves of contraction called peristalsis force food along the gut.

Submucosa - 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 others it absorbs products.

Epithelium - Layer of cells in contact with food.

Question 7

Name 11 parts of the human digestion system and associated glands and organs

Answer 7

Buccal cavity (mouth)
Oesophagus
Stomach
liver
duodenum
Pancreas
ileum
Colon
Rectum
Anus

Question 8

Describe the role of the buccal cavity in digestion

3 points

Answer 8

Ingestion (cutting and grinding of food by the teeth)

Chemical digestion of startch into maltose by amylase in saliva which is excreted by the salivary glands.
saliva (slightly alkaline) maintains pH for enzyme activity

The tounge rolls food into a bolus so it can be swollowed

Question 9

Describe the role of the oesophagus in digestion

Answer 9

peristaltic waves of muscle contraction (longditudinal and cicular muscle) push the bolus of food down
to the stomach. Mucus lubricates the way

Question 10

Describe the role of the stomach in digestion

3 points

Answer 10

gastric glands in the mucosa
produce gastric juice:

The Oxyntic cells produce hydrochloric acid (HCl) that kills bacteria and lowers the pH to 2.

The chief cells produce pepsinogen, the inactive form of endopeptidase/ pepsin. This is activated by the
HCl.

The goblet cells produce mucus to protect the stomach lining.

Question 11

Describe the role of the Liver in digestion

Answer 11

Produces bile ( stored in the Gall bladder). Bile emulsifies lipids
to increase the surface area available
for lipase enzymes to digest them.

It also neutralises stomach acid to
create a slightly alkaline pH in the
duodenum for the pancreatic
enzymes.

Question 12

Describe the role of the pancreas in digestion

Answer 12

Secretes an alkaline fluid called pancreatic juice.

Pancreatic juice consists of enzymes such as Tripepsinogen(activated by enterokinase, carbohydrases and lipase

Question 13

Describe the role of the duodenum in digestion

Answer 13

Further digestion occurs on the epithelial cells of the villi:

Sucrose digested into glucose and fructose by sucrase

Maltose digested into alpha
glucose by maltase.

Lactose digested into glucose
and galactose by lactase.

Further digestion of polypeptides by
endopeptidases and exopeptidase.

Question 14

State the difference between endopeptidase and exopeptidase

Answer 14

endopeptidases hydrolyse peptide bods between specific amino acids in the middle of the polypeptide chain to form shorter polypeptide chains.

Exopeptidases hydrolyse peptide bonds on the end of peptides, from the free amino end or the free carboxyl end.

Question 15

Describe the role of the illeum in absorption

Answer 15

They have villi and microvilli for a large SA they also have a good blood supply and epithelial cells have a large amount of mitochondria to provide ATP for active transport.

Absorption mainly occurs here by diffusion, facilitative diffusion and active transport Eg:

Amino acids are actively transported into the epithelial cells of the villi; facilitated diffusion then occurs into the capillaries in the villi.

Glucose and other monosaccharides move into epithelial cells by co-transport with sodium ions;
facilitated diffusion then occurs into the capillaries in the villi.

Fatty acids and glycerol diffuse into epithelial cells and are reassembled into triglycerides and carried
by the lacteal to the lymphatic system.

Question 16

Where does water absorption mainly take place in the digestive system

Answer 16

caecum and colon

also have mutalistic microorganisms here and they secrete vitamin K

Question 17

Describe the dentition adaptations of the herbivore

Answer 17

Premolars and molars – move in a horizontal plane so these interlocking teeth grind food. Teeth have open, unrestricted roots and so grow throughout life. as griunfng wears them down.

Diastema – space where tongue can
push food to the grinding cheek teeth.

Incisors – occur on lower jaw and cut
vegetation against a horny pad on
the upper jaw. Canines are absent
or indistinguishable.

Question 18

Describe the dentition adaptations of the carnivore

Answer 18

Incisors - on upper and lower jaw grip and tear flesh.

Canines – long and pointed to pierce flesh and seize and kill prey

Carnassial teeth - act like shears, sliding past each other to rip muscle from bone.

Premolars and molars - have sharp
cusps that cut and crush. The jaw
has strong muscles and moves in a
vertical plane opening wide and
strongly clamping down to hold
prey.

Question 19

Describe the adaptations of the carnovores Gut

3 points

Answer 19

Relatively short gut.

Usually a large stomach for digestion of mostly protein diet.

Small caecum.

Question 20

Describe the gut of a non rumninant herbivore

Answer 20

Very long gut for the difficult process of cellulose digestion.

Large caecum containing bacteria that produce cellulase for cellulose digestion.

Question 21

Describe the process of a ruminant gut

Answer 21

Grass is mixed with saliva and chewed forming Cud and swollowed

Cud enters the rumen. cellulose digesting bacteria produce cellulase
this ferments into organic acids which are absorbed into the blood stream
produced alot of CO2 and methane

Fermented cud from the rumen
enters the second stomach chamber,
the reticulum. The cud is regurgitated
from here and the rumen back into the
mouth to be rechewed.

Rechewed cud is swollowed and enters the third chamber of the stomach the omasum water absorption occurs here

The remaining Cud enters the fourth and final chamber called the abomasum where protein is digested

The products of digestion are absorbed into the blood in the small intestine