Biology WJEC BY2 Notes for 2.5 Adaptations for Nutrition

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Preview of Biology WJEC BY2 Notes for 2.5 Adaptations for Nutrition

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WJEC BY2.5 Adaptations for Nutrition
Nutrition is the process by which organisms obtain energy to maintain life functions and matter to create
and maintain structure. These are obtained from nutrients.
Autotrophic organisms such as green plants use the simple organic materials carbon dioxide and water
to manufacture energy -containing complex organic compounds, whereas heterotrophic organisms
consume complex organic food material.
Autotrophic nutrition
Living organisms that can make their own food are called autotrophs.
They provide food for all other life forms and so they are also known as producers. There are two types
of autotrophic nutrition:
Photosynthesis is the process by which green plants build up complex organic molecules such as
sugars, from carbon dioxide and water. The source of energy for this process comes from sunlight
which is absorbed by chlorophyll and related pigments. Algae and certain types of bacteria can also
photosynthesise using energy from sunlight.
Chemosynthesis is a process carried out by autotrophic bacteria. They use the energy derived
from special methods of respiration to synthesise organic food.
Heterotrophic nutrition
Cannot make their own food; have to consume complex organic food material produced by autotrophs.
They eat or consume ready-made food and so are known as consumers
Holozoic feeders ­ includes nearly all animals. Take their food into their bodies and break it down by
digestion. Most carry this out within a specialised digestive system
Saprophytic Digestion ­ Fungi and bacteria which use dead organic compounds as food therefore
are heterotrophs. To digest that food they
Secrete enzymes onto organic material for extracellular digestion
Digestion hydrolyses bonds in organic material e.g. protein, starch,
cellulose, sucrose
This produces small soluble molecules e.g. amino acids, glucose
which are absorbed by diffusion

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Fungi are made up from tiny threads called HYPHAE ­ enzymes are secreted from the tips
Human digestion
Humans, like all animals, use holozoic nutrition, which consists of these stages:
o Ingestion- taking large pieces of food into the body through the mouth
o Digestion- breaking down large insoluble food molecules into small soluble food
molecules by mechanical and chemical means
o Absorption- taking up the soluble digestion products into the blood
o Egestion- eliminating the undigested food
Do not confuse egestion, which is the…read more

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Humans are omnivores, they eat both plant and animal material. The teeth are not particularly
specialised but having four different types of teeth to carry out different functions reflects a
mixed diet. In total humans have 32 teeth and these are made up of:
o Eight chisel -shaped incisors at the
front of the mouth for biting and
o Four pointed canines that function
as incisors.
o Ten large, flat teeth on each side
used for chewing. These are the
premolars and molars.…read more

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Dentition in carnivores
Carnivorous mammals, such as a tiger, have teeth adapted for catching and killing prey, cutting
or crushing bones and for tearing meat.
The sharp incisors grip and tear flesh from bone. The canine teeth are large, curved and
pointed for seizing prey, for killing and also tearing flesh.
The premolars and molars are for cutting and crushing. Carnivores have a pair of specialised
cheek teeth, called carnassials, which slide past each other like the blades of gardening
shears.…read more

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In humans the site of ingestion/digestion/absorption is the gut which is a long tube that extends from
the mouth to the anus together with a number of associated glands
In simple organisms, feeding on only one type of food the gut is undifferentiated, however in more
advanced organisms the digestive system is made up of different tissues doing different jobs
Structure of the gut always has these four basic layers:
Mucosa ­ Glands in the stomach secretes gastric juices.…read more

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Muscle layer - is made of smooth muscle, under involuntary control is subdivided into inner circular
muscle (which squeezes the gut when it contracts) and outer longitudinal muscle (which shortens
the gut when it contracts).
Serosa - a tough layer of connective tissue that holds the gut together, and attaches it to the
abdomen.…read more

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Amylase Maltase
Starch Maltose
Protein ­ digestion takes part in 2 stages
Endopeptidase Exopeptidase
Protein Polypeptide Amino Acids
Endopeptidases hydrolyse peptide bonds along the length of the amino acid chain to provide more
`free ends' for exopeptidases to act on
These are NOT polymers!
Bile Lipase
Lipids Lipids Fatty acids + Glycerol
(large (small
globules) globules)
Bile emulsifies large fat droplets to small droplets
To increase surface area for lipase action
Bile also neutralises acidic stomach contents
*N.B.…read more

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Enzyme/chemical Site of Site of action Substrate Product
Amylase Salivary glands Mouth
Starch Maltose
Pancreas Duodenum
Endopeptidase Gastric glands Stomach
Protein Polypeptides
Pancreas Duodenum
Exopeptidase Epithelial cells at Ileum Polypeptides Amino Acids
tips of villi
Maltase Epithelial cells at Ileum Maltose Glucose
tips of villi
Lipase Pancreas Duodenum Lipid Fatty Acids +
Bile Liver Duodenum Large Lipid Small Lipid
Globules Globules
The specialized regions of the mammalian have different pHs therefore the different enzymes have
different optimum pH
Regional specialisations
The Mouth
Mechanical…read more

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The duodenum makes up the first 20cm of the small intestine and receives secretions from both the
liver and the pancreas
Bile salts are produced in the liver and stored in the gall bladder from where it passes into the
duodenum via the bile duct. It contains no enzymes but the bile salts are important in emulsifying
the lipids present in the food
The pancreas secretes pancreatic juice into the duodenum through the pancreatic duct.…read more

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Mechanisms for Absorption
Glucose is absorbed by diffusion and active transport into capillaries and then travel via the
hepatic portal vein to the liver
Glucose is absorbed from the blood by cells, for energy release in respiration, and any excess is
converted to fat for storage
Amino acids are absorbed by diffusion and active transport into capillaries and then travel via
the hepatic portal vein to the liver
Amino acids are absorbed for protein synthesis; excess cannot be stored so undergoes
deamination, whereby…read more



this is amazing thank youuuu!


amazing notes thank you

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